proteins. what is protein? n proteins are a sequence of amino acids n of the 20 amino acids that...
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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)