Proteins

WHAT IS PROTEIN? n Proteins are a sequence of amino acids n Of the 20 amino acids that exist, 9 are essential amino acids, and 11 are non- essential n There are also 4 amino acids that can be considered conditionally essential: arginine, tyrosine, glutamine, and cysteine

AMINO ACIDS: Structure n Consist of a central carbon atom bonded to: a hydrogen, a carboxylic acid, an amino group, and an additional side group that is unique to each amino acid

DENATURING of PROTEINS n Acid, alkaline, heat, alcohol, and agitation can disrupt the chemical forces that stabilize proteins and can cause them to lose their shape (denature) n Denaturing of proteins happens during food preparation (cooking, whipping, adding acids) or digestion (in the stomach with hydrochloric acid)

PROTEINS: Function Structural Functions: n Collagen – is the most abundant protein in mammals, and gives bone and skin their strength n Keratin – provides structure to hair and nails

ENZYMES n Enzymes are proteins that catalyze chemical reactions without being used up or destroyed in the process n Used in – digestion, releasing of energy from nutrients for fuel, triggering reactions that build muscle and tissue PROTEIN: Functions

HORMONES n Hormones are chemical messengers that are made on one part of the body, but act on cells in other parts of the body n Insulin, Glucagon n Antidiuretic Hormone (ADH)

PROTEIN: Functions IMMUNE FUNCTION n The Immune Response is a series of steps your body takes to mount an attack against invaders n Antibodies are blood proteins that attack and inactivate bacteria and viruses n Once an antibody has been made for a certain invader, your body can more quickly respond (Immunization)

PROTEIN: Functions FLUID BALANCE n Fluids in the body are intracellular or extracellular (interstitial and intravascular) and must remain balanced

PROTEIN: Functions FLUID BALANCE n Blood proteins like albumin and globulin help to regulate this balance by remaining in the capillaries and attracting fluid n Edema is the result of fluid imbalance

PROTEIN: Functions ACID-BASE BALANCE n Proteins help to maintain a stable pH level in our body fluid by picking up extra hydrogen ions when conditions are acidic, and donating hydrogen ions when conditions are alkaline n Otherwise, the resulting conditions of acidosis or alkalosis could lead to coma or death

PROTEIN: Functions TRANSPORT n Lipoproteins (chylomicrons, LDL, HDL) n Albumin transports a variety of nutrients such as calcium, zinc, and Vitamin B6 n Transferrin transports iron (hemoglobin – a protein, contains iron, but it transports oxygen) n Proteins may also acts as channels or pumps across the cell membrane

Catabolism of Protein n Breakdown of protein to AA n AA converted to fat when excess AA n N from AA is reused for AA synthesis; excess is excreted in urine –May cause loss of Ca in urine –Kidney disease problem

Protein Quality n Complete Protein High quality All essential AA in needed amounts Animal sources n Incomplete Protein Plant sources n 70% of protein from animal sources in US

Complementary Protein n Plant protein (legume) with limiting AA combined with different plant protein (grain) different limiting AA eaten together give complete protein

Plants provide Incomplete Protein n Low in one or more ess. AA n Eat in combo to “complete” the AA balance

Protein Requirements n.8 gm/kg body weight n Protein RDA 46 gm for women 58 gm for men 10-12% kcal from protein n Actual US Intake >80 gm >110 gm ~17% kcal from protein

Protein Sources Almonds (1 cup)24 grams Pinto Beans (1 cup)15 grams Cheese (1 oz.)7 grams Ham (3 oz.)18 grams 1 Egg6 grams 2% Milk (1 cup)8 grams Clams (3 oz.)60 grams Whole Wheat Bread3 grams Lean Hamburger30 grams Peanut Butter (1 T)4 grams Salmon (3 oz.)20 grams Tofu (4 oz.)9 grams Yogurt (8 oz.)10 grams White rice (1 cup)4 grams

Food Sources of Proteins n Meat n Fish n Poultry n Eggs Beef & pork rich in iron but high in fat

More Good Protein Sources n Dairy products select low fat (butter not protein) n Legumes n Cereal grains n Seeds n Nuts n Plant sources of protein are low in fat

What about protein for athletes? n Athlete needs 1.26 gm / Kg (~90 gm) n (but typical US male eats >110 gm and female eats >80 gm) n Thus… supplements not needed n What does the body do with the added amino acid? n What builds muscle: exercise and a good diet

Amino Acid Supplement n High intake of a single AA leads to AA imbalance and is harmful n Many AA supplements on market, n Surplus of AA causes diarrhea, loss of appetite, GI upsets n Tryptophan supplements were banned in 1990 n Athletes

Vegetarian Diets n Semi-vegetarian: –lacto vegetarian –ovo vegetarian n Strict vegetarian: –“Vegan” –healthy diets use complementary proteins n Macrobiotic diet: locally grown and whole foods; Yin(“cold”)&yang(“warm”) foods

Vegetarian Diets & Health n Associated with low risk of chronic diseases n May lead to n Vegans: vitamins B 12 and D, Ca, Zn are at risk n Adequately planned vegetarian diets can n The key to achieve healthy diet: variety

Protein deficiency--Marasmus n Chronic food deprivation,diseases n Protein & calories n Impairs brain development & learning n Severe weight loss n Infection, diarrhea

Protein deficiency -- Kwashiorkor n Deficiency in protein but not calories n Children 1-3 years n Some weight loss n Edema n Hair: dry, brittle, changes color (lack of AA to make melanin)