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Biochemistry 2 > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

glycolysis overview

A

glucose (6 carbon sugar) is broken down into 2 pyruvates (3 carbons) and ATP (energy)

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2
Q

where does glycolysis happen?

A

cytoplasm of ALL CELLS

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3
Q

does glycolysis need oxygen?

A

NO

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4
Q

2 phases of glycolysis

A

energy consuming phase (uses ATP)

energy producing phase (produces ATP and reduced NADH)

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5
Q

what can NADH be used for?

A

creating ATP

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6
Q

after eating, glucose must be moved from where to where?

A 
from the small intestine to the bloodstream
uses GLUTs (glucose transporters)
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7
Q

where are GLUTs located?

A

cell membrane

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8
Q

GLUT2

A

liver and pancreas

more responsive to glucose in the presence of insulin

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9
Q

how do we keep glucose in the cell once GLUTs bring it there?

A

kinases (hexokinase and glucokinase) phosphorylate glucose at C6 (changes shape so it can’t easily diffuse out of the cell)
this initial phosphate comes from breakdown of ATP to ADP
we are at -1 ATP!

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10
Q

Glycolysis step 1

A

Glucose to Glucose-6-phosphate

enzyme: hexokinase/glucokinase phosphorylates glucose at C6
keeps glucose inside cell!

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11
Q

hexokinase vs glucokinase

A

hexokinase: found in all cells
glucokinase: induced by insulin
- found in liver and pancreas

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12
Q

Glycolysis step 2

A

glucose-6-phosphate to fructose-6-phosphate

enzyme: phosphoglucoisomerase

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13
Q

Glycolysis step 3

A

fructose 6-phosphate to fructose 1,6-bisphosphate

enzyme: phosphofructokinase-1 (PFK1) adds phosphate to C1 on fructose

uses ATP as phosphate source
-2 ATP!

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14
Q

rate determining step of glycolysis?

A

Phosphofructokinase 1 (PFK1)

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15
Q

what regulates PFK1?

A

PFK2!

PFK2 phosphorylates fructose-6-phosphate at C2, making fructose 2,6-bisphosphate

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16
Q

PFK2 regulation well fed

A

well fed = increase in insulin = increase in PFK2 = more fructose-2,6-bisphosphate = more PFK1 = more glucose to more energy

17
Q

PFK2 regulation fasting

A

fasting = increase in glucagon = inhibits PFK2 = less fructose-2,6-bisphosphate = inhibits PFK1 = less glycolysis

18
Q

what else controls PFK1?

A

high energy state = lots of ATP and citrate = inhibition of PFK1

we have enough energy, don’t need to make more

19
Q

glycolysis step 4

A

glucose 1,6-bisphosphate to glyceraldehyde 3-phosphate (G3P) and dihydroacetone-phosphate (DHAP)

enzyme: aldolase cleaves

20
Q

difference between G3P and DHAP

A

only G3P can go down glycolysis pathway

21
Q

glycolysis step 5

A

DHAP to G3P
enzyme: isomerase
1 glucose: 2 G3P

22
Q

glycolysis step 6

A

glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate

enzyme: G3P dehydrogenase
- removes H from G3P and gives H to NAD+
- makes NADH as a by product
- also adds phosphate to C1 of G3P

we have 2 (1,3-BPG) so we end up with 2 NADH that enter electron transport chain

23
Q

what happens to NADH from G3P dehydrogenase rxn?

A

2 NADH go onto electron transport chain and go on to make 3 ATP each

24
Q

glycolysis step 7

A

1,3-bisphosphoglycerate to 3-phosphoglycerate
enzyme: phosphoglycerate kinase
-removes phosphate from 1,3-BPG and gives it to ADP to make ATP
2 ATP made here (it happens twice)

25
Q

glycolysis step 8

A

3-phosphoglycerate to 2-phosphoglycerate

enzyme: mutase moves a phosphate from C3 to C2

26
Q

glycolysis step 9

A

2-phosphoglycerate to phosphoenolpyruvate (PEP)

enzyme: enolase
- removes a water from 2-phosphoglycerate

27
Q

glycolysis step 10

A

phosphoenolpyruvate to pyruvate

enzyme: pyruvate kinase
-transfers phosphate from phosphoenolpyruvate to ADP (makes ATP)
2 ATP made

28
Q

pyruvate kinase up-regulation

A

fructose 1,6-bisphosphate upregulates pyruvate kinase through feed-forward regulation

29
Q

pyruvate kinase down-regulation

A

increase in ATP or Alanine downregulate pyruvate kinase

high levels of Alanine signal that more glucose needs to be made, not broken down during glycolysis

30
Q

where does Alanine come from?

A

skeletal muscle breakdown during fasting

31
Q

What is Alanine used for?

A

as a substrate for new glucose

32
Q

where does pyruvate go after glycolysis?

A

it can go to the mitochondria where it has access to oxygen and can undergo the Krebs cycle and citric acid cycle
END UP WITH 30-32 ATPs

33
Q

where does pyruvate go in a low oxygen state?

A

low oxygen = exercising skeletal muscle cells or red blood cells with no mitochondria

lactate dehydrogenase takes an H from NADH and gives it to pyruvate
makes lactate and NAD+

34
Q

why do we need NAD+?

A

to work with G3P dehydrogenase and keep glycolysis going

Biochemistry 2 (32 decks)

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