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Cellular Respiration
Plant cells harvest energy from the sun, and store
it as glucose. That glucose must be transformed
into energy the cell can use, specifically ATP. This
takes place in the mitochondria of cells.
There are two ways that a cell can harvest energy
from the food (glucose) it takes in:
Anaerobic Cell Respiration (Fermentation) –
glucose metabolism in the absence of oxygen
that produces 2ATP molecules and either ethanol
or lactic acid. Involves 2 stages:
Glycolysis
Fermentation
Aerobic Cellular Respiration – glucose
metabolism with oxygen that produces 36 ATP
molecules, CO2 and H2O. Involves 4 stages:
Glycolysis
Pyruvate oxidation
Krebs cycle
Electron transport and chemiosmosis
Stage 1 – Glycolysis
glucose is broken
down through a
series of steps to
produce 2 – 3carbon
molecules of
pyruvate and net 2
ATP.
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Stage 2 – Fermentation
in the absence of oxygen, NADH generated
from glycolysis passes its H atoms to either
acetaldehyde to produce ethanol or to
pyruvate to produce lactic acid.
The miracle of fermentation
Products of fermentation include:
– wine
– beer
– soy sauce
– bread
– carbonated beverages
– cheese
Lactic acid production causes:
– muscle cramps
– soreness
– stiffness
– fatigue
These are all signs of oxygen debt
in the muscles.
During
Fermentation,
NAD+ is restored.
This gives cells the
opportunity to
continue with
cellular respiration
if oxygen becomes
available.
Cellular Respiration
Stage 1 – Glycolysis
glucose is
broken down
through a
series of
steps to
produce 2 –
3carbon
molecules of
pyruvate and
net 2 ATP.
Stage 2 – Pyruvate oxidation
CO2 is removed from pyruvate, NAD+ is
reduced to NADH, and co-enzyme A is
attached to the remaining 2 carbon
molecule to form acetyl Co-A.
Stage 3 – Krebs cycle
a series of reactions that transfers
energy from organic molecules to ATP,
NADH, and FADH2 and removes carbon
as CO2.
Concepts in Biochemistry - Interactive
Animations
Stage 4 – Electron Transport Chain and
Chemiosmosis
NADH and FADH2 carry hydrogen atoms
and electrons to a series of compounds in
the mitochondria that pump H+ ions into
the intermembrane space. As H+ ions
move through channels down the
concentration gradient, ATP is produced.
Oxygen is the final electron acceptor in
the ETC. Without it, electrons cannot
move through the chain and no energy is
made.
Electron transport system
Chemiosmosis
Overview of Cellular Respiration
The Products of Cellular Respiration
What do we get?
Stage
CO2
produced
NADH
produced
FADH2
produced
2
Glycolysis
ATP
consumed
ATP
produced
Net ATP
produced
2
4
4
6
(NADH)
6
( NADH)
Pyruvate
oxidation
2
2
Kreb’s
Cycle
4
6
2
2
24
4 (FADH)
18 (NADH)
TOTAL
6
10
2
38
6
36