Module B4: The processes of life
B4.1 How do chemical reactions take place in living things?
1. understand that the basic processes of life carried out by all
living things depend on chemical
reactions within cells that require energy released by respiration
2. understand the role of photosynthesis in making food molecules and
energy available to
living organisms through food chains
3. describe photosynthesis as a series of chemical reactions that use
energy from sunlight to
build large food molecules in plant cells and some microorganisms (e.g.
phytoplankton)
4. describe respiration as a series of chemical reactions that release
energy by breaking down
large food molecules in all living cells
5. recall that enzymes are proteins that speed up chemical reactions
6. recall that cells make enzymes according to the instructions carried
in genes
7. understand that molecules have to be the correct shape to fit into
the active site of the
enzyme (the lock and key model)
8. understand that enzymes need a specific constant temperature to work
at their optimum,
and that they permanently stop working (denature) if the temperature is
too high
9. explain that enzyme activity at different temperatures is a balance
between:
a. increased rates of reaction as temperature increases
b. changes to the active site at higher temperatures, including
denaturing
Candidates are not expected to explain why rates
of reaction increase with
temperature
10. recall that an enzyme works at its optimum at a specific pH
11. explain the effect of pH on enzyme activity in terms of changes to
the shape of the
active site.
B4.2 How do plants make food?
1. recall the names of the reactants and products of photosynthesis,
and use the word
equation:
(light
energy)
carbon dioxide + water → glucose + oxygen
2. recall the formulae of the reactants and products of photosynthesis,
and use the
symbol equation:
(light energy)
6CO2 + 6H2O → C6H12O6 + 6O2
3. recall the main stages of photosynthesis:
a. light energy
absorbed by the green chemical chlorophyll
b. energy used to
bring about the reaction between carbon dioxide and water to
produce glucose (a
sugar)
c. oxygen produced
as a waste product
4. recall that glucose may be:
a. converted into
chemicals needed for growth of plant cells, for example cellulose,
protein and
chlorophyll
b. converted into
starch for storage
c. used in
respiration to release energy
5. recall the structure of a typical plant cell, limited to
chloroplasts, cell membrane, nucleus,
cytoplasm, mitochondria, vacuole and cell wall
6. understand the functions of the structures in a typical plant cell
that have a role in
photosynthesis, including:
a. chloroplasts
contain chlorophyll and the enzymes for the reactions in photosynthesis
b. cell membrane
allows gases and water to pass in and out of the cell freely while
presenting a
barrier to other chemicals
c. nucleus
contains DNA which carries the genetic code for making enzymes and other
proteins used in
the chemical reactions of photosynthesis
d. cytoplasm where
the enzymes and other proteins are made
7. recall that minerals taken up by plant roots are used to make some
chemicals needed by
cells, including nitrogen from nitrates to make proteins
8. understand that diffusion is the passive overall movement of
molecules from a region of their
higher concentration to a region of their lower concentration
9. recall that the movement of oxygen and carbon dioxide in and out of
leaves during
photosynthesis occurs by diffusion
10. understand that osmosis (a specific case of diffusion) is the
overall movement of water from
a dilute to a more concentrated solution through a partially permeable
membrane
11. recall that the movement of water into plant roots occurs by
osmosis
12. understand that active transport is the overall movement of
chemicals across a cell
membrane requiring energy from respiration
13. recall that active transport is used in the absorption of nitrates
by plant roots
B4.3 How do living organisms obtain energy?
1. understand that all living organisms require energy released by
respiration for some
chemical reactions in cells, including chemical reactions involved in:
a. movement
b. synthesis of
large molecules
c. active
transport
2. understand that synthesis of large molecules includes:
a. synthesis of
polymers required by plant cells such as starch and cellulose from
glucose in plant
cells
b. synthesis of
amino acids from glucose and nitrates, and then proteins from amino
acids in plant,
animal and microbial cells
3. recall that aerobic respiration takes place in animal and plant
cells and some
microorganisms, and requires oxygen
4. recall the names of the reactants and products of aerobic
respiration and use the word
equation:
glucose + oxygen → carbon dioxide + water (+ energy released)
5. recall the formulae of the reactants and products of aerobic
respiration and use the
symbol equation:
C6H12O6 + 6O2 → 6CO2 + 6H2O
6. recall that anaerobic respiration takes place in animal, plant and
some microbial cells in
conditions of low oxygen or absence of oxygen, to include:
a. plant roots in
waterlogged soil
b. bacteria in
puncture wounds
c. human cells
during vigorous exercise
7. recall the names of the reactants and products of anaerobic
respiration in animal cells and
some bacteria, and use the word equation:
glucose → lactic acid (+ energy released)
8. recall the names of the reactants and products of anaerobic
respiration in plant cells and
some microorganisms including yeast, and use the word equation:
glucose → ethanol + carbon dioxide (+ energy released)
9. understand that aerobic respiration releases more energy per glucose
molecule than
anaerobic respiration
10. recall the structure of typical animal and microbial cells
(bacteria and yeast) limited to:
a. nucleus
b. cytoplasm
c. cell membrane
d. mitochondria
(for animal and yeast cells)
e. cell wall (for
yeast and bacterial cells)
f. circular DNA
molecule (for bacterial cells)
B4.3 How do living organisms obtain energy?
11. understand the functions of the structures in animal, plant,
bacteria and yeast cells that have
a role in respiration, including:
a. mitochondria
contain enzymes for the reactions in aerobic respiration (in animals,
plants and yeast)
b. cell membrane
allows gases and water to pass in and out of the cell freely while
presenting a
barrier to other chemicals
c. nucleus or circular
DNA in bacteria contains DNA which carries the genetic code for
making enzymes
used in the chemical reactions of respiration
d. cytoplasm where
enzymes are made and which contains the enzymes used in
anaerobic
respiration
12. describe examples of the applications of the anaerobic respiration
of microorganisms,
including the production of biogas and fermentation in bread making and
alcohol production.
© OCR 2011 GCSE Science A
