Transcript AP Biology Summer Session Lecture 6

Chapter 9: Cellular Respiration
AP Biology
Mrs. Ramon
ATP
ATP Structure
Close packing of the 3 negatively charged P result in an unstable, E storing arrangement
ADP
ATP
Energy
Energy
Partially
charged
battery
Adenosine triphosphate (ATP)
Fully
charged
battery
Pathways
 Fermentation
 Anaerobic respiration
 w/o oxygen
 Partial degradation of sugar
 Cellular Respiration
 Aerobic respiration
 w/ oxygen
 Mitochondria
How does the decomposition of
glucose lead to E production?
 In cellular respiration, glucose and other fuel molecules are
oxidized, releasing energy.
 C6H12O6 + 6O2  6CO2 + 6H2O
 Glucose is oxidized, oxygen is reduced, and electrons loose potential
energy.
 Molecules that have an abundance of hydrogen are excellent
fuels because their bonds are a source of “hilltop” electrons that
“fall” closer to oxygen.
Oh no! Chemistry again?!?
 What’s an redox reaction?
 Oxidation-reduction or redox reactions
 Transfer of e Oxidation: loss of e Reduction: addition of e Example
 Na + Cl  Na+ + Cl-
What does a redox reaction look like?
How does a redox reaction produce E?
 E is needed/required to pull an e- away from an atom
(uphill)
 E is lost/released when an e- shifts away from a less
electronegative atom to a more electronegative atom
(downhill)
Play it again Sam
 In cellular respiration, glucose and other fuel molecules are
oxidized, releasing energy.
 C6H12O6 + 6O2  6CO2 + 6H2O
 Glucose is oxidized, oxygen is reduced, and electrons loose potential
energy.
 Molecules that have an abundance of hydrogen are excellent
fuels because their bonds are a source of “hilltop” electrons that
“fall” closer to oxygen.
Cellular Respiration

3 metabolic stages:
Glycolysis
2. The Krebs cycle
3. ETC and Oxidative
phosphorylation
1.
In the absence of O2 - Alcoholic Fermentation

Pyruvate is converted to
ethanol in two steps:
1. Pyruvate is converted to a
two-carbon compound,
acetaldehyde by the removal
of CO2.
2. Acetaldehyde is reduced by
NADH to ethanol.
In the absence of O2 - Lactic Acid Fermentation
Pyruvate is reduced directly by
NADH to form lactate (ionized form of
lactic acid).
When O2 is scarce cells will undergo
lactic acid fermentation
The waste product, lactate,
may cause muscle fatigue,
but ultimately it is
converted back to
pyruvate in the liver.
With O2 - Into the mitochondria
 The Krebs cycle
consists of eight
steps.
ATP Synthase
 A protein complex, ATP
synthase, in the cristae
actually makes ATP from
ADP and Pi.
 ATP uses the energy of
an existing proton gradient
to power ATP synthesis.
 This proton gradient
develops between the
intermembrane space
and the matrix.
Options
Facultative anaerobes can survive
using either fermentation or
respiration.
Human muscle cells can behave as
facultative anaerobes, but nerve
cells cannot.
For facultative anaerobes,
pyruvate is a fork in the
metabolic road that leads to two
alternative routes.
Other macromolecules also provide E
Carbohydrates, fats, and
proteins can all be
catabolized through the
same pathways.
Stop!


Control of catabolism is
based mainly on regulating
the activity of enzymes at
strategic points in the
catabolic pathway.
One strategic point occurs
in the third step of
glycolysis, catalyzed by
phosphofructokinase