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Glycolysis Flashcards

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1
Q

Name the stages of cellular respiration

A
  1. Glycolysis
  2. Citric Acid Cycle
  3. Electron Transport Chain
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2
Q

Glycolysis is an [anabolic/catabolic] reaction.

A

catabolic

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3
Q

Where does glycolysis take place?

A

In the cytoplasm

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4
Q

What is the only source of energy for red blood cells?

A

glycolysis

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5
Q

How is ATP generated from glucose in glycolysis?

A

By substrate-level phosphorylation

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6
Q

How does glucose enter cells?

A
  • Na+-monosaccharide co-transporter system (SGLT1)

- Na+-independent, facilitated diffusion transport system (GLUT-1 to GLUT-14)

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7
Q

GLUT2 is a [high/low] affinity transporter.

A

low

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8
Q

Where is GLUT2 found?

A

in hepatocytes

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9
Q

When the glucose concentration drops below Km for GLUT2, what happens to much of the remainder of glucose?

A

It leaves the liver and enters the peripheral circulation

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10
Q

Do skeletal muscles have the enzyme that converts glucose 6-phosphate to glucose?

A

no

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11
Q

What serves as the glucose sensor for insulin release?

A

GLUT-2 and glucokinase (found in the β-islet cells of the pancreas)

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12
Q

What happens in the first phase of glycolysis?

A

First phase converts glucose to 2 glyceraldehyde 3-phosphate

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13
Q

What happens in the second phase of glycolysis?

A

Second phase produces 2 pyruvate

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14
Q

How many ATP molecules are invested in generating phosphorylated intermediates? (first phase)

A

2 ATP

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15
Q

Second phase of glycolysis generates how many ATP molecules?

A

4 ATP

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16
Q

Which two very high energy phosphate intermediates are involved in the second phase of glycolysis?

A
  • 1,3 bisphosphoglycerate (1,3BPG)

- Phosphoenolpyruvate (PEP)

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17
Q

1,3-BPG can be converted to?

A

2,3-BPG

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18
Q

What are the 3 regulated steps of glycolysis? And what enzymes do they involve?

A
  • Steps 1,3, and 10

- Hexokinase, phosphofructokinase, and pyruvate kinase

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19
Q

What converts glucose into glucose-6-phosphate allowing “trapping” inside cell?

A

hexokinase

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20
Q

The feedback of hexokinase is inhibited by?

A

glucose-6-phosphate

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21
Q

Why does the feedback inhibition by glucose 6-phosphate product not apply to glucokinase in the liver and pancreas?

A

Because we need to accumulate or store glucose! Glycogen synthesis needs glucose-6-phosphate.GLUTs cant help out with glucose-6-phosphate

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22
Q

Why waste time phosphorylating glucose?

A

Because the plasma membrane generally lacks transporters for phosphorylated sugars, the phosphorylated glycolytic intermediates cannot leave the cell.

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23
Q

What happens when you have excess glucose?

A

It will accumulate in form of glycogen inside the liver

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24
Q

Does the liver normally use glucose as fuel?

