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Figure 7.2
Light
energy
ECOSYSTEM
CO2  H2O
Photosynthesis
in chloroplasts
Cellular respiration
in mitochondria
ATP
Heat
energy
© 2014 Pearson Education, Inc.
Organic
 O2
molecules
ATP powers
most cellular work
To review from last time…..
 Energy flows through nature in the form of chemical energy,
which is stored in bonds, especially C-C, C-H
 Mitochondria are the site of energy production in eukaryotic
cells
 Compounds can be oxidized or reduced, in respiration, fuels
(glucose) are oxidized while O2 is reduced
 Respiration has three main steps: Glycolysis, Citric Acid Cyle,
and Oxidative Phosphorylation (ETC)
 You must be able to explain this equation and its importance
© 2014 Pearson Education, Inc.
Figure 7.UN06
Glycolysis
ATP
© 2014 Pearson Education, Inc.
Pyruvate
oxidation
Citric
acid
cycle
Oxidative
phosphorylation
ATP
ATP
Glycolysis harvests chemical energy by oxidizing
one glucose (6C) to two pyruvate (3C) molecules
 Glycolysis occurs in the cytoplasm and has two major
phases
 Energy investment phase
 Energy payoff phase
 Glycolysis occurs whether or not O2 is present
 In bacteria, glycolysis occurs extracellularly
 No carbon is released in the process
 Products are: 2 pyruvates, 2 ATP (net), 2 NADH, 2 H+
 While energy is released, it is a small amount
© 2014 Pearson Education, Inc.
Figure 7.8
Energy Investment Phase
Glucose
2 ADP  2 P
2 ATP
used
4 ATP
formed
Energy Payoff Phase
4 ADP  4 P
2 NAD  4 e−  4 H
2 NADH  2 H
2 Pyruvate  2 H2O
Net
Glucose
4 ATP formed − 2 ATP used
2 NAD  4 e−  4 H
© 2014 Pearson Education, Inc.
2 Pyruvate  2 H2O
2 ATP
2 NADH  2 H
Figure 7.UN07
Glycolysis
ATP
© 2014 Pearson Education, Inc.
Pyruvate
oxidation
Citric
acid
cycle
Oxidative
phosphorylation
ATP
ATP
Figure 7.10a
When O2 is present, pyruvate enters a
Mitochondrion and is oxidized
Pyruvate
CYTOSOL
(from glycolysis,
2 molecules per glucose)
CO2
NAD
CoA
NADH
 H
MITOCHONDRION
© 2014 Pearson Education, Inc.
Acetyl CoA
CoA
• 2 molecules pyruvate/glucose
• This means all downstream
reactions occur 2X/glucose
• After entering:
• Enzymes remove CO2
• NAD+ is reduced to
become NADH
• Becomes acetyl-CoA
• Acetyl-CoA takes its
acetyl group to the citric
acid cycle
 From 1 molecule of glucose:
2 molecules CO2
2 NADH, + 2 H+
2 acetyl-CoA