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MAMS BCH > Glycolysis > Flashcards

Glycolysis Flashcards

2
Q

Enzyme for Glucose –> Glucose-6-P

A

Hexokinase

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3
Q

Enzyme for G6P –> Fructose-6-P

A

Phosphoglucose isomerase

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4
Q

Bis vs Di

A

Bis is Phosphate on two different carbons, while bi is on the same carbon

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4
Q

What is an inositol?

A

6 carbon ring with 6 OH groups

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5
Q

Enzyme for F6P –> Fructose-1,6-Bisphosphate

A

Phosphofructokinase

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6
Q

Enzyme for Fructose-1,6-bisphosphate –> Dihydroxyacetone P or Glyceraldehyde-3-P and interconversion for DHP to G-3-P

A

Aldolase and Triose-P isomerase

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7
Q

Enzyme for G-3-P –> 1,3-BPG

A

Glyceraldehyde-3-P dehydrogenase

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8
Q

Enzyme for 1,3-BPG –> 3-P-Glycerate

A

Phosphoglycerate kinase

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9
Q

Enzyme for 3-P-Glycerate –> 2-P-Glycerate

A

P-Glycerate mutase

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10
Q

Enzyme for 2-P-Glycerate –> Phosphoenolpyrvuate

A

Enolase

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11
Q

Enzyme for Phosphoenolpyruvate –> Pyruvate

A

Pyruvate Kinase

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12
Q

Which enzymes in glycolysis are capable of interconversion and which reactions do they catalyze?

A

Phsophoglucose isomerase
Triose-P-Isomerase
Phosphoglycerate mutase
Enolase

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13
Q

Which enzymes use ATP to catalyze their reaction?

A

Hexokinase
Phosphofructokinase

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14
Q

Which enzymes use ADP to catalyze their reaction?

A

Phosphoglycerate kinase
Pyruvate Kinase

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15
Q

Which enzymes convert NAD+Pi to NADH in their reaction

A

Glyceraldehyde-3-P dehydrogenase

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16
Q

What are the 3 rate-limiting steps and their enzymes in glycolysis

A

1) Glucose –> G-6-P, Hexokinase
2) F-6-P –> F-1,6-Bis, Phosphofructokinase
3) Phosphoenolpyruvate –> Pyruvate, Pyruvate Kinase

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17
Q

What is Iodoacetate and how does it function?

A

A non-specific inhibitor of G-3-P dehydrogenase, preventing oxidation of NAD

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18
Q

How is NADH reoxidized back to NAD for use in Glycolysis?

A

In aerobic conditions:
- NADH -> shuttles -> ETC -> O2
In anaerobic conditions:
- NADH+pyruvate -> NAD+lactate (via lactate dehydrogenase)

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19
Q

Fate of pyruvate

A

Anaerobic conditions:
- Pyruvate+NADH -> lactate+NAD
- via Lactate dehydrogenase
Aerobic conditions:
- Pyruvate -> Acetyl-CoA -> TCA or FAs
- via pyruvate dehydrogenase

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20
Q

Fate of pyruvate in yeast

A

Pyruvate -> acetaldehyde
acetaldehyde -> EtOH
- via EtOH dehydrogenase and oxidation of NADH to NAD

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21
Q

Why does Glucokinase have a high Km?

A

Acts as glucose sensor. In liver, ensures that it only functions when hepatocyte glucose is elevated (meal). Also regulates insulin release from pancreatic ß-cells

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22
Q

Which reactions in glycolysis consume ATP?

A

Glucose to G6P
F6P to F6BisP

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23
Q

Why is anaerobic glycolysis important?

A

Allows for the production of ATP in cells that lack mitochondria (RBC and parts of eye) or cells in hypoxia

24
Q

2 ways Glucose is transported into the cell

A

1) Facilitate diffusion
2) Countertransport with Na+

25
Q

What type of transporters are used in facilitated diffusion of glucose?

A

Tissue-specific GLUT1-14 uniporters

26
Q

What type of transporters are used in counter transport of glucose and what creates the gradient?

A
  • SGLT transporters found in the intestinal epithelium
  • Na+ gradient out of the cell created by Na+/K+ ATPase
27
Q

GLUT for liver

A

GLUT-2

28
Q

GLUT for brain

A

GLUT-1

29
Q

GLUT for muscle and adipose tissue

A

GLUT-4, requires insulin

30
Q

How is PFK-1 activated?

A

non-covalent allosteric activation by AMP, ADP and F-2,6-BP (important in liver)

31
Q

How is PFK-1 inhibited?

