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3.2: Starch Protein Teacher's Preparation Notes - Biology

3.2: Starch Protein Teacher's Preparation Notes - Biology


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In this activity, students learn about the scientific method by carrying out key components of a scientific investigation, including:

  • Developing experimental methods
  • Generating hypotheses
  • Designing and carrying out experiments to test these hypotheses
  • If appropriate, using experimental results to revise these hypotheses.

The Student Handout provides information and questions to guide students in designing the first experiment, which evaluates two indicator solutions to see whether they can be used to test for starch and/or for protein. Then, students use the results from the first experiment and inductive reasoning to formulate hypotheses concerning which types of food contain starch and which types of food contain protein (some or all foods derived from animals or plants or both). Next, students use deductive reasoning based on their hypotheses to make predictions for a second experiment to test their hypotheses. Finally, students carry out the second experiment and use the results to evaluate their hypotheses and, if necessary, modify these hypotheses.

In order to complete the experimental portion of Part 1 in 50 minutes, you may want to discuss the material on page 1 and the top of page 2 of the Student Handout in a pre-laboratory session. You will probably want a second 50-minute laboratory period for Part 2.

Learning Goals

Students Engage in Scientific Practices

"Planning and carrying out investigations" – Students should be able to:

  • "Decide what data are to be gathered … and how measurements will be recorded."
  • "Decide how much data are needed to produce reliable measurements and consider any limitations on the precision of the data."
  • "Plan experimental… procedures, identifying… the need for controls."

"Analyzing and interpreting data" – Students should be able to:

  • "Analyze data systematically, either to look for salient patterns or to test whether data are consistent with an initial hypothesis."
  • "Evaluate the strength of the conclusion that can be inferred from any data set…"

Additional Learning Goals

  • Accurate, consistent methods and replication of experiments are needed to produce reliable experimental results.
  • Inductive reasoning can provide useful generalizations based on specific observations, but the results of inductive reasoning should be treated with caution, since additional specific observations may show exceptions to the generalization.
  • To test a hypothesis, scientists use deductive reasoning to predict specific experimental results expected on the basis of the hypothesis.
  • Experiments to test a hypothesis often produce results that stimulate scientists to modify their original hypothesis; then scientists perform additional experiments to test their modified hypothesis.
  • An indicator is a substance that changes color in the presence of a particular type of organic compound.
  • To evaluate the specificity of an indicator, it is important to include negative controls.
  • Food contains organic compounds made by other organisms such as plants and animals.
  • Starch is only found in foods derived from plants (since animals do not make starch).
  • Protein is found in some foods derived from animals and some foods derived from plants.

Supplies

  • Indicator Solution 1 = Iodine-Potassium Iodide Solution (~12 mL per class; available from http://www.carolina.com/; if not in an opaque container, should be stored in the dark)
  • Indicator Solution 2 = Biuret reagent (~50 mL per class; available from http://www.carolina.com/; Biuret reagent should be fresh since old Biuret reagent is less sensitive as a protein indicator.)
  • Dropper bottles for the indicator solutions (bare minimum of one for each indicator solution; ideally, as many as the number of student groups in your largest class, so each pair of student groups can share a pair of dropper bottles; available from http://www.carolina.com/; search for plastic dropping bottles)
  • Containers for testing (28 if you have containers that will be washed and reused; you may want to use small disposable plastic or Styrofoam cups, which are especially useful if you do not have sinks available, but you would need 48 per class; white containers or transparent containers placed on a white background make it easier to see the color change in the indicator solutions)
  • Marker and masking tape for labeling these containers
  • Stirrers (1 or 2 per student group in your largest class; more if you do not want students to have to wash stirrers during the experiment)
  • Water (tap water should be fine; ~50 mL per class for Part 1/~10 mL per class for Part 2 + water for washing unless you have enough containers and stirrers so students do not need to wash them)
  • Gloves (minimum of 1 per student group per day)
  • Samples for Part 1 (You will probably want a little extra of each of these.)
    • Corn starch (~2 mL per class; can be found in the baking needs aisle)
    • Potato starch (~2 mL per class; can be found in the baking needs aisle)
    • Powdered egg whites (~2 mL per class; can be found in the baking needs aisle)
    • Sucrose = "table sugar" (~2 mL per class)
    • Unsweetened Gelatin (~1 mL per class)
    • Vegetable oil (~4 mL per class)
  • Samples for Part 2 (You will probably want a little extra of each of these.)
    • Beans (canned beans, we have had good success with white beans; ~8 beans per class)
    • Butter (~4 mL per class)
    • Jelly (~4 mL per class; you may want to check the label to make sure your jelly does not contain gelatin)
    • Bread (~4 mL per class; whole-grain breads preferred because they have somewhat more protein; many breads contain a little bit of milk or milk product (whey); since Part 2 of the activity analyzes the starch and protein content of foods derived from plants vs. animals, you probably want to have a sample of bread that does not include any milk, whey or eggs)
    • Yogurt (~4 mL per class; you should check the ingredients list to make sure you have a brand of yogurt (e.g. Dannon or Stonyfield) that does not contain starch)

Suggestions for Implementation and Discussion

Part 1: Which Indicator Solutions can be used to Test for Starch and for protein?

Depending on your preference, you can have students measure the amount of sample and water precisely or just estimate the approximate amount (which works equally well).

To evaluate whether each indicator solution is a good indicator for starch or for protein, students should look for color changes when the indicator is added to:

  • More than one type of starch
  • More than one type of protein
  • Negative controls, including water, sugar, and oil.

The negative controls are important to establish that an indicator solution shows color change only for starch or only for protein. The expected results are that, in the presence of starch, iodine will change color from yellow-brown to blue-black, and, in the presence of protein, Biuret reagent will turn from blue to purple. Biuret reagent is a little less reliable than the iodine indicator; it is important to use fresh Biuret reagent and it would be good to double-check this test yourself ahead of time. You may want to show your students the color change for each of the indicator solutions before they begin their testing, so they will know what to look for.

Question 4 can be used to introduce the advantages of replication of each test. You may want to introduce the concept of false positives (which could occur if there were contamination) and false negatives (which could result from insufficient amounts of sample and/or indicator solution). Also, if there is only a small color change, this may be interpreted as a positive response by some observers, but not others.

To accomplish the goals of having negative controls and replicating results, the experimental design should have duplicate tests with each indicator for each sample for a total of 2 replicates x 2 indicator solutions x 7 samples = 28 tests. I suggest that you have your students work in groups of four, and have replicate tests done by different groups (so whatever experimental error one group might make won't affect the replicate test).

If there are any differences between replicate tests, you should lead a class discussion of methodological factors that may have influenced the test results and then repeat the test with the optimum methodology to resolve the conflict. You can point out to your students that an important and necessary part of scientific research is to refine and standardize methods in order to get consistent and reliable results.

