1. The Proteins & Amino Acids
Chapter Five
The Proteins & Amino Acids

4. I. What Proteins Are Made of
Amino Acids
Amine Group
Acid Group
Side Group
All protein molecules contain nitrogen atoms.

8. A. Essential & Nonessential Amino Acids
Nine amino acids
Cannot be made (synthesized) by the body from other amino acids
Protein foods must be eaten daily that contain these amino acids
11 amino acids
Can be made from other parts
Nitrogen (other proteins)
Backbone (carbohydrates and fats)

10. Cont’d
Some amino acids are considered essential at different stages of life or in states of illness.
“Conditionally essential”

11. B. Synthesis of Proteins
Peptide bond
Between amino end &
acid end

14. B. Synthesis of Proteins
Different places along the chain of amino acids & side chains may be attracted to others

16. B. Synthesis of Proteins
Strand coils & folds back on itself, giving the protein a distinct shape.
Shapes of proteins affect how they are used in the body

19. C. Denaturation of Proteins
First step in its destruction
Excess heat, alcohol, acids or salts of heavy metals can damage the body’s proteins
Stomach acid opens up the protein’s structure and permits digestive enzymes to act upon the protein.

22. II. The Functions of Proteins
Growth & Maintenance
Dietary protein ensures that amino acids are available to build the proteins needed for new tissue.
Nearly all cells are constantly replaced, requiring protein.

24. B. Enzymes
Proteins such as enzymes are catalysts that help chemical reactions take place.
Each enzyme is specific for a particular reaction.

26. C. Hormones Some hormones, but not all, are proteins
Hormones signal the appropriate enzymes to act.

27. D. Antibodies Formed in response to foreign substances in the body.
Each antibody is specific to one foreign substance.
Once an antibody is made for the substance, the body develops immunity to that substance.

29. E. Fluid Balance Fluid Balance:
Proteins help regulate the quantity of fluids to help maintain fluid balance.
Cells and the spaces between cells must contain a constant flux of and amount of fluid.
Water can diffuse freely in and out of a cell; proteins can not

31. F. Acid-Base Balance
Normal body processes produce acids & bases that must be excreted
pH: concentration of hydrogen ions
Acids: release hydrogen ions
Bases: accept hydrogen ions
Acid-Base Balance: equilibrium between acids and bases in body

33. Cont’d Blood proteins act as buffers for acid-base balance.
Buffers: can give up or add extra hydrogen to maintain balance
Acidosis or alkalosis may occur if acid-base balance is upset

35. G. Transport Proteins
Move nutrients and other molecules in and out of cells
Turn on and off
Hormones do the switching
Move substances from one organ to another
Lipoproteins
Vitamins and minerals

37. G. Energy
Protein may be sacrificed to provide energy if insufficient carbohydrate and fat are eaten.
Amino acids are degraded for energy.
Amino acids will only make proteins if carbs and fat are providing protein-sparing energy.
Protein-sparing: Leave amino acids alone to make proteins

39. III. Digestion & Absorption of Protein
Begins in the stomach with denaturation
Breaks into dipeptides, tripeptides and free amino acids into small intestine

41. HOW BODY HANDLES PROTEIN
Amino acids taken up by cells
Protein synthesis takes place
If “non-essential” amino acid is missing, the body can make it
If “essential” amino acid is missing, the protein synthesis stops and all of the amino acids in place are dismantled and the protein is not made

43. IV. Protein Quality
A measure of the essential amino acid content of a protein relative to the essential amino acid needs of the body
Biological value (BV) – how well supports nitrogen balance
Reference protein – egg white protein, the standard to which other proteins are compared = 100 score

44. Complete and Incomplete Proteins
Complete protein: contains all the essential amino acids in the right proportion relative to need
Meat, dairy products, and many soybean products
High Biological Value
Incomplete protein: lacking or low in one or more of the essential amino acids
Most plant based proteins
Low Biological Value

47. Complimentary Proteins
Two or more food proteins whose amino acid assortments complement each other in such a way that the essential amino acids limited in or missing from each are supplied by the others.

50. V. Recommended Protein Intakes
Covers the need to replace protein-containing tissue that people lose and wear out daily

51. TWO WAYS TO ESTIMATE
The RDA for the healthy adult is 0.8 grams of protein per kilogram of body weight
Use desirable weight
220 pounds = 100 kg
100 kg x 0.8 = 80 grams
Percentage of total calories
Dietary Goals
12-15 % of total calories
2500 calories x .12 to .15 = 300 – 375 calories
75 – 94 grams

53. Protein & Health A. Too Little Protein
Protein-Energy Malnutrition (PEM)
The world’s main form of malnutrition
Kwashiorkor: a deficiency disease caused by inadequate protein in the presence of adequate food energy
Marasmus: an energy-deficiency disease; starvation

56. B. Too Much Protein No benefits to eating too much protein
Risks associated with overconsumption
Many protein-rich animal sources are high in fat
Zinc loss is observed in animal studies

57. Cont’d
If amino acids are in excess of needs, the body will remove the amine group and convert the residues to glucose and glycogen or to fat.
High protein intake also increased excretion of calcium
Extra stress on kidneys

58. C. Choosing Protein Wisely
More is not necessarily better
Select 1/3 or less of protein from animal sources
Include legumes:
Garbanzo beans, great northern beans, kidney beans
Lentils, lima beans, pinto beans, split peas, white navy beans, soybeans
High quality protein, fat free, high in fiber