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

Valencik: Carbohydrate metabolism Flashcards

1
Q

What is the direction of a reaction dependent on?

A

Sum of free energies

The conc of [A] and [B]

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2
Q

What is the direction of a reaction regulated by?

A

Enzyme availability

Enzyme activity

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3
Q

Things that affect metabolism

A 
DNA
Hormones
Vitamins
Allosteric effectors
Epigenetics
Toxins
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4
Q

Ways to regulate enzymatic activity

A
  1. Alter amount of enzyme
  2. Alter availability
  3. Modulate activity
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5
Q

Main carbohydrate transported in humans?

A

Glucose

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6
Q

Roles of carbohydrate metabolism

A

Generate energy from glucose
Maintain blood glucose levels
Channel alternative monosaccharides into energy producing pathways
Synthesize biosynthetic monosaccharide precursors

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7
Q

Blood glucose sources

A

Food
Glycogen
Gluconeogenesis

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8
Q

Main source of glucose for the blood

A

Liver

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9
Q

What process converts glycogen to glucose?

A

Glycogenolysis

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10
Q

What process takes glucose to lactate?

A

Glycolysis

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11
Q

What process takes lactate to glucose?

A

Gluconeogenesis

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12
Q

What process takes glucose to glycogen?

A

Glycogenesis

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13
Q

Steps in glycolysis

A 
Glucose
G6P
Fructose6P
Fructose1,6BP
DAG + GAP
GAP-->1,3BPG
3PG
2PG
PEP
Pyruvate
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14
Q

Where is GLUT1 expressed? What is its function?

A

Expressed in most tissues; functions in basal glucose uptake

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15
Q

Where is GLUT2 expressed? What is its function?

A

Expressed in liver, intestine, pancreatic Beta cells; functions in high capacity glucose uptake

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16
Q

Where is GLUT3 expressed? What is its function?

A

Expressed in the brain; functions in neuronal glucose uptake

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17
Q

Where is GLUT4 expressed? What is its function?

A

Expressed in muscle, adipose tissue, and the heart; functions in insulin-dependent glucose uptake

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18
Q

Where is GLUT5 expressed? What is its function?

A

Expressed in the intestine; functions in fructose transport

19
Q

Is the first step in glycolysis (Glucose –> G6P) reversible?

A

No! The phosphate traps glucose in the cell!

20
Q

What enzyme takes G6P to F6P?

A

Phosphohexose isomerase

21
Q

What enzyme takes F6P to F1,6BP? What is unique about this step?

A

PFK; this is the committed step of glycolysis

22
Q

What takes F1,6BP to GAP and DHAP? This reaction is energetically unfavorable, so what drives it forward?

A

Aldolase; G3P is consumed right away

23
Q

What coenzyme does GAP to 1,3BPG require?

24
Q

What enzyme takes DHAP to G3P?

A

triose phosphate isomerase

25
What enzyme takes G3P to 1,3BPG? What coenzyme does this require? This reaction is unfavorable. What reaction is it coupled to?
G3P dehydrogenase; NAD+; 1,3BPG-->3PG which generates ATP
26
What enzyme takes 1,3BPG to 3PG? What is produced in this rxn?
PG kinase; ATP
27
What enzyme takes 3PG to 2PG?
PG mutase
28
What enzyme takes 2PG to PEP? What is lost in this reaction?
Enolase; H20
29
What enzyme takes PEP to pyruvate? What is produced in this reaction?
Pyruvate kinase; ATP
30
What pushes the pyruvate kinase reaction forward?
The tautomerism of the enol form to the keto form, which is more energetically favorable
31
Investment vs payoff of glycolysis
Invest 2 ATP | Net: 2 ATP + 2NADH
32
Lactate dehydrogenase takes pyruvate to lactate and regenerates what coenzyme for the G3P DH reaction?
NAD+
33
3 irreversible steps in glycolysis
1. Glucokinase (traps glucose inside of cell) 2. PFK (committed step, irreversible) 3. Pyruvate kinase
34
With lots of glucose present, you want to stimulate (blank), but with little glucose present, you want to inactivate (blank).
Glucokinase
35
PFK is stimulated by what effectors? When ATP is high what happens to PFK activity? When ATP is low what happens to PFK activity?
ATP and AMP; lower activity when ATP is high; higher activity when ATP is low
36
F6P can make what in the liver?
F2,6BP
37
What is F2,6BP?
An allosteric effector of PFK1 (takes F6P to F1,6BP)
38
What is an allosteric effector of pyruvate kinase?
F1,6BP
39
What is the most important modulator that turns on glycolysis?
F2,6BP, which activates PFK1, the committed step of glycolysis
40
Fluoride inhibits what enzyme in glycolysis?
Enolase
41
Arsenite poisons what enzyme in glycolysis?
Pyruvate DH
42
What toxin forms an unstable intermediate with G3P, resulting in no net ATP production?
Arsenate
43
What takes the place of 1,3BPG as the major phosphorylated intermediate in glycolysis in RBCs?
2,3BPG
44
What step in glycolysis is bypassed in RBCs after conversion of 1,3BPG to 2,3BPG?
1,3BPG --> 3PG, which generates an ATP

Block 3 Week 1 Meg (17 decks)

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