In discussing the last part of questions 7 and 8, you will want to include the limitations of inductive reasoning (see e.g. http://www.bio.miami.edu/ecosummer/lectures/lec_sci entific_method.html), especially when only a limited number of samples have been tested. To be more certain of conclusions concerning whether either of these indicator solutions can be used to test for starch or for protein, it would be desirable to test each indicator solution on a wider variety of samples, including, for example, glucose and amino acids (the monomers of starch and protein, respectively), as well as additional types of starch and protein.

Part 2: What Types of Food Contain Starch? What Types of Foods Contain Protein?

In this part, students:

  • First, use the data from Part 1 to generate hypotheses about what types of food contain starch and protein,
  • Then, design and carry out experiments to test these hypotheses,
  • Interpret the results to see whether they support the hypotheses,
  • And, if the initial hypotheses were not supported or only partially supported, formulate newly revised hypotheses.

You will probably want to point out to your students that this is how real scientists work as they develop a progressively better understanding of a research question.

Student hypotheses in response to question 10 will probably vary. This provides the opportunity to mention that this type of disagreement also happens in "real science" when different scientists have different interpretations of the same evidence; typically, these disagreements are resolved by obtaining additional evidence. Some of the student hypotheses may provide the opportunity to discuss how people formulate hypotheses based on both the results of the current experiment and also prior knowledge; this can be a useful part of the scientific process and contribute to cumulative improvements in our understanding of scientific questions. All of the student hypotheses should be compatible with the results from Part 1 which should show that:

  • Some, but not all, foods derived from plants contain starch.
  • At least some foods derived from animals do not contain starch.
  • At least some foods derived from animals contain protein.
  • At least some foods derived from plants do not contain protein.

In response to question 12, students should describe the need to test each of the samples listed in question 11 with each of the indicator solutions, as well as the need to replicate each of these tests. Thus, you will want a total of 5 samples x 2 indicator solutions x 2 replicates = 20 tests.

In interpreting the results of their tests, students should be aware that their tests may not be sensitive enough to detect small amounts of starch or protein. The level of protein is high enough to be easily detected in concentrated sources of protein such as egg whites, beans or milk (where it provides nutrition for the growing bird embryo, plant seedling, or baby mammal, respectively). The color of the protein test varies somewhat for different foods; for example, the protein test typically shows a darker purple for bread than for the egg white or gelatin samples. You may want to discuss how scientific results are sometimes ambiguous, and scientists try to improve their methodology and repeat the experiment to clarify any ambiguity.

Comparing the results of testing the samples in Part 1 vs. Part 2 for protein demonstrates the risk of generalizing from a limited set of observations. In Part 1 none of the foods derived from plants and all of the foods derived from animals have significant amounts of protein, but in Part 2 beans and bread have a significant amount of protein and butter has almost no protein. You may want to point out that generating the hypotheses in question 10 requires inductive reasoning (generalizing from specific examples to more general hypotheses, which has the risk of overgeneralizing, as demonstrated in this activity), whereas making the predictions in question 11 requires deductive reasoning (reasoning from general hypotheses to specific predictions, often used to test hypotheses).

Only plants produce starch, but starch is not present in significant amounts in some foods derived from plants, because the food is derived from a part of the plant that has little or no starch and/or because preparation of the food product has removed starch that was initially present. You will probably want to talk about the energy storage function of starch for plants, and you may want to talk about the energy storage function of glycogen in animals and fat in animals and seeds (where the greater amount of energy per unit of weight in fat is useful for mobility).

Professional nutritional analysis provides the following values for starch and protein content for the food samples in this activity (% by weight; – = missing data; data from www.nutritiondata.com).

Food

Starch*

Protein*

Corn starch

~91%

0%

Potato starch

Vegetable oil (corn oil)

0%

0%

Dried egg whites

81%

Gelatin, unsweetened

0%

86%

Whole wheat bread

13%

White bread

41%

8%

Butter

0%

1%

Jellies

0%

Low-fat vanilla yogurt#

0%

5%

White beans (canned)

7%

Kidney beans (canned)

9%

5%

Note

* Foods that contain more water tend to have a lower percentage of starch and protein.

# These figures apply to brands like Dannon and Stonyfield which do not add starch; read the ingredients list on the label to purchase a type of yogurt which does not have starch added.

Additional Resources for Teaching about the Scientific Method

A wealth of resources for teaching and understanding the scientific process are provided in

"Understanding Science – How science really works", available at http://undsci.berkeley.edu/

"Using the Scientific Method" (available at http://www.biologycorner.com/worksheets/scientific_method_plant_exp.html) is a simulation of a simple experiment with questions to guide the students in describing and analyzing their simulated experiment; the simulation can be carried out quickly, so students can spend most of their time on learning about important issues in experimental design and interpretation, including the need to have all variables except the experimental variable the same for the control and experimental groups in order to test the effect of the experimental variable.

"The Strange Case of Beri beri" (available at http://www.njuhsd.com/webpages/tkirwan/resources.cfm?subpage=1082070, click on "The Scientific Method in Action".

"Battling Bad Science" is an entertaining talk about the errors and deceptions behind misleading nutritional or medical advice, available at http://www.ted.com/talks/ben_golda cre_battling_bad_science.html (the first 7.5 minutes are the most relevant).

Additional Hands-on Activities in Which Students Design Experiments and Interpret the Results:

"Moldy Jell-O", available at http://serendip.brynmawr.edu/sci_edu/waldron/#jello

Students design experiments to determine how substrate and environmental conditions influence the growth of common molds. Students carry out their experiments, analyze and interpret their evidence, and prepare a report.

"Enzymes Help Us Digest Food", available at http://serendip.brynmawr.edu/sci_edu/waldron/#enzymes

Experiments with the enzyme lactase and discussion questions help students to learn about enzyme function, enzyme specificity and the molecular basis of lactose intolerance. Students also learn about the scientific method by interpreting evidence to test hypotheses and designing the second and third experiments to answer specific scientific questions about lactase.

"Investigating Osmosis", available at http://serendip.brynmawr.edu/sci_edu/waldron/#osmosis

Students make predictions about the effects of osmosis and design an experiment to test these predictions.

"Regulation of Human Heart Rate", available at http://serendip.brynmawr.edu/sci_edu/waldron/#heart

Students learn how to measure heart rate accurately. Then students design and carry out an experiment to test the effects of an activity or stimulus on heart rate, analyze and interpret the data, and present their experiments in a poster session.

Discussion Activities for Learning about the Process of Science

"Carbohydrate Consumption, Athletic Performance and Health – Using Science Process Skills to Understand the Evidence", available at http://serendip.brynmawr.edu/exchang...vities/sciproc

This discussion/worksheet activity is designed to develop students' understanding of the scientific process by having them design an experiment to test a hypothesis, compare their experimental design with the design of a research study that tested the same hypothesis, evaluate research evidence concerning two hypothesized effects of carbohydrate consumption, evaluate the pros and cons of experimental vs. observational research studies, and finally use what they have learned to revise a standard diagram of the scientific method to make it more accurate, complete and realistic.

