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Biochemistry PMY-3 > Glycolysis 1 > Flashcards

Glycolysis 1 Flashcards

1
Q

Briefly Describe glycogen conversion to lactate

A
  • glycogen undergoes glycolysis to become glucose in the bloodstream
  • glucose in the bloodstream undergoes glycolysis to become lactate
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2
Q

Briefly describe how lactate is concerted to glycogen

A
  • lactate undergoes gluconeogenesis to become glucose in the blood
  • glucose in the blood undergoes glycogenesis to become glycogen
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3
Q

What are the glucose consuming processes?

A
  • Glycogenesis

- glycolysis

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4
Q

What are the glucose producing processes?

A
  • Glycogenolysis

- gluconeogenesis

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5
Q

Outline the function of glucose transporters/ glucose uptake

A

Glucose is taken into the cell through trans membrane proteins called GLUT transporters

It is taken up along its concentration gradient

-uses facilitated diffusion (requires no ATP)

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6
Q

Where are GLUT 1 transporters located?

A

Brain and erythrocytes

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7
Q

Where are GLUT 2 transporters located?

A

Liver

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8
Q

Where are GLUT 3 transporters located?

A

Neurons, placenta and testes

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9
Q

Describe the GLUT 4 transport protein

A

Adipocytes, skeletal and cardiac muscle

- insulin dependent
- increases in number with the presence of insulin
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10
Q

Describe SGLT as glucose transport proteins

A

SGLT: intestinal cells, renal tubules

 - secondary active transport 
 - Uses sodium gradient for glucose absorption, maintained by the Na- K ATPase channel
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11
Q

Describe the tissue specific metabolism of glucose in the brain

A

Glucose is completely metabolized to CO2 in the brain

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12
Q

Describe the tissue specific metabolism of glucose in the liver

A

Liver: completely metabolized to CO2, lactate , divert to fat, deliver glucose to blood

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13
Q

Describe the tissue specific metabolism of gluc9se in adipose tissue

A

Adipose: metabolized to Acetyl CoA, then fat

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14
Q

Describe the tissue specific metabolism of glucose in the muscle

A

Muscle: completely metabolized to CO2, lactate

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15
Q

Describe tissue specific metabolism of glucose in erythrocytes

A

Erythrocytes: glucose metabolized to lactate

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16
Q

What is glycolysis?

A

One of the principal pathways for ATP generation- considered as a catabolic pathway

In brain; erythrocytes and actively contracting skeletal muscle

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17
Q

Why does red blood cells contain mitochondria?

A

Because glycolysis is the only source of ATP they have

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18
Q

Where are glycolysis enzymes present?

A

Present in the cytosol

19
Q

Glycolysis can generate ATP in the presence and absence of __________ and __________

A

Oxygen

Mitchondria

20
Q

What are the input and output of glycolysis?

A

Glycolysis consumes 2 ATP but produces 4 ATP (net gain of 2)

Also converts 2 NAD+ to 2 NADH

21
Q

What is the difference between aerobic glycolysis and anaerobic glycolysis ?

A

Aerobic glycolysis: NADH produces from conversion of Glyceraldehyde 3-P to 1,3-bisphosphoglycerate is used for oxidative phosphorylation

Anaerobic glycolysis: NADH produced from conversion of Glyceraldehyde 3-P to 1,3 bid-phosphoglycerate is used in the conversion of Pyruvate to lactate(reversible)

22
Q

What is the overall yield of one molecule of glucose in aerobic glucose?

A

2 ATP and 2 NADH

23
Q

What is the overall yield of of anaerobic glycolysis?

A

Anaerobic glycolysis

-2 ATP (NADH is used to convert Pyruvate to lactate)
24
Q

What is the energy investment stage of glycolysis?

A
  • preparatory phase
  • phosphorylation of glucose and it’s conversion to Glyceraldehyde 3-phosphate
  • net loss of 2 ATP
25
Q

Describe the first of step of glycolysis

A

Step 1: formation of glucose 6-phosphate

  • Glucose is phosphorylated to glucose 6-phosphate by ATP and Hexokinase/Glucokinase
  • this reaction traps glucose as glucose 6-pohosphate as phosphorylated molecules cannot easily cross membranes
  • irreversible reaction; exergonic
26
Q

Differentiate Glucokinase and Hexokinase

A

Glucokinase- in liver and beta cells of pancreas, high Km and high Vmax and NO product inhibition of glucose 6-phosphate

Hexokinase- located in all other tissues, has low Km and low Vmax and HAS product inhibition of glucose 6-phosphate

