Functions of liver: maintenance of blood glucose levels

Question 1

What percent of liver weight is glycogen stores?

Answer 1

2-8%

Question 2

general insulin effects on liver

Answer 2

• stimulation of protein synthesis
• inhibition of protein degradation
• glycogen synthesis
• inhibition of gluconeogenesis
• lipogenesis

Question 3

where does glucose-6-phosphatase occur?

Answer 3

only in the liver and the kidney

Question 4

what does glucose-6-phosphatase do?

Answer 4

breaks down glycogen to release glucose into bloodstream

Question 5

What are the key enzymes in the conversion of galactose to glucose?

Answer 5

• gal kinase
• P-gal uridyl transferase
• epimerase

Question 6

why is P-gal uridyl transferase deficiency an issue?

Answer 6

key enzyme in galactose to glucose conversion, deficiency leads to accumulation of gal-I-P which is toxic

Question 7

what happens to the majority of fructose in the liver?

Answer 7

phophorylated by fructokinase to fructose-I-P

Question 8

fructose-I-P

Answer 8

• toxic intermediate in fructose to glucose conversion that can accumulate due to certain aldolase deficiency
• this is why fructose can never replace glucose as an intravenous nutrient in diabetics. the aldolase enzyme is the rate limiting step even in normal metabolism and would cause the accumulation of fructose-I-P

Question 9

why can excessive amounts of fructose ingestion cause diarrhea?

Answer 9

protective measure because too much fructose can be damaging to the liver, GLUT5 transport is not very effective at absorbing fructose

Question 10

5 things that can be turned into glucose in the liver

Answer 10

1) galactose
2) fructose
3) lactate
4) amino acids
5) glycerol

Question 11

what are the key gluconeogenic enzymes?

Answer 11

• pyruvate carboxylase
• PEP carboxykinase
• fructose-1,6-P phosphatase