Cellular Respiration Part 2
Glycolysis - Pages 93 to 95
Overview: Cellular Respiration
• Cellular Respiration takes place in three steps:
▫ Glycolysis – initial breakdown of glucose; very
little direct energy production; takes place in
cytoplasm
▫ Krebs Cycle – finishes the breakdown of glucose;
very little direct energy production; takes place in
the matrix of the mitochondria
▫ Oxidative Phosphorylation – major energy
producing process; takes place in the cristea of the
mitochondria
Fig. 9-6-3
Electrons
carried
via NADH and
FADH2
Electrons
carried
via NADH
Citric
acid
cycle
Glycolysis
Pyruvate
Glucose
Oxidative
phosphorylation:
electron
transport
and
chemiosmosis
Mitochondri
on
Cytosol
ATP
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Oxidative
phosphorylation
Glycolysis
• 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
Fig. 9-8
Energy investment
phase
Glucos
e
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 Pyruvate
Net
Glucose
4 ATP formed – 2 ATP used
2 NAD+ + 4 e– + 4 H+
2 Pyruvate
2 ATP
2 NADH + 2 H+
Glycolysis
• Takes place in the cytoplasm
• Believed to be the oldest metabolic process –
shared by all organism
• ATP produced during the process via substrate
level phosphorylation
Glycolysis – summarized in words
• 2 molecules of ATP are used to start the process –
phosphorylating (energizing) the 6 carbon molecule–
unstable 6C
• Unstable 6 C splits into to 3 C called G3P
• Oxidation of 2-3C (G3P) and reduction of 2 NAD+ to
2NADH releases enough energy to phosphorylate the 3C
molecule
• Phosphates removed from 2-3C molecules in substrate
level phosphorylation to produce 4 ATP; end with
pyruvate
Glycolysis Summary
• Reactants
▫ Glucose, 2ATP and 2NAD+
• Products
▫ Pyruvate, 4 ATP, and 2 NADH
• Net gain of ATP
▫ 2 ATP
• Do you need to know all of the intermediates in the
process?
▫ NO – understand that it occurs in several steps, each
step involves different enzymes & results in a different
carbon compound