"Vitamins and Health – Why Experts Disagree", available at http://serendip.brynmawr.edu/exchang...ities/vitamins

In this discussion/worksheet activity, research concerning the health effects of vitamin E is used as a case study to help students understand why different research studies may find seemingly opposite results. Students learn useful approaches for evaluating and synthesizing conflicting research results, with a major focus on understanding the strengths and weaknesses of different types of studies (laboratory experiments, observational studies, and clinical trials). Students also learn that the results of any single study should be interpreted with caution since results of similar studies vary (due to random variation and differences in specific study characteristics).

Related Activity

"Who took Jerell's iPod? – An organic compound mystery" (available at http://serendip.brynmawr.edu/sci_edu/waldron/#organic) uses some of the same experimental procedures but focuses on student learning about different types of organic compounds and engages students in testing for these organic compounds in the context of solving a mystery.


Practical Work for Learning

Demonstration

To follow the progress of a starch digestion or starch synthesis reaction, you could track the changing concentration of starch with a colorimeter.

To convert colorimeter absorbance readings to concentration, you need to make up some standard solutions of starch, add a fixed volume of iodine solution, and take colorimeter readings. Plotting the colorimeter readings against concentration gives you a curve. Then, during the course of your experiment, you can convert colorimeter readings (from the starch solution in your reaction vessel) into concentrations by comparison with the curve and interpolation of the values.

Lesson organisation

This could be a simple demonstration to show students how to make up solutions at different concentrations, how to use the colorimeter and/ or how to plot and use a calibration curve. If all your students make up solutions and add iodine following instructions as closely as possible, you can discuss how reliable any one calibration curve is.

Apparatus and Chemicals

For the demonstration

Colorimeter – set to read absorbance in the ‘orange’ range of the spectrum (610 nm)

Soluble starch (0.5–1.0 g) – to make up to 100 cm 3 of 1% starch

Health & Safety and Technical notes

Wear eye protection when dispensing iodine solution.

1 Starch solution Add a weighed amount of starch (0.5 g or 1.0 g) to a little heated water, mix to a paste, then dilute to 50 or 100 cm 3 .

2 Iodine solution Iodine is only sparingly soluble in water (0.3 g per litre) it is usual to dissolve it in potassium iodide solution (KI) to make a 0.01 M solution (by tenfold dilution of a 0.1 M solution) to use as a starch test reagent. Refer to CLEAPSS Recipe card 33.

For 100 cm 3 of 0.1 M solution, measure out 3.0 g of potassium iodide (KI) into an appropriate beaker. Moisten the potassium iodide with a few drops of water. Measure out 2.54 g of iodine (see Hazcard 54: iodine is harmful) and add to the moistened potassium iodide. Add a small volume of water and stir. When no more iodine appears to dissolve, add more water and stir. Repeat until all the iodine has dissolved. Pour the solution into a measuring cylinder and dilute to the final volume. If there are any bits of iodine remaining, return the solution to the beaker, and leave it on a magnetic stirrer for several minutes. Add the solution to a labelled bottle and mix well.

Procedure

SAFETY: Wear eye protection when dispensing iodine solution.

a Make up 50 cm 3 or 100 cm 3 of 1% soluble starch in distilled water. Use a graduated pipette to measure 0.5 cm 3 , 1 cm 3 , 2 cm 3 , 3 cm 3 , 5 cm 3 , 7 cm 3 and 10 cm 3 of the solution into a series of test tubes.

b Make each tube up to 10 cm 3 with distilled water from another clean graduated pipette.

c Place 10 cm 3 of water in a final test tube.

d Add one drop of iodine solution to each tube and mix thoroughly.

e With each solution in turn, transfer enough of the solution to fill a clean colorimeter cuvette. Take a reading of absorbance at ‘orange’ wavelengths (610 nm).

f Plot a graph of absorbance against concentration. The spreadsheet you can download below gives a sample set of results.

g Use the graph to calculate concentration from absorbance readings gained during an investigation.

Health & Safety checked, May 2009

Downloads

Download Starch concentration calibration curve (15 KB) which shows a typical set of results for this calibration.

Related experiments

Quantitative food test – this also involves making a calibration curve for protein concentration, by plotting time taken for powdered milk solution to clarify after adding a known volume of protease.

© 2019, Royal Society of Biology, 1 Naoroji Street, London WC1X 0GB Registered Charity No. 277981, Incorporated by Royal Charter


Experiment to Test the Presence of Starch in the Given Food Sample

To test the presence of starch in the given food sample.

Apparatus and materials required:

Test tubes, test-tube stand, test-tube holder, spirit lamp, dropper, filter paper, iodine solution, distilled water, and foodstuff (potato, rice, wheat or maize grains).

Theory:

Starch, a complex carbohydrate, is composed of 15%-20% amylose and 80%-85% amylopectin. It is found in different kinds of cereals such as rice, wheat, maize, etc. After reacting with iodine solution starch forms a dark, blue-black compound. The appearance of blue-black colour is due to the presence of amylase in starch.

Procedure:

1. Take a few small, freshly cut pieces of potato or a few grains of rice or wheat or maize in a clean test tube.

2. Pour 10 mL distilled water into the test tube.

3. Now, boil the contents of the test tube for about 5 minutes.

4. Allow the test tube to cool.

5. Filter the contents of the test tube through a filter paper.

6. Test the obtained filtrate for the presence of starch by the following method.

Precautions:

1. Use test-tube holder for holding the test tubes and keep the mouth of the test tube away from yourself while heating.

3. Do not use too much of iodine solution.

Experiment 3.2:

Objective:

To test the presence of the adulterant metanil yellow in dal (pulse)

Apparatus and materials required:

Test tubes, test-tube stand, test-tube holder, conc. HCl, mortar-pestle, filter paper, distilled water and a sample of dal

Theory:

Metanil is a cheap dye which is commonly used in colouring non-food items like clothes. Government of India has introduced “Prevention of Food Adulteration Act” to prevent the use of harmful chemicals such as this dye in foodstuffs.

Procedure:

1. Grind 3-5 g of dal in a mortar-pestle.

2. Take this powdered dal in a clean test tube.

3. Pour 10 mL distilled water into the test tube and shake it well.

4. Filter the contents of the test tube through a filter paper and use the filtrate to test for metanil yellow by the following method.

