MIDTERM: GLYCOLYSIS

Question 1

• is the main pathway of glucose metabolism

Answer 1

GLYCOLYSIS

Question 2

importance of glycolysis:

Answer 2

• ## Energy Production

Question 3

• it occurs in the cytosol of all cells, and can function either aerobically or anaerobically , depending on the availability of oxygen and electron transport chain.

Answer 3

GLYCOLYSIS

Question 4

• results from various causes including impaired activity of pyruvate dehydrogenase , especially in thiamin deficiency

Answer 4

LACTIC ACIDOSIS

Question 5

end product of glycolysis

Answer 5

PYRUVATE

Question 6

The enzymes that catalyzes the phosphorylation of glucose to form glucose-6-phosphate in the first step of glycolysis. This is one of the main regulatory steps of this pathway.

Answer 6

HEXOKINASE

Question 7

• The function of __________ in the liver is to remove glucose from the hepatic portal blood following a meal, so regulating the concentration of glucose available to peripheral tissues.
• It is also found in pancreatic β-islet cells and it is used for glycogen synthesis and lipogenesis

Answer 7

GLUCOKINASE

Question 8

Glucose-6-phosphate is converted into fructose-6-phosphate by the enzyme ______________

Answer 8

PHOSPHOHEXOSE ISOMERASE

Question 9

Fructose-6-phosphate is further phosphorylated by the enzyme
__________ using ATP to form fructose-1,6-bisphosphate.

Answer 9

PHOSPHOFRUCTOKINASE (PHOSPHOFRUCTOKINASE -1 (PFK-1))

Question 10

Fructose-1,6-bisphosphate is split into two three-carbon molecules:
______________ &______________by the enzyme __________

Answer 10

• DIHYDROXYACETONE & GLYCERALDEHYDE - 3 - PHOSPHATE
• ALDOLASE

Question 11

Dihydroxyacetone phosphate is isomerized into another molecule of glyceraldehyde-3-phosphate by the enzyme __________.

Answer 11

TRIOSE PHOSPHATE ISOMERASE

Question 12

Each molecule of glyceraldehyde-3-phosphate is oxidized by ___________ producing NADH and converting an inorganic phosphate (Pi) into a high-energy phosphate group on 1,3-bisphosphoglycerate

Answer 12

GLYCERALDEHYDE - 3 - PHOSPHATE DEHYDROGENASE

Question 13

_________ then transfers the high-energy phosphate group from 1,3-bisphosphoglycerate to ADP, generating ATP and converting it into 3-phosphoglycerate.

Answer 13

PHOSPHOGLYCERATE KINASE

Question 14

3-Phosphoglycerate is converted into 2-phosphoglycerate through an isomerization reaction catalyzed by ___________

Answer 14

PHOSPHOGLYCERATE MUTASE

Question 15

At the end of glycolysis, one glucose molecule has been converted into ___ _molecules of pyruvate, and a net gain of_____ATP and____NADH molecules has been produced.

Answer 15

2 PYRUVATE
2 ATP
2 NADH

Question 16

Give the overall equation for glycolysis from glucose to lactate

Answer 16

Glucose + 2 ADP + 2 Pi→ 2 Lactate + 2 ATP + 2 H2O

Question 17

These three are markedly exergonic and must therefore be considered to be physiologically irreversible and major sites of regulation of glycolysis.

Answer 17

• HEXOKINASE
• PHOSPHOFRUCTOKINASE
• PYRUVATE KINASE

Question 18

• is the end product of glycolysis under ANAEROBIC conditions
  (eg, in exercising muscle) and in erythrocytes, where there are no
  mitochondria to permit further oxidation of pyruvate

Answer 18

LACTATE

Question 19

Glycolysis is regulated by three enzymes catalyzing non equilibrium reactions

Answer 19

• HEXOKINASE
• PHOSPHOFRUCTOKINASE
• PYRUVATE KINASE

Question 20

tissues that derived energy from glycolysis and produced lactate

Answer 20

• BRAIN
• GASTROINTESTINAL TRACT
• RENAL MEDULLA
• RETINA
• SKIN

Question 21

lactase production is also increased in ____________ and many cancers produce lactase

Answer 21

SEPTIC SHOCK

Question 22

organs that normally take up lactate

Answer 22

• LIVER
• KIDNEY
• HEART
  normally take up lactase,

Question 23

in aerobic glycolysis, how many ATP are produced total (this is including the ATP that NADH could go on to make)?

Answer 23

2

GROSS: 9
NET: 9-2 = 7

Question 24

glucose to glycogen

Answer 24

GLYCOGENESIS

Question 25

breakdown of glycogen to glucose

Answer 25

GLYCOGENOLYSIS

Question 26

formation of pyruvate from non-carbohydrate sources

Answer 26

GLUCONEOGENESIS

Question 27

the breakdown of glucose into pyruvate

Answer 27

GLYCOLYSIS

Question 28

is the synthesis of glycogen from glucose

Answer 28

GLYCOGENESIS

Question 29

is the breakdown of glycogen back into glucose for energy utilization

Answer 29

GLYCOGENOLYSIS

Question 30

Can glycolysis occur aerobically? Anaerobically? Under what conditions?

