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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?

A

NAD+

24
Q

What enzyme takes DHAP to G3P?

A

triose phosphate isomerase

25
Q

What enzyme takes G3P to 1,3BPG? What coenzyme does this require? This reaction is unfavorable. What reaction is it coupled to?

A

G3P dehydrogenase; NAD+; 1,3BPG–>3PG which generates ATP

26
Q

What enzyme takes 1,3BPG to 3PG? What is produced in this rxn?

A

PG kinase; ATP

27
Q

What enzyme takes 3PG to 2PG?

A

PG mutase

28
Q

What enzyme takes 2PG to PEP? What is lost in this reaction?

A

Enolase; H20

29
Q

What enzyme takes PEP to pyruvate? What is produced in this reaction?

A

Pyruvate kinase; ATP

30
Q

What pushes the pyruvate kinase reaction forward?

A

The tautomerism of the enol form to the keto form, which is more energetically favorable

31
Q

Investment vs payoff of glycolysis

A

Invest 2 ATP

Net: 2 ATP + 2NADH

32
Q

Lactate dehydrogenase takes pyruvate to lactate and regenerates what coenzyme for the G3P DH reaction?

A

NAD+

33
Q

3 irreversible steps in glycolysis

A
  1. Glucokinase (traps glucose inside of cell)
  2. PFK (committed step, irreversible)
  3. Pyruvate kinase
34
Q

With lots of glucose present, you want to stimulate (blank), but with little glucose present, you want to inactivate (blank).

A

Glucokinase

35
Q

PFK is stimulated by what effectors? When ATP is high what happens to PFK activity? When ATP is low what happens to PFK activity?

A

ATP and AMP; lower activity when ATP is high; higher activity when ATP is low

36
Q

F6P can make what in the liver?

A

F2,6BP

37
Q

What is F2,6BP?

A

An allosteric effector of PFK1 (takes F6P to F1,6BP)

38
Q

What is an allosteric effector of pyruvate kinase?

A

F1,6BP

39
Q

What is the most important modulator that turns on glycolysis?

A

F2,6BP, which activates PFK1, the committed step of glycolysis

40
Q

Fluoride inhibits what enzyme in glycolysis?

A

Enolase

41
Q

Arsenite poisons what enzyme in glycolysis?

A

Pyruvate DH

42
Q

What toxin forms an unstable intermediate with G3P, resulting in no net ATP production?

A

Arsenate

43
Q

What takes the place of 1,3BPG as the major phosphorylated intermediate in glycolysis in RBCs?

A

2,3BPG

44
Q

What step in glycolysis is bypassed in RBCs after conversion of 1,3BPG to 2,3BPG?

A

1,3BPG –> 3PG, which generates an ATP

Block 3 Week 1 Meg (17 decks)

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