Observation:

Precautions:

1. Always use clean test tubes.

2. Use test-tube holder at the time of adding conc. HCI and keep the mouth of the test tube away from yourself.


3.2 Carbohydrates

Carbohydrates provide energy for the cell and structural support to plants, fungi, and arthropods such as insects, spiders, and crustaceans. Consisting of carbon, hydrogen, and oxygen in the ratio CH2O or carbon hydrated with water, carbohydrates are classified as monosaccharides, disaccharides, and polysaccharides depending on the number of monomers in the macromolecule. Monosaccharides are linked by glycosidic bonds that form as a result of dehydration synthesis. Glucose, galactose, and fructose are common isomeric monosaccharides, whereas sucrose or table sugar is a disaccharide. Examples of polysaccharides include cellulose and starch in plants and glycogen in animals. Although storing glucose in the form of polymers like starch or glycogen makes it less accessible for metabolism, this prevents it from leaking out of cells or creating a high osmotic pressure that could cause excessive water uptake by the cell. Insects have a hard outer skeleton made of chitin, a unique nitrogen-containing polysaccharide.

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 4 of the AP ® Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP ® Biology course, an inquiry-based laboratory experience, instructional activities, and AP ® Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices.

Big Idea 4 Biological systems interact, and these systems and their interactions possess complex properties.
Enduring Understanding 4.A Interactions within biological systems lead to complex properties.
Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule.
Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales.
Learning Objective 4.1 The student is able to refine representations and models to explain how the subcomponents of a biological polymer and their sequence determine the properties of that polymer.
Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule.
Science Practice 1.3 The student can refine representations and models of natural or man-made phenomena and systems in the domain.
Learning Objective 4.2 The student is able to refine representations and models to explain how the subcomponents of a biological polymer and their sequence determine the properties of that polymer.
Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule.
Science Practice 6.1 The student can justify claims with evidence.
Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models.
Learning Objective 4.3 The student is able to use models to predict and justify that changes in the subcomponents of a biological polymer affect the functionality of the molecules.

The Science Practice Challenge Questions contain additional test questions for this section that will help you prepare for the AP exam. These questions address the following standards:
[APLO 4.15] [APLO 2.5]

Molecular Structures

Most people are familiar with carbohydrates, one type of macromolecule, especially when it comes to what we eat. To lose weight, some individuals adhere to “low-carb” diets. Athletes, in contrast, often “carb-load” before important competitions to ensure that they have enough energy to compete at a high level. Carbohydrates are, in fact, an essential part of our diet grains, fruits, and vegetables are all natural sources of carbohydrates. Carbohydrates provide energy to the body, particularly through glucose, a simple sugar that is a component of starch and an ingredient in many staple foods. Carbohydrates also have other important functions in humans, animals, and plants.

Carbohydrates can be represented by the stoichiometric formula (CH2O)n, where n is the number of carbons in the molecule. In other words, the ratio of carbon to hydrogen to oxygen is 1:2:1 in carbohydrate molecules. This formula also explains the origin of the term “carbohydrate”: the components are carbon (“carbo”) and the components of water (hence, “hydrate”). Carbohydrates are classified into three subtypes: monosaccharides, disaccharides, and polysaccharides.

Monosaccharides

Monosaccharides (mono- = “one” sacchar- = “sweet”) are simple sugars, the most common of which is glucose. In monosaccharides, the number of carbons usually ranges from three to seven. Most monosaccharide names end with the suffix -ose. If the sugar has an aldehyde group (the functional group with the structure R-CHO), it is known as an aldose, and if it has a ketone group (the functional group with the structure RC(=O)R'), it is known as a ketose. Depending on the number of carbons in the sugar, they also may be known as trioses (three carbons), pentoses (five carbons), and or hexoses (six carbons). See Figure 3.5 for an illustration of the monosaccharides.

The chemical formula for glucose is C6H12O6. In humans, glucose is an important source of energy. During cellular respiration, energy is released from glucose, and that energy is used to help make adenosine triphosphate (ATP). Plants synthesize glucose using carbon dioxide and water, and glucose in turn is used for energy requirements for the plant. Excess glucose is often stored as starch that is catabolized (the breakdown of larger molecules by cells) by humans and other animals that feed on plants.

Galactose (part of lactose, or milk sugar) and fructose (found in sucrose, in fruit) are other common monosaccharides. Although glucose, galactose, and fructose all have the same chemical formula (C6H12O6), they differ structurally and chemically (and are known as isomers) because of the different arrangement of functional groups around the asymmetric carbon all of these monosaccharides have more than one asymmetric carbon (Figure 3.6).


Proteins in the Diet

S.R. Nadathur , . L. Scanlin , in Sustainable Protein Sources , 2017

1.3.3 Product Trends

Plant proteins may also fit into “freedom foods,” as stated by Christopher Shanahan, Global Program Manager for Frost & Sullivan ( Gelski, 2015 ). In particular, “freedom foods” are not constrained by worries pertaining to human disease, animal welfare, and food safety concerns specific to animal-based proteins. In fact, plant proteins from pulses, seeds, and grains have significant roles within “freedom foods,” “free-from,” and “good-for-you” foods. Five to ten grams or more of plant protein per serving are often promoted on many foods, beverages, and healthy snacks. Plant proteins are regularly associated with energy and labels may include wording such as “plant-powered protein,” “powered by,” “energized,” and “fueled by.” Plant proteins have been marketed to offer a “boost” of protein for energetic workouts, as well as for good breakfasts and most important part of the day to keep you moving. Plant proteins that have been recently highlighted in this manner include pea and other pulses, sunflower and pumpkin seeds, cashews, almonds, amaranth, quinoa, macadamia nuts, sesame seeds, hazelnuts, and walnuts. Above all accounts, soybean protein has been directly linked to heart health. According to US Code of Federal Regulations, Title 21, 101.82 the following health claim can be made on a food product containing at least 6.25 g soy protein per reference amount of that food item: “As part of a diet low in saturated fat and cholesterol, 25 g soy protein per day may reduce the risk of heart diseases.” On a product such as this, one may also find the label adorned with wording such as “heart health” and “heart healthy protein.”

Many plant-based powders, beverages, and meal replacements today have advertisements on consumer-facing labels such as “plant-based protein,” “organic plant protein,” “vegan,” “green protein powder,” “super-food,” “complete and balanced protein,” and/or “healthy alternative.” Plant-based foods are also marketed to break down potential consumer barriers to entry. For example, plant-based foods draw special attention to calcium comparisons to dairy milk or omega levels relative to salmon. In addition, plant proteins in the form of sprouted grains and seeds with increased enzyme activity are increasing in popularity because of an association with disease healing, aid in digestion, nutrient absorption, and increased protein and nutrient density. Sprouted seeds include but are not limited to pumpkin, watermelon, chia, flax, hemp, and sunflower. On websites and in the media, plant protein is marketed as the future of protein. Although leading this movement are lentils, grains, and nuts in whole or minimally processed forms, there is some consideration spent on meat and dairy analogs (in general, analogs are highly processed plant ingredients made to simulate animal products). Often, manufacturers of plant-based meat analogs have heavy marketing campaigns that call out the meat industry on animal welfare and slaughterhouse issues, food safety concerns, environmental downsides with livestock, climate change and water scarcity, use of antibiotics and growth hormones, and negative health impacts of cholesterol and saturated fats.