27
Q

Describe the second step of glycolysis

A

Step 2: formation of fructose 6-phosphate

  • Phosphoglucose isomerase catalyzes the conversion of glucose 6-P (aldose) to fructose 6-P(ketose)
  • Aldo-keto interconversion ; reaction is reversible
28
Q

Describe the 3rd step of glycolysis

A

Step 3: formation of fructose 1,6-bisphosphate

Fructose 6-phosphate is phosphorylated to fructose 1,6-bisphosphate

-this is done by Phosphofructosekinase-1 and is the second irreversible reaction of glycolysis and also the most important regulated step(allosteric regulated enzyme)

Is the rate limiting step

29
Q

What is the rate limiting step of glycolysis ?

A

PFK-1 and ATP phosphorylates fructose 6-phosphate to fructose 1,6-bisphosphate

30
Q

What are steps 4 and 5 of glycolysis?

A
  • Aldolase (step 4)cleaves fructose 1,6 bisphosphate into two trioses(3C) glyceraldehyde 3-phosphate and dihydroxyacetone phosphate
  • The triose phosphate isomerase (step 5) converts to dihydroxyacetone phosphate to glyceraldehyde 3-phosphate to to enable it to be further metabolized by glucolysis.
  • both reactions are reversible
31
Q

Describe the energy generation phase of glycolysis

A
  • “payoff phase”
  • oxidative conversion of glyceraldehyde3-phosphate to pyruvate and the coupled formation of ATP and NADH
  • gain of 4 ATP and 2 NADH
32
Q

Describe the 6th step of glycolysis

A

Step 6: formation of 1,3-bisphosphoglycerate

  • Glyceraldehyde 3-phosphate dehydrogenase results in the formation of 1,3 Bisphosphoglycerate (high energy compound ) and NADH
  • Oxidation reaction
  • Addition of phosphate(not by ATP)
33
Q

How does arsenic effect glycolysis?

A
  • Pentavelent arsenic (arsenate) is a substrate for Glyceraldehyde 3-PDH (competing with Pi)
  • Arsenate bond is Labile, and easily breaks, - non-enzymatic—
  • Arsenate: bypasses the Biphosphoglycerate intermediate, and loss of ATP production
34
Q

Describe the 7th step of glycolysis

A

Phosphoglycerate kinase removes phosphate from 1,3-bisphosphoglycerate(high energy intermediate) to convert ADP to ATP (substrate phosphorylation without involvement of mitochondrial electron transport chain

Reversible

35
Q

Where and when are substrate level phosphorylation reactions important?

A

Important during periods of low oxygen(hypoxia) and in RBC (which lack mitochondria)

36
Q

Describe the 8th step of glycolysis

A

Step 8:

Phosphoglycerate mutate catalyzes the reversible isomeration of 3-P-glyceraldehyde( 3PG) to 2-P-glycerate (2PG)

37
Q

Describe step 9 of glycolysis

A

Step 9: dehydration reaction to form a high energy enol phosphate compound

2-phosphoglycerate(2PG) converted to phosphoenolpyruvate(PEP) (High energy compound) by enolase

38
Q

How does fluoride affect glycolysis? What are the applications?

A

Enolase catalyzes 2PG —> PEP

Enolase is inhibited by fluoride- so… 1) NaF is added to tubes when collecting blood samples for glucose assays

2) addition of fluoride to water reduces lactate production by mouth bacteria, decreasing tooth decay

39
Q

What is the 10th step of glycolysis?(last step)

A
  • Pyruvate kinase(step 10) results in the formation of the 2nd ATP
  • Pyruvate kinase is an irreversible reaction
  • Phosphoenolpyruvate(PEP) is converted to Pyruvate by Pyruvate kinase, Mg2+ and K+
  • From a molecule of glucose(6C), 2 molecules of Pyruvate (3C) are formed as a result of glycolysis
40
Q

What is the net Gibbs free energy of the formation of Pyruvate from PEP?

A

About -30 kjmol-1

41
Q

What is the net Gibbs free energy of ATP Hydrolysis in the formation of ATP?

A

Hydrolysis of ATP. Net G= -30.5 kjmol-1

42
Q

Describe phosphoenolpyruvate

A

Phosphoenolpyruvate is a high energy compound that results in the formation of ATP, without the involvement of the ETC in mitochondria (substrate level phosphorylation)

43
Q

Give an example of a regulated and disorder -related step in glycolysis

A

The conversion of Phosphoenolpyruvate to Pyruvate

Catalyzes by Pyruvate kinase and converts. ADP to ATP

Biochemistry PMY-3 (37 decks)

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