L20: AA Metabolism (may)

Question 1

What is Kwashiorkor?

Answer 1

A severe form of protein malnutrition

Question 2

What are the effects of Kwashiorkor?

Answer 2

• Muscle wasting
• Decreases the body’s ability to produce digestive enzymes and new intestinal epithelial cells.
• osmotic imbalance in the GI system

Question 3

What does osmotic imbalance in the GI system lead to?

Answer 3

Gut swelling (edema or retention of water)

Question 4

What is the aim of digestion of dietary proteins?

Answer 4

To hydrolyze proteins into di- and tri- peptides and free amino acids.

Question 5

Where does the digestion of proteins begin and end?

Answer 5

it starts in the stomach and ends in the small intestine.

Question 6

Proteolytic enzymes are produced by?

Answer 6

1. Stomach
2. Pancreas
3. Small intestine

Question 7

What is HCl secreted by?

Answer 7

parietal cells of the stomach

Question 8

HCL is too dilute (pH 2-3) to hydrolyze proteins, therefore it functions to…

Answer 8

denature proteins and kill some bacteria

my explanation: 3shan y5aleehum more susceptible to subsequent hydrolysis by proteases

Question 9

What is pepsin?

Answer 9

an endopeptidase

which hydrolyses protein to polypeptides

Question 10

What is pepsin secreted by? as what?

Answer 10

Secreted by the chief cells as an active zymogen: pepsinogen

Question 11

shnu zymogen

Answer 11

an inactive enzyme

Question 12

Pepsinogen is activated to pepsin by?

Answer 12

1. HCL (low pH)

2. Autocatalytic activation (by other pepsin molecules)

Question 13

What is the function of pepsin?

Answer 13

it releases peptides and a few free amino acids from dietary proteins

Question 14

The release of pancreatic zymogens are mediated by?

Answer 14

2 digestive tract hormones:

1. Cholecytokinin
2. Secretin

Question 15

How are pancreatic zymogens activated?

Answer 15

A duodenal enteropeptidase (aka enterokinase) converts the pancreatic zymogen trypsinogen to trypsin

Question 16

shnu trypsin?

Answer 16

It is the common activator of all other pancreatic zymogens

Question 17

“trypsin cleaves ONLY after arganine or lysine?” this statement proves what?

Answer 17

that each enzyme has a different specificity for the amino acid

Question 18

What is an aminopeptidase?

Answer 18

Exopeptidase

an enzyme that removes an amino acid from the end with a free amino group

Question 19

where can you find aminopeptidase?

Answer 19

on the luminal surface of the intestine

Question 20

what is the function of an aminopeptidase?

Answer 20

it repeatedly cleaves the N-Terminus residue from oligopeptides –> to produce even smaller peptides and free amino acids

Question 21

Free AA are absorbed by?

Answer 21

intestinal enterocytes by a Na+ linked secondary transport system

Question 22

Di- & Tri- peptides are absorbed by?

Answer 22

H+ linked transport system

Question 23

Free AA are released into?

Answer 23

the general circulation by a facilitated transporter

Question 24

Free AA are metabolised in the?

Answer 24

liver

Question 25

free amino acids in ECF

Answer 25

in active transport systems which require ATP

Question 26

Mnu uhma elly 3ndhum a common transport for AA uptake? w she9eer etha kan fee a genetic defect in one of them?

Answer 26

the small intestine and the proximal tubule of the kidney, etha fee defect y9eer Cystinuria (IEM)

Question 27

Shnu Cystinuria?

Answer 27

a genetic defect which causes the inability to absorb particular AA into the gut and into the kidney tubules.