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Block 3 Week 1 Meg > Valencik: Carbohydrate metabolism II > Flashcards

Valencik: Carbohydrate metabolism II Flashcards

1
Q

Pyruvate has four fates: Through transamination, it can generate what?

A

alanine

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2
Q

Pyruvate has four fates: Through carboxylation, it can generate what?

A

OAA

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3
Q

Pyruvate has four fates: Through oxidative decarboxylation, it can generate what?

A

Acetyl-CoA

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4
Q

Pyruvate has four fates: Through reduction, it can generate what?

A

Lactate

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5
Q

What reaction does pyruvate dehydrogenase catalyze?

A

Pyruvate + NAD+ + CoA-SH –> Acetyl-CoA + NADH + CO2

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6
Q

Pyruvate diffuses through the pores in the outer mitochondrial membrane and is transported across the inner mitochondrial membrane into the (blank), where it is oxidatively decarboxylated to (blank).

A

mitochondrial matrix; acetyl-CoA

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7
Q

Pyruvate dehydrogenase catalyzes an irreversible reaction. What kind of reaction is this considered?

A

an oxidative decarboxylation

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8
Q

What kind of dehydrogenase is pyruvate DH?

A

an alpha-ketoacid dehdrogenase

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9
Q

3 catalytic enzymes of the PDH complex

A 
E1 = pyruvate dehydrogenase
E2 = DLTA
E3 = DLDH
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10
Q

5 coenzymes of the PDH complex

A 
TPP
CoA
NAD+
FAD+
Lipoamide
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11
Q 
What vitamins do these coenzymes require?
TPP
CoA
NAD
FAD
Lipoamide
A 
TPP --> thiamine (B1)
CoA --> Panthothenic acid (B5)
NAD --> Niacin (B3)
FAD --> Riboflavin (B2)
Lipoamide --> none
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12
Q

TPP is the coenzyme form of what?

A

Vitamin B1

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13
Q

Lipoamide is required for which catalytic enzyme? It is a carrier of what?

A

E2; an acetyl group

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14
Q

Which catalytic enzyme requires CoA?

A

DLTA

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15
Q

NAD and FAD are required for what catalytic enzyme?

A

DLDH

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16
Q

NAD+ functions in (blank) transfers, while FAD functions in (blank) transfers.

A

hydride; electron

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17
Q

How is the pyruvate dehydrogenase complex regulated? When is it active vs. inactive?

A

Regulated by phoshorylation; INACTIVE when phosphorylated

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18
Q

Beriberi is caused by a deficiency in this amino acid.

A

A deficiency in thiamine

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19
Q

Complete glucose oxidation begins where and ends where?

A

Begins in cytoplasm and ends in mitochondria

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20
Q

What molecule is the GATEWAY to oxidative metabolism of the food we eat?

A

Acetyl-CoA

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21
Q

How many NADH and FADH2 are generated for each turn of the TCA cycle?

A

3; 1

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22
Q

What is the limiting substrate of the TCA cycle?

A

OAA

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23
Q

3 blood glucose sources

A

Food
Glycogen degradation
Gluconeogenesis

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24
Q

What three things can gluconeogenesis produce glucose from?

