Kin 110 Lecture 5 Ch 6 Proteins 1

Kin 110 Lecture 5 Ch. 6 Proteins 1

Overview of Proteins • Thousands of substances in body are make of protein • Major non-water component of lean tissue (16 %) • 20 different amino acids – building blocks of protein – 9 essential - must be obtained from diet • Complete protein – high quality - all essential a. a. • Incomplete protein – lower quality - lack sufficient amount of one or more essential a. a. – simple combinations - complementary 2

Overview of Protein • Proteins crucial for thousands of body processes • each function requires specific protein • sequence of a. a. determines structure and function • body uses a. a. form diet as building blocks for many configurations and sizes of proteins for these varied functions • without proper essential a. a. in diet, body functions slow, immune system begins to fail 3

Amino Acids • Amino acids have general structure • variations in ‘R’ region determine functional characteristics (p. 176) • 20 a. a. - 9 essential - can not be made by the body • Table 6 -1, p 177 • Physiologically essential – PKU - Phenylketonuria – inability to process phenylalanine (ess. ) into tyrosine (non-ess. ) – Tyrosine becomes an ess. a. a. 4

Dietary Considerations (ess. vs. non-ess. ) • Complete protein – contains all 9 ess a. a. – Animal and Soy protein • Incomplete protein – lacks one or more ess a. a. – most plant proteins • Important as all a. a. are necessary for protein synthesis • All or None Principle of protein synthesis – ALABAMA eg. 5

Complementary Proteins • Various plant sources can compensate for ess a. a. deficiencies • Adults should have little concern, combination over entire day is important • more attention required for young children • Fig. 6 -2, p 179 • * know traditional combinations that make complete protein in diet * 6

Protein • Amino acids joined by peptide bonds – thousands of different proteins – Letters making sentences, paragraphs • order directed by DNA, genes • Creates specific and unique 3 -D structure, necessary for functioning • Eg. Sickle cell anemia 7

Denaturing of Protein • • Acid, alkaline, Heat or agitation alters protein 3 -D structure destroys normal function Cooking, makes foods safer to eat and facilitates further digestion (exposure to enzymes) • * recall - we dismantle proteins for the a. a. building blocks* 8

Digestion and Absorption • Begins in stomach – Enzyme Pepsin – breaks proteins into smaller a. a. sequences (selected bonds) • Creates Peptones • Hormone Gastrin controls release of Pepsin and Acid – acid activates pepsin and denatures proteins 9

S. I. And Protein • Protein and Fat in SI trigger pancreatic juice to be released • Divides peptones into smaller sequences • Broken into a. a. and short sequences for absorption • travel to liver (portal circulation) – recombined into protein – converted to glucose or fat – released to blood 10

Functions of Proteins • To ensure availability of ingested protein for these functions, you must take in sufficient carbohydrates and fat for energy needs • Vital body constituents – most are in a constant state of breakdown , rebuilding and repair – most a. a. can be recycled, by some are lost, requiring constant intake in small amounts. 11

Other Protein Functions • Fluid balance – Blood Proteins – albumin and globulins bring fluid back into the bloodstream after in leaves at the capillaries • prevent edema (swelling) • Acid Base Balance – proteins in membranes pump ions in an out – buffers; take away and add acid (H+) as required 12

Other Protein Functions • Hormones, Enzymes and Neurotransmitters • Immune Functions • Antibodies • Rapid production requires ample protein availability • excess protein does not boost immune function • Formation of glucose and Fat • Provision of Energy – costly processing 13

Protein Intake • Protein equilibrium • need to balance intake with output • output measure as nitrogen in urine (protein broken down) • fig 6 -6 p 189 • Positive balance - required for growth, recovery from illness, training – requires insulin, growth hormone, testosterone • Negative balance - occurs with inadequate intake, infections, bed rest 14

RNI for Protein • • . 8 g/Kg healthy body weight double for infants 56 g for 155 lb man 44 g for 120 lb woman 2 -3 servings per day Table 6 -3 p 191 mental stress and physical labor do not increase requirement • World class athletes may benefit from up to 1. 5 g /Kg • Pregnancy inc. need by 10 -15 g • elderly may have higher needs 15

High Protein Diet? • Increased saturated fat intake, lower fiber intake • May increase loss of calcium • may relate to colon cancer • may accentuate heart disease – homocysteine • Recommended not to exceed 2 X RNI • whole foods NOT supplements • average diet already 1. 5 -2 X RNI • athlete diet already larger, take in more protein with balanced diet 16

Protein Source • • • Animal - most dense source 65 % animal protein in US 20 % in Africa, parts of Asia Plant sources - complementary high in Magnesium and Fiber no cholesterol and little saturated fat 17

Vegetarianism • Why ? • Political, Ecological, Health reasons • soy protein – lowers LDL – antioxidant – vascular dilation • Vegan - only plant foods • Lacto-vegetarian - plant and dairy • Lacto-ovo vegetarian - plants, dairy and eggs • Omnivore - both plant and animal • Concerns - essential a. a. , essential fatty acids, vitamin B-12, calcium 18