Download Ch.9 Cell Respiration Notes

Chapter 9.1 Notes
“Cellular Respiration: An Overview”
 Food serves as a source of energy for us.
o When you are hungry you feel weak because you are
lacking energy that food provides.
o Food is made of chemical energy (a type of potential
energy). When the bonds within food are broken
down, energy is released.
 The energy within food is measured in calories.
o 1 calorie = the amount of energy needed to raise 1g of
water 1°Celsius
o A Calorie on food labels = 1 kilocalorie (1000 calories)
How our bodies release the energy that food contains:
Cellular Respiration – the process that releases energy from
food in the presence of oxygen
Oxygen + Glucose  Carbon Dioxide + Water + Energy
6 O2 + C6H12O6  6 CO2 + 6 H2O + Energy
 This reaction occurs in many separate steps. The above
equation is a summary of the reactions that take place.
 Three stages of cellular respiration:
o Glycolysis
o The Krebs cycle
o The Electron Transport Chain
Aerobic Respiration: Krebs cycle and electron transport chain
 Requires oxygen
Anaerobic Respiration: Glycolysis
 Oxygen is not required
Photosynthesis and respiration are opposite processes.
 Photosynthesis “deposits” energy (in the form of a fuel
– glucose).
 Cellular respiration “withdraws” energy (by breaking
down glucose).
 Photosynthesis removes CO2. Cellular respiration
adds it back to the atmosphere.
 Photosynthesis releases O2 into the atmosphere.
Cellular respiration removes it.
 Photosynthesis only occurs in autotrophic organisms
(green plants, algae, some bacteria).
 Cellular respiration occurs in nearly all life (plants,
protists, animals, most bacteria).
Chapter 9.2
“The Process of Cellular Respiration”
Glycolysis – occurs in the cytoplasm
 Each molecule of glucose that is broken down
results in the formation 2 molecules of ATP and 2
molecules of NADH.
o Glucose – a 6-Carbon sugar is broken down to
two 3-Carbon compounds (pyruvic acid –
pyruvate)
o 4 molecules of ATP are produced
o 2 molecules of NADH are produced from NAD+.
These enter the electron transport chain.
o Explain why there is a net yield of two ATP, not
4, in glycolysis.
Krebs Cycle: aerobic – requires oxygen
most of the energy from glucose is in pyruvate molecules
from glycolysis
 The series of reactions that break down pyruvate into
carbon dioxide is the Krebs cycle (aka. tricarboxylic
acid cycle (TCA) or citric acid cycle).
 First each pyruvate reacts with coenzyme A (CoA) to
form acetyl CoA.
o Acetyl CoA moves into the mitochondrial matrix –
innermost compartment of the mitochondria.
o Acetyl CoA combines with a 4-C compound to
make citric acid.
o Citric acid is broken down to release 2 carbon
dioxide and 1 ATP.
o Net gain of 2 ATP (because this starts with 2
pyruvate molecules).
o FADH2 and NADH are electron carriers that enter
into the electron transport chain.
Electron Transport: high energy electrons are used to convert
ADP into ATP
 These electrons are generated from glycolysis and the
Krebs cycle and are carried by electron carriers – NAD+
and FAD+.
 Aerobic
 Most ATP is produced
 Occurs along the inner mitochondrial membrane in
eukaryotes and along the cell membrane of prokaryotes.
 ATP produced using chemiosmosis – ATP synthase in the
membrane spins as H+ ions cross through. With each
rotation a phosphate group is added to an ADP.
 On average each pair of electrons that pass down the
electron transport chain generate enough energy to
produce 3 ATP
 Oxygen is the final electron acceptor.
 Protons and electrons are transferred to oxygen to form
water.
 36 ATP produced from cellular respiration