Complete notes for A-Levels BiologyCIE according to syllabus objectives - updated 2025
Biology (9700) notes A-Level - Photosynthesis (CIE)
Photosynthesis as an energy transfer process
● Structure of chloroplasts: Stroma has the enzymes required
for the reactions of light dependent stage.Matrix of the
mitochondrion and the stroma of the chloroplast contains small
ribosomes and small circle of DNA used to synthesise proteins.
Stroma also contains starch grain which store some of the
A2
carbohydrate made( in insoluble form).The membranes of
lamellae and thylakoids hold carrier molecules that work as an
ETC (Electron Transport Chain). Photosynthetic pigments in
them absorb energy from a certain wavelength of light.
s
abundant is chlorophyll a and b. Other pigments are carotene
am
and xanthophyll.
● In the light dependent stage, the energy in ATP and the energy
in hydrogen molecules in the reduced NADP are used to reduce
Ex
carbon dioxide and produce carbohydrates. This stage is known
as the Calvin Cycle.
● Within a chloroplast, the thylakoids ( thylakoid membranes and
ck
spaces), which occur in stacks called grana, are the site of the
light-dependent stage and the stroma is the site of the
light-independent stage.
ra
● Chlorophyll-a absorbs slightly longer wavelengths of light than
chlorophyll-b. Carotene is also found in plants that absorb blue
C
light.
● Absorption spectrum: Graph showing the absorbance of
different wavelengths of light by photosynthetic pigments.
CRACK EXAMS A2 1
, Complete notes for A-Levels BiologyCIE according to syllabus objectives - updated 2025
Picture from Biology A-Level Coursebook
● Action spectrum: Graph showing the effect of different
A2
wavelengths of light on processes (e.g. rate of photosynthesis)
s
am
Ex
Picture from Biology A-Level CourseBook
● Chromatography is used to separate and identify chloroplast
ck
pigments. (Rf value= Distance travelled by spot/ Distance
travelled by solvent.
ra
● Cyclic and non-Cyclic Photophosphorylatiom occur during the
light-dependent stage of photosynthesis.
C
● Cyclic Photophosphorylation: Light energy is absorbed by
photosystem-1 and is passed to the reaction centre. The
energy excites an electron in the chlorophyll a molecule to a
higher energy level, so that it is actually emitted from the
chlorophyll molecule. This is called photoactivation. The
excited electrons are captured by an electron acceptor in the
thylakoid membrane and passed along a chain of electron
CRACK EXAMS A2 2
Biology (9700) notes A-Level - Photosynthesis (CIE)
Photosynthesis as an energy transfer process
● Structure of chloroplasts: Stroma has the enzymes required
for the reactions of light dependent stage.Matrix of the
mitochondrion and the stroma of the chloroplast contains small
ribosomes and small circle of DNA used to synthesise proteins.
Stroma also contains starch grain which store some of the
A2
carbohydrate made( in insoluble form).The membranes of
lamellae and thylakoids hold carrier molecules that work as an
ETC (Electron Transport Chain). Photosynthetic pigments in
them absorb energy from a certain wavelength of light.
s
abundant is chlorophyll a and b. Other pigments are carotene
am
and xanthophyll.
● In the light dependent stage, the energy in ATP and the energy
in hydrogen molecules in the reduced NADP are used to reduce
Ex
carbon dioxide and produce carbohydrates. This stage is known
as the Calvin Cycle.
● Within a chloroplast, the thylakoids ( thylakoid membranes and
ck
spaces), which occur in stacks called grana, are the site of the
light-dependent stage and the stroma is the site of the
light-independent stage.
ra
● Chlorophyll-a absorbs slightly longer wavelengths of light than
chlorophyll-b. Carotene is also found in plants that absorb blue
C
light.
● Absorption spectrum: Graph showing the absorbance of
different wavelengths of light by photosynthetic pigments.
CRACK EXAMS A2 1
, Complete notes for A-Levels BiologyCIE according to syllabus objectives - updated 2025
Picture from Biology A-Level Coursebook
● Action spectrum: Graph showing the effect of different
A2
wavelengths of light on processes (e.g. rate of photosynthesis)
s
am
Ex
Picture from Biology A-Level CourseBook
● Chromatography is used to separate and identify chloroplast
ck
pigments. (Rf value= Distance travelled by spot/ Distance
travelled by solvent.
ra
● Cyclic and non-Cyclic Photophosphorylatiom occur during the
light-dependent stage of photosynthesis.
C
● Cyclic Photophosphorylation: Light energy is absorbed by
photosystem-1 and is passed to the reaction centre. The
energy excites an electron in the chlorophyll a molecule to a
higher energy level, so that it is actually emitted from the
chlorophyll molecule. This is called photoactivation. The
excited electrons are captured by an electron acceptor in the
thylakoid membrane and passed along a chain of electron
CRACK EXAMS A2 2
