Cellular Respiration
Topic 3.7 and 3.8
Assessment Statements: SL
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.
Cellular Respiration: Standard level
How does the process of cellular respiration
yield ATP (chemical energy) from food?
1.What do you already know about cellular
respiration?
2.What organelle in the cell is the
“powerhouse” that makes energy for the cell?
What is ATP?
• Energy ‘currency’ used by all cells
• Adenosine triphosphate
• Organic molecule containing high-energy
phosphate bonds
Chemical Structure of ATP
Adenine Base
3 Phosphates
Ribose Sugar
How Do We Get Energy From ATP?
By breaking the highenergy bonds
between the last
two phosphates in
ATP
ATP hydrolase
(ATP’ase) catalyses
the breakdown of
ATP into ADP + Pi
Each day, you hydrolyse 1025 ATP molecules
ATP-ase
ATP Synthetase
HYDROLYSIS (Adding H2O)
H 2O
How is ATP re-made?
• Substrate-level phosphorylation
(using enzymes: in the cytoplasm of the cell
and the matrix of the mitochondrion)
• Chemiosmosis (in the mitochondria, using
ATP synthase)
Substrate level phosphorylation and
chemiosmosis
Definition of cellular respiration
Controlled release
of energy from
organic
compounds to
produce ATP
• Cells break down
organic compounds by
SLOW oxidation
• Chemical energy is
stored in covalent
bonds
• By releasing energy in a
controlled way, it can be
trapped in the ‘useful’
form of ATP
Cellular Respiration
Breakdown of one
glucose results in 36
to 38 ATP molecules
• Metabolic Pathway
that breaks down
carbohydrates
• Process is exergonic as
high-energy glucose is
broken into CO2 and
H2O
• Process is also catabolic
because glucose breaks
into smaller molecules
Equations for aerobic respiration
All of these are fine!....
Equation for Cellular Respiration
C6H12O6
+ 6O2
YIELDS
6CO2 + 6H20 + e- + 36-38ATP
+ heat
Stages of Cellular Respiration
1.
Glycolysis ALWAYS
OCCURS
2.
Anaerobic pathways if no
oxygen available (Lactic
acid and Ethanol
fermentation)
3.
Aerobic pathways if
oxygen available (Link
reaction, Krebs cycle,
electron transport chain)
Where Does Cellular Respiration
Take Place?
glycolysis occurs in
the cytoplasm
Krebs Cycle & ETC Take place
in the mitochondria
Glycolysis: Always the initial
stage of respiration
•
•
•
•
Location: cytoplasm
Substrate: glucose
Requires input of 2 ATP
Products: pyruvate,
(NADH), 4 ATP
Glycolysis is an
anaerobic process: no
oxygen required
the movie...
Glycolysis
If no oxygen is
available, glycolysis
(anaerobic) is
followed by
fermentation
(anaerobic)
Why fermentation?
In the absence of oxygen, glycolysis soon
stops unless there is an alternative
acceptor for the electrons produced from
the glycolytic pathway
Fermentation
1. Alcoholic
fermentation
Pyruvate is
converted into
ethanol plus
carbon dioxide
and NAD+
2. Lactate
fermentation
Pyruvate is
converted into
lactate and NAD+
Alcoholic fermentation in yeast
Alcoholic fermentation in yeast
• Pyruvate is produced from glycolysis
• 3-carbon pyruvate is converted to 2-carbon ethanol and
carbon dioxide
• Generation of carbon dioxide helps bread products to rise
• Yeast is used to produce ethanol
Lactate fermentation in mammals
• Lactate is a 3carbon molecule
• NAD+ is
regenerated to
allow glycolysis to
continue
Aerobic respiration
• Takes place in the
mitochondria of eukaryotic
cells
• Substrate: pyruvate
• Produces LOTS of ATP (28
– 38 ATP): 90% of total ATP
from respiration
• Also produces carbon
dioxide, water and heat
• Oxygen is the final electron
acceptor
Aerobic respiration: the most efficient
pathway for ATP generation
Aerobic respiration
• 2 pyruvate molecules
enter the
mitochondrion
• Pyruvate loses a CO2
molecule and becomes
acetyl CoA
• Krebs cycle produces 2
ATP and CO2
• Electron transport chain
produces 34 ATP and
water
• Aerobic respiration
completely oxidises a
glucose molecule
• Anaerobic respiration
does not completely
oxidise glucose –
ethanol, lactate and
carbon dioxide are byproducts
Some practice questions on
respiration…
1. How do cells capture the energy released
by cell respiration?
A. They store it in molecules of carbon
dioxide.
B. They produce glucose.
C. The energy is released as pyruvate.
D. They produce ATP.
(Total 1 mark)
Some practice questions on
respiration…
2. Which process produces the most ATP
per molecule of glucose?
A. Anaerobic respiration in a yeast cell
B. Aerobic respiration in a bacterial cell
C. Glycolysis in a human liver cell
D. The formation of lactic acid in a human
muscle cell
(Total 1 mark)
Some practice questions on
respiration…
3. Which of the following is the best definition of cell respiration?
A.
A process needed to use energy, in the form of ATP, to produce
organic compounds
B.
A process used to provide oxygen to the atmosphere
C.
A controlled release of energy, in the form of ATP, from organic
compounds in cells
D.
A controlled release of energy in the production of food from
organic compounds
(Total 1 mark)
Some practice questions on
respiration…
4. Which of the following processes produces CO2?
I.
Glycolysis
II.
Alcohol (ethanol) fermentation
III. Lactic acid production
A.
I only
B.
II only
C.
I and II only
D.
I, II and III
(Total 1 mark)
Some practice questions on
respiration…
4. Which of the following processes produces CO2?
I.
Glycolysis
II.
Alcohol (ethanol) fermentation
III. Lactic acid production
A.
I only
B.
II only
C.
I and II only
D.
I, II and III
(Total 1 mark)
Some practice questions on
respiration…
4. State a word equation for anaerobic cell
respiration in humans.
(1 mark)