NTR 306: Exam 2 Review. Questions & Answers.

1. Describe the structure of an amino acid. How does a protein’s composition differ from carbohydrates and fats? a. Contain C, H, and O (like carbs and fats), but ALSO have N; nitrogen gives name amino b. Central C atom, H atom, amino group (NH2), acid group (COOH), and side group/side chain that distinguishes each amino acid 2. What are essential and non-essential amino acids? Be able to recognize the names of the 20 amino acids that are used for protein synthesis in the body (do not need memorize which amino acids are essential / nonessential). a. Essential – those the body cannot make, must be provided in the diet b. Nonessential – produced by body, can become conditionally essential c. Histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, alanine, arginine, asparagines, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, tyrosine 3. What is denaturation and how does it occur? Does denaturation of protein affect the nutritional content of the protein? Name some examples of protein denaturation in foods. a. Denaturation – change in protein’s shape and consequent loss of function brought by heat, agitation, acid, base, alcohol, heavy metals, other agents b. Hardening of egg when cooked, curdling of milk when acid added, stiffening of egg whites when whipped c. No effect on nutritional content 4. Describe the process of protein digestion in the GI tract. (In your description include the digestive juices / enzymes secreted) a. Mouth – chewing, moisten proteins, mixed with saliva b. Stomach – hydrolysis: HCl uncoils (denatures) proteins so that digestive enzymes can attack peptide bonds, HCl converts enzyme pepsinogen to pepsin which breaks polypeptides into smaller polypeptides c. Small intestine – pancreatic and intestinal proteases hydrolyze polypeptides further, peptidase enzymes on membrane surfaces of intestinal cells hydrolyze more and absorb amino acids 5. Into what circulatory system are amino acids absorbed? a. Vascular (circulatory) system 6. What provides the instructions for all proteins synthesized in the body? a. DNA 7. Name the amino acids that are used to synthesize: (Read in text) a. Vitamin Niacin – synthesized by tryptophan b. Neurotransmitters (serotonin, epinephrine/norepinephrine) – synthesized by tyrosine; chemicals that are released at the end of a nerve cell when a nerve impulse arrives there, they diffuse across the gap to the next cell and alter the membrane of that second cell to either inhibit or excite it b.i. Serotonin – tryptophan, helps in sleep regulation, appetite control, sensory perception c. Melanin – synthesized by tyrosine; pigment responsible for brown hair, eye, and skin color 10. Describe the following functions of proteins: