Lipids & Proteins

Question 1

Steps in Protein Metabolism

Answer 1

Mechanical

Low pH denatures proteins; activates pepsinogen

Lumenal proteases digest to tripeptides, dipeptides, and amino acids

Tripeptides, dipeptides and amino aicds are transported into the intestinal epithelial cell

Intracellular peptidases digest tri- and dipeptides to amino acids

Amino acids are transported into the blood

Question 2

What turns trypsinogen into trypsin

Answer 2

enteropeptidase

Question 3

what turns pepsinogen into pepsin

Answer 3

H+ and pepsin

Question 4

what turns chymotrypsinogen, proelastase and procarboxypeptidases into active forms

Answer 4

trypsin

Question 5

specificity of endopeptidases determined by

Answer 5

side chain of the carbonyl containing AA

Question 6

patients with CF have deficient secretion of proteases & lipases due to _________ and can result in _______

Answer 6

In patients with cystic fibrosis, secretion of proteases & lipases is deficient because of blockage of the pancreatic duct. Malabsorption of protein & lipids and other nutrients can result.

Question 7

how are amino acids transported across intestinal epithelial cells

Answer 7

secondary active transport w/ overlapping substrate specificity

Question 8

Hartnup disease

Answer 8

Inherited mutations in the SLC6A9 transporter (Bo) result in Hartnup disease. This condition results in the symptoms of pellagra because tryptophan is not absorbed or resorbed and can not be used to synthesize niacin.

Question 9

Cystinuria

Answer 9

Inherited mutations in SLC7A9 (B0+) or SLC3A1 (rBAT) cause cystinuria. Patients develop kidney stones.

Question 10

Alternative way for amino acids to be transported across cellular membranes

Answer 10

reacting with glutathione
This pathway is important for glutathione synthesis, but not a major contributor to the transport of dietary amino acids.

Question 11

GGT in the serum indicates damage to

Answer 11

bile duct

Question 12

sources of intracellular amino acid pool

Answer 12

Extracellular amino acids

Protein degradation

de novo synthesis from glycolysis or TCA cycle intermediates

Question 13

mTORC1 complex

Answer 13

activates protein synthesis and inhibits autophagy.

Question 14

AMPK activation

Answer 14

inhibits protein synthesis and promotes autophagy.

Question 15

3 key cofactors for enzymes in AA metabolsim

Answer 15

pyridoxal phosphate (PLP)
tetrahydrofolate
tetrahydrobiopterin

Question 16

PLP important for

Answer 16

transaminations, deaminations, carcon chain transfers

Question 17

PLP deficiency results in

Answer 17

seizures, diarrhea, anemia, EEG abnormalities

Question 18

FH4 important in

Answer 18

1 carbon transfers

Question 19

FH4 deficiency results in

Answer 19

megaloblastic anemai

Question 20

BH4 important in

Answer 20

ring hydroxylations (Phe –> Tyr)

Question 21

BH4 deficiency results in

Answer 21

seizures, developmental delay

Question 22

The hormones secretin and cholecystokinin promote

Answer 22

secretion of bile and lipases into the lumen of the gut.

Question 23

fat consumed as

Answer 23

as triacylglycerol, phospholipids, and cholesterol esters.

Question 24

triacylglycerol =

Answer 24

glycerol w/ ester linkages to 3 fatty acids

Question 25

Triacylglycerol + pancreatic lipase

Answer 25

2 fatty acids + 2-monoacylglycerol

Question 26

where do lipases cut

Answer 26

ester linkages

Question 27

what lipids can be taken up by gut epithelial cells

Answer 27

2 FA and 2 monoacylglycerol, medium and short chain fatty acids

Question 28

what happens to fatty acids and monoacylglycerol in gut epithelial cells

Answer 28

made back into triacylglycerol and put into chylomicrons

short and medium FA chains can be sent to portal blood

Question 29

Fat consumed as cholesterol esters is degraded by

Answer 29

pancreatic cholesterol esterase. to cholesterol + FA

Question 30

Fat consumed as phospholipids can be broken down by

Answer 30

pancreatic phosholipase A2 to lysophospholipi d

Question 31

major apoprotein of chylomicrons

Answer 31

ApoB 48

encoded by same gene as ApoB-100 (apoprotein of VLDL)

Question 32

apoprotein of VLDL

Answer 32

ApoB-100

Question 33

how to get ApoB-48 from ApoB-100

Answer 33

RNA editing produces ApoB-48 in intestinal epithelial cells. The unedited transcript produces full length ApoB-100 in hepatocytes.

Question 34

After chylomicrons enter blood, receive ___ apoproteins from _____

Answer 34

After chylomicrons enter the blood, they receive ApoCII and ApoE from high density lipoprotein (HDL).

Question 35

HDL’s function is to

Answer 35

maintain cholesterol and apoprotein homeostasis

Question 36

LPL =

Answer 36

lipoprotein lipase

extracellular lipase in capillary beds of muscle and adipose tissue

Question 37

LPL activated by

Answer 37

Apo CII

Question 38

Fatty acids and cholesterol taken up by the liver from chylomicron remnants can be repackaged with ___ as ___

Answer 38

ApoB100 as very low density lipoprotein (VLDL).

Question 39

VLDL function

Answer 39

To deliver fatty acid fuels to the tissues of the body. (similar to chylomicrons)

Question 40

why adipocytes can store TAG only in fed state

Answer 40

the glycerol 3-phosphate backbone can only be produced by glycolysis in adipocytes.

Question 41

Apoprotein that liver recognizes

Answer 41

ApoE