Chapter 6 Student Notes PDF

Proteins Chapter 6 Learning Objectives  6.1 Describe the structure of proteins and explain why adequate amounts of all the essential amino acids are required for protein synthesis  6.2 Describe protein digestion, absorption and metabolism  6.3 List and describe the roles of protein...

Proteins Chapter 6 Learning Objectives  6.1 Describe the structure of proteins and explain why adequate amounts of all the essential amino acids are required for protein synthesis  6.2 Describe protein digestion, absorption and metabolism  6.3 List and describe the roles of protein in the body  6.4 Explain protein balance  6.5 Characterize food terms of protein amount and quality and also identify proteins that are complementary  6.6 State the Food and Nutrition Board recommendation AMDR for protein. Calculate an individual’s recommended protein intake (DRI)  6.7 Describe the characteristics and consequences of protein-calorie malnutrition  6.8 Describe how genes and nutrition interact and the current reality of using genetic testing to assess an individual’s disease risk  6.9 Identify the strengths and limitations of vegetarian and meat-containing diets. Objective 6.1 Describe the structure of proteins and explain why adequate amounts of all the essential amino acids are required for protein synthesis Amino Acids—Building Blocks of Proteins  20 different amino acids make up all proteins. Contain nitrogen, carbon, hydrogen, and oxygen.  9 essential amino acids Not synthesized, must be consumed from diet.  11 nonessential amino acids Can be synthesized in body.  Typically supply 4 kcal per gram.  Protein Functions: Regulates and maintains body functions. 4 Structure of Amino Acid Carbon Hydrogen Oxygen Nitrogen Table 6-1: Classification of Amino Acids Essential Amino Acids Nonessential Amino Acids Histidine Alanine Isoleucine* Arginine Leucine* Asparagine Lysine Aspartic acid Methionine Cysteine Phenylalanine Glutamic acid Threonine Glutamine Tryptophan Glycine Valine* Proline Serine *A branched-chain amino acid. Tyrosine 6 Amino Acids Linked Together  Protein Organization and Synthesis  Proteins linked together by chemical bonds Peptide bonds  Bonds form between amino group of one amino acid and acid (carboxyl) group of another. Dipeptides, 2 groups Tripeptides, 3 groups Oligopeptides, 4 to 9 groups Polypeptides, 10 or more groups  Most proteins are polypeptides, 50 to 2,000 groups. 8  Shape is dictated by the order of the amino acids in the protein chain Section 6.2: Protein Organization and Synthesis—Concepts 1. Why is the amino acid order within a protein important? 2. What is the role of DNA in protein synthesis? 3. What are the steps of protein synthesis? 4. What are some of the ways a protein can become denatured? 12 Protein Organization The blood protein hemoglobin The order (sequence) of amino acids in a protein Determines its ultimate shape (structure) Protein’s final structure: determines its function in body DNA in cell nucleus contains instructions: which specific amino acids are to be placed in a protein and in which order If the DNA code contains errors: this is a genetic defect an incorrect amino acid will be added an incorrect polypeptide chain will be produced 13 Making a Protein: DNA 1. DNA contains the information necessary to produce proteins Making a Protein: Transcription to mRNA 2. Transcription or copying of a segment of DNA results in mRNA, a copy of the information in DNA needed to make a protein Nucleotides: Adenine (A) pairs with uracil (U) Guanine (G) pairs with cytosine (C) Making a Protein: Ribosome and tRNA 3. The mRNA leaves the nucleus and goes to a ribosome 4. Amino acids, the building blocks of proteins, are carried to the ribosome by the tRNAs containing the code that matches that on the mRNA Making a Protein: Order and Sequence  Mutations and polymorphisms Sickle-cell anemia An example of errors in DNA coding of proteins. https://evolution.berkeley.edu/dna-and-mutations/a-case-study-of- the-effects-of-mutation-sickle-cell-anemia/ Objective 6.2  Digestion, absorption and metabolism of proteins/amino acids Denaturation of Proteins  Denaturation: Alteration of a protein’s three-dimensional structure  Denaturing agents Digestion (stomach acid) Heat, enzymes, acid, alkaline solutions, and agitation (whipping of egg whites) Amino Acid “Pool”--Fate of amino acids in cells Dietary protein Existing body proteins/organs Converted into a Amino acid “pool” nonessential amino acid: Transamination Used as energy: Deamination Energy Synthesis (glucose, Nitrogen of non fat) converted protein to urea molecules Protein Turnover  Turnover: breakdown and synthesis.  Cell responds to changing environment  Amino acids can be recycled.  