Block 2 Lecture 1 -- Digestion & Absorption

Question 1

essential AAs

Answer 1

1) Phe
2) Val
3) Try
4) Thr
5) Ile
6) Met
7) His
8) (arg)
9) Leu
10) Lys

**Arg for growth

Question 2

2 families of pancreatic enzymes

Answer 2

1) exopeptidases

2) endopeptidases

Question 3

characterize the exopeptidases

Answer 3

1) aminopeptidases cleave from N-terminus

2) carboxypeptidases cleave from C-terminus—–A after hydrophobes—–B after basic

Question 4

How do exopeptidases work?

Answer 4

cleave from a terminal end one AA at a time

Question 5

What are examples of pancreatic peptidases?

Answer 5

1) trypsin
2) chymotrypsin
3) elastase

Question 6

Function of trypsin

Answer 6

– most specific endopeptidase– after Lys or Arg

Question 7

Function of chymotrypsin

Answer 7

cleaves after hydrophobic AAs– Phe, Tyr, Trp, Leu

Question 8

Function of elastase

Answer 8

cleaves AAs with small side chains– Ala, Gly, Ser

Question 9

What conditions yield a negative N Balance?

Answer 9

starvation, disease, 1 essential AA deficiency

Question 10

What conditions yield a positive N balance?

Answer 10

growth
pregnancy
illness recovery
re-feeding post-starvation

Question 11

inorganic sources of N

Answer 11

N2
NO2
NO3

Question 12

pathophysiology of kwashiorkor

Answer 12

protein deficiency –> decreased albumin –> edema

Question 13

pathophysiology of acute pancreatitis

Answer 13

gall stones, EtoH– ducts blocked, enzymes attack self

Question 14

pathophysiology of whipple’s dz

Answer 14

Tropheryma whippelii infects SI to cause malabsorption– diarrhea, GI bleeding, abdominal pain

Question 15

Treatment for kwashiorkor

Answer 15

re-feed pt slowly since pts lose ability to digest

Question 16

What AAs make up gluten?

Answer 16

15% Pro, 30% Gln

Question 17

Where is gluten found?

Answer 17

wheat, barley, rye, oats

Question 18

Pathophys of celiac dz

Answer 18

1) Gln deamidated by transglutaminase
2) Product binds to APC
3) Peptide-DQ2 triggers Th1 proliferation in gut mucosa
4) villi damage due to immune reaction

Question 19

Treatment for celiac dz

Answer 19

avoid gluten

Question 20

pathophys of cystinuria

Answer 20

1) transport defect for cysteine & basic AAs (Lys, Arg, Ornithine)
2) cysteine oxidized in blood –> cystine
3) kidney stones….this is a genetic dz

Question 21

Tx for Hartnup dz

Answer 21

niacin (b3) + hi-protein diet

Question 22

Pathophys of hartnup dz

Answer 22

….genetic dz……

1) neutral AA transport defect in intestine & kidney—essentials = Ile, Leu, Phe, Thr, Trp, Val
2) NAD deficiency (derived from Trp)
3) hyperaminoaciduria, photosensitivity rash, ataxia

Question 23

How are amino acids degraded?

Answer 23

1) 30% via lysosomal degradation

2) 70% via ubiquitin-proteasome

Question 24

how is polyubiquination accomplished?

Answer 24

26S = 20S + 1/2 19S caps

1) 19S binds (reqs ATP)
2) 20S unfolds protein (req’s ATP)
3) generates small peptides

Question 25

Asp TA pair

Answer 25

OAA

Question 26

Ala TA pair

Answer 26

pyruvate

Question 27

Glu TA pair

Answer 27

alpha-KG

Question 28

Which AAs do not have TA pairs?

Answer 28

1) Lys 2) Thr 3) Pro

Question 29

Where is ALT / GPT found?

Answer 29

hepatocytoplasm

Question 30

Where is AST / GOT found?

Answer 30

hepato, cardio, & myocytes

Question 31

What does ALT/GPT stand for?

Answer 31

Ala TA | glutamic pyruvic TA

Question 32

What does AST / GOT stand for?

Answer 32

Asp TA | glutamic oxaloacetic TA

Question 33

How is trypsin activated?

Answer 33

enteropeptidase (brush border)

Question 34

What enzymes involved in protein digestion are pancreatic?

Answer 34

1) chymotrypsinogen2) proelastase 3) procarboxypeptidases 4) trypsinogen

Question 35

How does pepsin cooperate with pancreatic enzymes?

Answer 35

= trypsin inhibitorpepsin inactivated by HCO3-

Question 36

Where do peptidases "cut" peptides?

Answer 36

after the carbonyl of the specified AA

Question 37

What elements are required for the gamma-glutamyl cycle?

Answer 37

1) ATP 2) covalent linkage 3) GGT 4) Glutathione (GSH)

Question 38

Glutathione is otherwise known as:

Answer 38

gamma-glutamyl-cysteinyl-glycine

Question 39

Describe the reaction catalyzed by 5-oxoprolinase.

Answer 39

g-Glutamyl-AA --> 5-oxoproline + AA

Question 40

Where is ATP required in the gamma-glutamyl cycle?

Answer 40

1) 5-oxoproline --> Glu 2) Glu + Cys --> gamma-glutamyl-cysteine 3) gamma-glu-cys --> GSH

Question 41

What transporters transport AA into cells?

Answer 41

1) primarily Na-dependent co-transporters 2) also facilitated diffusion transporters 3) GI transporters are genetically & specifically different

Question 42

How do AA transporters differ from glucose transporters?

Answer 42

AA transporters are primarily Na-dependent in all locations.Glucose transporters are Na-dependent only in liver/kidney

Question 43

Describe the AA transporters in an intestinal epithelial cell.

Answer 43

1) luminal side = 6 Na-dependent co-transporters OR GGT | 2) basal side = facilitated transporters

Question 44

Where does the gamma-glutamyl cycle take place?

Answer 44

intestine & kidney

Question 45

What are the products of lysosomal degradation?

Answer 45

1) FREE AAs 2) Glucose 3) FAs

Question 46

What diseases cause excessive protein degradation via the lysosomal pathway?

Answer 46

cancer, RA

Question 47

How many proteasomes in a single cell?

Answer 47

~ 30,000

Question 48

What is the rate of polyubiquination in resting vs. dividing cells?

Answer 48

1) resting = 5 * 10^5 proteins/min | 2) dividing = 2 * 10^6 proteins/min

Question 49

What are the mechanisms of protein degradation?

Answer 49

1) poly-ubiquination | 2) lysosomal degradation

Question 50

What is the product of the ubiquitin-proteasome pathway?

Answer 50

small peptides 8-11 AAs in length

Question 51

What diseases cause excessive protein degradation via polyubiquination?

Answer 51

1) cancer 2) RA 3) other autoimmune diseases

Question 52

What drugs target the 26S proteasome?

Answer 52

Carfilzomib, Bortezomib