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BCHEM 2201 > 4. Glycolysis > Flashcards

4. Glycolysis Flashcards

1
Q

Catabolism & two examples

A

(breakdown)
-all biochemical reactions
by which a cell OBTAINS ENERGY and simple chemical NUTRIENTS

-exergonic
ex. release energy in form of ATP!
1.aerobic cell resp
C6H12O6 + 6 O2 + 6 H2O → 12 H2O + 6 CO2
2.fermentation

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2
Q

Anabolism

A

(building up)
-all of the biochemical reactions by which a cell BUILDS UP COMPLEX biological MOLECULES, using energy and simple chemical nutrients

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3
Q

glycolysis developed before _______ when the world was still _____and ______

A

before photosynthesis

when the world was still anaerobic and reducing

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4
Q

how did early organisms extract free energy from glucose (2 steps)

A

1st - activate glucose by phosphorylation to increase glucose reactivity
2nd - collect energy from the high-energy (phosphorylated) metabolites

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5
Q

phosphorylation allows pathway intermediates to ________ the cell

A

remain inside the cell

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6
Q

primary energy storage in plants vs animals

A

plants - starch
animals - glycogen

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7
Q

hydrolysis of energy storage polysaccharides (2)

A
  • from non-reducing ends (branched polymers have many n.r ends)
  • allows for rapid mobilization of glucose
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8
Q

where does glucose mobilization take place?

A
  • smooth ER
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9
Q

how many stages/steps are in glycolysis ?
what is the net produced from glycolysis ?

A
  • 2 stages with 10 steps
    -1. preparatory phase (energy investment)
    -2. energy payoff phase

NET = 2 pyruvate, 2 ATP and 2 NADH

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10
Q

overview of what happens in stage 1

A

(activation of glucose by phosphorylation)
glucose + 2ATP → 2 ADP + glyceraldehyde-3-p (G3P) + dihydroxyacetone phosphate (DHAP)

results in 2 G3P

(steps 1-5)

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11
Q

Step #1

A

phosphorylation of glucose (via hexokinase)

-irreversible (-delta G)
-to activate glucose & increase reactivity & to trap glucose
-add phosphate to C6

—glucose— ATP + Mg2+ → ADP → —glucose
hexokinase 6-phosphate—

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12
Q

what enzyme would work in step #1 if it was a prokaryote?

A
  • glucokinase
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13
Q

Step #2

A

isomerization of glucose-6-P to fructose-6-P
(via phosphohexose Isomerase)

-reaction is coupled to step #3
-creates another OH for next phosphate on C1 of fructose-6-P
-small “uphill” step

glucose-6-P(aldose) Mg2+ & p.i → fructose-6-
P(ketose)

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14
Q

Step #3

A

phosphorylation of fructose-6-P
(via phosphofructokinase-1)

-!!first irreversible step (-delta G) that is UNIQUE to glycolysis!!
-committed step !
-most regulated step / control point for glycolysis
-add phosphate to C1

fructose-6-P ATP + Mg2+ → ADP → fructose
PFK-1 1,6-biphosphate

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15
Q

which step is the control point for glycolysis ?

A
  • step #3
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16
Q

which steps are irreversible ?

A
  • steps #1,3, and 10
17
Q

which step is a committed step and what does that mean?

A
  • step #3

means that fructose 1,6-biphosphate is committed to become pyruvate and yield energy

18
Q

what would happen if you could not couple step #3 to ATP hydrolysis?

