Metabolic Biochemistry

Lecture 9August 19, 2005

Oxidative phosphorylationOther Pathways of

Carbohydrate Metabolism

Photosynthesis

Import of

NADH

into mitochondria

LNC 19-27

Example of a shuttle for oxidizing NADH from the cytosol

LNC 19-26

Getting ATP and ADP

in and out of

mitochondria

LNC 19-25

Biological work

for NADH: P/O ratio ~ 2.5for succinate: P/O ratio ~ 1.5

SUBSTRATE LEVEL PHOSPHORYLATION

GAP + Pi + NAD+ NADH + 1,3 bisphosphoglycerate

1,3 bisphosphoglycerate + ADP ATP + 3 phosphoglycerate

1 ATP produced per NAD+ reducedper GAP used upper 3-PG produced

There is a precise stoichiometry

OXIDATIVE PHOSPHORYLATION

NADH + 1/2 O2 + H+ NAD+ + H2O~ 3 ADP + ~ 3 Pi ~ 3ATP

<3 ATP produced per NADH oxidizedper H2O producedper 1/2 O2 consumed

(P/O ratio ~ 2.5)

There is no precise stoichiometry, because protons can find other paths to return to the matrix

When succinate is the substrate, the P/O ratio is ~1.5,

because only two pumps are used (only 6 protons are pumped per succinate)

Regulation of OXPHOS:

Mitochondria contain DNA (~16.5 kb)

mtDNA encodes

2 rRNAs22 tRNAs

13 proteins (in animals)

mtDNA can have mutations causingmitochondrial diseases

GLUCONEOGENESIS

LNC Chapter 14, Section 14.4

PENTOSE PHOSPHATE SHUNT

LNC Chapter 14, Section 14.5

LNC Fig. 14-15

PhosphoenolpyruvatePEP

fructose-1,6 bisphosphate

phosphatase

phosphatase

pyruvate

first bypass

third bypass

second bypass

LNC Fig. 14-16

BIOTIN is a co-factor utilized for

CARBOXYLATION REACTIONS

THIAMINE PYROPHOSPHATE (TPP)

is a co-factor utilized for

DECARBOXYLATION REACTIONS

LNC Fig. 14-18

in muscle

in liver

first bypass

LNC Fig. 14-19

Chapter 15, Section 15.3 (pp.575)

Coordinated Regulation of Glycolysis and Gluconeogenesis

emphasis on regulation of

phosphofructokinase-1 and

fructose 1,6 bisphosphatase

LNC Fig. 14-16

Phosphofructokinase-1

4 identical subunits (two shown)

1 active site per subunit

1 site for allosteric regulator (ADP/ATP)

LNC Fig. 15.18

Phosphofructokinase-1PFK-1

Fructose bis-phosphataseFBPase

LNC Fig. 15-22

LNC Fig. 15-23

THE PENTOSE PHOSPHATE PATHWAYSection 14.5

two significant products: ribose-phosphate

NADPH

End of Lecture 9

August 19, 2005