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Metabolism & Nutrition > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

Major pathway for ATP synthesis in tissues that lack mitochondria such as the RBC ?

A

Glycolysis

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2
Q

Where does glycolysis take place ?

A

Cytosol

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3
Q

The ability of glycolysis to provide ATP in the absence of O2 is especially important for what tissue ?

A

Skeletal muscle

Allows muscles to perform at very high levels when O2 is insufficient & allows them to survive anoxic episodes.

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4
Q

What is the final product of glycolysis ?

A

Pyruvate

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5
Q

Under anaerobic conditions, what does pyruvate converts to ?

A

Lactate

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6
Q

Under aerobic conditions, what pathway does pyruvate take ?

A

Oxidative decarboxylation of pyruvate to Acetyl CoA which in turns enters the TCA cycle.

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7
Q

Which tissues has low glycolytic activity and poorly survives under ishemic conditions ?

A

Heart muscle

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8
Q

SGLT is what type of transporter ?

A

Na+ dependent transporter

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9
Q

GLUT is what type of transporter?

A

Na+ independent transporter

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10
Q

What enzyme catalyzes the first step reaction of glycolysis, *irriversibly *phosphorylating the glucose molecule.

A

Hexokinase converts glucose to glucose-6-phosphate, traping it in the cytosol, creating a high energy phosphate bond.

The formation of G-6-P does NOT commit glucose to glycolysis. It may undergo glycolysis or be stored as glycogen or used in the pentose phosphate pathway (the way glucose that make up DNA & RNA is formed).

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11
Q

Glucose phosphorylation in step 1 of glycolysis requires what as a substrate ?

(Hexokinase reaction)

A

Mg-ATP complex

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12
Q

What catalyzes the phosphorylation of glucose in MOST tissues, even when tissues concentrations of glucose are low ? What does that imply?

A

Hexokinase

Has low Km
High affinity for glucose
Functions at low [glucose]

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13
Q

In liver cells and b cells of the pancreas, what enzyme is responsible for the phosphorylation of glucose ?

(Also called Hexokinase type IV)

A

Glucokinase

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14
Q

Specifically in b cells of the pancreas what enzyme functions as a glucose sensor, determining threshold for insulin secretion ?

A

Glucokinase

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15
Q

In the liver, glucokinase facilitates what exactly ?

A

Glucose phosphorylation in hyperglycemic state.

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16
Q

What enzyme is the main player for first step of glycolysis in the fed state ?

A

Glucokinase

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17
Q

What enzyme is the main player for first step of glycolysis in the fasted state ?

A

Hexokinase

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18
Q

In RBCs, what enzyme would catalyze the first reaction of glycolysis ?

A

Hexokinase

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19
Q

In the liver, what enzyme would catalyze the first reaction of glycolysis?

A

Glucokinase

Glucokinase functions only when [glucose] in hepatocytes is î.

** I.e. after a CHO rich meal

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20
Q

Which enzyme has high Vmax, allowing the liver to effectively remove the flood of glucose delivered to the portal blood ?

A

Glucokinase

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21
Q

Maturity onset diabetes of the young type 2 (MODY 2) is a rare type of diabetes that results from ?

A

Mutations that result in decreased activity of Glucokinase.

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22
Q

What enzyme is inhibited (negative feedback) by glucose-6-phosphate ?

A

Hexokinase

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23
Q

X does not undergo feeback inhibition, allowing the liver to take up & phosphorylate glucose at higher concentrations than peripheral tissues ?

A

Glucokinase

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24
Q

Which enzyme works independently of fed or fasted state ?

A

Hexokinase

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25
Q

What is the rate limiting enzyme that catalyzes ATP(Mg2+) dependant phosphorylation of fructose-6-phosphate to fructose 1,6-bisphosphate ?

A

PFK-1

Irriversible & most important regulatory enzyme of glycolytic pathway.

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26
Q

Name 2 inhibitors of PFK-1

A

ATP
Citrate

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27
Q

Name 2 activators of PFK-1

A

Fructose 2,6 bisphosphate
ADP

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28
Q

What enzyme of the glycolytic pathway gives off NADH as a source for the electron transport chain ?

A

Glyceraldehyde 3-phosphate dehydrogenase

29
Q

Glyceraldehyde 3-phosphate dehydrogenase uses Inorganic phsophate as a substrate. What toxic compound can possibly compete with this substrate ?

A

Arsenic

30
Q

Besides Arsenic, what other molecule also inhibits glyceraldehyde 3-phosphate dehydrogenase?

A

Iodoacetate

31
Q

What are the 2 enzymes involved in generation of ATP by substrate level phosphorylation ?

A

Phosphoglycerate kinase
Pyruvate kinase

32
Q

Formation of ATP from 1,3-Bisphosphoglycerate is mediated by what enzyme ?

A

Phosphoglycerate kinase

33
Q

Fluoride inhibits this enzyme, preventing glycolysis to go on as a technique used in lab to preserve blood samples for measurements of blood glucose ?

A

Enolase

34
Q

The conversion of phosphoenolpyruvate to pyruvate by this enzyme results in formation of ATP ?

A

Pyruvate kinase.

