12 Energy and respiration
Energy is a fundamental concept in biology. All living organisms require a source of cellular energy to drive their
various
... [Show More] activities. All organisms respire by using enzyme-catalysed reactions to release energy from energy-rich
molecules such as glucose and fatty acids and transfer that energy to ATP. ATP is the universal energy currency
of cells. In eukaryotes, aerobic respiration occurs in mitochondria.
The practical activities in this topic give opportunities for candidates to plan investigations, analyse and interpret
data and evaluate experimental procedures and the quality of the data collected.
12.1 Energy Learning outcomes
Candidates should be able to:
1 outline the need for energy in living organisms, as illustrated
by active transport, movement and anabolic reactions, such as
those occurring in DNA replication and protein synthesis
2 describe the features of ATP that make it suitable as the
universal energy currency
3 state that ATP is synthesised by:
• transfer of phosphate in substrate-linked reactions
• chemiosmosis in membranes of mitochondria and
chloroplasts
4 explain the relative energy values of carbohydrates, lipids and
proteins as respiratory substrates
5 state that the respiratory quotient (RQ) is the ratio of the
number of molecules of carbon dioxide produced to the number
of molecules of oxygen taken in, as a result of respiration
6 calculate RQ values of different respiratory substrates from
equations for respiration
7 describe and carry out investigations, using simple
respirometers, to determine the RQ of germinating seeds or
small invertebrates (e.g. blowfly larvae)
12.2 Respiration Learning outcomes
Candidates should be able to:
1 State where each of the four stages in aerobic respiration occurs
in eukaryotic cells:
• glycolysis in the cytoplasm
• link reaction in the mitochondrial matrix
• Krebs cycle in the mitochondrial matrix
• oxidative phosphorylation on the inner membrane of
mitochondria
2 outline glycolysis as phosphorylation of glucose and the
subsequent splitting of fructose 1,6-bisphosphate (6C) into
two triose phosphate molecules (3C), which are then further
oxidised to pyruvate (3C), with the production of ATP and
reduced NAD
3 explain that, when oxygen is available, pyruvate enters
mitochondria to take part in the link reaction
12.2 Respiration continued Learning outcomes
Candidates should be able to:
4 describe the link reaction, including the role of coenzyme A in
the transfer of acetyl (2C) groups
5 outline the Krebs cycle, explaining that oxaloacetate (4C) acts
as an acceptor of the 2C fragment from acetyl coenzyme A to
form citrate (6C), which is converted back to oxaloacetate in a
series of small steps
6 explain that reactions in the Krebs cycle involve decarboxylation
and dehydrogenation and the reduction of the coenzymes NAD
and FAD
7 describe the role of NAD and FAD in transferring hydrogen to
carriers in the inner mitochondrial membrane
8 explain that during oxidative phosphorylation:
• hydrogen atoms split into protons and energetic electrons
• energetic electrons release energy as they pass through
the electron transport chain (details of carriers are not
expected)
• the released energy is used to transfer protons across the
inner mitochondrial membrane
• protons return to the mitochondrial matrix by facilitated
diffusion through ATP synthase, providing energy for ATP
synthesis (details of ATP synthase are not expected)
• oxygen acts as the final electron acceptor to form water
9 describe the relationship between the structure and function of
mitochondria using diagrams and electron micrographs
10 outline respiration in anaerobic conditions in mammals (lactate
fermentation) and in yeast cells (ethanol fermentation)
11 explain why the energy yield from respiration in aerobic
conditions is much greater than the energy yield from
respiration in anaerobic conditions (a detailed account of the
total yield of ATP from the aerobic respiration of glucose is not
expected)
12 explain how rice is adapted to grow with its roots submerged
in water, limited to the development of aerenchyma in roots,
ethanol fermentation in roots and faster growth of stems
13 describe and carry out investigations using redox indicators,
including DCPIP and methylene blue, to determine the effects
of temperature and substrate concentration on the rate of
respiration of yeast
14 describe and carry out investigations using simple respirometers
to determine the effect of temperature on the rate of
respiration [Show Less]