Pp 78-83
3.7 Cell
respiration
 3.7.1 Define cell respiration.
 3.7.2 State that, in cell respiration, glucose in the
cytoplasm is broken down by glycolysis into pyruvate, with
a small yield of ATP.
 3.7.3 Explain that, during anaerobic cell respiration,
pyruvate can 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 and water with a large yield of ATP.
Syllabus Definition
 Cell respiration is the
controlled release of energy
from organic compounds
in cells to form ATP
 Metabolize/breakdown/ “slow oxidation”
Oxidation
 Oxidation involves the loss of electrons from an
element, whereas reduction involves the gain of
electrons and that oxidation frequently involves
gaining oxygen or losing hydrogen, whereas reduction
frequently involves losing oxygen or gaining hydrogen.
 “Biology” definition of “oxidation”
cell respiration
 Takes place in cytoplasm
(glycolysis) and the
mitochondria (Krebbs and
Electron Tranport Chain)
 Glucose is the major
substrate for respiration
 Adenosine triphosphates
(ATP) is the product and
the molecule which
directly fuels the majority
of biological reactions.
Why cell respiration?
Cells require a
constant source of
energy (renewed
daily) to perform
various tasks e.g.
Metabolism, Synthesis, Active Transport, Locomotion,
Cell Structure, Cell Communication, DNA/RNA
Synthesis, tRNA Protein Synthesis
Types of Respiration
(i) Anaerobic Respiration
(ii) Aerobic Respiration
Occurs in the absence of Oxygen
Occurs in presence of Oxygen
Occurs in the cells’ cytoplasm
Occurs in the cells’ mitochondria
Yields small amount of ATP (2
molecules) per molecule of glucose
Yields large amount of ATP (38
molecules) per molecule of glucose
Involves fermentation of pyruvate to
lactate in muscles/CO2 & ethanol in
plant & yeast
Does not involve fermentation
Comparison between Aerobic & Anaerobic Respiration -Animals
Adenosine triphosphate (ATP):
 ATP is the chemical
molecule which directly
fuels the majority of
biological reactions
 About 1025 ATP
molecules are hydrolysed
to ADP and inorganic
phosphate (Pi) daily
 ADP is reduced back to
ATP using the free
energy from the
oxidation of organic
molecules
ATP Cycle
Anaerobic Cell Respiration
 anaerobic cell respiration occurs in the
absence of oxygen
 during glycolysis glucose is broken breakdown
in the cytoplasm
 leading to the production of pyruvate,
 production of small amount of energy (2 ATP
molecules per molecule of glucose)
 in muscles, pyruvate is converted into lactic
acid during lactic acid fermentation
 anaerobic respiration occurs in animals during
intense muscular activity
 in yeast & plant cells, pyruvate is converted into
alcohol (ethanol) & CO2 during alcoholic
fermentation
 no additional APT is produced during
fermentation
“Three stages” of aerobic respiration
 Stage 1: 2 ATP
 Glycolysis (energy investment)

4 ATP is made, 2 is used –
 Stage 2 (and 3): 38 ATP
 Krebs Cycle (oxidation of pyruvate)

Lots of energy carriers - Generation of CO2
 Oxidative Phosphorylation

Generation of most ATP
Outline the process of aerobic respiration
 during glycolysis glucose is
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partially oxidized in the
cytoplasm
small amount ATP produced
during glycolysis
two pyruvate molecules are
formed by glycolysis
pyruvate absorbed into
mitochondrion
pyruvate is broken down in
the mitochondrion in the
presence of oxygen
to produce carbon dioxide &
water
large amount of energy in
form of ATP is produced per
glucose molecule
Stage 1: Glycolysis
 Where
 Cell’s cytoplasm
 Why
 To break
glucose down
into pyruvate,
which feeds into
the Krebs Cycle
 To regenerate
NAD, an
electron carrier
Krebs Cycle
Structure of a mitochondrion
 the electron micrograph on
the left shows the structure
of a mitochondrion as seen
under the electron
microscope
 draw a labelled diagram to
show the structure of a
mitochondrion
 explain the relationship
between the structure of
the mitochondrion and its
function
Structural adaptation of mitochondrion to its function
 large inner surface area of
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cristae for respiratory
complexes such as electron
transport chains
matrix contains DNA and
ribosomes for protein
(enzyme) synthesis
it also contains Krebs cycle
enzymes
double membrane(s) isolates
metabolic processes from the
rest of the cytoplasm
small intermembrane space
between inner and outer
membranes allows
accumulation of protons for
chemiosmosis
Aerobic respiration
Three stages of respiration
Summary