wk 12

Question 1

control of protein synthesis

Answer 1

synthesis = breakdown (nitrogen balance), significant turnover throughout the day, 70-100 g dietary = most balance, huge reservoir but mostly conserved due to functions (not just for E)

Question 2

anabolism

Answer 2

protein synthesis, increases following ingestion of food, enhanced by PA

Question 3

fast proteins

Answer 3

whey & soy, AA mixtures, pro hydrolysates are rapidly absorbed and utilized for muscle protein synthesis

Question 4

slow proteins

Answer 4

casein, stay elevated longer in plasma and can be used to prevent protein breakdown

Question 5

catabolism

Answer 5

1-2% total body protein turned over daily, synthesis/degradation account for 10-25% of resting energy expenditure

Question 6

degradation =

Answer 6

AA, mostly reused by body tissues, flux of AAs through the cytosol that can be used for cellular growth/maintenance (AA pool), excessive catabolism occurs during fasting/physiological stress

Question 7

hormonal control

Answer 7

insulin, glucagon, cortisol

Question 8

hormonal synthesis

Answer 8

insulin, promotes cellular uptake and use of AA for synthesis, increased uptake of AA transporters and activity of transporters, growth hormone, testosterone, PA

Question 9

antagonizes enzymes

Answer 9

responsible for AA oxidation, inhibited by insulin

Question 10

hormonal control catabolism

Answer 10

glucagon stimulates AA for gluconeogenesis, cortisol increases catabolism

Question 11

oral cavity

Answer 11

only mechanical breakdown

Question 12

stomach

Answer 12

HCl denatures proteins (going from advanced folding to primary structure), pepsin begins breakdown peptide bonds, yields lg polypeptides, some oligopeptides, free AA

Question 13

g cell, chief, parietal cell

Answer 13

g cell - secrete gastrin to stimulate parietal & chief cells
chief - pepsinogen > pepsin > directly digests proteins
parietal - HCl, denatures proteins, converts pepsinogen

Question 14

small digestion

Answer 14

acidic chyme stimulates release of secretin and CCK, yields dipeptides, tripeptides, free AA

Question 15

Secretin

Answer 15

stimulates release of alkaline pancreatic juice to neutralize acidic chyme

Question 16

CCK

Answer 16

stimulates the secretion of pancreatic enzymes - direct protein digestion

Question 17

enterocytes of SI

Answer 17

produce several peptidases that aid in protein digestion (brush border enzymes)

Question 18

zymogen

Answer 18

cleaved to be active

Question 19

AA absorption

Answer 19

occurs in duodenum & jejunum, facilitated by transporters (sodium dependent), BCAAs & essential AA absorbed the fastest, basolateral of membrane and into blood use same carrier systems

Question 20

AA absorption into enterocyte steps

Answer 20

1. Na+ binds
2. AA binds
3. Co-transport
4. Na+ pumped out in exchange for K+

Question 21

peptide absorption

Answer 21

majority of AA absorbed as di/tripeptides rather than free - 67%, PEPT1 (transporter, ^ rapidly than AA). hydrolyzed by cytoplasmic peptidase to AA w/n enterocyte