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biochem > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

Name the stages of cellular respiration

A
  1. Glycolysis
  2. Citric Acid Cycle
  3. Electron Transport Chain
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2
Q

Glycolysis is an [anabolic/catabolic] reaction.

A

catabolic

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3
Q

Where does glycolysis take place?

A

In the cytoplasm

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4
Q

What is the only source of energy for red blood cells?

A

glycolysis

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5
Q

How is ATP generated from glucose in glycolysis?

A

By substrate-level phosphorylation

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6
Q

How does glucose enter cells?

A
  • Na+-monosaccharide co-transporter system (SGLT1)

- Na+-independent, facilitated diffusion transport system (GLUT-1 to GLUT-14)

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7
Q

GLUT2 is a [high/low] affinity transporter.

A

low

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8
Q

Where is GLUT2 found?

A

in hepatocytes

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9
Q

When the glucose concentration drops below Km for GLUT2, what happens to much of the remainder of glucose?

A

It leaves the liver and enters the peripheral circulation

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10
Q

Do skeletal muscles have the enzyme that converts glucose 6-phosphate to glucose?

A

no

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11
Q

What serves as the glucose sensor for insulin release?

A

GLUT-2 and glucokinase (found in the β-islet cells of the pancreas)

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12
Q

What happens in the first phase of glycolysis?

A

First phase converts glucose to 2 glyceraldehyde 3-phosphate

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13
Q

What happens in the second phase of glycolysis?

A

Second phase produces 2 pyruvate

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14
Q

How many ATP molecules are invested in generating phosphorylated intermediates? (first phase)

A

2 ATP

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15
Q

Second phase of glycolysis generates how many ATP molecules?

A

4 ATP

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16
Q

Which two very high energy phosphate intermediates are involved in the second phase of glycolysis?

A
  • 1,3 bisphosphoglycerate (1,3BPG)

- Phosphoenolpyruvate (PEP)

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17
Q

1,3-BPG can be converted to?

A

2,3-BPG

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18
Q

What are the 3 regulated steps of glycolysis? And what enzymes do they involve?

A
  • Steps 1,3, and 10

- Hexokinase, phosphofructokinase, and pyruvate kinase

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19
Q

What converts glucose into glucose-6-phosphate allowing “trapping” inside cell?

A

hexokinase

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20
Q

The feedback of hexokinase is inhibited by?

A

glucose-6-phosphate

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21
Q

Why does the feedback inhibition by glucose 6-phosphate product not apply to glucokinase in the liver and pancreas?

A

Because we need to accumulate or store glucose! Glycogen synthesis needs glucose-6-phosphate.GLUTs cant help out with glucose-6-phosphate

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22
Q

Why waste time phosphorylating glucose?

A

Because the plasma membrane generally lacks transporters for phosphorylated sugars, the phosphorylated glycolytic intermediates cannot leave the cell.

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23
Q

What happens when you have excess glucose?

A

It will accumulate in form of glycogen inside the liver

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24
Q

Does the liver normally use glucose as fuel?

A

no

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25
Q

What is the function of glucokinase in the liver?

A

To phosphorylate glucose to reduce hyperglycemia

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26
Q

Why is glucokinase induced by insulin?

A

To store glucose in liver after a meal

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27
Q

What is the function of glucokinase in β cells of pancreas?

A

Glucokinase functions as blood glucose sensor and release insulin accordingly

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28
Q

Glucokinase is mutated in the rare form of diabetes called?

A

Maturity Onset Diabetes of the Young type 2 (MODY2)

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28
Q

Glucokinase is mutated in the rare form of diabetes called?

A

Maturity Onset Diabetes of the Young type 2 (MODY2)

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28
Q

Glucokinase is mutated in the rare form of diabetes called?

A

Maturity Onset Diabetes of the Young type 2 (MODY2)

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29
Q

Hexokinase has [low/high] Km and [low/high] Vmax

A

low, low

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30
Q

What is the effect of hexokinase having low Vmax?

