Exam 1 Ch 16

Question 1

What is glycogen

Answer 1

multi-branched polysaccharide conatianing repeating units of glucose. 8-14 glucose units.
It’s the storage form of glucose.

Question 2

What are glycosidic bonds

Answer 2

bonds that link glucose units together

Question 3

WHat’s the storage form of glucose

Answer 3

Glycogen

Question 4

How does glycogen go to glucose?

Answer 4

Liver converts glycogen to glucose-1-phosphate, then glucose-6-phosphate,
and lastly to glucose

Question 5

What are the three enzymes involved in the breakdown of glycogen?

Answer 5

Glycogen phosphorylase (breaks a glycosidic bond by phosphate substitution)
Glycogen debranching enzymes (removes branches on glycogen)
Phosphoglucomutase (catalyzes the isomerization of G1P to G6P)

Question 6

What are the two binding sites of human liver glycogen phosphorylase (the enzyme that does phosphate substitution)

Answer 6

Active site and allosteric site

Question 7

What is glycogenesis?

Answer 7

Glycogen synthesis

Question 8

Three enzymes involved in Glycogen synthesis

Answer 8

UDP-glucose pyrophosphorylase (catalyzes the phosphoanhydride exchange from UTP to G1P to make UDPG)
Glycogen synthase (Extension of glycogen chains)
Glycogen branching enzyme (transfer of 7 glucose glycogen segments. it’s a transferase)

Question 9

What’s UDP-Glucose pyrophosphorylase main job?

Answer 9

Preparation of linking glucose.

Question 10

What’s glycogen synthase’s job

Answer 10

linking glucose to glycogen. Elimination of UDP, nucleophilic attack, deprotonation for bond formation

It is Sn1

Question 11

What’s glycogen branching enzyme’s job

Answer 11

transfer the 7-residue segment to chain via alpha-1,6-glycosidic linkages

Question 12

How are glucose chains bonded in glycogen?

Answer 12

alpha-1,4-glycosidic linkages (7-13 glucose per chain)

Question 13

how are glucose branches bonded?

Answer 13

α-1,6-glycosidic linkages (12 branch tiers)

Question 14

Glycogen Catabolism (Glycogenolysis)

Answer 14

 Glycogen Debranching Enzyme
 Glycogen Phosphorylase
 Phosphoglucomutase

Question 15

Glycogen(A)4 + Glycogen(B)n → Glycogen(B)n+3 + Glycogen(A)1

Answer 15

Glycogen Debranching Enzyme

Question 16

Glycogen + P𝑖 → Glycogen−1 + G1P

Answer 16

Glycogen Phosphorylase

Question 17

G1P ⇌ G6P

Answer 17

Phosphoglucomutase

Question 18

Glycogen Anabolism (Glycogenesis)

Answer 18

Glycogen Anabolism (Glycogenesis)
 UDP-glucose Pyrophosphorylase
 Glycogen Synthase
 Glycogen Branching Enzyme

Question 19

G1P + UTP → UDPG + 2P𝑖

Answer 19

UDP-glucose Pyrophosphorylase

Question 20

UDPG + Glycogenn → UDP + Glycogenn+1

Answer 20

Glycogen Synthase

Question 21

Glycogen(A)n → Glycogen(A)n−7 + Glycogen(B)7

Answer 21

Glycogen Branching Enzyme

Question 22

How is glycogen regulated? (whether to break it down or build it)

Answer 22

By phosphorylation (covalent modification). Increased phosphorylation leads to activation of glycogen phosphorylase and inhibition of glycogen synthase. Dephosphorylation is the opposite.

Hormonal control (allosteric modification). Insulin+glucose leads to glycogen synthesis. Glucogen +epinephrine leads to glycogen breakdown

Question 23

What does increased phosphorylation of glycogen do? Dephosphorylation?

Answer 23

activates glycogen phosphorylase and inhibits glycogen synthase. Inhibites glycogen phosphorylase and activates glycogen synthase.

Question 24

Difference between Glycogenesis and gluconeogenesis

Answer 24

Glycogenesis is the storage of glucose as glycogen. Gluconeogenesis is the creation of new glucose.

Question 25

What enzymes are involved in gluconeogenesis?

Answer 25

Stage II 1. Pyruvate Carboxylase 2. Phosphophenolpyruvate Carboxykinase (PEPCK) Those two steps convert pyruvate to phosphoenolpyruvate. * Stage I 3. Fructose bisphosphatase 4. Glucose-6-phosphatase

Question 26

What occurs in the cytosol?

Answer 26

Glycolysis, fermentation, glycogen metabolism, and most gluconeogenesis

Question 27

What occurs in the mitochondria

Answer 27

Citric acid cycle, oxidative phosphorylation, and conversion of pyruvate to oxaloacetate

Question 28

What three steps in glycolysis are irreversible?

Answer 28

The irreversible glycolysis steps are coupled to ATP  Pyruvate Kinase phosphorylates ATP from PEP  Phosphofructokinase phosphorylates F6P with ATP  Hexokinase phosphorylates glucose to G6P with ATP

Question 29

Which step of gluconeogenesis is coupled to a energy-high molecule?

Answer 29

The second step. Oxaloacetate to Phosphoenolpyruvate. GTP is the high energy. PEPCK phosphorylates oxaloacetate to PEP. It's a lyase. The first step is pyruvate carboxylase which is a ligase

Question 30

What happens in the last two steps of gluconeogeneis?

Answer 30

simple hydrolysis and releasing inorganic phosphate. Fructobisphosphatase hydrolyzes FBP and glucose-6-phosphatase hydrolyzes G6P

Question 31

what role does cAMP play in all this

Answer 31

cAMP is a secondary messenger that breaks down glycogen when hormonal peptides say to