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Chapter 6:

Chapter 6 Protein and Amino Acids Copyright © 2012, 2007 Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 1


LEARNING OBJECTIVES 1. Identify the structure and functions of protein. 2. Differentiate between essential and nonessential amino acids. 3. Differentiate between complete and incomplete protein. 4. Discuss the potential health benefits of a vegetarian dietary pattern. 5. Distinguish between different types of protein-energy malnutrition: marasmus and kwashiorkor. 2

Structure of Protein:

Structure of Protein Proteins: organic compounds formed from chains of amino acids Amino acids: compounds containing carbon, hydrogen, oxygen, and nitrogen Linked into chains to form proteins 20 amino acids from which all the proteins required by plants and animals are made Essential amino acids (EAAs) Nonessential amino acids (NEAAs) 3

Amino Acids:

Amino Acids 2 amino acids bond together Dipeptide 3 amino acids bond together Tripeptide Additional amino acids joining chain make Polypeptides Body has tremendous range of possible amino acid links ..leading to 50,000 different kinds of proteins 4

Protein structural levels :

Protein structural levels Primary structure Sequential order of amino acids Secondary Spiral shape due to chemical bond between the amino acids Tertiary and quaternary Further folding into a unique 3 dimensional shape 5

Protein Function:

Protein Function Protein lose shape(denaturation eg. a folded chain unfolds )when Heat(cooking) Acids and bases(vinegar) Alcohol ex.Milk curdling and egg white turning white when heated Denaturation is irreversible loss of protein function 6

Protein as a Nutrient in the Body Digestion and Absorption:

Protein as a Nutrient in the Body Digestion and Absorption Mouth Site of only mechanical digestion of protein Stomach Digestion of protein begin in stomach Hydrochloric (HCL)acids break down protein structure Activates pepsin the enzyme that breaks down proteins to short polypeptides and amino acids 7

Digestion and Absorption, cont’d:

Digestion and Absorption, cont’d Small intestine Digestion in small intestines Pancreatic enzymes (proteases complete digestion of the polypeptides into single amino acids Small intestine and pancreas produce trypsin, dipeptidase result in hydrolysis to amino acids Absorption through intestinal wall by active transport requires vitamin B 6 8


Metabolism Anabolism and catabolism Most protein functions result of anabolism (synthesis) in cells Catabolism (breakdown) begins in liver cells through deamination Deamination-Liver conversion of ammonia to urea; excreted in urine ….and keto acid which may enter the tricarboxylic acid cycle(TCA) to be used for energy 9

Metabolism, cont’d:

Metabolism, cont’d Protein excess Increased deamination Health effects: increased risk of CAD High in cholesterol and saturated fats some cancers osteoporosis May cause excess calcium excretion leading to bone loss 10

Nitrogen Balance:

Nitrogen Balance Nitrogen-balance studies: measurement of amount of nitrogen (N) entering body compared with amount excreted 11


Functions Growth and Maintenance Amino acids for muscle, tissue, bone formation, and cells Collagen; hair, nails, and skin composed of similar protein substances Creation of Communicators and Catalysts Communicators: hormones, immune system Catalysts: enzymes Blood clotting: fibrogen 12

Functions, cont’d:

Functions, cont’d Immune System Response Antibodies protect against disease Fluid and Electrolyte Regulation Balance among intravascular , intracellular and interstitial fluids Acid-base balance Buffering effect: maintains proper pH level ENERGY SOURCE ….ONLY AFTER ALL OTHERS USED UP! 13

Functions, cont’d:

Functions, cont’d Transportation Transport nutrients and other vital substances Protein pumps nutrients in and out of cells Lipoproteins carry nutrients in blood (minerals, lipids, vitamins and electrolytes) Hemoglobin and myoglobin 14

Food Sources, cont’d:

Food Sources, cont’d High quality protein contains best balance and assortment of essential and nonessential amino acids for protein synthesis highest quality protein foods eggs and human milk Incomplete protein lack one or more of essential amino acids Better sources grains and legumes Protein RDA factors include age, gender, physiologic state, and protein sources Protein RDA: 0.8 g/kg for adults(46 g-female, 56 g males) 10% intake as protein 15


Vegetarianism Vegan dietary pattern Only plant foods No animal-derived foods consumed Lacto-vegetarian dietary pattern Only plant-derived foods consumed plus dairy products Ovo-lacto vegetarian dietary pattern Only animal-derived foods eaten are dairy products and eggs 16

Vegetarianism, cont’d:

Vegetarianism, cont’d Benefits of Vegetarianism Health : Lower intake of total fat, saturated fat, and cholesterol High in fiber Reduced risk of obesity, CAD, type 2 DM, hypertension, gastrointestinal disorders, and certain cancers Spiritual: nonharmful to animals; animal rights Economic/environmental: Concern over food safety 17

Vegetarianism, cont’d:

Vegetarianism, cont’d Drawbacks of Vegetarianism Vegan: potential deficiencies Adequate nutrients except for vitamins D and B 12 Potential deficiencies of iron, zinc, and calcium Effects on social health MyPyramid food patterns for vegetarians 18

PowerPoint Presentation:


PowerPoint Presentation:

Proteins are actually made up of hundreds to thousands of these, connected by peptide bonds: a. monosaccharides b. amino acids c. pepsinogens d. lipoproteins 20

PowerPoint Presentation:

2. Someone who practices a vegan lifestyle is most likely to be deficient in which nutrient? a. Vitamin D b. Vitamin C c. Potassium d. Glucose 21

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