A

no

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25
What is the function of glucokinase in the liver?
To phosphorylate glucose to reduce hyperglycemia
26
Why is glucokinase induced by insulin?
To store glucose in liver after a meal
27
What is the function of glucokinase in β cells of pancreas?
Glucokinase functions as blood glucose sensor and release insulin accordingly
28
Glucokinase is mutated in the rare form of diabetes called?
Maturity Onset Diabetes of the Young type 2 (MODY2)
28
Glucokinase is mutated in the rare form of diabetes called?
Maturity Onset Diabetes of the Young type 2 (MODY2)
28
Glucokinase is mutated in the rare form of diabetes called?
Maturity Onset Diabetes of the Young type 2 (MODY2)
29
Hexokinase has [low/high] Km and [low/high] Vmax
low, low
30
What is the effect of hexokinase having low Vmax?
It cannot phosphorylate more sugars than the cell can use
31
Hexokinase is inhibited by?
glucose-6-phosphate
32
Glucokinase has [low/high] Km and [low/high] Vmax
high, high
33
What is the effect of hexokinase having low Km?
Higher affinity for glucose, which permits the efficient metabolism of glucose even when tissue concentrations of glucose are low
34
What is the effect of glucokinase having high Km?
Lower affinity for glucose, functions only when the intrahepatic glucose concentration is high
35
What is the effect of glucokinase having high Vmax?
Allowing the liver to effectively remove glucose minimizing hyperglycemia during the absorptive period
36
Glucokinase is activated by?
insulin
37
Where is hexokinase found?
In all cells
38
What prevents glucose-6-phosphate from diffusing across the plasma membrane?
the negative charge
39
What is the most important control point in glycolysis?
Step 3 which uses phosphofructokinase
40
___________ is both the rate-limiting step and the committed step for glycolysis.
Step 3
41
PFK-1 is activated by?
- AMP | - Fructose 2,6-bisphosphate
42
PFK-1 is inhibited by?
- ATP | - Citrate
43
Fructose 2,6-bisphosphate is synthesized by?
Phosphofructokinase-2 (PFK-2)
44
Levels of fructose 2,6-bisphosphate are [increased/decreased] in the well-fed state.
increased
45
Levels of fructose 2,6-bisphosphate are [increased/decreased] in the starvation state.
decreased
46
What is the hormone that is released in well-fed state?
insulin
47
The formation of _________ is a positive effector for enzymes so it will stimulate the enzyme PFK-1.
fructose 2,6-bisphosphate
48
What activates PFK-2?
insulin
49
PFK-2 is found where?
only in the liver
50
F2,6-BP activates _______.
PFK-1
51
What inhibits PFK-2?
glucagon
52
Insulin stimulates PFK-1 to form _______ which is the stimulator for glycolysis
F2,6-BP
53
What level of phosphorylation occurs in the final step of glycolysis?
second substrate level phosphorylation
54
The final step of glycolysis is activated by?
fructose 1,6-bisphosphate
55
Pyruvate kinase deficiency results in?
Decreased ATP generation
56
An inability to maintain Na+/K+ ATPase leads to _________.
RBC swelling and RBC lysis: hemolytic anemia
57
What causes a decrease in O2 affinity of hemoglobin?
increase in 2,3-BPG
58
Are there Heinz bodies in pyruvate kinase deficiency?
no
59
_________ impairs glycolysis in all cells, but most acute effect on RBCs.
inherited deficiency of pyruvate kinase
60
Embryonic death occurs when there is a [deficiency/complete loss] of pyruvate kinase activity.
complete loss
61
Synthesis of enzymes is controlled by?
hormones
62
High levels of insulin [activate/inhibit] enzyme synthesis.
activate
63
High levels of glucagon [activate/inhibit] enzyme synthesis.
inhibit
64
What is the role of glyceraldehyde 3-phosphate dehydrogenase?
It converts D-glyceraldehyde 3-phosphate into 1,3-bisphosphoglycerate.
65
The conversion of D-glyceraldehyde 3-phosphate into 1,3-bisphosphoglycerate is which reaction number?
Reaction number 6
66
Where is the phosphate coming from?
It is an inorganic phosphate added to the substrate by oxidation-reduction reaction.
67
Why do we need to add this inorganic phosphate?
Because we need energy
68
Which enzyme transfers the high-energy phosphate from substrate to ADP?
3-Phosphoglycerate kinase
69
What is the name of the enzyme that catalyzes first substrate-level phosphorylation in glycolysis?
3-Phosphoglycerate kinase
70
What is the name of the enzyme that catalyzes second substrate-level phosphorylation in glycolysis?
Pyruvate kinase
71
Lactate is formed from pyruvate under [anaerobic/aerobic] conditions.
anaerobic
72
Pyruvate is oxidized into Acetyl-CoA under [anaerobic/aerobic] conditions.
aerobic
73
The fate of pyruvate depends on?
oxygen availability
74
What happens to pyruvate under aerobic conditions?
Pyruvate is oxidized to acetyl-CoA which enters the Krebs cycle
75
What happens to pyruvate under anaerobic conditions?
Pyruvate is reduced in order to oxidize NADH back to NAD+ (as an alternative to electron transport chain)
76
State the fates of pyruvate
Fate 1: Oxidative decarboxylation of pyruvate Fate 2: Reduction of pyruvate to lactate (Anaerobic Condition) in human Fate 3: Alcohol fermentation in bacteria and yeast
77
In the mitochondrial matrix, pyruvate is converted to acetyl CoA by _________ [AEROBIC CONDITIONS]
pyruvate dehydrogenase complex
78
________ and _______ will inhibit the oxidative decarboxylation of pyruvate.
Acetyl-CoA and NADH
79
Pyruvate dehydrogenase requires how many coenzymes?
5 coenzymes
80
Cofactors and coenzymes used by pyruvate dehydrogenase include?
- Thiamine pyrophosphate (TPP) from the vitamin thiamine - Lipoic acid - Coenzyme A (CoA) from pantothenate - FAD(H2) from riboflavin - NAD(H) from niacin (some may be synthesized from tryptophan)
81
What is the final product of anaerobic glycolysis in eukaryotic cells?
lactate
82
_______ reduces pyruvate to lactate.
lactate dehydrogenase
83
The formation of lactate is the major fate for pyruvate in what parts of the body?
in lens and cornea of the eye, kidney medulla, testes, leukocytes and red blood cells (all are poorly vascularized and/or lack mitochondria)
84
________ is a type of metabolic acidosis.
lactate accumulation
85
Explain lactate formation in muscles
- During intense exercise, lactate accumulates in muscles, causing a drop in the intracellular pH, potentially resulting in cramps - Much of this lactate eventually diffuses into the bloodstream, and can be used by the liver to make glucose
86
When does lactic acidosis occur?
when there is a collapse of the circulatory system, such as in myocardial infarction, pulmonary embolism, and uncontrolled hemorrhage
87
The failure to bring adequate amounts of oxygen to the tissues results in _________ and _________.
impaired oxidative phosphorylation and decreased ATP synthesis
88
Alcohol fermentation occurs in?
in yeast and some bacteria
89
Alcohol fermentation is an [anaerobic/aerobic] reaction.
anaerobic
90
In alcohol fermentation, pyruvate is converted to?
ethanol and CO2
91
Aerobic metabolism of glucose produces ______ net ATP via malate-aspartate shuttle.
32
92
Anaerobic glycolysis produces _______ net ATP per glucose molecule.
2
93
Arsenic causes glycolysis to produce ____ net ATP.
93
Arsenic causes glycolysis to produce ____ net ATP.
0

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