35
Q

Anaerobic respiration net production of ATP

A

2 ATP

No net production of NADH because it it reutilized in the formation of lactate.

36
Q

Aerobic respiration net NADH production ?

A

2 NADH

Oxidation of most this NADH is by the electron transport chain, producing 3 ATP for each NADH.

37
Q

What step of glycolysis is bypassed in RBCs

A

Phosphoglycerate kinase step

converts 1,3-Bisphosphoglycerate to 3-phosphoglycerate

38
Q

What is the molecule produced by bypass of the phosphoglycerate kinase step in the RBC in context of hypoxia ?

A

2,3 bisphosphoglycerate
(2,3 BPG)

2,3 BPG has higher affinity for o2 than Hb

39
Q

Transfused blood will have lower levels of what making it less efficient at delivering oxygen to peripheral tissues?

A

2,3 BPG

40
Q

What is the enzyme that allows the bypass of the first step of ATP synthesis in the hypoxic RBC?

A

Bisphosphoglycerate mutase

41
Q

What are the 3 levels at which hormonal regulation is exerted in glycolysis ?

Inuslin/glucagon

A

Glucokinase
PFK-1
Pyruvate kinase

42
Q

Since the mature RBC lacks mitochondria, it is completely dependent on what process for the production of ATP ?

A

Anaeorobic glyocolysis

43
Q

What happens if the RBC does not have adequate level of ATP ?

A

Inability to maintain shape, difficulty passing into narrow capillaries, lysis of the cell.

44
Q

Chronic hemolysis would lead to compensatory î of what molecule ?

A

2,3 BPG

45
Q

How is the NADH produced in the cytosol during glycolysis moved to the mitochondria to be used in phosphorylative oxidation ?

A

Glycerophosphate shuttle
Malate shuttle

46
Q

Net yield of energy if glycerophosphate shuttle is used ?

A

1.5 ATP

Uses FAD

47
Q

2,3 BPG combines with Hb and causes it to ?

A

Unload more oxygen in the tissues.

Shifts the O2-Hb binding curve to the right

48
Q

Energy yield if Malate shuttle is used ?

A

2.5 ATP

49
Q

Oxaloactetate needs to coverts to what to be exported out ?

A

malate

50
Q

Why does the glycerophosphate shuttle only yields 1.5 ATP?

A

NAD Linked with FAD in the inner mitochondrial membrane.

51
Q

Type of chemical reaction that results in the formation of ATP by the direct transfer of a phosphate group to ADP from a reactive intermediate?

A

Substrate level phosphorylation

Substrate-level phosphorylation provides a quicker, less efficient source of ATP, independent of external electron acceptors. This is the case in human erythrocytes, which have no mitochondria, and in oxygen-depleted muscle.

52
Q

What are the 3 control steps of the glycolytic pathway?

A

Hexokinase
Phosphofructokinase
Pyruvate kinase

53
Q

**What compound needs to be regenerated from glycolysis to proceed ?

A

NAD+

54
Q

3 Fates of pyruvate ?

A

TCA cycle (Acetyl CoA)
Lactate
Alanine

55
Q

Major fate of pyruvate in cells that lack mitochondria?

RBC, testes, leukocytes, cornea of eye, medulla of kidney..

A

Lactate

56
Q

For continuous running of glycolysis, supply of what molecule is necessary?

A

NAD+

57
Q

The conversion of pyruvate to lactate by lactate dehydrogenase uses what molecule as a cofactor ?

A

NADH

high NADH/NAD ratio favorises conversion of pyruvate to lactate.

58
Q

The accumulation of what molecule in muscle causes a drop in pH and cramps ?

A

Lactate

59
Q

Fate of pyruvate in the liver ?

A

Converted to glucose (gluconeogenesis)
Oxidized in the TCA cycle

60
Q

The series of 10 reactions are called aerobic glycolysis when oxygen is required to reoxidize X ?

A

NADH

61
Q

The conversion of glucose to lactate is called what when it can occur without the participation of O2 ?

A

Anaerobic glycolysis

62
Q

Despite the production of some ATP during glycolysis, the end products (pyruvate or lactate) still contain most of the energy originally contained in glucose. What process is required to release that energy completely?

A

TCA cycle

63
Q

For 1 molecule of glucose, how many pyruvate are generated ?

A

2

64
Q

What is the BGP shunt?

A

Bypassing the first site of ATP synthesis in the glycolytic pathway in the context of hypoxia (low PO2) in order to generate 2,3 BPG which shifts the O2-Hb binding curve to the right, allowing Hb to unload more O2 to peripheral tissues.

65
Q

A deficiency in this enzyme would cause hemolytic anemia :

A

Pyruvate kinase deficiency

Second most common genetic deficiency causing hemolytic anemia.

This enzyme produces ATP. Decrease in ATP production results in change of shape of the erythrocyte. The loss of its characteritic biconcave shape signals its destruction in the spleen.

66
Q

What is the most common genetic deficiency causing hemolytic anemia ?

A

G6PDH deficiency

67
Q

The glycerophosphate shuttle is mainly found in ?

A

The brain

68
Q

What shuttle system is of more universal utility?

A

Malate shuttle

Metabolism & Nutrition (9 decks)

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