During any day, an adult degrades and makes about 250 grams of protein. Typical consumption: more than the 65 to 100 grams.  If protein intake is low for long period Rebuilding and repairing body proteins will slow down. Muscles, blood proteins, and vital organs will lose protein and decrease in size or volume. 31 Objective 6.3 List and describe the roles of protein in the body Overview of Protein  Body made up of thousands of proteins.  Contains nitrogen, carbon, hydrogen, and oxygen.  North Americans generally consume more than they need to maintain health.  Functions: Forms important structures in body. Makes up key part of blood. Regulates and maintains body functions (blood clotting, hormone and enzyme production, vision, substance transport, cell repair) Provides essential nitrogen (in the form of amino acids). Can fuel body cells. 33 Functions of Proteins Regulate and maintain body functions Produce body components (e.g., hemoglobin) and important structures (muscles and connective tissue) Maintain fluid balance Contribute to acid–base balance Form enzymes and hormones Contribute to immune function Can fuel cells: glucose production to provide energy and increase satiety Provide essential nitrogen Contributing to Satiety  Satiety: No longer a desire to eat; feeling of satisfaction.  Potential to increase satiety and control appetite:  Greater for protein than for carbohydrates and/or fats.  Moderately higher protein diets are appropriate if:  Nutritionally sound.  Moderate in fat.  Have enough fiber. 35  Proteins transport lipids, vitamins, minerals, Function: Transport and oxygen around the body Hemoglobin and oxygen transport Albumin and nutrient transport Lipoproteins and fat transport Channel proteins: regulate flow of substances through cell membrane Function: Fluid Balance Proteins in the blood (like albumin) counteract the force of blood pressure and help draw fluid back into the vessels. Objective 6.4 Explain Protein (Nitrogen) Balance Nitrogen balance 50 grams of nitrogen consumed 50 grams of nitrogen excreted Balance: 0 50 grams of nitrogen consumed 40 grams of nitrogen excreted Balance: +10 50 grams of nitrogen consumed 80 grams of nitrogen excreted Balance: -30 Objective 6.5 Characterize food terms of protein amount and quality and also identify proteins that are complementary Dietary Protein Quality  High-quality (complete) proteins: Contain ample amounts of all nine essential amino acids. Animal protein contains all nine essential amino acids. D. Hurst/Alamy  Lower quality (incomplete) proteins: Low in or lack one or more essential amino acids.  Plant proteins in grains are often low in one or more of the nine essential amino acids. Limiting amino acids --> need for complementary plant protein sources ❖ All-or-none principle in protein synthesis 42 Biological Value (100= 100% of Nitrogen incorporated) A measure of the protein’s “usability” in the body Whey Protein: 96 Defatted soy flour: 81 Whole Soy Bean: 96 Fish: 76 Human milk: 95 Beef: 74.3 Chicken egg: 94 Immature bean: 65 Soybean milk: 91 Full-fat soy flour: 64 Buckwheat: 90+ Soybean curd (tofu): 64 Cow milk: 90 Whole wheat: 64 Cheese: 84 White flour: 41 Quinoa: 83 Rice: 83 Source: Wikipedia Complementary Proteins  Combining two food protein sources that make up for each other’s inadequate supply of specific essential amino acids.  Together they yield a sufficient amount of all nine essential amino acids and so provide high-quality (complete) protein for the diet. Examples  Rice and beans  Vegetables combined with nuts 45 Figure 6-8: Plant Group Combinations  falafel: Jennifer Barrow/123RF; Mixed nuts, L A Heusinkveld/Alamy; pasta: tomato, olegdudko/123RF; green beans with toasted almonds: Robyn Mackenzie/123RF; vegan Buddha bowl salad: Ekaterina Kondratova/123RF 46 Examples: Combining proteins + + + + Figure 6-9: Closer Look at Plant Sources of Proteins Legumes: an edible seed enclosed in a pod - garden peas - black-eyed peas - chickpeas - black beans - pinto beans - kidney beans - great northern beans - lentils - soybeans - peanuts  dairy alternatives: Pixtal/AGE Fotostock; whole grains: Tetra Images/ Getty Images; nuts and seeds: Thomas Northcut/Getty Images; vegetables: ©Pixtal 48 Animal Proteins  Eating patterns rich in  High in substances such as animal products: saturated fat.  Not recommended by the  Low in beneficial substances Dietary Guidelines for found in plant sources. Americans or the  Fiber, some vitamins, American Heart some minerals, and Association. phytochemicals  Potential to increase risk for cardiovascular and other diseases.  Excessive intake of processed red meat is linked with colon cancer.  