3. Introduction to Cell Respiration
and Fermentation
• Cellular Respiration- is a metabolic process used
to obtain energy from organic compounds or food
• With or without O2
• Catabolic pathways
• Occurs in the cytoplasm and mitochondria
• 3 main steps:
– Glycolysis
– Kreb Cycle, also known as the citric acid cycle
and tricarboxylic acid cycle
– ETC (electron transport chain)
6. ATP Produced?
• Oxidative phosphorylation, which produces 90% of
all ATP.
•
• Substrate-level phosphorylation
• Ultimately 38 ATP are produced per glucose
12. The Kreb Cycle Overview
• Named after Hans Krebs who was mainly responsible
for discovering its pathways in the 1930’s.
• 8 enzyme assisted steps.
• 75% of the original energy in glucose is still present in
the 2 molecules of pyruvate
• With oxygen present the pyruvate enter the in the
mitochondrion
• Products: 6 NADH, 2 ATP, 2 FADH2, 4 CO2 (byproduct)
16. ETC
• The majority of the ATP produced comes from the
energy carried in the electrons of NADH (and
FADH2) that were produced by the Krebs Cycle.
• There are thousands of ETC’s found in each
mitochondria, which can number in the 100’s
depending on the cell type.
• Makes 34 of 38 ATP
• Driven by molecular O- final electron acceptor
18. Chemiosmosis: The Energy-Coupling Mechanism
• ATP
synthase
INTERMEMBRANE
SPACE
H+
H+
H+
H+
H+
H+ H+
H+
P i
+
ADP
ATP
A rotor within the
membrane spins
clockwise when
H+ flows past
it down the H+
gradient.
A stator anchored
in the membrane
holds the knob
stationary.
A rod (for “stalk”)
extending into
the knob also
spins, activating
catalytic sites in
the knob.
Three catalytic
sites in the
stationary knob
join inorganic
Phosphate to ADP
to make ATP.
MITOCHONDRIAL
MATRIX
Figure 9.14
19.
20. Fermentation Overview
• Produces ATP without oxygen.
• No ETC is present since there is no oxygen
• NAD+ gets recycled by use of an organic hydrogen
acceptor like lactate or ethanol.
• Common in prokaryotes and very useful to humans.
• Two type lactic acid and alcohol fermentation.
21. Alcohol Fermentation
• Pyruvate is
converted to
ethanol in
two steps.
• Alcohol
fermentation
by yeast is
used in
brewing and
winemaking.
