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Cellular Respiration:
Harvesting Chemical
Energy
Rs - Equation
C6H12O6 + 6 O2
6 CO2 + 6 H2O
and energy
The energy is released from the
chemical bonds in the complex
organic molecules.
Respiration - Preview
The
process of releasing
Energy from food.
Food - Stored Energy in
chemical bonds.
ATP - Useable Energy for cell
work.
Oxidation- Reduction
Reactions
Transfer
of one or more
electrons (e-) from one
reactant to another
Redox Reactions
Oxidation - definitions
Loss
of electrons.
Loss of energy.
Loss of Hydrogens
Reduction - definitions
Gain
of electrons.
Gain of energy.
Gain of Hydrogens
Redox reactions
Generalized Reaction
Xe-
X
+ Y 
X + Ye-
= reducing agent
(substance being oxidized)
Y = oxidizing agent
(substance being reduced)
Redox reactions
Reactions
are usually paired
or linked together.
Look for these links as we
study Respiration (Rs).
Many of the reactions will be
done by phosphorylation
Cellular Respiration
Overall
Which
Equation:
substance is being
oxidized, which is being
reduced?
Phosphorylation
Adding
a phosphate group to
a molecule.
The phosphate group adds
“energy” to the molecule for
chemical reactions.
Two Types of
Phosphorylation
Substrate-Level
Phosphorylation
Small
amount of ATP formed this
way in cells
Oxidative
Phosphorylation or
Chemiosmotic Phosphorylation
Most
ATP formed this way in cells
Substrate -Level
Phosphorylation
Formation
of ATP from ADP and
an inorganic phosphate (Pi)
ADP + Pi  ATP (endergonic rxn)
Energy
is required - comes from
an exergonic reaction in the cell
An enzyme transfers a
phosphate group (Pi) from a
substrate molecule to ADP
Substrate-Level
Phosphorylation
Oxidative or Chemiosmotic
Phosphorylation
H+
atoms are deposited into the
outer compartment of
mitochondria and this creates an
“electrochemical” gradient
across the membrane
As H+ atoms move from [high] to
[low] energy is given off
This energy is captured by ADP
+ Pi to produce ATP
Cell Respiration 4 parts
1. Glycolysis: 10 step process in
cytoplasm
2. Pyruvate Oxidation: 1 step process in
mitochondrial matrix
3. Krebs Cycle (Citric Acid Cycle): 8 step
cyclical process in mitochondrial
matrix
4. Electron Transport and Chemiosmosis:
a multistep process in inner
mitochondrial membrane
3 Goals of Rs



1. Break bonds between 6C
glucose to make 6CO2
2. Move H+ from glucose to
oxygen, forming 6H2O
3. Trap as much free energy
in the form of ATP
Glycolysis
Glyco-
glucose.
-lysis: to split
Universal step in all Rs types.
Likely to be earliest type of
cell energy processes.
Glycolysis
Function
- To split glucose
and produce NADH and ATP.
Location - Cytoplasm.
Overview of Glycolysis
Glycolysis -Requirements
Glucose
2
ATP
4 ADP
2 NAD+
Glycolysis - Products
2

2
Pyruvic Acids (pyruvate)
(a 3C acid)
ADP
4 ATP
2 NADH
Net Result
2
ATP per glucose
2 NADH
Energy Investment Phase
Energy Harvest Phase
Pyruvate Oxidation
- occurs twice for each pyruvate
Transition step between
Glycolysis and Krebs Cycle


1.
2.
3.
Occurs between cytoplasm and
mitochondrial matrix
Removes CO2 from pyruvate to
form acetate molecule
Forms NADH + H+
Co-enzyme A attaches to acetate
molecule
Formation of Acetyl CoA
Structure of
Mitochondrion

