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Biochemistry Exam 2 > Chapter 17: Gluconeogenesis > Flashcards

Chapter 17: Gluconeogenesis Flashcards

1
Q

Where are the major sites of gluconeogenesis?

A

Liver and kidneys

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2
Q

Gluconeogenesis is important for maintaining ________ during _____.

A

Normal blood glucose levels during starvation

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3
Q

Brain uses only glucose, therefore the liver essentially works to…

A

Make the brain happy by maintaing blood glucose levels

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4
Q

Most of the glucose generated in gluconeogenesis is used by _____ and ______.

A

Brain and contracting muscle

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5
Q

Gluconeogenesis converts ______ to ______.

A

Pyruvate to Glucose

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6
Q

What are the three precursors for gluconeogenesis?

A
  1. Lactate (muscle)
  2. Amino acids
  3. Glycerol (adipose tissue)

Not present in glycolysis

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7
Q

Glycerol enters gluconeogenesis as…

A

Dihydroxyacetone phosphate

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8
Q

The 3 irreversible reactions of glycolysis are…

A

Bypassed in gluconeogenesis by new steps/enzymes

7/10 Enzymes are the same

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9
Q

Pyruvate kinase reaction (irreversible) of glycolysis is bypassed by:

A
  • Pyruvate carboxylase
  • Phosphoenolpyruvate carboxykinase (PEP)
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10
Q

Step 1 of gluconeogenesis

A

Pyruvate carboxylated to oxaloacetate by pyruvate carboxylase (mitochondrial enzyme)

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11
Q

First step of gluconeogenesis occurs in the…

A

Mitochondrial matrix

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12
Q

Oxaloacetate is transported to the cytosol as…

A

Malate

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13
Q

Once reoxidized in the cytoplasm, oxaloacetate is decarboxylated and phosphorylated to…

A

PEP by PEP carboxykinase

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14
Q

In glycolysis, PFK controls the rate. What enzyme controls the rate of gluconeogenesis, bypassing the PFK reaction?

A

Fructose 1,6-bisphosphatase (FBPase)

*Allosteric enzyme that controls gluconeogenesis

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15
Q

Which enzyme is critical for free glucose levels?

A

Glucose 6-phosphatase

*Reverse of hexokinase

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16
Q

Free glucose is generated mainly in the…

A

Liver

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17
Q

Glucose 6-phosphatase is present only in…

A

Liver and kidney

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18
Q

Glucose 6-phosphate is hydrolyzed to ______ in the _______.

A

Glucose in the ER lumen

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19
Q

When glucose is abundant, which process will predominate?

A

Glycolysis

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20
Q

When glucose is scarce, which process will take over?

A

Gluconeogenesis

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21
Q

Both glycolysis and gluconeogenesis are highly _____ under cellular conditions.

A

Exergonic

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22
Q

When synthesizing glucose from pyruvate, __________ are spent.

A

6 high transfer-potential phosphoryl transfer groups (4 ATP and 2 GTP)

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23
Q

What is lactic acidosis?

A

Accumulation of lactic acid in the blood (lowers the pH) which is caused by a deficiency in gluconeogenic enzymes

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24
Q

What is hypoglycemia?

