Regulations and Info about pathways, enzymes, etc

Question 1

Regulation by Fructose-2,6-bisphosphate in the Fasting State:

Answer 1

Increased glucagon –> Increased cAMP –> Increased Protein Kinase A –> Increased FBPase-2, Decreased PFK-2 == Less glycolysis and more gluconeogenesis

Question 2

Regulation by Fructose-2,6-bisphosphate in the Fed State:

Answer 2

Increased Insulin –> Decreased cAMP –> Decreased Protein Kinase A –> Decreased FBPase-2, Increased PFK-2 == More glycolysis and less gluconeogenesis

Question 3

4 Different Pyruvate Metabolic Pathway Products and Enzymes:

Answer 3

1. Alanine via Alanine Aminotransferase (ALT)
2. Oxaloacetate via Pyruvate Carboxylase
3. Acetyl-CoA via Pyruvate Dehydrogenase
4. Lactate via Lactic Acid Dehydrogenase

Question 4

Alanine Aminotransferase:

1. Cofactor
2. Function

Answer 4

1. B6

2. Alanine carries amino groups to the liver from muscle

Question 5

Pyruvate Carboxylase:

1. Cofactor
2. Function

Answer 5

1. Biotin

2. Supplies oxaloacetate to replenish TCA cycle or to be used in gluconeogenesis

Question 6

Pyruvate Dehydrogenase:

1. Cofactor
2. Function

Answer 6

1. B1, B2, B3, B5, Lipoic Acid

2. Transition from glycolysis to TCA Cycle

Question 7

Lactic Acid Dehydrogenase:

1. Cofactor
2. Function

Answer 7

1. B3

2. End of anaerobic glycolysis (major pathway in RBC, WBC, kidney medulla, lens, testes, and cornea)

Question 8

Function of Urea Cycle

Answer 8

Excess nitrogen generated from amino acid catabolism is converted to Urea and excreted by the kidneys via the Urea Cycle

Question 9

Proteins of the Urea Cycle

Answer 9

Ornithine
Citruline
Aspartate
Argininosuccinate
Fumarate
Arginine
Urea
(Ordinarily, Careless Crappers Are Also Frivolous About Urination)

Question 10

Hyperammonemia:

1. Cause
2. Results in
3. Treatment

Answer 10

1. Acquired (eg. liver disease) or Hereditary (Urea cycle enzyme deficiencies)
2. Excess NH4+ –> Depletes alpha ketoglutarate –> Inhibits TCA Cycle
3. Limit protein in diet. Benozate or Phenylbutyrate can be given to decrease ammonia levels (by binding amino acids leading to excretion)

Question 11

N-acetylglutamate Synthase Deficiency:

1. Results in
2. Symptoms

Answer 11

1. Required cofactor for carbamoyl phosphate synthetase 1, so absence leads to hyperammonemia
2. Presents in neoates as poorly regulated respiration and body temp, poor feeding, developmental delay, and intellectual disability. (Idential to carbamoyl phosphate synthetase I deficiency)

Question 12

Ornithine Transcarbamylase Deficiency:

1. Cause
2. Results in
3. Symptoms

Answer 12

1. X-Linked Recessive
2. Interferes with body’s ability to eliminate ammonia and is often evident within first few days of life. Excess carbamoyl phosphate is converted to orotic acid
3. Increased Orotic Acid in blood and Urine, Decreased BUN, symptoms of hyperammonemia. No megaloblastic anemia.

Question 13

Cholesterol Synthesis:

1. Function of cholesterol
2. Rate limiting step

Answer 13

1. Cholesterol needed to maintain cell membrane integrity and to synthesize bile acids, steroids, and vitamin D
2. HMG-CoA Reductase (Reversibly inhibited by Statins)

Question 14

Function of Pancreatic Lipase

Answer 14

Degradation of dietary triglycerides in small intestine

Question 15

Function of Lipoprotein Lipase

Answer 15

Degradation of triglycerides circulating in chylomicrons and VLDLs. Found on vascular endothelial surface

Question 16

Function of Hepatic Triglyceride Lipase

Answer 16

Degradation of triglycerides remaining in IDL

Question 17

Function of Hormone-Sensitive Lipase

Answer 17

Degradation of triglycerides stored in adipocytes

Question 18

Function of Lecithin-Cholesterol Acyltransferase (LCAT)

Answer 18

Catalyzes esterification of cholesterol

Question 19

Function of Cholesterol Ester Transfer Protein (CETP)

Answer 19

Mediates transfer of cholesterol esters to other lipoprotein particles

Question 20

Apo-E:

1. Function
2. Involved with

Answer 20

1. Mediates remnant uptake

2. Chylomicron, Chylomicron Remnant, VLDL, IDL, and HDL

Question 21

Apo-AI:

1. Function
2. Involved with

Answer 21

1. Activates LCAT

2. Chylomicron and HDL

Question 22

Apo-CII:

1. Function
2. Involved with

Answer 22

1. Lipoprotein lipase cofactor

2. Chylomicron, VLDL, HDL

Question 23

Apo-B48:

1. Function
2. Involved with

Answer 23

1. Mediates chylomicron secretion

2. Chylomicron, Chylomicron remnants

Question 24

Apo-B100:

1. Function
2. Involved with

Answer 24

1. Binds LDL Receptor

2. VLDL, IDL, LDL

Question 25

Lipoprotein:

1. Composition
2. Functions

Answer 25

1. Lipoproteins are composed of varying proportions of cholesterol, triglycerides, and phospholipids.
2. Carry cholesterol (LDL and HDL carry the most)

Question 26

Chylomicron function

Answer 26

Delivers dietary TG to peripheral tissue
Delivers cholesterol to liver in the form of chylomicron remnants which are mostly depleted of their TG
Secreted by intestinal epithelial cells

Question 27

VLDL Function

Answer 27

Delivers hepatic TG to peripheral tissue

Secreted by liver

Question 28

IDL Function

Answer 28

Formed in degradation of VLDL

Delivers TG and cholesterol to liver

Question 29

LDL Function

Answer 29

Delivers hepatic cholesterol to peripheral tissue
Formed by hepatic lipase modification of LDL in the peripheral tissue
Taken up by target cells via receptor-mediated endocytosis

Question 30

HDL Function

Answer 30

Mediates reverse cholesterol transport from periphery to liver
Acts as a repository for apolipoproteins C and E (needed for chylomicron and VLDL metabolism)
Secreted from both liver and intestine.
Alcohol increases synthesis