Ingram Publishing/SuperStock 50 Objective 6.6 State the Food and Nutrition Board recommendation (AMDR) for protein. Calculate an individual’s recommended protein intake (RDA). Protein Needs  Protein balance or equilibrium Balancing protein intake with protein (nitrogen) losses.  Estimating protein need RDA: 0.8 gram of protein per kilogram of healthy body weight for sedentary adult. 154 pound woman = 70 kilograms 70 kilograms x 0.8 grams/kg = 56 grams of protein. 55 RDA for Protein  RDA: 0.8 gram of protein per kilogram of body weight.  Acceptable Macronutrient Distribution Range: 10% to 35% of total calories. Calculation of protein recommendation if require 2000 kcal MIN: 2000 kcal × 0.10 = 200 kcal/4 kcal/g = 50 grams MAX: 2000 kcal × 0.35 = 700 kcal/4 kcal/g = 175 grams  Typical consumption: Men: 100 grams/day. Women: 65 grams/day. Athletes: from 1.2 to 2 grams per kilogram of healthy body weight is to optimize athletic performance.  Excess protein cannot be stored as protein. 57 Activity  Calculate your RDA in grams based on body weight.  What are your estimated energy needs? (from Myplate ch 2)  How does this compare to the AMDR? Protein Intake Recommendations: Dietary Guidelines for Americans 1  Dietary Guidelines for Americans recommend a variety of protein foods:  Seafood, lean meats and poultry, eggs, legumes (beans and peas), nuts, seeds, and soy products.  The following shifts are also recommended to increase variety in protein food choices and to make more nutrient-dense choices:  Select from the seafood subgroup or the beans, peas, and lentils subgroup more often to help meet recommendations while still ensuring adequate protein consumption. 59 Protein Intake Recommendations: Dietary Guidelines for Americans 2 Most consumption of meats and poultry should be from fresh, frozen, or canned, and in lean forms (e.g., chicken breast or roasted turkey) versus processed meats (e.g., hot dogs, sausages, bacon, luncheon meats). Replace processed or high-fat meats (e.g., hot dogs, sausages, bacon) with  seafood to help lower intake of saturated fat and sodium, nutrients that are often consumed in excess of recommended limits.  beans, peas, and lentils to obtain similar benefits, as well as increasing dietary fiber, a dietary component of public health concern. 60  Figure 6-7: Food Sources of Protein  The dairy group provides much protein (8 to 10 grams per serving), as does the protein group (~7 grams per ounce). 1 cup of beans: 15 g banana: Alamy Stock Photo; Brussel Sprouts: Pixtal/age footstock; dairy: Photodisc/Getty Images; oatmeal: McGraw-Hill Education; tuna: FotografiaBasica/E+/Getty Images; MyPlate: U.S. Department of Agriculture 1 cup of lentils: 18 g Source: U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, 2019. fdc.nal.usda.gov. 65 MyPlate and protein intake 2000 Pro (g) 2400 Pro (g) 2800 Pro (g) kcals kcals kcals Grains oz 6 18 8 24 10 30 Veg C 2.5 10 3 12 3.5 14 Fruit C 2 0 2 0 2.5 0 Milk C 3 24 3 24 3 24 Meat oz 5.5 39 6.5 46 7 49 Total (g) 91 106 117 % ADMR 18% 18% 17% General protein amounts by food group serving: Fruit: 0 g Grains: 3 g/oz Milk: 8 g/1 cup Veg: 2 g/ ½ C Meat: 7 g/oz  Food group Protein (g) # of Total  150 pound person /serving Servings grams What is the RDA? Grain 3 6  Grams protein? Veg 2 2  How many grams of protein/kg Fruit 0 4 body weight? Dairy 8 3 Protein 7 5  Food group Protein (g) # of Total  RDA? 54 g /serving Servings grams  Grams protein? 81 g Grain 3 6 18  How many grams of protein/kg body weight? 1.2 g/kg Veg 2 2 4  Assume total calories is 2000, what percent of calories is coming from Fruit 0 4 0 protein? Dairy 8 3 24 Protein 7 5 35 81  Food group Protein (g) # of Total  170-pound person /serving Servings grams  Grams protein? Grain 3 6 18  How much protein (g) / kg body weight? Veg 2 2 4  Assume total calories is 2000, what percent of ADMR? Fruit 0 4 0 Dairy 8 3 24 Protein 7 5 35 81 Protein Requirements Per Meal  Maintain more equal distribution of protein at each meal.  Important for more optimal function of protein.  Consume 20 to 30 grams of protein at each meal.  Positive effects on optimizing muscle protein synthesis.  Protein at breakfast especially critical. 70 Protein Needs for Older Adults  Responses to dietary protein decline with advancing age or reduced physical activity.  Recommendation of the PROT-AGE Study Group:  Increase daily protein intake to more than 1.0 gram per kilogram for older adults.  Focus on meal quantity and timing of protein.  Consume meals with greater than 20 grams of protein.  Include more than 2.2 grams of leucine, to optimize protein synthesis in skeletal muscle. 71 Protein eating advice  Fillhalf your plate with produce, such as salad, cooked vegetables, and/or fruit.  