oxidation reduction product...as a cofactor for oxidation reactions bind nad+ and the substrate. 2....

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Product

Enzyme

NAD+

NAD+ NAD NAD

2e–

H+

+H+

Energy-rich molecule

NAD+

1. Enzymes that use NAD+

as a cofactor for oxidation reactions bind NAD+ and the substrate.

2. In an oxidation–reduction reaction, 2 electrons and a proton are transferred to NAD+, forming NADH. A second proton is donated to the solution.

3. NADH diffuses away and can then donate electrons to other molecules.

Reduction

Oxidation

H H

H H H

H

H H

1


2e– Electrons from food

High energy

Low energy

2H+ 1 / 2 O2

Energy released for ATP synthesis

H2O

2

2H H+

Reduction

Oxidation


3


– ADP

Enzyme Enzyme

– ATP

PEP Pyruvate

P

P P

P

P

Adenosine

P

4

Outer mitochondrial

membrane

Intermembrane space

Mitochondrial matrix

CO2

ATP H2O FAD O2

Inner mitochondrial

membrane


ATP

e– Electron

Transport Chain Chemiosmosis ATP Synthase

e–

H+

e– NAD+

NADH

Glycolysis

Pyruvate

Glucose

Pyruvate Oxidation

Acetyl-CoA NADH

Krebs Cycle

CO2

ATP

NADH

FADH2

5


Glycolysis

NADH

Pyruvate Oxidation

ATP

Electron Transport Chain Chemiosmosis

Krebs Cycle

6-carbon sugar diphosphate

NAD+ NAD+

Pri

min

g R

eact

ion

s C

leav

age

Oxi

dat

ion

an

d A

TP

Fo

rmat

ion

STEPS C and D

NADH NADH

P P

P P

STEP A

ATP ATP

ADP ADP

STEP B

3-carbon sugar phosphate

3-carbon sugar phosphate

Pi Pi

ADP ADP

ATP ATP

ATP

ADP ADP

ATP

3-carbon pyruvate

3-carbon pyruvate

6-carbon glucose (Starting material)

Glycolysis begins with the addition of energy. Two high- energy phosphates (P) from two molecules of ATP are added to the 6-carbon molecule glucose, producing a 6-carbon molecule with two phosphates.

Then, the 6-carbon molecule with two phosphates is split in two, forming two 3-carbon sugar phosphates.

An additional Inorganic phosphate ( Pi ) is incorporated into each 3-carbon sugar phosphate. An oxidation reaction converts the two sugar phosphates into intermediates that can transfer a phosphate to ADP to form ATP. The oxidation reactions also yield NADH giving a net energy yield of 2 ATP and 2 NADH.

6


NADH NAD+ NADH Pi NAD+

Glucose Hexokinase

Phosphofructokinase

Glucose 6-phosphate

Fructose 6-phosphate

Fructose 1,6-bisphosphate Isomerase Aldolase

Pyruvate Pyruvate

Enolase

Pyruvate kinase

AD P

10

Glu

cose

Gly

cera

ldeh

yde

3-p

ho

sph

ate

Pyr

uva

te

Glycolysis: The Reactions Glycolysis NADH

Pyruvate Oxidation

H2O

ATP

ADP


Krebs Cycle

ATP

ATP

Phosphoglucose isomerase

Glyceraldehyde 3- phosphate (G3P)

Dihydroxyacetone phosphate

1. Phosphorylation of glucose by ATP.

2–3. Rearrangement, followed by a second ATP phosphorylation.

4–5. The 6-carbon molecule is split into two 3-carbon molecules—one G3P, another that is converted into G3P in another reaction.

6. Oxidation followed by phosphorylation produces two NADH molecules and two molecules of BPG, each with one high-energy phosphate bond.

7. Removal of high-energy phosphate by two ADP molecules produces two ATP molecules and leaves two 3PG molecules.

8–9. Removal of water yields two PEP molecules, each with a high-energy phosphate bond.