A

It cannot phosphorylate more sugars than the cell can use

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31
Q

Hexokinase is inhibited by?

A

glucose-6-phosphate

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32
Q

Glucokinase has [low/high] Km and [low/high] Vmax

A

high, high

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33
Q

What is the effect of hexokinase having low Km?

A

Higher affinity for glucose, which permits the efficient metabolism of glucose even when tissue concentrations of glucose are low

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34
Q

What is the effect of glucokinase having high Km?

A

Lower affinity for glucose, functions only when the intrahepatic glucose concentration is high

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35
Q

What is the effect of glucokinase having high Vmax?

A

Allowing the liver to effectively remove glucose minimizing hyperglycemia during the absorptive period

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36
Q

Glucokinase is activated by?

A

insulin

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37
Q

Where is hexokinase found?

A

In all cells

38
Q

What prevents glucose-6-phosphate from diffusing across the plasma membrane?

A

the negative charge

39
Q

What is the most important control point in glycolysis?

A

Step 3 which uses phosphofructokinase

40
Q

___________ is both the rate-limiting step and the committed step for glycolysis.

A

Step 3

41
Q

PFK-1 is activated by?

A
  • AMP

- Fructose 2,6-bisphosphate

42
Q

PFK-1 is inhibited by?

A
  • ATP

- Citrate

43
Q

Fructose 2,6-bisphosphate is synthesized by?

A

Phosphofructokinase-2 (PFK-2)

44
Q

Levels of fructose 2,6-bisphosphate are [increased/decreased] in the well-fed state.

A

increased

45
Q

Levels of fructose 2,6-bisphosphate are [increased/decreased] in the starvation state.

A

decreased

46
Q

What is the hormone that is released in well-fed state?

A

insulin

47
Q

The formation of _________ is a positive effector for enzymes so it will stimulate the enzyme PFK-1.

A

fructose 2,6-bisphosphate

48
Q

What activates PFK-2?

A

insulin

49
Q

PFK-2 is found where?

A

only in the liver

50
Q

F2,6-BP activates _______.

A

PFK-1

51
Q

What inhibits PFK-2?

A

glucagon

52
Q

Insulin stimulates PFK-1 to form _______ which is the stimulator for glycolysis

A

F2,6-BP

53
Q

What level of phosphorylation occurs in the final step of glycolysis?

A

second substrate level phosphorylation

54
Q

The final step of glycolysis is activated by?

A

fructose 1,6-bisphosphate

55
Q

Pyruvate kinase deficiency results in?

A

Decreased ATP generation

56
Q

An inability to maintain Na+/K+ ATPase leads to _________.

A

RBC swelling and RBC lysis: hemolytic anemia

57
Q

What causes a decrease in O2 affinity of hemoglobin?

A

increase in 2,3-BPG

58
Q

Are there Heinz bodies in pyruvate kinase deficiency?

A

no

59
Q

_________ impairs glycolysis in all cells, but most acute effect on RBCs.

A

inherited deficiency of pyruvate kinase

60
Q

Embryonic death occurs when there is a [deficiency/complete loss] of pyruvate kinase activity.

A

complete loss

61
Q

Synthesis of enzymes is controlled by?

A

hormones

62
Q

High levels of insulin [activate/inhibit] enzyme synthesis.

A

activate

63
Q

High levels of glucagon [activate/inhibit] enzyme synthesis.

A

inhibit

64
Q

What is the role of glyceraldehyde 3-phosphate dehydrogenase?

A

It converts D-glyceraldehyde 3-phosphate into 1,3-bisphosphoglycerate.

65
Q

The conversion of D-glyceraldehyde 3-phosphate into 1,3-bisphosphoglycerate is which reaction number?

A

Reaction number 6

66
Q

Where is the phosphate coming from?

A

It is an inorganic phosphate added to the substrate by oxidation-reduction reaction.

