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glycolysis and krebs > glycolysis n krebs > Flashcards

glycolysis n krebs Flashcards

1
Q

why do we need glycerol 3 phosphate shuttle?

A

ETC is located in the inner membrane of mitochondria which is impermeable to the NADH that has been produced OUTSIDE the mitochondria (like in glycolysis) Howver the NADH produced in the mitochondria is fine because its already there

  1. NADH is used to reuced DHAP giving us glycerol 3 p. by the enzyme glycerol 3 p DH 1
  2. A similar enzyme is located in the outer mitchondrial membrane which glycerol 3 phosphate 2 uses FAD to take the H from glycerol 3 phosphate, reforming DHAP
  3. FADH2 gives the H to co enzyme q
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2
Q

how many NADH produced by glycolysis

A

2

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3
Q

substrate level phosphorylation

A

in glycolysis when we form ATP when 1,3 biphosphoglycerate gives a phosphate to ADP we form overall 2 atps and also the last step with pyruvate kinase

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4
Q

how does glucose enter the cell

A

through NA glucose transporter, examples of secondary active transport because the na gradient was created by a pump

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5
Q 
GLUT 1 
GLUT 2
3
4
5
A
  1. all cells but especially brain and RBC
  2. liver,SI,kidney (hyper) low affinity high KM
    3.Brain neurons (hypo) high affinity but low Km
    adipose tissue and muscle
    5 enterocytes
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6
Q

what is the fate of glucose in liver

A

enzyme glucokinase makes glucose 6 phospate and then proceeds to make glycogen

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7
Q

glucose and pancrease

A

glucose enters glycolysis, atp produced increases ca2+ levels and then triggers insulin release by exocytosis

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8
Q

regulatory enzymes of glycolysis

A

ALL OF THE KINASES
1. hexokinase- inhibited by its products
2. phosphofructokinase
- :( ATP
:( reducing equivalents
:( citrate
:) activated by fructose 2,6 bisphosphate
3. PK
AAAF
:( alanine, acetyl coa , atp, fatty acids
:) fructose 1,6 biphosphate

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9
Q

comparison of hexokinase and glucokinase

A

H

  • found in all cells
  • not specific to just glucose
  • inhibited by product glucose 6 p
  • high affinity for glucose
  • has 4 isoforms
  • not activated by insulin

G

  • found only in liver
  • low affinity for glucose
  • not inhibited by its product
  • is most effective when the level of glucose is high in the blood so after a meal which means its activated insulin
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10
Q

committed step in glycolysis

A

phosphofructokinase

  • highly regulated
  • highly exergonic reaction
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11
Q

fate of pyruvate

A

depends on whether its anaerobic or aerobic

anaerobic- produce lactic acid (RBC, muscles) LDH
aerobic_ oxidative decarboxylation of pyruvate to acetyl co- A

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12
Q

what is an additional function of pyruvate

A

serves as a fuel source for cardiac muscle and brain nerurons

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13
Q

phosphofructokinase

A

major regulatory enzyme
- :( citrate (makes sense because its a catabolic process)
:) fructose 2,6 bisphosphate (is an indicator of high glucose level)
:( ATP + reducing equivalents

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14
Q

fructose 1,6 bisphosphate and fructose 2,6 biphosphate

A

1,6 - :) PK

2,6 :) phosphofrcutokinase

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15
Q

regulation of pyruvate kinase

A

AAAF- atp,alanine,acetyl coa , fatty acids
:) fructose 1,6 bisphosphate
similar to glycogen synthase is active in its OH form

insulin - activate
glucagon-inactivate

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16
Q

when do you mention the glycerol 3 phosphate

A

glycolysis

fatty acid synthesis

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17
Q

what is the point of citrate shuttle and explain it (draw)

A

need to get the acetyl coa from mitochondria to cytoplasm for e.g fatty acid synthesis

in mitochondria acetyl coa+ oxaloacetate to make citrate
citrate leave mitochondria to go cytoplasm where its cleaved back to products (citrate lyase)

the oxaloacetate, its goal is to be converted back to pyruvate.

