Electrons from food 2e Energy released Product for ATP ......Copyright © The McGraw-Hill Companies,...

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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

Adenosine

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

SEGME

NT B

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

Electrons from food 2e Energy released Product for ATP ......Copyright © The McGraw-Hill Companies,...

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Transcript of Electrons from food 2e Energy released Product for ATP ......Copyright © The McGraw-Hill Companies,...