67
Q

Why do we need to add this inorganic phosphate?

A

Because we need energy

68
Q

Which enzyme transfers the high-energy phosphate from substrate to ADP?

A

3-Phosphoglycerate kinase

69
Q

What is the name of the enzyme that catalyzes first substrate-level phosphorylation in glycolysis?

A

3-Phosphoglycerate kinase

70
Q

What is the name of the enzyme that catalyzes second substrate-level phosphorylation in glycolysis?

A

Pyruvate kinase

71
Q

Lactate is formed from pyruvate under [anaerobic/aerobic] conditions.

A

anaerobic

72
Q

Pyruvate is oxidized into Acetyl-CoA under [anaerobic/aerobic] conditions.

A

aerobic

73
Q

The fate of pyruvate depends on?

A

oxygen availability

74
Q

What happens to pyruvate under aerobic conditions?

A

Pyruvate is oxidized to acetyl-CoA which enters the Krebs cycle

75
Q

What happens to pyruvate under anaerobic conditions?

A

Pyruvate is reduced in order to oxidize NADH back to NAD+ (as an alternative to electron transport chain)

76
Q

State the fates of pyruvate

A

Fate 1: Oxidative decarboxylation of pyruvate
Fate 2: Reduction of pyruvate to lactate (Anaerobic Condition) in human
Fate 3: Alcohol fermentation in bacteria and yeast

77
Q

In the mitochondrial matrix, pyruvate is converted to acetyl CoA by _________ [AEROBIC CONDITIONS]

A

pyruvate dehydrogenase complex

78
Q

________ and _______ will inhibit the oxidative decarboxylation of pyruvate.

A

Acetyl-CoA and NADH

79
Q

Pyruvate dehydrogenase requires how many coenzymes?

A

5 coenzymes

80
Q

Cofactors and coenzymes used by pyruvate dehydrogenase include?

A
  • Thiamine pyrophosphate (TPP) from the vitamin thiamine
  • Lipoic acid
  • Coenzyme A (CoA) from pantothenate
  • FAD(H2) from riboflavin
  • NAD(H) from niacin (some may be synthesized from tryptophan)
81
Q

What is the final product of anaerobic glycolysis in eukaryotic cells?

A

lactate

82
Q

_______ reduces pyruvate to lactate.

A

lactate dehydrogenase

83
Q

The formation of lactate is the major fate for pyruvate in what parts of the body?

A

in lens and cornea of the eye, kidney medulla, testes, leukocytes and red blood cells (all are poorly vascularized and/or lack mitochondria)

84
Q

________ is a type of metabolic acidosis.

A

lactate accumulation

85
Q

Explain lactate formation in muscles

A
  • During intense exercise, lactate accumulates in muscles, causing a drop in the intracellular pH, potentially resulting in cramps
  • Much of this lactate eventually diffuses into the bloodstream, and can be used by the liver to make glucose
86
Q

When does lactic acidosis occur?

A

when there is a collapse of the circulatory system, such as in myocardial infarction, pulmonary embolism, and uncontrolled hemorrhage

87
Q

The failure to bring adequate amounts of oxygen to the tissues results in _________ and _________.

A

impaired oxidative phosphorylation and decreased ATP synthesis

88
Q

Alcohol fermentation occurs in?

A

in yeast and some bacteria

89
Q

Alcohol fermentation is an [anaerobic/aerobic] reaction.

A

anaerobic

90
Q

In alcohol fermentation, pyruvate is converted to?

A

ethanol and CO2

91
Q

Aerobic metabolism of glucose produces ______ net ATP via malate-aspartate shuttle.

A

32

92
Q

Anaerobic glycolysis produces _______ net ATP per glucose molecule.

A

2

93
Q

Arsenic causes glycolysis to produce ____ net ATP.

A
93
Q

Arsenic causes glycolysis to produce ____ net ATP.

A

0

biochem (8 decks)

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