Exam 3

Question 1

How many grams of glucose does glycogen store in the body?

Answer 1

180-200 g

Question 2

Where in the body does gluconeogenesis occur?

Answer 2

liver and kidneys

Question 3

2 reasons why gluconeogenesis is not the reversal of glycolysis

Answer 3

1) requires manipulation of energetics to reverse glycolysis (-ΔG)
2) they are reciprocally regulated

Question 4

Where in the cell does gluconeogenesis occur?

Answer 4

the cytoplasm

Question 5

How does biotin function in gluconeogenesis?

Answer 5

acts as a coenzyme to deliver bicarbonate to pyruvate carboxylase

Question 6

Where does pyruvate carboxylase function?

Answer 6

converts pyruvate to oxaloacetate in the mitochondria

Question 7

Where does glucose-6-phosphatase function?

Answer 7

membrane of the ER

Question 8

Where is glucose-6-phosphatase located in the body? Why?

Answer 8

Liver and kidneys to make gluconeogenesis possible

Question 9

What is included in the glucose-6-phosphatase system?

Answer 9

a phosphatase, and transport proteins T1, T2, and T3

Question 10

What does T1 do?

Answer 10

moves G-6-P into ER to be hydrolyzed by phosphatase

Question 11

What do T2 and T3 do?

Answer 11

export glucose (T2) and Pi (T3) from ER into the cytosol

Question 12

What does GLUT2 do?

Answer 12

transports glucose made by gluconeogenesis into blood to enter circulation

Question 13

Cori cycle

Answer 13

1) lactate from LDH in muscle and returned to liver
2) Liver re-oxidizes lactate to pyruvate and makes glucose (via gluconeogenesis)
3) glucose returned to muscle

Question 14

Glycogen

Answer 14

polymer of glucose molecules attached to glycogenin used for short term energy storage

Question 15

What enzyme catabolizes glycogen and starch consumed via diet

Answer 15

amylase

Question 16

Amylase function

Answer 16

cleaves amylopectin or glycogen to maltose, maltotriose, or oligosaccharides

Question 17

Oligosaccharides

Answer 17

sugar of <10 monomers

Question 18

Purpose of debranching enzymes

Answer 18

cleaves limit dextrins/branches to allow amylase to cut at branch points; cannot cut near them

Question 19

Key difference between catabolism of glycogen from diet and tissue

Answer 19

diet - unregulated
tissue - high regulated; serves as important energy storage

Question 20

Glycogen phosphorylase

Answer 20

cleaves glucose from ends of glycogen molecule in tissues

Question 21

What enzyme catabolizes tissue glycogen

Answer 21

glycogen phosphorylase

Question 22

Product from glycogen phosphorylase

Answer 22

glucose-6-phosphate

Question 23

Glycogenin

Answer 23

first molecule of glycogen links to glycogenin protein via the OH on tyrosine

Question 24

Glycogen synthase

Answer 24

transfers glycosyl units for UDP-glucose to end of growing glycogen chain

Question 25

2 ways insulin modulates glycogen synthesis

Answer 25

1) binds to receptor triggering protein kinase signal cascade that activate glycogen synthase 2) promotes glucose uptake; providing substrate for glycogen synthesis and G-6-P which allosterically activates inactive glycogen synthase

Question 26

cellular metabolic effects of insulin reception

Answer 26

+ active transport **+ glycolysis + glycogen synthesis** + lipid synthesis + protein synthesis - lipid breakdown **- gluconeogenesis**

Question 27

Where is glucagon released? Where does it effect?

Answer 27

Pancreas Liver and adipose tissue

Question 28

Where is epinephrine released? Where does it effect?

Answer 28

adrenal glands liver and muscles

Question 29

Overall purpose of epinephrine and glucagon

Answer 29

generate glucose

Question 30

Glucagon purpose

Answer 30

long-term maintenance of steady-state glucose levels in the blood via glycogen breakdown and liver gluconeogenesis

Question 31

Epinephrine purpose

Answer 31

fight or flight rapidly mobilizes large amounts of energy

Question 32

Glucocorticoids

Answer 32

steroid hormones with distinct effects on liver, skeletal muscles, and adipose tissue

Question 33

Cortisol

Answer 33

primarily catabolic, promotes breakdown and decreases protein synthesis in skeletal muscle

Question 34

4 functions of cortisol in the cell

Answer 34

1) stimulate gluconeogenesis 2) increase glycogen synthesis 3) activate enzymes of amino acid metabolisms 4) stimulate urea cycle