A correlation has been discovered between Western diets high in meats, refined sugars, and fats, that is both unhealthy for humans as well as the planet ( Tilman & Clark, 2014 ). Ecologists Tilman and Clark estimate that by 2050 food production for such diets will lead to an 80% increase in agriculture-based global greenhouse gas emissions. Production for Western-style diets has already caused damage, including deforestation in underdeveloped countries. The current increasing demand for Western foods will drive an escalation of land cleared for meat production and major oil crops soya and palm. Tilman and Clark’s study unfolded quickly in media articles targeting Western diets as bad for human health and the environment ( Healy, 2014 Skirble, 2014 ). Therefore, replacing traditional diets by Western-style diets is not sustainable. This dietary shift has accompanied a rise in type 2 diabetes, coronary heart disease, and other chronic Western diseases. A global trilemma of poor diet, health, and environment will require dietary, policy, and business solutions. This trilemma is likely to be exacerbated by the projected increase in the global population by 30% in the next 30 years and a further 10% by the turn of the century. Growing nutritious food for this large number of people will become vital. Below we will discuss how humanity can tackle this situation, and prepare to make critical choices.


Contents

Starch granules are insoluble in cold water and will absorb only little water. They form a suspension that quickly settles once agitation stops. As the water is heated (50+ C) more and more water is absorbed and the granules start to swell [Narziss, 2005]. The water absorbed during this process can be up to 30 times the weight of the starch granule. This uptake of water initially happens within the amorphous growth rings. At this point the granule starts to leach amylose and the crystalline layers break open and separate from the starch granule as gelatinous sheets. At this point the crystalline structure is lost and the process becomes irreversible with respect to the shape of the starch granule [Shetty, 2006]. The starch granule has gelatinized.

While the temperature range during with gelatinization occurs has been found to be quite narrow for individual starch granules (

1C) the temperature range between the gelatinization of the first granules and the complete gelatinization of all granules can be quite large. Figure 1 shows the temperature ranges for gelatinization for a number of starches. It can be seen that not all these starches fully gelatinize at temperatures that are encountered in a saccharification rest. If this is not the case they will have to be gelatinized before that rest though either a cereal mash or the use of pre-gelatinized (e.g. flaked) forms. Another interesting aspect is the different gelatinization temperature ranges that have been determined for large and small barley granules. 90% of the starch in barley are large granules which will be gelatinized at saccharification rest temperatures while the rest are small starch granules which may not fully gelatinize until higher temperatures are reached. This can explain some of the efficiency benefits that can be gained from a mash-out or a decoction mash.

Gelatinization is a process that requires free water for the swelling and breaking the hydrogen bonds that hold the crystalline structures in place. If free water is limited due to a high concentration of starch (e.g. overly thick mash conditions) less swelling takes place and a melting of the crystalline section needs to occur [Donald, 2004]. This leads to an increase in the gelatinization temperature. A limitation of free water can also be caused by the presence of sugars other dissolved solids. For corn starch, for example, it has been shown that a 25% sucrose solution increases the gelatinization temperature from 70 to 78C [Donald, 2004]. This is assumed to be one of the factors why thick mashes showed a lower efficiency compared to thin mashes in the Mashing Experiments.

As starch starts to gelatinize the viscosity of the liquid will increase. This can be noticed in brewing to some extend but by far less that what is commonly seen in cooking. The reason for that is the presence of enzymes (in particular α-amylase) that will start breaking down the amylose and amylopectin molecules as soon as they become accessible. This process reduces the viscosity of the mash and is therefore called liquification [Kunze, 2007]. This effect is used for mitigating the risk of scorching the mash during a decoction boil by resting them at 70-74C before continuing to heat them to a boil.

A strong increase in viscosity can however become a problem in cereal mashes. Especially when using rice starch which is known to swell very intensely. This can lead to scorching or even the immobilization of mash agitators [Kunze, 2007]. To counteract that some malt should be added to cereal mashes and a short liquification rest might be held between 75 and 80C (just before all the α-amylase gets denatured) before it is then heated to boiling.

The gelatinization temperature also depends on growing conditions and crop year [Kunze, 2007]. And Kessler showed that a reasonable correlation exists between the VZ 45C malt analysis number and the gelatinization temperature [Kessler, 2008]. VZ 45C is the ratio between the extract that can be extracted through mashing at 45C and the amount that can be extracted with a congress mash. This number is given on some (mainly German) malt analysis sheets. Figure 2 shows the data that was published by Kessler. According to Weyermann the VZ45 for their malts can be as low as 35. This may result in a gelatinization temperature as high as 65C. While this temperature should not be a problem when using a single saccharification rest, it can become problematic when a maltose rest is held at 63C at which temp the starch will not be fully gelatinized. If this is the case an extended rest at 65C needs to be held in order to achieve the desired fermentability of the produced wort.


Physical Properties of Proteins

  1. Colour and Taste
    Proteins are colourless and usually tasteless. These are homogeneous and crystalline.
  2. Shape and Size
    The proteins range in shape from simple crystalloid spherical structures to long fibrillar structures. Two distinct patterns of shape
    have been recognized :
    A. Globular proteins- These are spherical in shape and occur mainly in plants, esp., in seeds and in leaf cells. These are bundles formed by folding and crumpling of protein chains. e.g., pepsin, edestin, insulin, ribonuclease etc.
    B. Fibrillar proteins- These are thread-like or ellipsoidal in shape and occur generally in animal muscles. Most of the studies regarding protein structure have been conducted using these proteins. e.g., fibrinogen, myosin etc.
  3. Molecular Weight
    The proteins generally have large molecular weights ranging between 5 × 103 and 1 × 106. It might be noted that the values of molecular weights of many proteins lie close to or multiples of 35,000 and 70,000.
  4. Colloidal Nature
    Because of their giant size, the proteins exhibit many colloidal properties, such as Their diffusion rates are extremely slow and they may produce considerable light-scattering in solution, thus resulting in visible turbidity (Tyndall effect).
  5. Denaturation
    Denaturation refers to the changes in the properties of a protein. In other words, it is the loss of biologic activity. In many instances the process of denaturation is followed by coagulation— a process where denatured protein molecules tend to form large aggregates and to precipitate from solution.
  6. Amphoteric Nature
    Like amino acids, the proteins are amphoteric, i.e., they act as acids and alkalies both. These migrate in an electric field and the direction of migration depends upon the net charge possessed by the molecule. The net charge is influenced by the pH value. Each protein has a fixed value of isoelectric point (pl) at which it will move in an electric field.
  7. Ion Binding Capacity
    The proteins can form salts with both cations and anions based on their net charge.
  8. Solubility
    The solubility of proteins is influenced by pH. Solubility is lowest at isoelectric point and increases with increasing acidity or alkalinity. This is because when the protein molecules exist as either cations or anions, repulsive forces between ions are high, since all the molecules possess excess charges of the same sign. Thus, they will be more soluble than in the isoelectric state.
  9. Optical Activity
    All protein solutions rotate the plane of polarized light to the left, i.e., these are levoratotory.

