Learner Resource 1 – Build up to Respiration
Teacher Answers
1.
a)
What is respiration?
The chemical reactions within a cell by which ATP is produced from respiratory substrates such
as glucose.
b)
What is the chemical equation for respiration?
Aerobic respiration of glucose: C6H12O6 + 6O2 → 6H2O + 6CO2
c)
Where does respiration occur?
Within cells. In eukaryotic cells glycolysis takes place in the cytoplasm and further stages occur
in the mitochondria (in the stroma and in/across the inner mitochondrial membrane).
d)
Why is it vital to us?
It produces ATP which is the energy currency of the cell.
e)
What is the difference between aerobic and anaerobic respiration?
Oxygen is used as the final electron acceptor in aerobic respiration and this allows the electron
transport chain to run resulting in much more ATP being produced (by oxidative
phosphorylation).
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f)
What is a respiratory substrate?
The chemical (e.g. glucose) which is broken down by the reactions of respiration.
2.
Define the following terms:Term
Definition
Metabolism
The chemical reactions going on in a cell.
Anabolism
The metabolic reactions that build up larger molecules.
Catabolism
The metabolic reactions that break molecules down.
Potential energy
The energy stored in a molecule due to the arrangement of atoms
(including bonds).
Condensation reaction
A reaction forming a bond and removing two hydrogen atoms and
one oxygen atom from the substrates.
Hydrolysis reaction
A reaction breaking a bond and adding a total of two hydrogen
atoms and one oxygen atom to the products.
Oxidation
The removal of electrons.
Reduction
The addition of electrons.
Redox reaction
A reaction in which electrons are transferred such that one
reactant is reduced and another is oxidised.
Phosphorylation
The addition of one or more phosphate groups.
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3. List some of the processes that use energy in cells:-
Any reasonable answers including: metabolic reactions, active transport, synthesis of
macromolecules (e.g. polynucleotides, polypeptides), intracellular movement (e.g. involving
microtubules / cytoskeleton), actin/myosin movement, neuronal repolarisation / maintaining
membrane polarity, signal transduction
4. ATP is a molecule which is used in all cells to transfer energy.
ATP can be produced by respiration and during photosynthesis.
a) Draw a simple molecule of ATP and label its parts:-
ATP: The Central molecule in metabolism
ADP + Pi
Condensation
ADP + Pi




cell respiration (and
photosynthesis = light stage)
ATP
Hydrolysis
active transport
protein synthesis
muscle contraction
heat energy
ATP
b) Add labels to show which is a condensation reaction and which is a hydrolysis reaction.
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c) Which reaction is described as phosphorylation?
ADP + Pi →ATP
d) Describe the components of ATP.
Three phosphate groups, a ribose sugar and a nitrogenous adenine.
ATP is water soluble and easily transported within a cell.
e) How does ATP release energy?
The bond between the second and third phosphate group is hydrolysed.
f) How much energy is released?
30.5 kJ mol-1
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5. How ATP is synthesised:Substrate level phosphorylation – Energy is built using energy released by reorganising
chemical bonds (As seen in Krebs cycle and glycolysis)
Oxidative phosphorylation - ATP built from energy release from the activity of electrons passing
down the electron transport chain in cristae (inner membrane of mitochondria) where oxygen is
the final electron acceptor
Photophosphorylation – ATP built from light energy as seen in light –dependent reaction of
photosynthesis
Why is it an advantage to organisms to hydrolyse ATP to meet its energy requirements rather than
hydrolyse glucose directly?
Glucose would release too much energy and heat in one go, which would be difficult to channel
into cellular activities. ATP hydrolysis releases just enough energy to drive one chemical
reaction, so is more efficient.
7.
a)
What is a coenzyme?
A molecule that is bound to an enzyme to allow it to perform its catalytic function.
b).
Name 2 important coenzymes in respiration
Coenzyme A
NAD
FAD
c)
How do they function?
Coenzyme A – transfers an acetyl group
NAD – transfers electrons
FAD – transfers electrons
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