Glycolysis

Question 1

Is glycolysis anaerobic or aerobic?

Answer 1

Glycolysis can function aerobically and anaerobically depending on availability of oxygen and ET chain.

Question 2

How do erythrocytes metabolize glycolysis?

Answer 2

B/c they lack mitochondria, they rely on glucose as their metabolic fuel & metabolize it anaerobically.

Question 3

How are skeletal muscles able to perform under low oxygen levels?

Answer 3

Ability of glycolysis to provide ATP during intense exercise helps tissues survive anoxic episodes.

Question 4

Diseases in which enzymes of glycolysis are deficient

Answer 4

Hemolytic anemias

Question 5

In fast growing cancer cells, glycolysis proceeds at _____?

Answer 5

High rate, forming a lot of PYRUVATEs, which are then reduced to lactate and exported.

Question 6

What transpires when muscle contracts under anaerobic conditions?

Answer 6

Glycogen disappears, lactate appears

Question 7

What is the end product of glycolysis of oxygen is involved?

Answer 7

PYRUVATE

Question 8

What is the price to pay when glycolysis occurs in anaerobic conditions?

Answer 8

Less ATP produced per mole of glucose oxidized

Question 9

What happens to PYRUVATE formed in anaerobic glycolysis in yeast and other microorganisms?

Answer 9

PYRUVATE is NOT reduced to lactate BUT decarboxylated and reduced to ETHANOL.

Question 10

All enzymes of glycolysis are…

Answer 10

cytosolic.

Question 11

Is the conversion of glucose to G6P reversible?

Answer 11

No. It is an irreversible reaction.

Question 12

What catalyzes the conversion of glucose to G6P?

Answer 12

Hexokinase

Question 13

How is hexokinase inhibited?

Answer 13

It is inhibited by its product — G6P.

Question 14

What is an isoenzyme of hexokinase found in liver and pancreatic B-islet cells?

Answer 14

Glucokinase

Question 15

Function of glucokinase in liver

Answer 15

Remove glucose from hepatic portal blood following a meal, regulating available concentration to peripheral tissues

Question 16

Function of glucokinase in pancreatic B-islet cells

Answer 16

Detects high concentrations of glucose in portal blood

Question 17

Increased glycolysis and increased ATP formation lead to…

Answer 17

closure of ATP-K channel, causing membrane depolarization & opening of voltage gated ca2+ channel.

Question 18

Influx of Ca++ leads to…

Answer 18

Fusion of insulin secretory granules w/ cell membrane & release of insulin

Question 19

How many ATPs were produced during the substrate level phosphorylation step of glycolysis?

Answer 19

2 ATPs since 2 triose phosphate molecules were created.

Question 20

Toxicity of arsenic is a result of what?

Answer 20

Competition of arsenate w/ Pi —-> 1-Arseno-3-phosphoglycerate

Question 21

What products are produced when 1-arseno-3-phosphoglycerate is hydrolyzed?

Answer 21

3-phosphoglycerate without ATP

Question 22

Under anaerobic conditions, what enzyme catalyzes PYRUVATE to lactate?

Answer 22

Lactate dehydrogenase

Question 23

What pathway does PYRUVATE follow in aerobic conditions?

Answer 23

PYRUVATE enters mitochondria and gets converted to acetyl coA through oxidative decarboxylation then gets oxidized to CO2 in CAC.

Question 24

Why does glycolysis in erythrocytes always terminates in lactate?

Answer 24

Subsequent reactions of PYRUVATE oxidation are mitochondrial and erythrocytes do not have mitochondria.

Question 25

What conditions produce lactate?

Answer 25

vigorous exercise, septic shock, cancer cachexia

Question 26

Lactate is oxidized to PYRUVATE in what organelle?

Answer 26

mitochondrion

Question 27

True or False:

Do Liver, kidneys, and heart Normally take up lactate?

Answer 27

True. but produce it Under hypoxia conditions

Question 28

What are the major sites of regulation of glycolysis and are markedly exergonic and irreversible?

Answer 28

hexokinase, phosphofructokinase, pyruvate kinase

Question 29

How does fructose enter glycolysis?

Answer 29

• bypasses main regulatory steps
• gets phosphorylated to fructose-1-phosphate
• more PYRUVATE and acetyl coA are formed than is required for ATP formation

In LIVER AND ADIPOSE TISSUE —-> increased lipogenesis

Question 30

How is PYRUVATE transported into the mitochondrion?

Answer 30

Proton symporter

Question 31

What enzyme decarboxylates PYRUVATE to hydroxyethyl derivative of thiazole ring of enzyme-bound thiamin diphosphate?

Answer 31

PYRUVATE dehydrogenase

Question 32

In thiamin deficiency, what happens to glucose metabolism?

Answer 32

Glucose metabolism is impaired and there is significant & potentially life threatening lactic and pyruvic acidosis.

Question 33

What inhibits PYRUVATE dehydrogenase?

Answer 33

NADH, acetyl CoA

Question 34

What regulates PYRUVATE dehydrogenase?

Answer 34

phosphorylation (kinase) of 3 serine residues on PYRUVATE dehydrogenase component of multienzyme complex —> decreased activity

Dephosphorylation (phosphatase) —> increased activity

Question 35

PYRUVATE dehydrogenase — glycolysis is inhibited WHEN

Answer 35

there’s adequate ATP available and when fatty acids are being oxidized

Question 36

What causes elevated levels of PYRUVATE?

Answer 36

• arsenite and mercuric ions inhibit PYRUVATE dehydrogenase

- thiamin deficiency

Question 37

What causes hemolytic anemia in erythrocytes?

Answer 37

Inherited aldolase a deficiency

PYRUVATE kinase deficiency

Question 38

Conditions that involve an impairment of PYRUVATE metabolism frequently lead to….

Answer 38

LACTIC ACIDOSIS