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Respiration
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RESPIRATION
! Breathing
! A mechanism for providing ATP, NADH
! The release of free energy by oxidationreduction reactions (and storage of part of that
free energy)
Example
glucose + O2 ---> CO2 + H2O
!G=-673 Kcal/mole glucose
Through coupled reactions, some of this free
energy can be applied to the formation of ATP,
NADH.
Respiration
(aerobic)
Animals
Plants
Protists
Fungi
Some bacteria
Fermentation
(anaerobic)
Fungi
Some bacteria
Animals and
plants (for
short periods
only)
Overall reaction of respiration
Inputs
glucose
C6H12O6
6 O2
36 ADP +
36 Pi
Outputs
6 H2 O
6 CO2
36 ATP +
36 H2O
Heat
Glycolysis: the initial metabolism of glucose
Heat
1
2 NAD+
2 (ADP + Pi)
2 (ATP + H2O)
2
2 NADH + H+
! 10 reactions, each with its own soluble enzyme; all
enzymes in endoplasm
! Converts 1 glucose (C6H12O6) to 2 pyruvic acids
(C3H4O3)
! Partial oxidation of glucose (- 4e-); reduction of
+
+
NAD to NADH + H
! Forms 2 ATP (net: uses 2, produces 4)
! Produces waste heat
Glycolysis: the initial metabolism of glucose
Uses ATP
Makes ATP
Pyruvic acid oxidation and Citric Acid Cycle
2
Heat
6 H2 O
6 CO2
2(GDP + Pi)
2(GTP + H2O)
! 9 reactions, each with its own enzyme, 8
arranged in a cycle; all but one soluble; all in
the matrix of the mitochondrion.
! Completely oxidizes pyruvic acid to CO2 (20e-); 16 to NADH + H+, 4 to FADH2
8NAD+ 2FAD 2FADH2 8NADH ! Adds 6 H2O
+ 8H+ ! Forms 2 GTP (like ATP but with a different
base)
! Produces waste heat
Pyruvic acid oxidation
and the Citric Acid Cycle
Makes NADH
Makes NADH
Makes FADH2
Makes GTP(ATP)
Electron transport chain: synthesis of ATP
10NADH 2FADH2 2FAD 10NAD+
Heat
6 O2
ELECTRON TRANSPORT
CHAIN
32(ADP + Pi)
12 H2O
32(ATP + H2O)
! Electron carriers in the membrane of the cristae
! All proteins (enzymes) with cofactors, FAD and
heme, which carry electrons (i.e., can be alternately
reduced and oxidized)
! Oxidize NADH and FADH2 (-2 e- per each
+
nucleotide, -24 total) to NAD , FAD
! Reduce O2 to H2O (6 O2 = 12 O = 24 e-)
! Synthesize 32 ATP from ADP + Pi (3*8
mitochondrial NADH+ 2*2 endoplasmic NADH +
2*2 FADH2)
! Produce waste heat
Electron transport chain: synthesis of ATP
Summary
! Free energy in glucose + O2 released through
glycolysis, pyruvic acid oxidation, citric acid
cycle
! Converted temporarily to free energy of NADH
and FADH2 + O2
! A fraction finally saved as free energy of ATP
(and GTP) + H2O
Next: how ATP is synthesized