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Carb Metabolism Flashcards

(46 cards)

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1
Q

What is the main function of the citric acid cycle?

A

The catabolism of acetyl-CoA to CO2 and H2O with generation of ATP.

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2
Q

What are the alternative names for the citric acid cycle?

A
  • Krebs cycle * Tricarboxylic acid (TCA) cycle
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3
Q

Where do the reactions of the citric acid cycle occur?

A

In the mitochondrial matrix.

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4
Q

What is the significance of the conversion of pyruvate to acetyl-CoA?

A

It links the glycolytic pathway with the citric acid cycle and is an irreversible step.

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5
Q

What happens to pyruvate under aerobic conditions?

A

It is converted to acetyl-CoA, which enters the TCA cycle.

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6
Q

What is the pyruvate dehydrogenase complex (PDH)?

A

A multi-enzyme complex that converts pyruvate to acetyl-CoA.

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7
Q

Name the three component enzymes of the PDH complex.

A
  • Pyruvate dehydrogenase * Dihydrolipoyl transacetylase * Dihydrolipoyl dehydrogenase
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8
Q

What is the total ATP generated per turn of the citric acid cycle?

A

10 ATP.

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9
Q

What are the coenzymes required for the pyruvate dehydrogenase complex?

A
  • Thiamine pyrophosphate (TPP) * Coenzyme A (CoA) * FAD * NAD+ * Lipoic acid
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10
Q

What is the role of oxaloacetate in the citric acid cycle?

A

It acts as a catalyst and is an important junction point in metabolism.

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11
Q

What is the amphibolic role of the TCA cycle?

A

It serves both catabolic and anabolic functions.

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12
Q

What is gluconeogenesis?

A

The synthesis of glucose from non-carbohydrate precursors.

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13
Q

What is glycolysis?

A

The oxidation of glucose to pyruvate and lactate.

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14
Q

What is the primary site of carbohydrate digestion?

A

Mouth and small intestine.

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15
Q

What enzyme initiates carbohydrate digestion in the mouth?

A

Salivary alpha amylase.

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16
Q

What is the significance of glycolysis in erythrocytes?

A

It is the only source of energy.

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17
Q

What are glucose transporters (GLUT)?

A

Proteins that facilitate glucose uptake in cells.

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18
Q

What is the main role of GluT4?

A

Insulin-mediated glucose uptake in muscle and adipose tissues.

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19
Q

Fill in the blank: The principal sites of carbohydrate digestion are the ______ and the small intestine.

20
Q

What are the two mechanisms responsible for the absorption of monosaccharides?

Study These Flashcards
A
  • Active transport * Facilitative transport
21
Q

What type of enzyme is hexokinase?

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A

An allosteric enzyme.

22
Q

True or False: Pyruvate kinase is activated by ATP.

23
Q

What is the net ATP generation from glycolysis under anaerobic conditions?

24
Q

What are the major metabolic pathways of carbohydrates?

Study These Flashcards
A
  • Glycolysis * Citric acid cycle * Gluconeogenesis * Glycogenesis * Glycogenolysis * Hexose monophosphate shunt * Uronic acid pathway * Galactose metabolism * Fructose metabolism
25
What inhibits citrate synthase in the TCA cycle?
Excess of ATP, NADH, and succinyl-CoA.
26
What is the role of anaplerotic reactions in the TCA cycle?
To replenish cycle intermediates.
27
What is the main function of SGluT-1, SGluT-2, GLUT-1, GLUT-2, GLUT-3, and GLUT-4?
They mediate the transport of carbohydrates ## Footnote These transporters facilitate the movement of glucose across cell membranes.
28
What type of enzyme is hexokinase?
Allosteric enzyme ## Footnote It is inhibited by its product, glucose-6-phosphate.
29
What activates Phosphofructokinase-I?
Fructose-6-phosphate, AMP, Fructose 2,6-bisphosphate ## Footnote These activators signal a low energy state.
30
What inhibits Phosphofructokinase-I?
Citrate, c-AMP, ATP ## Footnote These inhibitors indicate a high energy state.
31
What is the effect of insulin on Phosphofructokinase-I?
Increases its synthesis ## Footnote It decreases in response to glucagon.
32
What is the first step of glycolysis?
Glucose is phosphorylated to glucose-6-phosphate by hexokinase or glucokinase ## Footnote ATP is required as a phosphate donor.
33
What are the differences between hexokinase and glucokinase?
Hexokinase: high affinity for glucose, present in extra-hepatic tissue, not affected by insulin Glucokinase: low affinity for glucose, present in liver, inducible by insulin ## Footnote Hexokinase ensures glucose supply, while glucokinase removes glucose from blood.
34
What causes muscle cramps during strenuous exercise?
Lactate accumulation ## Footnote The body utilizes Cori’s cycle to manage lactate levels.
35
What is the Cori cycle?
A process where glucose is converted to lactate in muscle, and lactate is reconverted into glucose in the liver ## Footnote This helps recycle lactate produced during anaerobic conditions.
36
What are the key enzymes involved in the regulation of glycolysis?
Hexokinase, Phosphofructokinase-I, Pyruvate kinase ## Footnote These enzymes catalyze irreversible steps in glycolysis.
37
What is substrate level phosphorylation?
A reaction process that traps energy directly from the substrate ## Footnote It does not involve electron transport chain reactions.
38
What is oxidative phosphorylation?
Energy is trapped by oxidation of NADH and FADH to produce ATP ## Footnote This process occurs in the mitochondria.
39
What is produced from pyruvate under anaerobic conditions?
Lactate ## Footnote This reaction is catalyzed by lactate dehydrogenase (LDH).
40
What did Carl Cori and Gerty Cori describe?
Lactic acid cycle or Cori’s cycle ## Footnote They were awarded a Nobel Prize in 1947 for this work.
41
What is the role of phosphohexose isomerase in glycolysis?
Converts glucose-6-phosphate to fructose-6-phosphate ## Footnote This involves isomerization and is a freely reversible reaction.
42
What is the significance of Phosphofructokinase-I in glycolysis?
It is a regulatory enzyme that catalyzes an irreversible step ## Footnote This step is crucial for controlling the flux through glycolysis.
43
What two three-carbon compounds are produced from the cleavage of fructose-1,6-bisphosphate?
Glyceraldehyde-3-phosphate and dihydroxyacetone phosphate (DHAP) ## Footnote DHAP is isomerized to glyceraldehyde-3-phosphate.
44
What happens in the oxidation of glyceraldehyde-3-phosphate?
It is converted to 1,3-bisphosphoglycerate by glyceraldehyde-3-phosphate dehydrogenase ## Footnote This reaction is NAD dependent and reversible.
45
What enzyme catalyzes the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate?
Phosphoglycerate kinase ## Footnote This step generates ATP at substrate level phosphorylation.
46
What inhibits enolase?
Fluoride ## Footnote This property can be used to prevent glycolysis in blood prior to glucose estimation.

Biochemistry (1 decks)

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