A

Elevated ATP and Citrate
- ATP is a substrate, but if it becomes too high, it starts binding to the allosteric site

32
Q

What inhibits Hexokinase?

A

G6P

33
Q

What inhibits Glucokinase?

A

F6P, activates Glucokinase Inhibitory Protein and causes sequestration of Glucokinase

34
Q

What does Citrate indicate in relation to PFK-1?

A

Citrate indicates alternative source of fuel is available and high level of acetyl-CoA in mitochondria. Since it can’t get into the cytosol, it is turned into citrate, so a rise in citrate concentration signals that there is energy, so it inhibits glycolysis

35
Q

If the PFK2/FBPase2 complex is phosphorylated, what does that mean?

A

Inhibition of Glycolysis

Glucagon activates PKA which phosphorylates the kinase (PFK2). This leads to activation of the phosphatase (F26BPase) which de-phosphorylates F26BP, turning it back into F6P, inhibiting the function of PFK-1 and stopping glycolysis.

36
Q

If the PFK2/FBPase2 complex is de-phosphorylated, what does that mean?

A

Activation of Glycolysis

Insulin triggers de-phosphorylation of the kinase (PFK2), leading to the phosphorylation of F6P, creating F26BP, which activates PFK-1.

37
Q

MODY2

A

inhibitory mutation of Glucokinase
- not enough uptake of glucose

38
Q

PHHI

A

Activating mutation of Glucokinase
- too much Insulin

39
Q

GLUT4 deficiency in muscle

A

Found in DM2 and non diabetic offspring, may contribute to development of diabetes

40
Q

Aldolase B deficiency

A

Deficiency in Fructolysis pathway, leads to loss of cellular ATP as it is tied up in F1P

41
Q

What is different about the Fructose pathway vs Glycolysis?

A

It bypasses the early checkpoints and skips straight to Aldolase step
Fructose -> F1P -> DHAP/Glyceraldehye -> Gald3P

42
Q

How does fructose increase glucose usage?

A

F1P inhibits the binding of GKRP to Glucokinase

43
Q

What effect does PFK2/F26BPase have on Glucokinase?

A

Binds Glucokinase and keeps it in the cytoplasm

44
Q

What is Galactosemia?

A

Accumulation of Galactose due to a galactokinase deficiency which leads to galactitol accumulation, which can lead to cataracts

45
Q

Galactose trapping

A

Deficiency in galactose 1-P uridyl transferase results in buildup of G1P and trapping of phosphate in this form

46
Q

What does Adenylate Kinase do and what is its significance

A

Adenylate Kinase interconverts 2 ADP <-> AMP+ATP
- AMP is an extremely sensitive indicator of [ATP] change

47
Q

How is PFK2/F26BPase regulated in muscle?

A

The concentration of F6P.

High [F6P] = PFK2 activity
Low [F6P] = F26BPase activity

48
Q

Inhibition of Pyruvate Kinase

A

1) ATP
2) Alanine: Inhibits PK to prevent PEP from being converted back to Pyruvate, after being converted to OAA in gluconeogenesis
3) Phosphorylation via PKA: low glucose in liver = glucagon = activation of PKA = phosphorylation of PK = inhibition of glycolysis/activation of gluconeogenesis

49
Q

Activation of Pyruvate Kinase

A

High concentrations of F16BP

Produced by PFK1, so feedforward regulation

50
Q

How does Fructose feed into Glycolysis?

A

Fructose is converted into Fructose-1-P by Fructokinase

Fructose-1-P is converted into Glyceraldehyde and DHAP by Aldolase B

Glyceraldehyde is converted into G3P by Triose Kinase

DHAP is converted into G3P by triose phosphate isomerase

ATP->ADP by Fructokinase and Triose Kinase

51
Q

What does an Aldolase B deficiency result in?

A

Lose of cellular ATP, as all the phosphate will be tied up in F1P

52
Q

Glucokinase Inhibitory Protein (aka GKRP)

A

Found in the liver, binds glucokinase and keeps it in the nucleus

  • inhibited by F1P, stimulating glucokinase activity
53
Q

How does Fructose increase glucose usage

A

F1P binds Glucokinase inhibitory protein, and releases Glucokinase from the cytoplasm

54
Q

Galactosemia

A

Accumulation of Galactitol because of Galactose pathway deficiency, which accumulates and causes cataracts

Treated by avoiding lactose and galactose

55
Q

PKM2

A

Fetal form of Pyruvate Kinase, present in some cancer cells

Inhibition causes purposeful buildup of glycolytic intermediates, so they can eb diverted to synthesize more cell constituents

56
Q
A

MAMS BCH (20 decks)

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