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Biology 105
Chapter 8: How cells make ATP
Pgs 172-191
Student Outcomes
Give an overview and analysis of the 4
stages of aerobic respiration
Describe the process by which the
proton gradient drives ATP synthesis
Student Outcomes
Summarize how the products of protein and
lipid catabolism enter the same metabolic
pathway that oxidizes glucose.
Describe the energy captured in each state
of aerobic respiration.
Respiration
Organismic respiration - process of gas
exchange between body and the
environment.
Cellular respiration - process of converting
food energy to chemical energy
Cellular respiration
Two types:
Aerobic - requires oxygen
Anaerobic - absence of oxygen, includes
fermentation
Both types are exergonic reactions (release
free energy)
Stage 1 of aerobic respiration
of glucose
• Known as glycolysis
• Takes place in the cytosol
• Glucose molecule is converted to two 3carbon molecules of pyruvate
• ATP and NADH are formed
Stage 1 of aerobic respiration
of glucose cont.
Glycolysis can occur in either
aerobic/anaerobic conditions
Glycolysis has 2 phases
Glycolysis
1st phase
 requires energy (ATP) - endergonic
reactions. (energy investment phase)
A phosphate is transferred from ATP to
the sugar. (phosphorylated)
Glycolysis formula
Glucose + ATP -> 2 G3P + 2 ADP
ATP- Adenosine Triphosphate
ADP- Adenosine Diphosphate
G3P- glyceraldehyde-3-phosphate
Glycolysis
 2nd phase- (energy capture phase)
 Each G3P is converted to pyruvate (a 3 carbon
compound)
 2 NADH and 4 ATP molecules are produced per
glucose molecule.
 2G3P + 2NAD +4ADP -> 2 Pyruvate + 2NADH + 4 ATP
Formation of acetyl
Coenzyme A (CoA)
2nd stage
Takes place in the mitochondria
NAD+ gains an electron and becomes
‘reduced’ to NADH
2 additional NADH are formed per glucose
molecule
2 CO2 molecules are produced
Citric Acid Cycle
3rd stage - also known as the Krebs cycle
(founder Hans Krebs)
Takes place in the mitochondria
3 molecules of NADH, 1 FADH2 and 1 ATP are
formed from each acetyl CoA molecule. Two
CoA molecules were formed after the 2nd
stage. This results in double the products.
ATP synthesis
4 ATP produced so far
2 ATP net in glycolysis
2 ATP in the citric acid cycle
Electron transport chain
4th stage - takes place in the mitochondria
Results in chemiosmosis - formation of ATP
as protons diffuse through transmembrane
channels.
This process is known as oxidative
phosphorylation
Results in 32-34 ATP formed
Body Heat
Most heat generated by a
warmblooded organism (and some
others) is through heat generated as a
byproduct of the electrons moving
down the electron chain. Acceptor
molecules are reduced and oxidized
creating small amounts of heat!
Total ATP
36-38 ATP produced by one molecule of
glucose in aerobic respiration.
36 in muscle, brain cells due to more energy
needed to perform the 4 stages. Loss of 2
ATP’s
Other Energy sources
Fatty acids and amino acids
1 glucose molecule = 36-38 ATPs
1 Lipid molecule = 44 ATPs
Anaerobic Respiration
Does not use oxygen
Electrons are transferred as glucose is
broken down to NADH.
Fermentation
No electron transport chain stage.
Ethyl Alcohol or lactate (lactic acid) are
produced as a byproduct (toxic to cells)
Lactate is used to make yogurt, sauerkraut
and Kimchee.
2 ATP’s produced from 1 molecule of
glucose.
Lactate
3 carbon compound
80% regenerated into glucose by the liver.
20% is metabolized in the muscle cells if
oxygen is present. (this is why heavy
breathing occurs for a short time after
activity)
Lactate fermentation
Short bursts of energy
Once believed that the accumulation
of lactate (lactic acid) in the muscle
cells results in muscle cramps, fatigue
and pain
Creatine Phosphate
CP - Found in muscle cells and aids in
the formation of ATP from ADP
Has short energy span 1-10 seconds,
but will regenerate every 2-3 minutes
Energy use
1 second to 10 seconds (Anaerobic and
CP)
10 seconds to 1 minute (Anaerobic)
1 minute - 4 minutes
(Anaerobic/Aerobic)
4 minutes + (Aerobic)