Cellular Respiration
Cellular respiration is the controlled release of
energy from organic compounds (lipids,
carbohydrates and proteins) in cells
to produce ATP.
OBJECTIVES
 Define ‘Cellular Respiration.
 State that, in cell respiration, glucose in the cytoplasm is
broken down by glycolysis into pyruvate, with a small yield of
ATP.
 Explain that, during anaerobic cell respiration, pyruvate
be converted in the cytoplasm into lactate, or ethanol
and carbon dioxide, with no further yield of ATP.
 3.7.4 Explain that, during aerobic cell respiration, pyruvate
can be broken down in the mitochondrion into carbon
dioxide & water with a large yield of ATP.
SOME GUIDING PRINCIPLES
The Laws of Thermodynamics
 First Law: Energy can be converted from one form to
another, but it cannot be created nor destroyed.
 Second Law: Energy cannot be converted from one
form to another without some loss of usable energy.
Energy is the ability to do work.
Cellular Respiration (The Basics)
Cellular respiration is the controlled release of energy
from organic compounds (lipids, carbohydrates and
protein) in cells to form ATP.
 Occurs in ALL ORGANISMS (even those organisms
like prokaryotes w/out mitochondria) because all
living cells need a continual supply of energy.
 Cellular respiration is considered a catabolic
reaction and involves a series of very complex
metabolic reactions involving numerous enzymes.
ATP: THE UNIT OF CELLULAR ENERGY
 ATP (adenosine triphosphate) releases energy when
the bond between the 2nd and 3rd phosphate group is
broken, forming a molecule called adenosine
diphosphate (ADP) and a free phosphate group.
Cellular Respiration Involves a Transformation of
Energy.
The Balanced Equation for Cellular Respiration
Can You Interpret the Equation?
Organisms obtain energy in this process.
Cellular Respiration and Breathing (Respiration)
Cellular Respiration occurs at the cellular
level and is NOT the same thing as breathing.
 Cellular Respiration occurs at the cellular
level (cytoplasm and mitochondrion in
eukaryotes) and inner cell membrane
(prokaryotes).
 Breathing delivers a reactant (oxygen gas)
for cell respiration and removes a waste
product (carbon dioxide).
Where Does Cellular Respiration Occur?
In prokaryotes, however, cell
Respiration occurs in the folds of the
Cell membrane.
Cellular Respiration Occurs in 2 Steps: Glycolysis
and Aerobic Respiration
In aerobic
cell
respiration,
approx.
36-38 ATP
are
produced per
glucose
Molecule.
Glycolysis (The 1st Step)
 Glucose is often, but not always, the organic compound used in cell
respiration. Chemical reactions in the cytoplasm break down glucose
into a simpler organic compound called pyruvate. A small amount of
ATP is released.
NET YIELD
 2 Molecules of ATP are
formed (net gain).
 2 Molecules of NADH are
formed.
 2 Pyruvate Molecules
THE KREBS CYCLE (2nd STEP)
 If oxygen is available, the two
pyruvate molecules enter the
mitochondrion (matrix). Most
of the energy from glucose is
still contained in pyruvate at
this point.




Net Yield
6CO2 molecules
2 ATP molecules
8 NADH molecules
2 FADH2 molecules
THE ELECTRON TRANSPORT CHAIN
 The final step in the breakdown of glucose.
 Oxygen is the terminal electron acceptor.
 Occurs in the inner membrane folds (cristae)
 A large amount of ATP (36-38 ATP molecules) is
produced from one glucose molecule.
The Electron Transport Chain
Anaerobic Cell Respiration
 If no oxygen is available, the pyruvate remains in the cytoplasm and is
converted into a waste product that can be removed from the cell. No
ATP is produced in these reaction. In humans, the waste product
lactate (lactic acid) is produced. In yeast, the products are ethanol
(alcohol) and carbon dioxide.
SUMMARY