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What Are Proteins? Proteins: large, complex molecules composed of amino acids DNA determines structure Contain nitrogen 20 different amino acids (AA) are used to make proteins Building blocks of proteins Amino Acids Amino acids are linked (bound) together by special chemical bonds: Peptide bonds The 20 amino acids can be bound together to make up to 50,000 different protein molecules Amino Acids The structure of an amino acid begins with a central carbon atom. 4 attachment sites The central carbon is surrounded by: 1. a hydrogen atom 2. an acid group 3. an amine group Identical on every amino acid 4. a side chain (R group) that is unique to each amino acid ○ Variations give each AA its distinct properties Amino Acids Amino Acids Essential amino acids: cannot be produced by our bodies Must be obtained from food 9 amino acids Nonessential amino acids: can be made by our bodies Using parts of nitrogen of other amino acids ○ Transamination 11 amino acids Amino Acids Conditionally essential amino acids: when nonessential amino acids can’t be made to meet body needs How Are Proteins Made? Proteins are long chains of amino acids. Amino acids are joined to each other by peptide bonds. The structure of each protein is dictated by a DNA of a gene. Genes carry the instructions for amino acid sequencing How Are Proteins Made? Dipeptide Two amino acids Tripeptide Three amino acids Oligopeptide Four to forty nine amino acids Polypeptide 50 to 100 amino acids Results in complex shapes Proteins Organization The three-dimensional shape of a protein: is determined by the amino acids in the protein is critical to the proper function of the protein ○ Tendons vs. red blood cells can uncoil due to damage by heat, acids, heavy metals, alcohol, and other substances ○ Denatured protein = lost function **Denaturation** Protein Structure Example Protein Structure Example Sickle-shaped cell Protein Denaturation Why Do We Need Proteins? contribute to cell growth, repair, and maintenance Growing children, damaged cells, new cells Why Do We Need Proteins? act as enzymes and hormones Inborn errors of metabolism (IEOM) Galactosemia Enzymes Why Do We Need Proteins? help maintain fluid balance Proteins help pull fluids out of tissues into blood vessels and cells ○ If insufficient protein intake: edema Why Do We Need Proteins? Transport nutrients Electrolytes, vitamins, minerals, glucose Help maintain pH balance Act as buffers against acids and bases Protect against disease Antibodies Serve as an energy source Gluconeogenesis We want to “spare” protein Proteins in the Diet Our bodies do not store proteins, but they do have a small supply of amino acids in reserve Pool of amino acids All essential amino acids need to be in the pool Limiting amino acid – essential amino acid that is missing or in shortest supply ○ May slow or halt protein synthesis (video) Limiting Amino Acids Proteins in the Diet Most proteins contain all of the essential amino acids (EAAs)!! (except gelatin) Complete proteins supply all the EAAs needed to meet biologic requirements when consumed at recommended amounts “high quality” Animal-based, except soybeans/quinoa Incomplete proteins also supply all of the EAAs, but usually one AA is limiting (low) “low quality” Plant-based Proteins in the Diet : using two incomplete proteins together to make a complete protein The 2 incomplete proteins that supply all EAAs: : two protein sources that together supply all nine essential amino acids in adequate quantities Do not have to be eaten at the same time Examples? Who might this be important for? Proteins in the Diet Soy Foods High quality, complete protein Contain vitamins, minerals, phytochemicals What about estrogen/hormones? Isoflavones not same as human estrogen Will not turn guys into gals Up to 3 servings per day Protein Supplementation Muscle growth = PRO synthesis > PRO breakdown Achieved with weight training and regular meal consumption PRO + CHO Eating excess protein does not lead to muscle gain May be helpful for certain people How Much Protein Should We Eat? Proper protein intake depends on: age activity level health status Dietary Reference Intake (DRI) 0.8 g protein per kg body weight (most adults) 1.2-1.7 g/kg for athletes 10% – 35% of total energy intake should be from protein (AMDR) How Much Protein Should We Eat? To convert pounds to kg, simply divide by 2.2 A person weighing 160 pounds is how many kg? 160 lbs ÷ 2.2 = ~73 kg If this person is an average adult, what is his/her PRO requirement? 73 kg x 0.8 g PRO/kg = 58 g PRO/day How Much Protein Should We Eat? People who require more protein include: children adolescents pregnant or lactating women More needed for growth and development Athletes ○ Carry more O2, make glucose, repair/make new tissue Vegetarians (some) ○ Plant proteins less well digested Sources of Protein Good sources of protein include: meats dairy products (milk, egg whites) soy products (considered “complete”) legumes (all varieties of dried beans, peas, peanuts) ○ Also considered a veggie choice!! whole grains (compliment the legumes) Nuts (Don’t discount leafy greens) Vegetarian Diets Vegetarianism: focusing the diet on foods of vegetable origin (including fruits, grains, nuts) There are many versions of vegetarianism. There are many reasons to adopt a vegetarian diet. Vegetarian Diets Why Vegetarianism? People choose vegetarianism for: ethical reasons concerns over food safety/antibiotics ecological reasons religious reasons health benefits Health Benefits of Vegetarianism Reduced risk of: obesity, type 2 diabetes heart disease and high blood pressure some types of cancer kidney disease, kidney stones, gallstones Fewer digestive problems Current guidelines emphasize eating plant protein sources Considerations of Vegetarianism Vegetarian diets can be low in some vitamins and minerals. Vegetarians (and everyone else) must carefully plan a balanced and adequate diet. Vegetarians (and everyone else) can use soy products as a protein source. Diet Comparison Nutrients of Concern Nutrients of Concern 1. Potassium 1. Vitamin B12 2. Vitamin A 2. Zinc 3. Vitamin C 3. Calcium 4. Vitamin E 4. Vitamin D 5. Vitamin K 5. Iron 6. Fiber 7. Calcium 8. Vitamin D 9. Iron S.A.D (Standard American Diet) Vegetarian/Vegan Vegetarian Food Guide Pyramid Vegetarian Eating Guides PCRM’s Power Plate Vegetarian Society of the United Kingdom Protein Imbalances Too little protein: Protein-energy malnutrition (PEM) ○ Marasmus ○ Kwashiorkor ○ Due to poverty, chronic disease, eating disorders Too much protein Marasmus Starving to death Insufficient PRO, energy, & nutrients Little to no subcutaneous fat Reduced brain growth Also seen in hospitalized patients Kwashiorkor Not enough protein Energy needs just marginally met Swollen abdomen Impaired growth, rash, impaired immune system, fatty liver Too Much Protein Do not exceed 2 grams/kg body weight Why not? Not getting enough plant foods Risk imbalances in diet Can You Eat Too Much Protein? The risks of too much protein may include: high cholesterol and heart disease Due to high saturated fat, low fiber intakes possible bone loss High-protein diets may cause excess calcium excretion leading to bone loss. Can You Eat Too Much Protein? The risks of too much protein may also include kidney disease. High-protein diets can be difficult for people with kidney problems. ○ Due to the demand placed on stressed kidneys to flush out excessive urea There is no evidence that high-protein diets cause kidney disease in healthy people. Increased cancer risk? RD Chuckle