A

Low blood glucose levels

-Liver cannot produce glucose to maintain normal glucose levels

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25
Gluconeogenesis and glycolysis are...
Coordinated
26
Rate of glycolysis is determined by...
Glucose concentration
27
Rate of gluconeogenesis is dependent on...
Lactate concentration and other precursors
28
When high levels of AMP...
Low energy Glycolysis turned on Gluconeogenesis turned off (AMP stimulates PFK, but inhibits Fructose 1,6-bisphosphatase)
29
When high levels of ATP...
High energy Turn off glycolysis (Citrate inhibits PFK)
30
Citrate is an activator of ________ and promotes \_\_\_\_\_\_\_\_.
Fructose 1,6-bisphosphatase and promotes gluconeogenesis
31
Pyruvate carboxylase - what activates/inhibits?
Activated by ADP Inhibited by acetyl CoA
32
PEP carboxykinase is inhibited by...
ADP
33
If ATP is required, ________ predominates.
Glycolysis
34
If glucose is required, ________ is favored.
Gluconeogenesis
35
Blood glucose levels regulate glycolysis and gluconeogenesis in _____ by changing \_\_\_\_\_\_\_.
Liver Fructose 2,6-bisphosphate levels
36
Fructose 2,6-bisphosphatase is an ________ and stimulates \_\_\_\_\_\_\_. Also inhibits \_\_\_\_\_\_\_\_\_\_.
Allosteric regulator Stimulates PFK Inhibits Fructose1,6-bisphosphatase
37
At high blood glucose levels, fructose 2,6-bisphosphate levels \_\_\_\_\_.
Increase
38
When blood glucose levels are low, fructose 2,6-bisphosphate is converted to...
Fructose 6-phosphate
39
PFK2 and FBPase2 are present in a single polypeptide chain. This is a ________ enzyme with three domains. What are they?
Bifunctional enzyme Domains: N-terminal regulatory, kinase and phosphatase
40
PFK2 and FBPase2 are controlled ________ by ________ of a single serine residue.
Reciprocally by phosphorylation
41
Phosphorylation activates _____ and inhibits _____ to turn off \_\_\_\_\_\_\_.
FBPase 2 activated PFK2 inhibited Turns off glycolysis
42
When glucose is scarce, _______ levels rise in the blood and trigger a cascade of _______ to activate \_\_\_\_. Which process is active? (Glycolysis/Gluconeogenesis)
Glucagon levels rise, trigger cyclic AMP and activate PKA Gluconeogenesis is active
43
When glucose is abudant, the enzyme becomes dephosphorylated, which activates _______ and inhibits \_\_\_\_\_\_\_\_. Which process is active? (Glycolysis/Gluconeogenesis)
Activates PFK2 Inhibits FBPase2 Glycolysis is active
44
Insulin levels rise after each meal in response to \_\_\_\_\_\_\_\_\_\_. Insulin promotes \_\_\_\_\_\_\_.
Increasing blood glucose levels Promotes glycolysis
45
Glucagon levels rise during ______ when glucose is \_\_\_\_\_. This promotes...
Fasting when glucose is scarce This promotes gluconeogenesis
46
Insulin normally inhibits \_\_\_\_\_\_\_. In type 2 diabetes, insulin \_\_\_\_\_\_\_\_\_. This condition is called \_\_\_\_\_\_\_\_\_\_.
Inhibits gluconeogenesis Insulin fails to do this in type 2 diabetes. This is called insulin resistance. (Liver does not react to insulin, it just keeps making glucose, even if starving)
47
What two factors enhance insulin sensitivity?
Exercise and diet
48
What is the Cori cycle?
**Lactate** produced by muscle during contraction is released into the blood. \*Interrelationship between liver and muscle _Liver_ removes the **lactate**, converts to glucose via gluconeogenesis which is released into the blood and taken up by _muscle_.
49
What are the 3 major factors that control glycolysis and gluconeogenesis?
1. ATP levels 2. Citrate 3. Blood glucose levels
50
Glycolysis: * Major control point * Fructose 2,6-bisphosphate * AMP * Citrate * Hormonal activation by
* PFK * Activates * Activates * Inhibits * Insulin
51
Gluconeogenesis: * Major control point * Fructose 2,6-bisphosphate * AMP * Citrate * Hormonal activation by
* FBPase * Inhibits * Inhibits * Activates * Glucagon
52
The hexokinase reaction of glycolysis is bypassed during gluconeogenesis by the enzyme:
Glucose 6-phosphatase
53
Which of the following molecules is NOT a precursor for gluconeogenesis?
Acetyl CoA
54
Which enzyme controls the rate of gluconeogenesis?
Fructose 1,6-bisphosphatase
55
Deficiencies in enzymes specific for gluconeogenesis lead to:
Lactic acidosis and hypoglycemia
56
When blood glucose levels are high, insulin activates _______ and stimulates \_\_\_\_\_\_\_.
Activates protein phosphatase-1; glycogen synthesis
57
Which enzyme converts pyruvate to oxaloacetate in gluconeogenesis?
Pyruvate carboxylase
58
Which compound is NOT a precursor for the synthesis of glucose by gluconeogenesis?
Acetyl CoA
59
Which enzyme controls the rate of gluconeogenesis?
Fructose 1,6-biphosphatase
60
Deficiencies in enzymes specific for gluconeogenesis lead to:
Lactic acidosis and hypoglycemia
61
What type of glycosidic bond causes the branching of glycogen?
alpha 1,6-glycosidic bond
62
Glycogen phosphorylase cleaves glycogen and produces:
Glucose 1-phosphate
63
When blood glucose levels are high, insulin activates\_\_\_\_\_\_\_\_\_\_\_\_ and stimulates \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.
Protein phosphatase-1; glycogen synthesis
64
Which enzyme is specific for the gluconeogenesis pathway?
Phosphoenolpyruvate carboxykinase
65
The enzyme _______________ controls the rate of gluconeogenesis and is allosterically inhibited by high levels of \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.
Fructose 1,6-bisphosphatase; fructose 2,6-bisphosphate
66
Glucagon ________________ glycogen degradation and signals the __________ state.
stimulates; fasted
67
Which enzyme is NOT specific for gluconeogenesis?
Phosphoglycerate mutase
68
. Gluconeogenesis occurs in the ____________ and is activated during \_\_\_\_\_\_\_\_\_\_\_\_\_\_.
Liver; starvation

Biochemistry Exam 2 (10 decks)

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