Cell Metabolism and Product Formation. Metabolic pathways catabolismanabolism proteins, carbohydrates lipids, nucleic acids glucose CO 2, H 2 O, energy.

Cell Metabolism and Product Formation

Metabolic pathways

• catabolism • anabolism

proteins, carbohydrateslipids, nucleic acids

glucose

CO2, H2O, energy

intermediates

glucose + energy

amino acids, sugarsfatty acids, nucleic acids

amino acids, sugarsfatty acids, nucleic acids

proteins, carbohydrateslipids, nucleic acids

Energy storage in cell

• adenosine triphosphate (ATP)

ATP + H2O ADP + Pi ∆Go = -7.3 kcal/mol

ADP + H2O AMP + Pi ∆Go = -7.3 kcal/mol

Adenine

CH

CH

O

CH

CH

CH2O

OHOH

P

O

OH

P

O

O

OH

OH

OH

O

O

P

Glycolysis via Embden-Meyerhof-Parnas (EMP) pathway

EMP pathway

glucose

pyruvic acid + ATP

CO2 + H2O + NADH + e-

Krebs, tricarboxylic acid,citric acid cycle

water + ATP

electron transport chain,respiration

O2

Important coenzymes

Oxidation Reductionreactions (redox)

oxidant + ne- reductant

redox couple

2H+ + 2e- H2

R

C

CH

C

N+

CH

CH

H

CONH2

HH

R

C

CH

C

N

CH

CH

CONH22H+ + 2e-

- 2H+

SH2

S

NAD

NADH2

oxid red

O

H

O

N

N

N

NCH3

CH3

R H

H O

H

O

N

N

N

NCH3

CH3

R

2H+ + 2e-

FAD oxidized form FAD reduced form

-2H+ oxid +2H+ redn -2H+ oxid +2H+ redn

CH3

COOHO

CH3

COOHO

lactic acid

pyruvic acid

NADH2

NAD

FAD

FADH

NAD oxidized form NADH reduced form

EMP Pathway

OH

O

H OH

OH H

H OH

H OH

OPO3H2

O

H OH

OH H

H OH

H OH

OPO3H2

OH

O

OH H

H OH

H OH

OPO3H2

OPO3H2

O

OH H

H OH

H OH

OPO3H2

H O

H OH

OH

OPO3H2

O

O OPO3H2

OPO3H2

H OH

O OH

OPO3H2

H OH

O OH

OH

H OPO3H2

O

CH2

OH

OPO3H2

OH2

O

CH3

OH

O

ATP ADP

hexokinase

glucose glucose-6-phosphate fructose-6-phosphate fructose 1,6-diphosphate

glyceraldehyde 3-phosphate 1,3-diphosphoglycerate 3-phosphoglycerate 2-phosphoglycerate

dihydroxyacetone phosphate phosphoenolpyruvate pyruvate

isomerase

ATP ADP

kinase

NAD+ NADH

Pi

dehydrogenase ADP ATP

kinase

mutase

triose phosphate isomerase

ADP ATP

kinase

aldolase

Overall reaction in glycolysis

glucose + 2 ADP + 2 NAD+ + 2 Pi 2 pyruvate + 2 ATP + 2 NADH + H+

net yield is 2 mol ATP/mol glucose

O

CH3

OH

O

CH3

O CO2+

CH3

OHpyruvate decarboxylase alcohol dehydrogenase

NADH NAD+

O

CH3

OH

OH

NADH NAD+

lactate dehydrogenase

lactic acid

acetyl-CoA + 3NAD+ + FAD + ADP + Pi + 2H2O

CoA + 3(NADH+H+) + FADH2 + ATP + 2CO2

TCA cycle

NAD+

NADH2

AH2

A

FADH

FAD

Fe3+

Fe2+

Fe2+

Fe2+

Fe2+

Fe3+

Fe3+

Fe3+

ferric (oxidized)

ferric (reduced)

*2H+ + 1/2 O2

H2O

ATP

ADP

ATP

ADP ADP

ATP

Cyt b Cyt c Cyt a Cyt a3

*2H+

protons and electrons electrons (negative positive e- potential)

1.14V reduction potential

Respiration: Electron transport chain, O2 as terminal electron acceptor

Theoretically: 4 ATP/2H+ + 2e-

Eucaryotes: Typically 3 ATPProcaryotes: Typically 1 ATP

Summary

glucose + 36 Pi + 36 ADP + 6 O2 6 CO2 + 6 H2O + 36 ATP

36 ATP = 263 kcal/mol glucose

free energy change is 686 kcal/mol

energy efficiency of glycolysis is 38% (under standard conditions)

real efficiency >60%