10. Removal of high-energy phosphate by two ADP molecules produces two ATP molecules and two

1,3-Bisphosphoglycerate (BPG)

1,3-Bisphosphoglycerate (BPG)

Glyceraldehyde 3-phosphate

dehydrogenase

Pi

ADP

Phosphoglycerate kinase

ADP

ATP

3-Phosphoglycerate (3PG)




H2O

ATP

Phosphoenolpyruvate (PEP)

Phosphoenolpyruvate (PEP)

ADP ADP

ATP ATP

Ph

osp

ho

eno

l-

pyr

uva

te

3-P

ho

sph

o-

gly

cera

te

1,3-

Bis

ph

osp

ho

- g

lyce

rate

G

luco

se

6-p

ho

sph

ate

Fru

cto

se

6-p

ho

sph

ate

Fru

cto

se

1,6-

bis

ph

osp

hat

e D

ihyd

roxy

acet

on

e P

ho

sph

ate

2-P

ho

sph

o-

gly

cera

te

CH2OH O

CH2 O O P

CH2 O O P

CH2OH

O CH2 CH2 O O P P

CHOH H C O CH2 O P

C O O CH2 P CH2OH

CHOH O C O CH2 O

P P

CHOH O–

C O CH2 O P

H C O O–

C O CH2OH P

C O O–

C O CH2

P

C O O–

C O CH3

8

9

10

7

4 5

3

2

1

6

Phosphoglyceromutase

7


Without oxygen

NAD+

O2 NADH

ETC in mitochondria

Acetyl-CoA

Ethanol

NAD+

CO2

NAD+

H2O

Lactate

Pyruvate

Acetaldehyde NADH

NADH

With oxygen

Krebs Cycle

8


Glycolysis

Pyruvate Oxidation

NADH

Krebs Cycle


Pyruvate Oxidation: The Reaction

NAD+

CO2

CoA

Acetyl Coenzyme A

Pyruvate

Pyr

uva

te

Ace

tyl C

oen

zym

e A

O

CH 3

C

O–

C O ⎯⎯

⎯⎯

S CoA

CH3

O C ⎯⎯

NADH

9


SEGMENT A Pyruvate from glycolysis is oxidized into an acetyl group that feeds into the citrate cycle. 2-C acetyl group combines with 4-C oxaloacetate to produce the 6-C compound citrate.

SEGMENT B Oxidation reactions produce NADH. The loss of two CO2's leaves a new 4-C compound. 1 ATP is directly generated for each acetyl group fed in.

CoA- (Acetyl-CoA)

CoA

4-carbon molecule

(oxaloacetate) 6-carbon molecule

(citrate)

NAD +

NADH

CO2

5-carbon molecule

NAD+

NADH

CO2

4-carbon molecule

ADP + P

Krebs Cycle

FAD

FADH2

4-carbon molecule

NAD+

NADH

SEGMENT C Two additional oxidations generate another NADH and an FADH2 and regenerate the original 4-C oxaloacetate. ATP

Glycolysis

Pyruvate Oxidation


NADH

FADH2

Krebs Cycle

ATP

SEGMENT A

SE

GM

EN

T C

4-carbon molecule

10


Glycolysis

NADH

F ADH2

Pyruvate Oxidation

ATP

Krebs Cycle: The Reactions

Citrate synthetase

NAD+

NADH

H2O

NAD+

NADH

CO2

F AD Isocitrate dehydrogenase

Fumarase

CoA-SH 1

2

Aconitase 3

4

8

9

7

CoA-SH

NAD+

CO2

5

6

NADH

CoA-SH

GDP + Pi

Acetyl-CoA

═

CH3 — C — S

O CoA —

Krebs Cycle

Malate dehydrogenase

α-Ketoglutarate dehydrogenase

Succinyl-CoA synthetase

GTP

ATP

ADP

Succinate dehydrogenase

FADH2

8–9. Reactions 8 and 9: Regeneration of oxaloacetate and the fourth oxidation

7. Reaction 7: The third oxidation

6. Reaction 6: Substrate-level phosphorylation

5. Reaction 5: The second oxidation

4. Reaction 4: The first oxidation

2–3. Reactions 2 and 3: Isomerization

1. Reaction 1: Condensation

Electron T ransport Chain Chemiosmosis

Oxaloacetate (4C)