A
  • delta G would become positive
19
Q

Step #4

A

cleavage of fructose 1,6-biphosphate
(via aldolase)

-reversible step
-the fate of glucose carbons

fructose 1,6-biphosphate into → dihydroxyacetone phosphate (DHAP) + glyceraldehyde-3-phosphate (G3P)

20
Q

how to overcome such a high +delta in step #4

A
  • convert all DHAP to G3P
21
Q

Step #5

A

conversion of dihydroxyacetone phosphate (DHAP) into glyceraldehyde-3-phosphate (G3P)
(via triose phosphate isomerase)

DHAP (ketose) → G3P (aldose)

-ONLY G3P is the SUBSTRATE for the next enzyme

Glucose carbons G3P
C4 or C3 → C1
C5 or C2 → C2
C6 or C1 → C3

22
Q

Overview of stage 2

A

the payoff phase (steps 6-10)

2 G3P + 4ADP + 2Pi + 2NAD+
→
2 pyruvate +4ATP +2NADH + 2H+

23
Q

Step #6

A

oxidation of G3P to 1,3-biphoglycerate
(via glyceraldehyde-3-phosphate dehydrogenase)

-oxidation/phosphorylation

-phosphorylation uses inorganic phosphate & yields a high energy product

-oxidation of G3P (NAD+ accepts 2 e- & 1 proton to form NADH)

G3P + inorganic phosphate
NAD+ →NADH + H → 1,3 bi-
G3P dehydrogenase phosphoglycerate

24
Q

what is the oxidizing agent in step #6

A

NAD+

25
Q

how many molecules of G3P are formed per one glucose (C6)

A

2 molecules of G3P per one glucose

26
Q

acyl-phosphate

A

high energy product that donates the phosphate group to ADP to make ATP in step #7

27
Q

which pathways are NAD+ vs NADP+

A

NAD+ = catabolic pathway
NADP+ = anabolic pathway

28
Q

explain how NAD+ turns into NADH

A

NAD+ + 2e- + H+ = NADH
→NAD+ being reduced
NADH being oxidized ←

29
Q

Step #7

A

ATP made by substrate level phosphorylation
(via phosphoglycerate kinase)

-phosphorylation of ADP to form ATP
-1,3-biphosphoglycerate donates phosphate group to ADP to make ATP
-reaction is reversible even though -delta G

1,3-biphosphoglycerate + ADP
Mg2+ & phosphoglycerate kinase
→
3-phosphoglycerate +ATP

30
Q

what is substrate level phosphorylation

A

-when a phosphate group is transferred from a substrate to ADP to form ATP, coupled with the release of free energy

31
Q

Step #8

A

conversion of 3-phosphoglycerate to 2-phosphoglycerate
(via phosphoglycerate mutase)

-reversible isomerization reaction
-shifts phosphate group from C3 to C2
-driven through by -delta G in step 10

3-phosphoglycerate
Mg2+ & phosphoglycerate mutase
→2-phosphoglycerate

32
Q

Step #9

A

dehydration of 2-phosphoglycerate to phosphoenolpyruvate (PEP)
(via enolase)

-want to create a better phosphoryl donor
-removal of H20
-low energy phosphate ester linkage into high energy ENOL phosphate linkage
- phosphate group attaches to OH group which binds to a C=C

2-phosphoglycerate H20 leaves
enolase
→phosphoenolpyruvate

33
Q

Step #10

A

second level substrate phosphorylation
(via pyruvate kinase)

-irreversible (-delta G)
-phosphorylation of ADP = transfers Pi from PEP to ADP to form ATP

phosphoenolpyruvate + ADP

                         Mg2+, K+  
                          pyruvate kinase 
          
                                           → pyruvate + ATP
34
Q

describe tautomerization in step #10

A

tautomers are isomers that differ only in position of protons/electrons
-lowers conc of immediate product
-drives reaction toward ATP formation

pyruvate with OH pyruvate with =O
(enol form) (keto form)

35
Q

high energy metabolites

A

-have delta G more negative than -25kJ/mol
-made by reaction between carboxylic acid group & phosphate group

P + hydroxyl group then binds to C=C

36
Q

what is the overall free energy change in glycolysis

A

-negative

37
Q

?? which steps are coupled ??

A
  • 1&3
  • 6 & 7
  • 8 - 10

BCHEM 2201 (14 decks)

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