Make up 25% of your plate protein foods. Eggs, meat, poultry, fish, beans, soy foods, low-fat dairy foods, nuts, and seeds are great options. Can include beans, soy foods, lentils, peas, or seeds on the plate.  Carbohydrates: Potatoes and whole grain forms of bread, cereal, rice, and pasta should cover at least 25% of the plate.  Include fat at meals through nuts or seeds, nut butters, hummus, salad dressing, or even avocado or guacamole. 72 Protein malnutrition  Slow growth  Impaired immune system  Impaired nutrient absorption  Impaired brain & kidney function  Muscle wasting  Somewhat rare in developed countries. Seen in alcoholics  In developing countries Stunts growth and increases risk of infection. Figure 6-18: Undernutrition in Children 75 Too Much Protein  Insufficient evidence for UL  Heart disease?  Kidney disease?  Bone loss?  Cancer?  Big muscles? Nutrition and Genetics  Genetic variation can directly affect proteins encoded by our genes and result in different: Nutrient requirements among individuals.  Effects of environmental factors (such as our diet) on our genes and proteins they make.  New field: potential for personalized nutrition recommendations 81 Objective 6.8 Describe how genes and nutrition interact and the current reality of using genetic testing to assess an individual’s disease risk. Nutrigenomics How food and its components interact with the genome Nutrigenetics How genes dictate individual nutrient requirements and susceptibility or resistance to certain nutrition-related diseases. General versus individualized dietary recommendations Nutrition and Genetics Terms Epigenome  Network of chemical compounds surrounding DNA that  modify the genome without altering the DNA sequences.  have a role in determining which genes are active (expressed) or inactive (silenced) in a particular cell. Epigenetics  Study of heritable changes in gene function that are independent of DNA sequence.  Exposure to substances and habits might turning genes “on” and “off” which might increase or decrease the risk of disease (CVD, cancer) 83 Gene-diet interaction and plasma lipid responses to dietary intervention, Biochem Soc Trans 30:68-73 A/A G/A G/G Objective 6.9 Identify the strengths and limitations of vegetarian and meat- containing diets. Why Do People Become Vegetarians? Ethics, religion, economics,  Encourages high intake and health. of Evolved over centuries from Complex necessity to an optional carbohydrates. choice. Vitamins A, E, and C Nutritional needs can be met and carotenoids. with a vegetarian dietary Magnesium pattern. Limits saturated fat and cholesterol intake, no trans fat. Ample mono/unsaturated fats Plenty of fiber  Mizina/Getty Images 91 Food Planning for Vegetarians o Lactovegetarians o Plant and dairy products. o Lactoovovegetarians o Plant products, dairy, eggs. o Vegan o More restrictive – only plant  D. Hurst/Alamy Stock Photo foods  Plant proteins, such as those in o Fruitarian soybeans, can be incorporated into one’s dietary pattern in o Eats fruits, nuts, honey, and numerous ways, such as the vegetable oils. edamame and tofu shown here. 92 Flexitarian Flexitarian diet: increasing plant-based foods and reducing, but not eliminating, animal foods. Yields similar health benefits, like reduced risk of heart disease and diabetes. Pick two small changes to implement each week. Swap cow’s milk with unsweetened almond or coconut milk. Make morning oatmeal with almond milk and stir in a tablespoon of peanut butter and chia seeds for protein boost. Try black bean enchiladas instead of chicken enchiladas For lunches, try power bowls made with wild rice or quinoa. For stir-fry night, swap the chicken for high-protein tofu. For pasta night, try one of the bean or lentil-based noodles. 93 Vegan Diets Requires complementary proteins. Concerns for infants and children. Nutrient deficiency concerns: Vitamin B-12. Iron. Zinc. Calcium.  Brand X Pictures/Getty Images Omega-3 fatty acids. 94 Nutrients of Concern on various vegan diets Omega 3 Vitamin Protein Riboflavin Fats B12 Vitamin D Calcium Zinc Iron Table 6-3: Food Plan for Vegetarians Based on MyPlate Food Group Lactovegetarian Vegan Key Nutrients Supplied Grains 6 to 11 8 to 11 Protein, thiamin, niacin, folate, vitamin E, zinc, magnesium, iron, and fiber Beans and other 2 to 3 3 Protein, vitamin B-6, zinc, legumes magnesium, and fiber Nuts, seeds 2 to 3 3 Protein, vitamin E, and magnesium Vegetables 3 to 5 (include 1 dark- 4 to 6 (include 1 Vitamin A, vitamin C, folate, green or leafy variety dark-green or vitamin K, potassium, and daily) leafy variety magnesium daily) Fruits 2 to 4 4 Vitamin A, vitamin C, and folate Dairy 3 — Protein, riboflavin, vitamin D, Fortified soy milk — 3 vitamin B-12, and calcium 96 Animal Diet vs. Vegetarian Diet