CH2

O ═ C

COO—

COO—

—

—

—

Citrate (6C)

HO — C — COO—

COO—

COO—

CH2

CH2

—

—

—

—

Isocitrate (6C)

HC — COO—

COO—

COO—

CH2

HO — CH

—

—

—

—

α-Ketoglutarate (5C)

CH2

COO—

COO—

CH2

C — O —

—

—

—

Succinyl-CoA (4C)

CH2

COO—

S — CoA

CH2

C ═ O

—

—

—

—

Succinate (4C)

COO—

CH2

COO—

CH2

—

—

—

Fumarate (4C)

HC

CH

═

COO—

COO—

—

—

Malate (4C)

HO — CH

COO—

CH2

COO—

—

—

—

11



NADH + H+

ADP + Pi

H2O

H+ H+

2H+ + 1 / 2 O2

Glycolysi s

Pyruvate Oxidatio n

2

Krebs Cycle ATP


NADH dehydrogenase bc1 complex Cytochrome

oxidase complex

FAD

Inner mitochondrial membrane

Intermembrane space

a. The electron transport chain

ATP synthase

ATP

b. Chemiosmosis

NAD+

Q

C

e–

FADH2

H+ H+

H+ H+

e– 2 2 e– 2 2

12


ADP+Pi

Catalytic head

Stalk

Rotor

H+

H+


Intermembrane space

H+ H+

H+

H+ H+

ATP

13


H2O

CO2

CO2

H+

H+

2H+

+ 1 / 2 O2

H+

e-

H+

32 ATP Krebs Cycle

2 ATP

NADH

NADH

FADH2

NADH

Pyruvate Oxidation

Acetyl-CoA

e-

Q

C

e-

Glycolysis

Glucose

Pyruvate

2 ATP

14


Chemiosmosis

Chemiosmosis

2 6

2 4

6 18

2

2

2 6 NADH

NADH

NADH

Total net ATP yield = 38 (36 in eukaryotes)

ATP

ATP

ATP

ATP

ATP

ATP

Krebs Cycle

Pyruvate oxidation

FADH2

Glycolysis 2

Glucose

Pyruvate

ATP

15


Glucose

Acetyl-CoA

Fructose 6-phosphate

Fructose 1,6-bisphosphate

Pyruvate

Pyruvate Oxidation

Krebs Cycle

Electron Transport Chain and

Chemiosmosis

Citrate

ADP

ATP

NADH

Inhibits

Inhibits

Activates

Inhibits

Phosphofructokinase

Pyruvate dehydrogenase

Glycolysis

16


CO2

2 Acetaldehyde

2 AD P

2 Lactate

Alcohol Fermentation in Yeast

2 ADP

Lactic Acid Fermentation in Muscle Cells

2 NAD+

2 NAD+

2 NADH

2 NADH

2 ATP

2 ATP

C O

C O

O–

CH3

C O

H

CH3

C O

C O

CH3

O–

CH3

H C OH

C O

O–

H

2 Ethanol

H C OH

CH3

17


Cell building blocks

Deamination β-oxidation

Glycolysis

Oxidative respiration

Ultimate metabolic products

Acetyl-CoA

Pyruvate

Macromolecule degradation

Krebs Cycle

Nucleic acids Polysaccharides

Nucleotides Amino acids Fatty acids Sugars

Proteins Lipids and fats

NH3 H2O CO2

18


Urea

NH3

19

oxidation reduction product...as a cofactor for oxidation reactions bind nad+ and the substrate. 2....

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