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Biochemistry > Carbohydrate Metabolism > Flashcards

Carbohydrate Metabolism Flashcards

1
Q

Where does glycolysis occur?

A

In the Cytosol of all mammalian cells

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2
Q

What is the substrate in glycolysis?

A

Glucose

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3
Q

What are the end products in glycolysis?

A

2 molecules of either:
1. Pyruvate
2. Lactate

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4
Q

Name the rate limiting enzyme in glycolysis?

A

Phosphofructokinase-1

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5
Q

Metabolic Process that is promoted by insulin.

A

Glycogenesis

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6
Q

Metabolic pathway that is responsible for maintenance of a normal serum glucose concentration in a patient rescued from being trapped under rubble in a building for 4 days.

A

Gluconeogenesis

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7
Q

What is the reverse process of glycolysis?

A

Gluconeogenesis

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8
Q

The immediate donor of the phosphoryl group to ADP in the production of ATP during glucose metabolism in erythrocytes.

A

Phosphoenolpyruvate

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9
Q

Reaction that is unique to gluconeogenesis

A

Oxaloacetate phosphoenolpyruvate

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10
Q

What is the rate limiting enzyme of gluconeogenesis?

A

Fructose-1,6-biphosphatase

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11
Q

Differentiate Hexokinase vs Glucokinase

A

Hexokinase
1. Present in most tissues
2. Can phosphorylate glucose & other hexoses
3. Inhibited by glucose-6-P
4. Low km
5. Low Vmax
6. High affinity
Glucokinase
1. Present only in liver parenchymal cells, Islets cells of the pancreas
2. Can phosphorylate glucose & other hexoses
3. Inhibited by frucose-6-P
4. High Km
5. High Vmax
6. Low affinity

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12
Q

Identify the 2 steps in glycolysis which produce ATP via substrate level phosphorylation.

A
  1. 1,3-Biphosphoglycerate to 3-Phosphoglycerate
    (Enzyme: Phosphoglycerate kinase)
  2. Phosphoenolpyruvate to Pyruvate
    (Enzyme: Pyruvate kinase)
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13
Q

What is the end product of anaerobic glycolysis?

A

Lactate

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14
Q

1 NADH = ____ ATP

A

2.5 ATPs

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15
Q

1 FADH2 = _______ ATP

A

1.5 ATP

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16
Q

Malate aspartate shuttle is primarily seen in which tissues?

A

Heart muscles & Most tissues

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17
Q

What enzyme joins monosaccharides to form a disaccharide?

A

Glycosyltransferase

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18
Q

How does the cell ensure that the glucose taken by GLUT remains inside rather than diffusing back out?

A

Hexokinases irreversibly catalyze the phosphorylation of intracellular glucose to glucose 6-P

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19
Q

How does insulin signaling effect the activity of PFK-1?

A

Insulin signaling activates PFK-1 activity

20
Q

What is the significance of 2,3-BPG ?

A
  1. Important allosteric effector of Hb
  2. It decreases the affinity of Hb for Oxygen , thereby increasing O2 delivery to tissues
21
Q

Why does a deficiency in PDHC activity cause lactic acidosis?
( Pyruvate Dehydrogenase Complex)

A

Deficiency results to:
1. Rise in pyruvate
2. Upregulate other reactions of pyruvate metabolism such as reduction to lactate by NADH-requiring LDH leading to lactic acidosis

22
Q

Which Step in Citric Acid Cycle generates GTP?

A

Substrate -level phophorylation of GDP to GTP occuRs during the conversion of Succinyl coA to Succinate via cleavage of the high energy thioester bond in succinyl coA

23
Q

What are the major TCA cycle regulation sites?
What are the effectors?

A

The major sites of cycle regulation:
1.Citrate Synthase - Inh by Citrate, its product.
2. Isocitrate dehydrogenase - Inh by NADH & ATP; Activated by ADP & Calcium
3. Alpha-KGD Complex - Inh by NADH & Succinyl CoA ; Activated by Calcium

24
Q

What other substrates can be used in gluconeogenesis?

A
  1. Glycerol
  2. Pyruvate
  3. Alpha-keto acids generated by the degradation of glucogenic amino acids produced from muscle proteolysis
25
Q

Is gluconeogenesis an endergonic or exergonic process?

A

Endergonic - uses energy from ATP and GTP hydrolysis

26
Q

In what 2 tissues and in what subcellular locale is glycogen stored?

A

Glycogen a branched homopolymer of glucose is stored in the cytosol of liver and muscle cells primarily.

27
Q

What is the role of glucose 6- phosphatase in glycogenolysis?

A

hydrolyzes glucose 6-p in the liver and the kidneys, generating free glucose that enter the blood stream

28
Q

Is the rate of fructose metabolism faster or slower than of glucose?

A

Fructose metabolism is faster because it bypasses the key rate-limiting enzyme of glycolysis , PFK-1 .

29
Q

What is the fate of the ribulose 5-P product of the oxidative reactions?

A

The ribulose-P can be reversibly isomerized to ribose 5-P and used in Purine and Pyrimidine nucleotide synthesis & xylulose 5-P that is used in sugar interconversions.

30
Q

Andersen disease is a deficiency of which enzyme?

A

Branching enzyme

31
Q

Hers disease is a deficiency of which enzyme?

A

Liver phosphorylase

32
Q

Pompe Disease is deficiency of which enzyme?

A

Lysosomal acid maltase

33
Q

Enzyme deficient in a infant presenting with vomiting, night sweats, tremors after ingesting fruit juices with positive reducing sugar in urine but negative for glucose.

A

Aldolase B deficiency- Hereditary Fructose Intolerance

34
Q

Characteristics of this step in glycolysis catalyzedd by phosphofructokinase and gluconeogenesis by fructose-1,6-biphosphatase?

A

Phosphofructokinase is inhibited more or less completely by physiologic concentrations of ATP

35
Q

This is the most common disease producing enzyme abnormality in humans

A

Glucose-6-Phosphate Dehydrogenase Deficiency

36
Q

This transporter on the luminal side of enterocytes absorbs glucose or galactose.

A

SGLT1

37
Q

Effects of insulin on GLUT4 transporter resulting in reduced serum glucose ?

A

It promotes GLUT 4 mobilization to the plasma membrane

38
Q

Among the transporters, only which requires insulin?

A

GLUT-4

39
Q

This type of glucose transporter is found within the small intestine and spermatocytes.

A

GLUT-5

40
Q

Ability to produce lactose in breastmilk of a female with classic galactosemia due to GALT deficiency

A

Galactose can be produced from a glucose metabolite by EPIMERIZATION

41
Q

NADPH produced from the HMP shunt is needed in the ff pathways? (5)

A
  1. Reductive reactions for FA and steroid synthesis
  2. Reduction of glutathione
  3. NO synthesis
  4. Respiratory burst
  5. CYP 450 reactions
42
Q

Disease, cherry red spot on macula + (+) hepatosplenomegaly?

A

Nieman Pick - Sphingomyelinase deficiency

43
Q

Disease cherry red spots ; (-) hepatosplenomegaly

A

Tay sach’s : Hexosaminidase A

44
Q

Enzyme deficient in Gaucher’s ?

A

Glucocerebrosidase

45
Q

Enzyme deficient in Krabbe’s?

A

Galactocerebrosidase

Biochemistry (19 decks)

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