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Proteins

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Building Blocks of Protein: Amino Acids All protein is composed of Amino Acids Amino Acids are Nitrogen bearing compounds that form the structural units of protein Amino means nitrogen containing Proteins have carbon, hydrogen, oxygen, and 16% nitrogen Each Amino Acid is joined by a peptide bond Two amino acids are called a dipeptide Polypeptides are chains of up to 100 amino acids

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Amino Acids When protein foods are eaten, proteins are broken down into amino acids Amino acids are reassembled in the body to form a variety of proteins The body requires 20 different amino acids which are classified as: Indispensable Dispensable Conditionally Indispensable

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Classes of Amino Acids (Page 47 table 4-1) Indispensable Amino Acids (Essential) Nine amino acids the body cannot manufacture in sufficient quantity Vital to life and health Dispensable Amino Acids (Non-Essential) Five amino acids that the body can synthesize from other amino acids Conditionally Indispensable Amino Acids (Non- Essential) Six amino acids that are normally synthesized in the body by other amino acids Under stress and illness these amino acids must be consumed in the diet

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Functions of Protein Structural Tissue Building Protein Balance Source of Energy Water and pH Balance Digestion Transportation Hormones Blood Plasma (hemoglobin) Body Defense System

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Tissue Building Fundamental structural material of every cell Comprises bulk of: Muscles (actin, myosin, troponin, tropomyosin), internal organs, brain, nerves, blood plasma (myoglobin, hemoglobin), skin, hair, nails, hormones, and enzymes Protein repairs worn-out, wasted, or damaged tissue (burns, cuts, and scrapes; muscle tears after exercise)

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Protein Balance Nitrogen balance indicates how well the bodys tissues are being maintained; it is achieved in healthy adults. Protein balance Catabolism: Breakdown Anabolism: Resynthesis (build-up) To maintain balance, nitrogen is converted to ammonia and excreted as urea in urine (deamination)

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Protein Balance Nitrogen balance (intake = excretion) Positive Nitrogen balance: body stores more than it excretes Pregnancy, Infancy, Childhood, Adolescence Negative Nitrogen balance: body takes in less than it excretes Illness and Malnutrition During a period of negative nitrogen balance the person is not getting enough protein in the diet and the body is breaking down tissue to provide energy or other critical functions Kwashiorkor: Protein deficiency disease

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Source of Energy Provides 4kcal/gram May provide body fuel if the supply of carbohydrate and fat is insufficient for needs Less efficient

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Water and pH Balance pH (potential of Hydrogen) is a measure of the acidity or alkalinity of a solution The value of pH can be between 0 and 14. The intermediate value is 7 (water); values lower than 7 indicate acidic and values higher than 7 indicate alkaline condition (soft drinks have a pH of 2.5) pH level of our bodies should be between 7.2 and 7.6 (blood is between 7.35 and 7.45) Proteins act as buffering agents (adjusts the pH of a solution) by releasing or taking up excess acid within the body

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Digestion, Transportation, and Hormones Enzymes are proteins necessary for digestion Proteases are enzyme proteins Transport agents Lipoproteins (HDLs and LDLs) Hemoglobin (oxygen carrier in red blood cells) Protein Hormones Insulin and Glucagon

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Body Defense System Proteins help build lymphocytes which are white blood cells Defend the body against infection Antibodies also called immunoglobulins which are large y- shaped proteins which function to identify and help remove foreign antigens such as viruses and bacteria

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Food Sources of Protein Complete Proteins: All 9 indispensable proteins in the quantity and correct ratio to maintain nitrogen balance and allow for tissue growth and repair Primarily of animal origin (egg, milk, meat, cheese, poultry, seafood) Soy products are the only plant sources of complete protein Incomplete Proteins: Deficient in one or more indispensable amino acids Grains, legumes, nuts, seeds, fruits, vegetables

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Whey Protein It is the liquid that is left behind after the first stages of cheese-making It looks like curdled milk The whey is the liquid component that separates from the solid particles. ("Curds and whey" is, essentially, cottage cheese.) High in protein and found in dairy products, protein shakes, bars, and many processed foods Also known as whey protein isolates, whey protein concentrate, whey protein hydolysate, and hydrolized protein

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Is Whey Protein Good For You? Whey protein supplements are just that, Supplements. They should never be used to replace protein obtained from a healthy daily diet. Whey protein may cause allergic reactions in people who suffer from lactose intolerance or who are generally allergic to dairy products. Whey proteins may be easier to digest

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Soy Research suggests that daily intake of soy protein may slightly lower levels of LDL cholesterol. However, the results have been inconsistent. There is not enough scientific evidence to determine whether soy supplements are effective for any other health uses Soy is considered safe for most people when used as a food Minor stomach and bowel problems such as nausea, bloating, and constipation are possible Allergic reactions such as breathing problems and rash can occur in rare cases

