Cellular Respiration Part II:
Glycolysis
Curriculum Framework
• f. Cellular respiration in eukaryotes
involves a series of coordinated enzymecatalyzed reactions that harvest free
energy from simple carbohydrates.
2
Big Energy Events of Respiration
– Glycolysis (breaks down glucose into
two molecules of pyruvate)
– The citric acid cycle (completes the
breakdown of glucose)
– Oxidative phosphorylation (accounts
for most of the ATP synthesis)
Big Energy Events of Respiration
Electrons
carried
via NADH
Glycolysis
Glucose
Electrons carried
via NADH and
FADH2
Pyruvate
oxidation
Citric
acid
cycle
Pyruvate
Acetyl CoA
CYTOSOL
ATP
Substrate-level
phosphorylation
MITOCHONDRION
ATP
Substrate-level
phosphorylation
Electrons
carried
via NADH
Glycolysis
Glucose
Pyruvate
Electrons carried
via NADH and
FADH2
Citric
acid
cycle
Pyruvate
oxidation
Acetyl CoA
CYTOSOL
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
MITOCHONDRION
ATP
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Oxidative
phosphorylation
Mitochondrion
Oxygen
Water
Carbon
dioxide
ATP
Fuel (glucose)
Curriculum Framework
GLYCOLYSIS
2.F.1 Glycolysis rearranges the bonds in
glucose molecules, releasing free energy to
form ATP from ADP and inorganic
phosphate, and resulting in the production
of pyruvate.
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Glycolysis
• Glycolysis is thought to be one of the oldest
metabolic pathways.
• This energy harvesting process occurs in the
cytoplasm of both prokaryotic and eukaryotic
cells.
8
Mitochondrion
ATP
Glucose
Glycolysis
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Glycolysis harvests chemical energy by
oxidizing glucose to pyruvate
• Glycolysis (“splitting of sugar”) breaks down glucose
into two molecules of pyruvate
• Glycolysis occurs in the cytoplasm and has two major
phases
– Energy investment phase
– Energy payoff phase
• Glycolysis occurs whether or not O2 is present
Electron carrier (NADH)
ATP
Pyruvic acid
Glycolysis
• Activation energy input
• Splitting the fructose
• Harvesting the energy
–2 NADH + H+, 2 ATP
–Two pyruvates (pyruvic acid)
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Substrate-Level Phosphorylation
Enzyme
Enzyme
ADP
P
Substrate
ATP
Product
Inputs
Outputs
Glycolysis
Glucose
2 Pyruvate  2
ATP
 2 NADH
Curriculum Framework
2.F.2. Pyruvate is transported from
the cytoplasm to the
mitochondrion, where further
oxidation occurs.
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What happens to the pyruvate?
Oxidation of Pyruvate to Acetyl CoA
• Before the citric acid cycle can
begin, pyruvate must be converted
to acetyl Coenzyme A (acetyl CoA),
which links glycolysis to the citric
acid cycle
• This step is carried out by a
multienzyme complex that catalyzes
three reactions
Outer mitochondrial membrane
Inner mitochondrial membrane
Pyruvic acid
Carbon dioxide
Electron carrier (NADH)
Acetyl CoA
MITOCHONDRION
CYTOSOL
CO2
Coenzyme A
3
1
2
Pyruvate
Transport protein
NAD
NADH
+ H
Acetyl CoA
Figure 9.6-3
Electrons
carried
via NADH
Glycolysis
Glucose
Pyruvate
Electrons carried
via NADH and
FADH2
Citric
acid
cycle
Pyruvate
oxidation
Acetyl CoA
CYTOSOL
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
MITOCHONDRION
ATP
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Oxidative
phosphorylation
Closing thoughts…
• What process is
represented by A?
• What process is
represented by B?
• C and D are products of A.
What could they represent?
• What process is occurring at
B?
• What does E represent?
• What is the fate of E?
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Created by:
Debra Richards
Coordinator of Secondary Science Programs
Bryan ISD
Bryan, TX