Answer 30

Glycolysis can function either aerobically or anaerobically depending on the AVAILABILITY OF OXYGEN and the ELECTRON TRANSPORT CHAIN (and hence of the presence of mitochondria).

Question 31

What is the enzyme that converts glucose to glucose-6-phosphate? How is this enzyme inhibited?

Answer 31

HEXOKINASE, it is allosterically inhibited by elevated concentrations of its product glucose 6-phosphate.

Question 32

Enolase is inhibited by what anticoagulant?

Answer 32

FLUORIDE.
Fluoride strongly inhibits the enzyme in the presence of inorganic phosphate. The inhibitory species is the fluorophosphate ion, which when bound to magnesium forms a complex with enolase and inactivates the enzyme.

Question 33

is the synthesis of glucose from non-carbohydrate precursors (such as lactate, amino acids, and glycerol). It is the reverse process of glycolysis and primarily occurs in the liver and to a lesser extent in the kidneys.

Net outcome: Glucose is produced.

Answer 33

GLUCONEOGENESIS

Question 34

This pathway involves no net yield of ATP from glycolysis, but provides 2,3-bisphosphoglycerate, which binds to hemoglobin, decreasing its affinity for oxygen, so making oxygen more readily available to tissues

Answer 34

BISPHOSPHOGLYCERATE PATHWAY IN ERYTHROCYTES

Question 35

How does fructose serve as a factor in the development of obesity?

Answer 35

Fructose enters glycolysis by phosphorylation to fructose-1-phosphate, and bypasses the main regulatory steps, so resulting in formation of more pyruvate and acetyl-CoA than is required for ATP formation. In the liver and adipose tissue, this leads to increased lipogenesis.

Question 36

What happen to “oxygen debt” after vigorous exercise

Answer 36

When lactate production is high, as in vigorous exercise, septic shock, and cancer cachexia, much is used in the liver for gluconeogenesis (see Chapter 19), leading to an increase in metabolic rate to provide the ATP and GTP needed. The increase in oxygen consumption as a result of increased oxidation of metabolic fuels to provide the ATP and GTP needed for gluconeogenesis is seen as oxygen debt after vigorous exercise.

• when we perform intense exercise, glucose is broken down to provide energy to our muscles , which produces lactic acid as a result . Oxygen is then used to break down the unwanted lactic acid into carbon dioxide and water.

Question 37

Summarize the glycolysis process

Answer 37

Glucose is initially phosphorylated by the enzyme hexokinase(or glucokinase in the liver) using ATP to form glucose-6-phosphate. This step traps glucose inside the cell and makes it more reactive.
- Glucose-6-phosphate is converted into fructose-6-phosphate by the enzyme phosphoglucoisomerase. This is an isomerization reaction.
- Fructose-6-phosphate is further phosphorylated by the enzyme phosphofructokinase-1 (PFK-1) using ATP to form fructose-1,6-bisphosphate. This step is the commitment step of glycolysis and is irreversible.
- Fructose-1,6-bisphosphate is split into two three-carbon molecules: dihydroxyacetone phosphate and glyceraldehyde-3-phosphate, by the enzyme aldolase.
- Dihydroxyacetone phosphate is isomerized into another molecule of glyceraldehyde-3-phosphate by the enzyme triose phosphate isomerase.
- Each molecule of glyceraldehyde-3-phosphate is oxidized by glyceraldehyde-3-phosphate dehydrogenase, producing NADH and converting an inorganic phosphate (Pi) into a high-energy phosphate group on 1,3-bisphosphoglycerate.
- Phosphoglycerate kinase then transfers the high-energy phosphate group from 1,3-bisphosphoglycerate to ADP, generating ATP and converting it into 3-phosphoglycerate.
- 3-Phosphoglycerate is converted into 2-phosphoglycerate through an isomerization reaction catalyzed by phosphoglycerate mutase.
- Enolase removes a water molecule from 2-phosphoglycerate, forming phosphoenolpyruvate (PEP), which is a high-energy compound.
- Pyruvate kinase catalyzes the transfer of a phosphate group from PEP to ADP, producing ATP and forming pyruvate.
- At the end of glycolysis, one glucose molecule has been converted into two molecules of pyruvate, and a net gain of 2 ATP and 2 NADH molecules has been produced.

Question 38

What is the enzyme that is dependent on the vitamin-derived cofactor thiamine diphosphate? What is its function?

Answer 38

Pyruvate dehydrogenase- linking glycolysis to citric acid cycle, energy production and regulation of metabolic pathways

Question 39

When there is impaired pyruvate metabolism, what is produced?

Answer 39

Lactate acid which leads to lactic acidosis

Question 40

key substrate in the pentose phosphate pathway

Answer 40

Pentose phosphate pathway