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Biochemistry 2 > E2 Glycogenesis > Flashcards

E2 Glycogenesis Flashcards

(66 cards)

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1
Q

Define glycogenesis.

A

glycogen synthesis

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2
Q

The first step in glycogenesis is to phosphorylate glucose. What enzyme will facilitate this rxn (glucose —> G-6-P)?

A

hexokinase (m)/ glucokinase (L)

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3
Q

What will inhibit hexo/glucokinase?

A

the product

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4
Q

T/F. Step one of glycogenesis utilizes ATP.

A

true

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5
Q

The second rxn of glycogenesis, G-6-P —> G-1-P, is facilitated by what enzyme?

A

phosphoglucomutase

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6
Q

T/F. Phosphoglucomutase is also used in glycogenesis.

A

true

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7
Q

The third step of glycogenesis requires two enzymes. What are the enzymes?

  1. G-1-P + UTP + H2O —> UDP glucose +PPi
  2. PPi —> Pi + Pi
A
  1. UDP- glucose pyrophosphorylase

2. pyrophosphorylase

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8
Q

What is the name of activated glucose?

A

UDP-glucose

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9
Q

T/F. G-1-P + UTP + H2O to UDP-glucose + PPi is an irreversible rxn.

A

false

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10
Q

What will make G-1-P + UTP + H2O to UDP-glucose + PPi is an irreversible rxn?

A

hydrolyzing pyrophosphate quickly, which drives rxn toward producing UDP-glucose

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11
Q

When pyrophosphate is hydrolyzed, why does it make G-1-P + UTP + H2O to UDP-glucose + PPi is an irreversible rxn?

A

because it is liberating energy and lots of energy is needed to reverse the rxn

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12
Q

The fourth step of glycogenesis adds glucose to glycogen an forms alpha (1-4) bonds via what enzyme?

A

glycogen synthase

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13
Q

T/F. During the formation of alpha (1-4) bonds, glucose is added to reducing ends of glycogen.

A

false; non-reducing ends

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14
Q

In order to form alpha (1-4) bonds, we need glucose. Where does this glucose come from?

A

activated glucose (UDP-glucose)

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15
Q

The fifth step of glycogenesis deals with branching via what enzyme?

A

glycosyl (4:6) transferase

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16
Q

What are the two actions of glycosyl (4:6) transferase?

A
  1. break alpha (1-4) bonds

2. form alpha (1-6) bonds

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17
Q

What is the integral protein that will catalyze the formation of the “primer” of a glycogen granule?

A

glycogenin

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18
Q

Glycogenin is required to initiate a new glycogen granule, but what does glycogenin require?

A

tyrosine

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19
Q

Within a glycogen granule, each chain has how many glucose residues?

A

12-14

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20
Q

When glycosyl (4:6) transferase breaks alpha (1-4) bonds, a segment is transferred to a hydroxyl group on carbon #__ of a chain to form a branch.

A

6

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21
Q

What enzyme is the key regulatory enzyme of glycogenesis?

A

Glycogen synthase

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22
Q

How many forms of glycogen synthase are there? Name them.

A

2

  1. glycogen synthase a
  2. glycogen synthase b
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23
Q

What form of glycogen synthase is the active, non-phosphorylated form?

A

glycogen synthase a

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24
Q

T/F. Glycogen synthase b is active and phosphorylated.

