Chapter 9: Cellular Respiration

• Living cells require transfusions of energy from
outside sources to perform tasks
• Energy flows into ecosystem as sunlight and
leaves as heat
• Chemical elements essential to life are recycled
• Cellular respiration breaks down fuel to generate
ATP, and the waste products become the reactants
for Photosynthesis
 Organic
compounds store energy in their
arrangement of atoms
- enzymes help break down products
to simpler waste products with less
 One catabolic process, fermentation is a
partial degradation of sugars that occurs
without the use of oxygen
 Cellular
Respiration- oxygen is
consumed as a reactant with organic fuel
- 2 of 3 processes take place in
- similar to combustion of gasoline
- CHO’s, proteins, and fats can
combust and consume fuel
Redox Reactions or Oxidation-reduction
reactions deal with the transfer of one or
more electrons from one reactant to
• Oxidation-the loss of electrons from one
• Reduction- the addition of electrons to another
• Reducing Agent-the electron donor
• Oxidizing agent- electron acceptor
 Reactions
do not occur all at once, but it
steps to properly harness energy
- gas tank explosion doesn’t drive car
Glucose broken in a series of catalyzed
steps by an enzyme
 NAD+ - a oxidizing agent or coenzyme
that will strip electrons along with a
proton (hydrogen)
 NADH is reduced form that is potential
energy and can make ATP
 Glycolysis-breaks
glucose into two
molecules of a compound pyruvate
- cytosol of cell
- does not require oxygen
- catabolic
 Citric
Acid Cycle- Completes the
breakdown of glucose by oxidizing a
derivative of pyruvate to carbon dioxide
- mitochondrial matrix
- redox reaction transfers electrons
and forms NADH
- Also referred to as the Krebs cycle
 Oxidative
phosphorylation: electron
transport and chemiosmosis
- inner membrane of mitochondria
-accounts for 90% of ATP generated
by respiration
synthesis that occurs when an
enzyme transfers a phosphate group
from the substrate to ADP
- generates a smaller amount of ATP
- substrate is generated from
catabolism of glucose
 Glycolysis-
(splitting of sugar) breaks a
six-carbon sugar into two three-carbon
 3 carbon sugars are oxidized and
remaining atoms form 2 molecules of
 10 steps in the reaction
 Energy
investment phase – 2 ATP are
spent in the initial break down of glucose
to its first 5 intermediates
 Energy Payoff phase – ATP is produced
by substrate-level phosphorylation and
NAD+ is reduced to NADH by electrons
released from oxidation of food
- produces 4 ATP molecules
 Net production is 2 ATP molecules