Proteins

WHAT IS PROTEIN? Proteins are a sequence of amino acids Of the 20 amino acids that exist, 9 are

essential amino acids, and 11 are non-essential

There are also 4 amino acids that can be considered conditionally essential: arginine, tyrosine, glutamine, and cysteine

AMINO ACIDS: Structure

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

Acid, alkaline, heat, alcohol, and agitation can disrupt the chemical forces that stabilize proteins and can cause them to lose their shape (denature)

Denaturing of proteins happens during food preparation (cooking, whipping, adding acids) or digestion (in the stomach with hydrochloric acid)

PROTEINS: Function

Structural Functions: Collagen – is the most abundant

protein in mammals, and gives bone and skin their strength

Keratin – provides structure to hair and nails

ENZYMES Enzymes are proteins that catalyze chemical

reactions without being used up or destroyed in the process

Used in – digestion, releasing of energy from nutrients for fuel, triggering reactions that build muscle and tissue

PROTEIN: Functions

PROTEIN: Functions

HORMONES Hormones are chemical messengers

that are made on one part of the body, but act on cells in other parts of the body

Insulin, Glucagon Antidiuretic Hormone (ADH)

PROTEIN: Functions

IMMUNE FUNCTION The Immune Response is a series of

steps your body takes to mount an attack against invaders

Antibodies are blood proteins that attack and inactivate bacteria and viruses

Once an antibody has been made for a certain invader, your body can more quickly respond (Immunization)

PROTEIN: Functions

FLUID BALANCE Fluids in the body are intracellular or

extracellular (interstitial and intravascular) and must remain balanced

PROTEIN: Functions

FLUID BALANCE Blood proteins like albumin and globulin

help to regulate this balance by remaining in the capillaries and attracting fluid

Edema is the result of fluid imbalance

PROTEIN: Functions

ACID-BASE BALANCE 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

Otherwise, the resulting conditions of acidosis or alkalosis could lead to coma or death

PROTEIN: Functions

TRANSPORT Lipoproteins (chylomicrons, LDL, HDL) Albumin transports a variety of nutrients

such as calcium, zinc, and Vitamin B6 Transferrin transports iron (hemoglobin – a

protein, contains iron, but it transports oxygen)

Proteins may also acts as channels or pumps across the cell membrane

Catabolism of Protein

Breakdown of protein to AA

AA converted to fat when excess AA

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 Complete Protein

High qualityAll essential AA in needed amounts Animal sources

Incomplete Protein

Plant sources 70% of protein from

animal sources in US

Complementary Protein

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

Plants provide Incomplete Protein

Low in one or more ess. AA

Eat in combo to “complete” the AA balance

Protein Requirements .8 gm/kg body weight Protein RDA

46 gm for women

58 gm for men

10-12% kcal from protein Actual US Intake

>80 gm

>110 gm

~17% kcal from protein

Protein SourcesAlmonds (1 cup) 24 grams

Pinto Beans (1 cup) 15 grams

Cheese (1 oz.) 7 grams

Ham (3 oz.) 18 grams

1 Egg 6 grams

2% Milk (1 cup) 8 grams

Clams (3 oz.) 60 grams

Whole Wheat Bread 3 grams

Lean Hamburger 30 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

Meat Fish Poultry Eggs

Beef & pork rich in iron but high in fat

More Good Protein Sources

Dairy products select low fat (butter not protein)

Legumes Cereal grains Seeds Nuts Plant sources of

protein are low in fat

What about protein for athletes? Athlete needs 1.26 gm /

Kg (~90 gm) (but typical US male

eats >110 gm and female eats >80 gm)

Thus… supplements not needed

What does the body do with the added amino acid?

What builds muscle: exercise and a good diet

Amino Acid Supplement

High intake of a single AA leads to AA imbalance and is harmful

Many AA supplements on market, Surplus of AA causes diarrhea, loss of

appetite, GI upsets Tryptophan supplements were banned

in 1990 Athletes

Vegetarian Diets

Semi-vegetarian:– lacto vegetarian– ovo vegetarian

Strict vegetarian:– “Vegan”– healthy diets use complementary proteins

Macrobiotic diet: locally grown and whole foods; Yin(“cold”)&yang(“warm”) foods

Vegetarian Diets & Health

Associated with low risk of chronic diseases

May lead to Vegans: vitamins B12 and D, Ca, Zn are

at risk Adequately planned vegetarian diets

can The key to achieve healthy diet: variety

Protein deficiency--Marasmus

Chronic food deprivation,diseases

Protein & calories Impairs brain

development & learning

Severe weight loss Infection, diarrhea

Protein deficiency --Kwashiorkor Deficiency in protein but

not calories Children 1-3 years Some weight loss Edema

Hair: dry, brittle, changes color (lack of AA to make melanin)