A

False; b= inactive and phosphorylated

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25
If glycogen synthase a is active, what state is it in?
R state
26
If glycogen synthase b is inactive, what state is it in?
T state (less active)
27
What are the three types of regulation for glycogenesis?
1. allosteric regulation 2. covalent modification 3. reciprocal regulation
28
Allosteric regulation of glycogenesis is activated by what enzyme?
glucose-6-phosphate
29
What tissue types will you find allosteric regulation of glycogenesis?
Liver and Muscle
30
T/F. Allosteric regulation is in a Fed state.
True
31
What type of glycogenesis regulation prevents glycogenolysis from occurring at the same time as glycogenesis?
covalent modification
32
What two hormones are associated with glycogenesis regulation?
glucagon and epinephrine
33
T/F. Reciprocal regulation of glycogenesis will stimulate the CAMP cascade.
False; covalent modification
34
What type of glycogenesis regulation states that the same conditions that stimulate glycogen breakdown will inhibit glycogen synthesis?
reciprocal regulation
35
What two hormones stimulate glycogen breakdown?
epinephrine and glucagon
36
What will stimulate protein phosphatase 1 (PP1)?
insulin and exercise
37
What is the function of protein phosphatase 1 (PP1)?
dephosphorylates the enzymes
38
When protein phosphatase 1 (PP1) dephosphorylates the enzymes, what enzymes become inactive? Active?
Inactive- glycogen phosphorylase and glycogen phosphorylase kinase Active- glycogen synthase
39
In the liver, PP1 is removing phosphate groups from glycogen synthase converting it to what form?
a form- active
40
What hormone will cause PP1 to dephosphorylate the glycogen synthase converting it to the more active (a) form?
insulin
41
When glycogen synthase is converted to the more active a form in liver, what process is stimulated?
glycogen synthesis (glycogenesis)
42
If glucose binds to the active site on phosphorylase a, it will shift from _____ state to ______ state.
R state ---> T State
43
T/F. If glucose binds to the active site of phosphorylase a, glycogenesis in the liver is inhibited.
False; inhibits glycogen degradation
44
In the muscle, what role does insulin have when it comes to glycogenesis?
when carbohydrate is available, we can stimulate glycogen synthesis to ensure we have fuel stored.
45
T/F. It is not important to replenish our glycogen because there should be enough stored.
False
46
What is the most potent stimulator of glycogen synthase in skeletal muscle?
low glycogen levels, like after exercise
47
Low glycogen levels, like after exercise, is the most potent stimulator of what enzyme in skeletal muscle?
glycogen synthase
48
What happens to glycogen synthase during low glycogen levels?
glycogen synthase, that is usually bound to the glycogen granule, is released when glycogen concentration falls
49
After intense exercise, when is glycogen synthesis at the highest rate?
initially; first 30 minutes
50
T/F. After intense exercise, glycogen synthesis rapidly declines to about 1/5th and then 1/9 by 60 minutes and 120 minutes respectively.
true
51
What are the two reasons why glycogen synthesis rapidly declines with time?
1. increased glucose uptake (GLUT4) | 2. increased enzyme activity (glycogen synthase)
52
T/F. In muscle, the rapid and slow phase are both insulin dependent.
False; rapid-independent
53
When does the rapid phase of glycogenesis occur in the muscle?
30-60 minutes after exercise
54
What two factors will stimulate the rapid phase of glycogenesis in the muscle?
1. muscle glycogen levels are low | 2. carb is provided immediately after exercise
55
When does the slow phase of glycogenesis occur in the muscle?
after the rapid phase
56
How long does the slow phase of glycogenesis last in the muscle?
can last a few hours
57
T/F. The slow phase of glycogenesis only needs carbohydrates or insulin response in order to be stimulated.
false; must have carbohydrates available and insulin response
58
T/F. Muscle glycogen synthesis rates may be 45% lower when carbohydrate ingestion post-exercise is delayed by 2 hours compared with immediate post-exercise consumption.
true
59
Why do muscle glycogen synthesis rates lower when carbohydrate ingestion post-exercise is delayed by 2 hours compared with immediate post-exercise consumption?.
the number of glucose transporters associated with the sarcolemma returns to pre-exercise concentration
60
What can be added to the diet to moderate carb intake?
protein/amino acids
61
What function will adding protein/amino acids to moderate carb intake have on muscle?
higher muscle glycogen synthesis rates than carbohydrate alone
62
T/F. If you have very high carbohydrate concentration and consumed protein, this will significantly increase glycogen synthesis rates.
False; if carbohydrate is very high, the protein doesn't matter
63
During carb loading, depleting glycogen reduces the power output of the muscle to ___%.
50%
64
What is the purpose of carb loading?
super compensation: store glucose above normal storage amount
65
What factors will stimulate glycogen phosphorylase to convert glycogen to G-1-P?
1. low energy charge (Low ATP; High ADP/AMP) 2. low levels of glucose 3. epinephrine 4. glucagon 5. calcium
66
What factors will stimulate glycogen synthase to convert G-1-P to glycogen?
1. high energy charge (High ATP) 2. high levels of glucose 3. insulin 4. low glycogen levels

Biochemistry 2 (14 decks)

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