A

amino acids, lactic acid, and glycerol

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25
Discuss the Cori cycle.
Lactate enters the liver and is converted to glucose, which can then be transported to RBCs and back to lactate.
26
Both of these cycles rely on gluconeogenesis in liver followed by delivery of glucose and its use in a peripheral tissue.
Cori cycle | Alanine cycle
27
What are the 3 irreversible steps of glycolysis?
Glucokinase PFK1 Pyruvate Kinase
28
2 enzymatic steps that take pyruvate back to PEP
1. pyruvate carboxylase | 2. PEP carboxykinase
29
What is the enzyme that takes F1,6BP back to F6P?
Fructose 1,6 Bisphosphatase (F1,6BPase)
30
What is the enzyme that takes G6P back to glucose?
Glucose 6 phosphatase
31
Where does the rxn catalyzed by pyruvate carboxylase occur?
In the mito
32
Where does the rxn catalyzed by PEP carboxykinase occur?
In the cytosol or in the mito
33
Where does the rxn catalyzed by Fructose 1,6 BPase occur?
In the cytosol
34
Where does the rxn catalyzed by Glucose 6 phosphatase occur?
In the ER
35
Pyruvate carboxylase take pyruvate to what intermediate? What cofactor is it dependent on? What does this reaction require?
OAA; Biotin; ATP
36
The second reaction in converting OAA back to PEP involves what enzyme? What does this reaction require?
PEP carboxykinase; GTP
37
What is the first bypass in gluconeogenesis?
Taking pyruvate back to PEP through a two step reaction
38
What is the second bypass in gluconeogenesis? What enzyme is required?
Taking F-1,6,BP to F6P; F-1,6BPase
39
What is the third bypass in gluconeogenesis? What enzyme is required?
Taking G6P to to glucose; G6Pase
40
Lactate generates (blank) when it is converted to Pyruvate, therefore there is no net loss of (blank) in gluconeogenesis from Lactate
NADH
41
Is it "cheaper" to make glucose from lactate or pyruvate?
From lactate, because you generate 2 NADH to cancel out the 2 NADH lost
42
How does ATP affect pyruvate kinase?
inhibits it
43
How does acetyl-CoA affect pyruvate carboxylase?
activates it
44
How do citrate and ATP affect F1,6BPase?
activate it
45
How do citrate and ATP affect PFK1?
inhibit it
46
Does F-2,6-BP inhibit or activate glycolysis? Does it inhibit or activate gluconeogenesis?
activates glycolysis, by stimulating PFK1 | inhibits gluconeogenesis by blocking F-1,6-BPase
47
What activates pyruvate kinase? What inhibits it?
F-1,6-BP; ATP, alanine, phosphorylation
48
What activates pyruvate carboxylase? What inhibits it?
Acetyl-CoA; ADP
49
What activates PFK1? What inhibits it?
F2,6BP; ATP, citrate
50
What activates F-1,6-BPase? What inhibits it?
ATP and citrate; F-2,6-BP
51
What does glucagon/epinephrine do to blood glucose levels?
Increases them
52
What does insulin do to blood glucose levels
Decreases
53
Describe the G-protein coupled receptor signaling that occurs with glucagon/epinephrine
``` Hormone binds receptor. GDP is released → GTP binds. Gα translocates to adenylate cyclase. cAMP is generated. Protein kinase A is ACTIVATED. Regulated proteins get phosphorylated. ```
54
What does glucagon do to pyruvate kinase? What effect does this have? What affect does this have on glycolysis?
phosphorylates it; inactivates it; turns glycolysis off
55
In the presence of insulin, which way does the following reaction go? F6P F-2,6-BP
To the right; insulin means there is plenty of blood glucose
56
In the presence of glucagon, which way does the following reaction go? F6P F-2,6-BP
To the left; glucagon signals fasting, so it will not want to produce F-2,6-BP because that activates further glycolysis. Need to store glucose!
57
In the presence of glucagon, what enzyme is phosphorylated so that it stops producing F-2,6-BP?
PFK2-F2,6BPase
58
A bifunctional enzyme with both kinase and phosphatase activity
PFK2-F2,6BPase
59
Stimulate gluconeogenesis by inducing the synthesis of gluconeogenic enzymes.
glucocorticoids
60
Besides carbohydrates, what else can be used to make glucose?
``` Lactate Alanine and some other AAs (not leucine or lysine) OAA Glycerol Odd chain fatty acids ```
61
Describe the steps in ethanol degradation
Ethanol --> Acetaldehyde --> Acetate --> Acetyl-CoA
62
What enzyme takes ethanol to acetaldehyde? Where does this reaction occur?
Alcohol dehydrogenase; in the cytoplasm
63
What enzyme takes acetaldehyde to acetate? Where does this step occur?
Aldehyde dehydrogenase; in the mito
64
What enzyme takes acetate to acetyl-CoA? Where does this step occur?
Acetyl-CoA synthase; mito or cytoplasm
65
What is the rate limiting step of alcohol metabolism?
Alcohol dehydrogenase
66
What step in the pathway of alcohol metabolism does antabuse block?
acetaldehyde --> acetate
67
Alcohol can be converted into one of two things
1. ketones | 2. fatty acids
68
In the liver, acetate is converted to Acetyl-CoA and ketones are made. What is an example of a ketones that can be generated?
alpha-3-hydroxybutyrate
69
Ketones cannot be metabolized by the liver and do what to the plasma pH?
decrease it leading to acidosis
70
Ethanol disrupts the metabolism of which two vitamins?
Vitamin A | Thiamine (Vit B1)
71
3 stages of liver damage
1. Fatty liver from increased TAG synthesis 2. Alcohol hepatitis 3. Cirrhosis
72
What is the major gluconeogenic organ?
Liver
73
The cori cycle and the alanine cycle both depend on gluconeogenesis in the (blank) followed by delivery of glucose and its use in a peripheral tissue
liver
74
A defect in glucose 6 phosphatase can cause this disease
von Gierke's disease
75
What converts alanine to pyruvate?
a transaminase
76
What converts lactate to pyruvate?
lactate dehydrogenase
77
Competitive inhibitor of F-1,6-BPase
F-2,6-BP
78
This enzyme of glycolysis is less activate when phosphorylated.
pyruvate kinase

Block 3 Week 1 Meg (17 decks)

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