Chemical Properties of Proteins

  1. Hydrolysis
    Proteins are hydrolyzed by a variety of hydrolytic agents.
    A. By acidic agents: Proteins, upon hydrolysis with conc. HCl (6–12N) at 100–110°C for 6 to 20 hrs, yield amino acids in the form of their hydrochlorides.
    B. By alkaline agents: Proteins may also be hydrolyzed with 2N NaOH.
  2. Reactions involving COOH Group
    A. Reaction with alkalies (Salt formation)
    B. Reaction with alcohols (Esterification)
    C. Reaction with amines
  3. Reactions involving NH2 Group
    A. Reaction with mineral acids (Salt formation): When either free amino acids or proteins are treated with mineral acids like HCl, the acid salts are formed.
    B. Reaction with formaldehyde: With formaldehyde, the hydroxy-methyl derivatives are formed.
    C. Reaction with benzaldehyde: Schiff ‘s bases are formed
    D. Reaction with nitrous acid (Van Slyke reaction): The amino acids react with HNO2 to liberate N2 gas and to produce the corresponding α-hydroxy acids.
    E. Reaction with acylating agents (Acylation)
    F. Reaction with FDNB or Sanger’s reagent
    G. Reaction with dansyl chloride
  4. Reactions involving both COOH AND NH2 Group
    A. Reaction with triketohydrindene hydrate (Ninhydrin reaction)
    B. Reaction with phenyl isocyanate: With phenyl isocyanate, hydantoic acid is formed which in turn can be converted to hydantoin.
    C. Reaction with phenyl isothiocyanate or Edman reagent
    D. Reaction with phosgene: With phosgene, N-carboxyanhydride is formed
    E. Reaction with carbon disulfide: With carbon disulfide, 2-thio-5-thiozolidone is produced
  5. Reactions involving R Group or Side Chain
    A. Biuret test
    B. Xanthoproteic test
    C. Millon’s test
    D. Folin’s test
    E. Sakaguchi test
    F. Pauly test
    G. Ehrlich test
  6. Reactions involving SH Group
    A. Nitroprusside test: Red colour develops with sodium nitroprusside in dilute NH4.OH. The test is specific for cysteine.
    B. Sullivan test: Cysteine develops red colour in the presence of sodium 1, 2-naphthoquinone- 4-sulfonate and sodium hydrosulfite.

3.2: Starch Protein Teacher's Preparation Notes - Biology

Despite efforts over the past half-century, there is still a need for internationally harmonized methods and data. In fact, as described in Chapter 1, the development of new methods for analysing specific components of the energy-yielding macronutrients has increased the complexity and made this need greater than ever.

This chapter discusses the commonly used analytical methods for protein, fat and carbohydrate, and makes recommendations regarding the preferred methods for the current state of the art and available technology. Methods that continue to be acceptable when the preferred methods cannot be used are also noted. Analytical methods for alcohol, which can be a significant source of energy in some diets, polyols and organic acids were not discussed, and hence no recommendations for methods are made.

2.1 ANALYTICAL METHODS FOR PROTEINS IN FOODS

For many years, the protein content of foods has been determined on the basis of total nitrogen content, while the Kjeldahl (or similar) method has been almost universally applied to determine nitrogen content (AOAC, 2000). Nitrogen content is then multiplied by a factor to arrive at protein content. This approach is based on two assumptions: that dietary carbohydrates and fats do not contain nitrogen, and that nearly all of the nitrogen in the diet is present as amino acids in proteins. On the basis of early determinations, the average nitrogen (N) content of proteins was found to be about 16 percent, which led to use of the calculation N x 6.25 (1/0.16 = 6.25) to convert nitrogen content into protein content.

This use of a single factor, 6.25, is confounded by two considerations. First, not all nitrogen in foods is found in proteins: it is also contained in variable quantities of other compounds, such as free amino acids, nucleotides, creatine and choline, where it is referred to as non-protein nitrogen (NPN). Only a small part of NPN is available for the synthesis of (non-essential) amino acids. Second, the nitrogen content of specific amino acids (as a percentage of weight) varies according to the molecular weight of the amino acid and the number of nitrogen atoms it contains (from one to four, depending on the amino acid in question). Based on these facts, and the different amino acid compositions of various proteins, the nitrogen content of proteins actually varies from about 13 to 19 percent. This would equate to nitrogen conversion factors ranging from 5.26 (1/0.19) to 7.69 (1/0.13).

In response to these considerations, Jones (1941) suggested that N x 6.25 be abandoned and replaced by N x a factor specific for the food in question. These specific factors, now referred to as “Jones factors”, have been widely adopted. Jones factors for the most commonly eaten foods range from 5.18 (nuts, seeds) to 6.38 (milk). It turns out, however, that most foods with a high proportion of nitrogen as NPN contain relatively small amounts of total N (Merrill and Watt, 1955 and 1973). [4] As a result, the range of Jones factors for major sources of protein in the diet is narrower. Jones factors for animal proteins such as meat, milk and eggs are between 6.25 and 6.38 those for the vegetable proteins that supply substantial quantities of protein in cereal-/legume-based diets are generally in the range of 5.7 to 6.25. Use of the high-end factor (6.38) relative to 6.25 increases apparent protein content by 2 percent. Use of a specific factor of 5.7 (Sosulski and Imafidon, 1990) rather than the general factor of 6.25 decreases the apparent protein content by 9 percent for specific foods. In practical terms, the range of differences between the general factor of 6.25 and Jones factors is narrower than it at first appears (about 1 percent), especially for mixed diets. Table 2.1 gives examples of the Jones factors for a selection of foods.

Because proteins are made up of chains of amino acids joined by peptide bonds, they can be hydrolysed to their component amino acids, which can then be measured by ion-exchange, gas-liquid or high-performance liquid chromatography. The sum of the amino acids then represents the protein content (by weight) of the food. This is sometimes referred to as a “true protein”. The advantage of this approach is that it requires no assumptions about, or knowledge of, either the NPN content of the food or the relative proportions of specific amino acids - thus removing the two problems with the use of total N x a conversion factor. Its disadvantage is that it requires more sophisticated equipment than the Kjeldahl method, and thus may be beyond the capacity of many laboratories, especially those that carry out only intermittent analyses. In addition, experience with the method is important some amino acids (e.g. the sulphur-containing amino acids and tryptophan) are more difficult to determine than others. Despite the complexities of amino acid analysis, in general there has been reasonably good agreement among laboratories and methods (King-Brink and Sebranek, 1993).