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Soy Soy's role in breast cancer is uncertain. Until more is known about soy's effect on estrogen levels, women who have or who are at increased risk of developing breast cancer or other hormone- sensitive conditions (such as ovarian or uterine cancer) should be careful about using soy and should discuss it with their doctors

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Vegetarian Diets Lacto-ovo vegetarian: Dairy products and eggs, excluding meat and fish, to complement diet of plant foods Lacto-vegetarian: Milk and milk products to complement diet of plant foods Ovo-vegetarian: Eggs are only animal foods to complement diet of plant foods Vegan: No animal foods, diet of plant foods only

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Health Benefits of Vegetarian Diets Lower levels of saturated fat and cholesterol Lower rates of death from cardiovascular disease (hypertension) Lower risk of type 2 diabetes and some forms of cancer (colon and prostate) Lower risk of dementia Lower risk of kidney disease Lower body mass index and prevalence of obesity Higher levels of antioxidants

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Vegetarian Diets Must combine foods to cover all amino acid needs Grains and peas, beans, or lentils; legumes and seeds; grains and dairy Brown rice and beans Whole grain bread with pea or lentil soup Wheat or corn tortilla with beans Peanut butter on whole wheat bread Falafel (chickpeas) on whole wheat pita bread Hummus on whole wheat pita bread Whole wheat pasta tossed with peas, almonds, or cheese Garden burger on a whole wheat bun

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Vegetarian/Vegan Tips to Meet Protein Requirements Add beans, seeds, or nuts to salads Eat pecans, almonds, walnuts, cashews and peanut butter for protein Make smoothies with soy milk or hemp milk Choose soy nuts over potato chips for a high-protein snack Substitute quinoa for rice or pasta Sprinkle nuts and seeds on cereal Crumple firm tofu into pasta sauces Add beans to soups Make your own trail mix and include soynuts and almonds

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Digestion of Proteins Mouth: Mastication (chewing) mixed with saliva to form a bolus; a semisolid food mass Stomach: Chemical digestion of protein begins in the stomach Hydrochloric acid changes pepsinogen into pepsin Pepsin is the main gastric enzyme of the stomach. It changes large amino acids into peptides

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Digestion of Proteins Small Intestine: Protein digestion is completed here by enzymes from pancreas and intestine Pancreas: Trypsin, Chymotrypsin, and Carboxypeptidase breaks up polypeptides into dipeptides Intestines: Aminopeptidase and Dipeptidase breaks up dipeptides into amino acids The free amino acids are ready to be absorbed into blood circulation

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Body Needs for Protein Tissue growth Dietary protein quality Chemical score (CS) Biologic value (BV) Net protein utilization (NPU) Protein efficiency ratio (PER)

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Body Needs for Protein Tissue Growth: During rapid growth periods, more protein per unit of body size is necessary to build new tissue. Chemical score: Value derived from the amino acid pattern of the food (an egg has a value of 100). Biologic value is based on nitrogen balance Net protein utilization is based on biologic value and the degree of digestibility. Protein efficiency ratio is based on weight gain relative to protein intake Table 4-2 page 57 compares protein food scores

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Dietary Deficiency or Excess Protein Energy Malnutrition (PEM) Kwashiorkor: Acute deficiency of protein. Characteristics are edema and bloated abdomen from lack of protein in blood to maintain fluid balance (figure 4-6 page 57) Marasmus: Chronic deficiency of protein (elderly and individuals with eating disorders) Excess protein Usually also means excess fat intake Protein displaces other healthy foods in diet Extra burden on kidneys

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High Protein Diets Generally higher in total fat, saturated fat, and cholesterol Initial weight loss is caused by ketosis and fluid loss from a lack of carbohydrates Extra work for the kidneys and liver to remove excess acids (deamination) Loss of muscle tissue from a lack of carbohydrates Risk of deficiency diseases

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Dietary Guidelines? Recommended Dietary Allowances (RDAs) Relate to age, sex, weight Highest at birth and slowly decline into adulthood Men and women: 0.8 to 2.0 g/kg of desirable weight Dietary Reference Intakes (DRIs) from National Academy of Sciences 10% to 35% of total caloric intake from protein (children and adults)

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Calculating Intake For Protein Calculate the protein needs of an individual consuming 2800 kcal/day based on the recommendations of 10% to 35% of total calories Calculate the protein needs of a woman who is 5 feet six inches tall and weighs 150 pounds based on the recommendations of.8 to 2.0 g/kg per day

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Nutrition Assignment Refer to page 61 in your nutrition book and answer Critical Thinking Questions 2 and 3