  1. reverse of krebs———malate (malate DH)
  2. Malic enzyme - produces Nadph gives pyruvate
    malate+NADP—–pyruvate co2 + NADPH
  3. pyruvate translocase transports to mitochondria
18
Q

anoplerotic reaction

A

pyruvate carboxylase forms oxaloacetate

19
Q

how do we reverse glycolysis

A

7 of the enzymes are the same apart from 3. 2/3 use simple hydrolysis reactions and the other one is split into 2 enzymes

  1. glucokinase
    glucose 6 phosphatase
  2. phosphofructokinase
    fructose 1, 6 biphosphatase
  3. PK
    pyruvate to oxaloacetate =pyruvate carboxylase

oxaloacetate —– phosphoenolpyruvate (phosphoenolpyruvate carboxykinase)

20
Q

when do you mention the malate shuttle

A

glycolysis

gluconeogeneisis

21
Q

fructose 1, 6 bisphosphatase

A

one of the bypass enzymes involved for gluconeogenesis
it breaks down fructose 1, 6 phosphate into fructose 6 phosphate

:) citrate
:(frucots 2, 6 bisphosphate because that is AN IDICATOR OF HIGH GLUCOSE AVAILABILITY

22
Q

what is the role of fructose 2,6 biphosphate

A

is an indicator of high glucose ability

23
Q

pyruvate carboxylase

A

a mitochondrial enzyme
b7
atp
needs acetyl coa (because theres no point of making oxaloacetate if there is no acetyl co a to facilitate krebs

24
Q

where does gluconeogenesis occur

A

cytoplasm!

25
Q

malate aspartate shuttle

A

In order for gluconeogenesis to occur need oxaloacetate which is produced in the mitochondria but gluconeogenesis happens in the cytosol. but oxaloacetate cannot leave through the inner mitochondrial membrane.

route 1- converted to malate
route 2 _ aspartate

26
Q

when do you mention the malate shuttle

A

gluconeogenesis

27
Q

deficiencies regarding gluconeogenesis

A
  • fructose 1,6 biphosphatase
    blocking of gluconeogenesis leading to hypoglycemia and LACTIC ACIDOSIS
    between meals the blood glucose is maintained only by glycogenolysis

Hypoglycemia of the neonate
-brain consumes a lot of glucose
-they have small amount of adipose tissue for an alternative fuel source
the enzymes of gluconeogenesis may not be completely functional at this time
-smaller glucose stores

28
Q

PFK1 isoforms

A

muscle
constitutive
high glycolysis during exercise .

liver
- inducible
- by insulin
specially activated by fructose 2, 6 biphosphaste

29
Q

name the products of krebs

A

citrate
cis aconitate
isocitrate
a ketoglutarat

30
Q

how many atps directly from krebs

A

1

31
Q

how many indirect atps

A

11
cos 3 Nads
1 fad

32
Q

which enzyme uses fad as a cofactor for krebs

A

succinate dh

33
Q

where do we generate the direct atp from

A

from the cleavage of succinyl coa````````````

34
Q

substrates and products of krebs

A

substrates (basically first step)
1. OAA
ACETYL COA
WATER

products

  • nadh
  • fadh2
  • co2
  • atp
35
Q

regulation of krebs

A

3 irreversible reactions

  1. citrate synthase
  2. isocitrate DH
  3. alpha k glutarate DH
36
Q

PDH regualtion

A

OH IM PYRUVATE AND IM ACTIVE:)
:(atp + reducing equivalents and acetyl coa
:) promoted by any sudden demand upon the cell signalled by calcium

37
Q

anoplerotic reaction

A

chemical reactions that form intermediates of a metabolic pathway like krebs. Because the intermediates don’t just have the sole purpose of making atp but other things to

38
Q

what other roles does oxaloacetate have

A
  • glucose

- aa (aspartate)

39
Q

functions of krebs

A
  1. ATP

2. Building blocks for other things

40
Q

what do the intermediates form in krebs

A 
citrate- fats 
a k glutatarate- aa glutamine and glutamate and GABA
succinyl- heme+porphyrin
oxaloacetate- aa aspartate + glucose
malate-glucose
41
Q

oxidative phosphorylation

A

process in which ATP is formed as a result of the transfer of electrons from NADH or FADH 2 to O 2 by a series of electron carriers. This process, which takes place in mitochondria, is the major source of ATP in aerobic organisms

glycolysis and krebs (1 decks)

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