TABLE 2.1
Specific (Jones) factors for the conversion of nitrogen content to protein content (selected foods)

Source: Adapted and modified from Merrill and Watt (1973).

  • foods used as the sole source of nourishment, such as infant formula
  • foods/formulas designed specifically for special dietary conditions
  • novel foods.

2.2 ANALYTICAL METHODS FOR FATS IN FOOD

There is perhaps more agreement on standardized methods of analysis for fat than for protein and carbohydrate. Most fat in the diet is in the form of triglyceride (three fatty acids esterified to a glycerol molecule backbone). There are also non-glyceride components such as sterols, e.g. cholesterol. While there is considerable interest in the roles that these non-glyceride components may play in metabolism, they are not important sources of energy in the diet (FAO, 1994).

There are accepted AOAC gravimetric methods for crude fat, which includes phospholipids and wax esters, as well as minor amounts of non-fatty material (AOAC, 2000). Total fat can be expressed as triglyceride equivalents determined as the sum of individual fatty acids and expressed as triglycerides (FAO, 1994). This method is satisfactory for the determination of fat in a wide variety of foods.

1) For energy purposes, it is recommended that fats be analysed as fatty acids and expressed as triglyceride equivalents, as this approach excludes waxes and the phosphate content of phospholipids, neither of which can be used for energy (James, Body and Smith, 1986).

2) A gravimetric method, although less desirable, is acceptable for energy evaluation purposes (AOAC, 2000).

2.3 ANALYTICAL METHODS FOR CARBOHYDRATES IN FOODS

FAO/WHO held an expert consultation on carbohydrate in 1997. The report of this meeting (FAO, 1998) presents a detailed description of the various types of carbohydrates and a review of methods used for analysis, which is summarized conceptually in the following paragraphs. Other recommendations from the 1997 consultation, e.g. the nomenclature of carbohydrates, were considered by the current technical workshop participants.

Total carbohydrate content of foods has, for many years, been calculated by difference, rather than analysed directly. Under this approach, the other constituents in the food (protein, fat, water, alcohol, ash) are determined individually, summed and subtracted from the total weight of the food. This is referred to as total carbohydrate by difference and is calculated by the following formula:

100 - (weight in grams [protein + fat + water + ash + alcohol] in 100 g of food)

It should be clear that carbohydrate estimated in this fashion includes fibre, as well as some components that are not strictly speaking carbohydrate, e.g. organic acids (Merrill and Watt, 1973). Total carbohydrate can also be calculated from the sum of the weights of individual carbohydrates and fibre after each has been directly analysed.

Available carbohydrate represents that fraction of carbohydrate that can be digested by human enzymes, is absorbed and enters into intermediary metabolism. (It does not include dietary fibre, which can be a source of energy only after fermentation - see the following subsections.) Available carbohydrate can be arrived at in two different ways: it can be estimated by difference, or analysed directly. [6] To calculate available carbohydrate by difference, the amount of dietary fibre is analysed and subtracted from total carbohydrate, thus:

100 - (weight in grams [protein + fat + water + ash + alcohol + dietary fibre] in 100 g of food)

This yields the estimated weight of available carbohydrate, but gives no indication of the composition of the various saccharides comprising available carbohydrate. Alternatively, available carbohydrate can be derived by summing the analysed weights of individual available carbohydrates. In either case, available carbohydrate can be expressed as the weight of the carbohydrate or as monosaccharide equivalents. For a summary of all these methods, see Table 2.2.

Dietary fibre is a physiological and nutritional concept relating to those carbohydrate components of foods that are not digested in the small intestine. Dietary fibre passes undigested from the small intestine into the colon, where it may be fermented by bacteria (the microflora), the end result being variable quantities of short-chain fatty acids and several gases such as carbon dioxide, hydrogen and methane. Short-chain fatty acids are an important direct source of energy for the colonic mucosa they are also absorbed and enter into intermediary metabolism (Cummings, 1981).

TABLE 2.2
Total and available carbohydrate

By difference: 100 - (weight in grams [protein + fat + water + ash + alcohol] in 100 g of food)
By direct analysis: weight in grams (mono- + disaccharides + oligsaccharides + polysaccharides, including fibre)

By difference: 100 - (weight in grams [protein + fat + water + ash + alcohol + fibre] in 100 g of food)
By direct analysis: weight in grams (mono- + disaccharides + oligosaccharides + polysaccharides, excluding fibre)*

* May be expressed as weight (anhydrous form) or as the monosaccharide equivalents (hydrous form including water).

Chemically, dietary fibre can comprise: cellulose, hemicellulose, lignin and pectins from the walls of cells resistant starch and several other compounds (see Figure 2.1). As more has been learned about fibre, a variety of methods for analysis have been developed. Many of these measure different components of fibre, and thus yield different definitions of, and values for, it. Three methods have had sufficient collaborative testing to be generally accepted by such bodies as AOAC International and the Bureau Communautaire de Reference (BCR) of the European Community (EC) (FAO, 1998): the AOAC (2000) enzymatic, gravimetric method - Prosky (985.29) the enzymatic, chemical method of Englyst and Cummings (1988) and the enzymatic, chemical method of Theander and Aman (1982). Monro and Burlingame (1996) have pointed out, however, that at least 15 different methods are applied for determining the dietary fibre values used in food composition tables. Their publication, and the FAO/WHO report on carbohydrates in human nutrition (FAO, 1998), discuss these issues in more detail. The effect of having such a variety of methods for dietary fibre, each giving a somewhat different value, affects not only the values in food composition tables for dietary fibre per se , but also those for available carbohydrate by difference.

1) Available carbohydrate is a useful concept in energy evaluation and should be retained. This recommendation is at odds with the view of the expert consultation in 1997, which endorsed the use of the term “glycaemic carbohydrate” to mean “providing carbohydrate for metabolism” (FAO, 1998). The current group expressed concerns that “glycaemic carbohydrate” might be confused or even equated with the concept of “glycaemic index”, which is an index that describes the relative blood glucose response to different “available carbohydrates”. The term “available” seems to convey adequately the concept of “providing carbohydrate for metabolism”, while avoiding this confusion.

2) Carbohydrate should be analysed by a method that allows determination of both available carbohydrate and dietary fibre. For energy evaluation purposes, standardized, direct analysis of available carbohydrate by summation of individual carbohydrates (Southgate, 1976 Hicks, 1988) is preferred to assessment of available carbohydrate by difference, i.e. total carbohydrate by difference minus dietary fibre. This allows the separation of mono- and disaccharides from starches, which is useful in determination of energy content, as discussed in Chapter 3.

3) Determination of available carbohydrate by difference is considered acceptable for purposes of energy evaluation for most foods, but not for novel foods or food for which a reduced energy content claim is to be made. In these cases, a standardized, direct analysis of available carbohydrate should be carried out.