See separate handout
Krebs Cycle
Also
called:
Citric
Acid Cycle
Tricarboxylic Acid Cycle
Krebs Cycle
Function:
Oxidize Acetyl coA
to CO2
Produce NADH and FADH2
Location: Mitochondrial
matrix
Krebs Cycle -Requirements
Acetly
coA (2C)
NAD+
1 ADP
1 FAD
Double this list for each
glucose.
3
Krebs Cycle - Products
2
CO2
3 NADH
1 ATP
1 FADH2
Double this list for each
glucose.
Krebs Cycle
Produces
most of the cell's
energy in the form of NADH
and FADH2
Does NOT require O2
Comment
The
ATPs produced directly
in Krebs Cycle and in
Glycolysis are by:
Substrate-level
phosphorylation
The Pi group is transferred
from a substrate to ADP.
Electron Transport
Chain
ETC
or Electron Transport
System (ETS).
A collection of proteins that
are structurally linked into
units.
ETC
Uses
sets of Cytochromes, Fe
containing proteins to pass
electrons.
The Cytochromes alternate
between RED and OX forms
and pass electrons down to O2
ETC
Function:
Convert NADH and
FADH2 into ATP.
Location: Mitochondria
cristae.
ETC - Requirements
NADH
ADP
O2
or FADH2
ETC - Products
NAD+
ATP
H2O
and FAD
ETC - ATP Yields
Each
NADH -- 3 ATP
Each FADH2 -- 2 ATP
Chemiosmotic
Hypothesis
ETC
energy is used to move
H+ (protons) across the
cristae membrane.
ATP is generated as the H+
diffuse back into the matrix.
ATP Synthase
Uses
the flow of H+ to make
ATP.
Works like an ion pump in
reverse, or like a waterwheel
under the flow of H+ “water”.
Alcoholic Fermentation
Done
by yeast, a kind of
fungus.
Movie
Alcoholic Fermentation
Uses
only Glycolysis.
An incomplete oxidation energy is still left in the
products (alcohol).
Does NOT require O2
Produces ATP when O2 is not
available.
Lactic Acid
Fermentation
Uses
only Glycolysis.
An incomplete oxidation - energy
is still left in the products (lactic
acid).
Does NOT require O2
Produces ATP when O2 is not
available.
Movie
Lactic Acid
Fermentation
Done
by human muscle cells
under oxygen debt.
Lactic Acid is a toxin and
causes soreness and
stiffness in muscles.
Fermentation Summary
Way
of using up NADH so
Glycolysis can still run.
Provides ATP to a cell even
when O2 is absent.
Aerobic vs Anaerobic
Aerobic
- Rs with O2
Anaerobic - Rs without O2
Aerobic - All three Rs steps.
Anaerobic - Glycolysis only.
Strict vs. Facultative
Strict
- can only do Rs this
one way.
Facultative - can switch Rs
types depending on O2
availability. Ex - yeast
Question
Since
yeast can do both
aerobic and anaerobic Rs,
which is the better process if
given a choice?
Check the ATP yields from
both processes.
ATP yields by Rs type
Anaerobic
- Glycolysis only
Gets 2 ATPs per glucose.
Aerobic - Glycolysis, Krebs,
and ETC. Generates many
more ATPs per glucose.
Aerobic ATP yield
Glycolysis
- 2 ATPS, 2 NADHs
Krebs - 2 ATPS, 8 NADHs,
2 FADH2
Each NADH = 3 ATP
Each FADH2 = 2 ATP
ATP Sum
10



NADH x 3 = 30 ATPs
2 FADH2 x 2 =
4 ATPs
2 ATPs (Gly) = 2 ATPs
2 ATPs (Krebs) = 2 ATPs
Max
= 38 ATPs per glucose
However...
Some
energy is used in
shuttling the NADH from
Glycolysis into the
mitochondria.
Actual ATP yield ~ 36/glucose
Yeast
Would
rather do aerobic Rs;
it has 18x more energy per
glucose.
But, anaerobic will keep you
alive if oxygen is not present.
Importance of Rs
Convert
food to ATP.
Provides materials for use in
other cellular pathways.
Other Importances of
Respiration
Alcohol
Industry - almost
every society has a
fermented beverage.
Baking Industry - many
breads use yeast to provide
bubbles to raise the dough.
Summary
Know
the 3 main reactions
(plus pyruvate oxidation) of
Rs and the 4 required items
for each.
Appreciate the importances
of Rs.