4) “Dietary fibre” is a useful concept that is familiar to consumers and should be retained on food labelling and in food tables. Because the physical characteristic of solubility/insolubility does not strictly correlate with fermentability/non-fermentability, the distinction between soluble and insoluble fibre is not of value in energy evaluation, nor is it of value to the consumer.

5) The AOAC (2000) analysis - Prosky (985.29) or similar method should be used for dietary fibre analysis.

6) Because dietary fibre can be determined by a number of methods that yield different results, when the Prosky method is not used the method used should be stated and the value should be identified by INFOODS tagnames [7] (Klensin et al ., 1989). In addition, the method should be identified with the tagname in food composition tables.

7) Further research and scientific consensus are needed in order to develop standardized methods of analysis of resistant starch.

Figure 2.1 - Dietary fibre: constituents and associated polysaccharide fractions


Colloids

Colloids contain large molecules that do not pass through semipermeable membranes. Colloids are IV fluids that contain solutes of high molecular weight, technically, they are hypertonic solutions, which when infused, exert an osmotic pull of fluids from interstitial and extracellular spaces. They are useful for expanding the intravascular volume and raising blood pressure. Colloids are indicated for patients in malnourished states and patients who cannot tolerate large infusions of fluid.

Human Albumin

Human albumin is a solution derived from plasma. It has two strengths: 5% albumin and 25% albumin. 5% Albumin is a solution derived from plasma and is a commonly utilized colloid solution. It is used to increase the circulating volume and restore protein levels in conditions such as burns, pancreatitis, and plasma loss through trauma. 25% Albumin is used together with sodium and water restriction to reduce excessive edema. They are considered blood transfusion products and uses the same protocols and nursing precautions when administering albumin.

The use of albumin is contraindicated in patients with the following conditions: severe anemia, heart failure, or known sensitivity to albumin. Additionally, angiotensin-converting enzyme inhibitors should be withheld for at least 24 hours before administering albumin because of the risk of atypical reactions, such as hypotension and flushing.

Dextrans

Dextrans are polysaccharides that act as colloids. They are available in two types: low-molecular-weight dextrans (LMWD) and high-molecular-weight dextrans (HMWD). They are available in either saline or glucose solutions. Dextran interferes with blood crossmatching, so draw the patient’s blood before administering dextran, if crossmatching is anticipated.

Low-molecular-weight Dextrans (LMWD)

LMWD contains polysaccharide molecules that behave like colloids with an average molecular weight of 40,000 (Dextran 40). LMWD is used to improve the microcirculation in patients with poor peripheral circulation. They contain no electrolytes and are used to treat shock related to vascular volume loss (e.g., burns, hemorrhage, trauma, or surgery). On certain surgical procedures, LMWDs are used to prevent venous thromboembolism. They are contraindicated in patients with thrombocytopenia, hypofibrinogenemia, and hypersensitivity to dextran.

High-molecular-weight Dextrans (HMWD)

HMWD contains polysaccharide molecules with an average molecular weight of 70,000 (Dextran 70) or 75,000 (Dextran 75). HMWD used for patients with hypovolemia and hypotension. They are contraindicated in patients with hemorrhagic shock.

Etherified Starch

These solutions are derived from starch and are used to increase intravascular fluid but can interfere with normal coagulation. Examples include EloHAES, HyperHAES, and Voluven.

Gelatin

Gelatins have lower molecular weight than dextrans and therefore remain in the circulation for a shorter period of time.

Plasma Protein Fraction (PPF)

Plasma Protein Fraction is a solution that is also prepared from plasma, and like albumin, is heated before infusion. It is recommended to infuse slowly to increase circulating volume.

Nursing Considerations for Colloid Solutions

The following are the general nursing interventions and considerations when administering colloid IV solutions:

  • Assess allergy history. Most colloids can cause allergic reactions, although rare, so take a careful allergy history, asking specifically if they’ve ever had a reaction to an IV infusion before.
  • Use a large-bore needle (18-gauge). A larger needle is needed when administering colloid solutions.
  • Document baseline data. Before infusion, assess the patient’s vital signs, edema status, lung sounds, and heart sounds. Continue monitoring during and after the infusion.
  • Monitor the patient’s response. Monitor intake and output closely for signs of hypervolemia, hypertension, dyspnea, crackles in the lungs, and edema.
  • Monitor coagulation indexes. Colloid solutions can interfere with platelet function and increase bleeding times, so monitor the patient’s coagulation indexes.

How to revise for bio IGCSE CIE paper 6?

Hi,
I have my biology paper 6 exam in 3 days and I dont know how to revise for it, i usually get a B in pastpapers, but there are so many questions that i just dont know how to answer, do you have any tips?
Thanks

Not what you're looking for? Try&hellip

Here's all you need, good luck!
I'm doing it tomorrow />. Here are some tips to help you revise for your exam />.


-Drawing: you will be asked to draw diagrams of fruits, insects..etc. in the exam. Make sure it's in pencil, drawn to the correct size, has definite outlines (no 'sketchy' lines), no shading, no arrow heads when labelling and make sure lines point exactly at the labelled part.


-Comparisons: Make sure the points you use to compare diagrams are visible in the diagrams. Use labels on the diagrams as your guide. And don't compare sizes unless you're given a scale. You can compare numbers shape and proportional sizes.


-Designing an experiment:
*Find the variable which is to be changed (from the question) and mention how you are going to change it (ex: to change temperature, use thermometer-controlled water bath at temperatures 10 to 50 degree Celsius).
*List all variables that you have to keep constant throughout the experiment (ex: room temperature, volume of water, insect species). Make sure there's only one variable for the investigation.
*Mention how long your experiment will last.
*Say how you will measure experiments' results (ex: if you're examining presence of starch, say that the food sample which turns the iodine solution a deeper blue contains more starch)
*Finally: say 'repeat experiment to get more reliable results and minimise error. It's guaranteed to gain you marks.
*If you can, set a control for your experiment. (ex: use boiled enzyme in an experiment to test for enzyme activity)


-Drawing a graph: take care of labels of axes, units, scale, using 'cuts' if needed. Always join points using a ruler unless asked to do otherwise (ex: line of best fit)


-Remember the rule: magnification: drawing/real


-Make sure you know how to test for the presence of water, oxygen, carbon dioxide, starch, reducing sugar, proteins, fats, acid and alkali.


-Look at the experiments in the past papers and make sure you understand them well, as this will help you a lot.


Finally, try answering a couple of exams from the past papers. They're sure to give you a good idea of what to expect tomorrow, and will certainly boost your confidence .
Here's a link to the Biology past papers: http://www.xtremepapers.net/CIE/index.ph&hellip
Just click on 'Cambridge IGCSE' and then choose 'Biology'.


Well..guess that's all. You're now good to go! />
Best of luck! />


Watch the video: Molecules and food tests - GCSE Biology 9-1 (May 2022).