photosynthesis Flashcards
what is photosynthesis?
synthesis of organic compounds by photolysis in the light independent reaction
what is the compensation point?
when up until a certain point, respiration can provide the CO2 needed by photosynthesis until the rates of these reactions are the same.
what is a limiting factor
something which directly affects the rate of a process if its quantity is changed.
what is the main site of photosynthesis in leaves?
the palisade cells
what can dicot plants do during the day to maximise the amount of light absorbed?
the leaves can change positions so that the upper surface is always at right angles to the direction of light
what can chloroplasts do to absorb more light?
move intracellularly in response to light intensity – they can orientate themselves and can also move around if more light is passing through one part of a cell than another.
what are the different types of photosynthetic pigments in chloroplast?
- chlorophyll a and b
- carotene
- xanthophyll
how can the photosynthetic pigments be separated?
through chromatography
what is the absorption spectrum?
the absorption of light by different pigments
what wavelengths are absorbed by chlorophyll molecules?
short/blue wavelengths and long/red wavelengths
what wavelength is reflected/transmitted by the chlorophyll molecules?
green light
how is the rate of photosynthesis measured?
as the volume of oxygen produced per minute
what is the action spectrum?
the rate of photosynthesis at different wavelengths
what are the two stages that take place for photosynthesis?
LDR and LIR (light independent reaction and light dependent reaction)
how are photosystems I and II arranged?
around 2 chlorophyll a molecules
what are the two main parts of the photosystems?
each have an antenna complex of all pigment types , and a reaction centre of two chlorophyll a molecules
What is the function of the antenna complex of the Photosystems?
harvests light energy and passes the excitation to the reaction centre (from one pigment molecule to another)
what happens at the reaction centre of the photosystems?
excited chlorophyll a molecules can each emit one electron
where does the light dependent reaction take place?
in the thylakoid membranes and thylakoid cavity
where does the light independent reaction (Calvin cycle) take place?
the stroma
what is the absorption peak of Photosystem I?
700nm, so referred as P700
what is the absorption peak of Photosystem II?
680nm, so referred to as P680
What is non-cyclic photophosphorylation also referred to as?
the Z scheme
What happens in the light dependent reaction?
The photolysis of water releases electrons and protons
where is nitrogen taken up by plants?
the roots
what is the law of limiting factors?
when the rate of a process is affected by more than one factor, then the overall rate is limited by the factor which is closest to its minimum value
how is nitrogen transported in the xylem and the phloem?
nitrates in the xylem and amino acids in the phloem
what is magnesium required for?
chlorophyll formation
symptoms of magnesium deficiency in plants
chlorosis between veins of older leaves as magnesium is taken up by newer leaves
what happens when there is a higher light intensity in the hydrogencarbonate indicator?
increased rate of photosynthesis, meaning less CO2 in solution so solution will be more alkaline (more purple in colour)
what is photolysis?
the splitting of water by light
what happens to the light energy produced by photosynthesis?
converted to chemical energy in ATP and NADPH
colour of chlorophyll A
blue/green
colour of chlorophyll B
yellow/green
colour of xanthophyll?
yellow
colour of beta carotene
orange
what is phaeophytin?
(grey) the breakdown colour of chlorophyll
what is the purpose of photosynthetic pigments?
they absorb light energy and begin its conversion to storable chemical energy. Different pigments absorb photons at different wavelengths
what is the Rf value?
distance moved by pigment / distance moved by solvent
what is in the matrix of the chloroplast
the matrix surrounding the grana contains all the enzymes needed to complete the process of photosynthesis and produce glucose
function of accessory pigment molecules?
helps funnel photons of light through the antenna complex to the reaction centre of two chlorophyll a molecules
How has chloroplast adapted
to maximise light absorption for photosynthesis?
Chlorophyll: absorbs light
Large surface area: The thylakoid membranes increase SA, allowing for more light absorption
Location in the cell: chloroplasts position themself for optimum light exposure
what are the two pathways of photophosphorylation?
non-cyclic photophosphorylation and cyclic photophosphorylation
what is non-cyclic photophosphorylation?
electrons from PSII pass to PSI and then pass to the final electron acceptor as they pass along the electron transport chain (also referred to as the Z scheme)
what is cyclic photophosphorylation?
excited electrons from PSI pass from electron carrier then back to PSI via the proton pump
what are the steps of non-cyclic photophosphorylation?
photons are absorbed by a pigment molecule of the antenna complex of PSII; the excitation is passed to the pair of chlorophyll a molecules in the reaction centre.
- electrons become excited and are passed to electron acceptors, reducing them, leave chlorophyll a molecules oxidised and pass via a series of electron carriers and are pumped from the stroma into the thylakoid space
- protons then pass through ATP synthetase
what is the final electron acceptor?
NADP
what is the last step of non-cyclic photophosphorylation?
photons are absorbed by a pigment molecule of the antenna complex of PSI and energy is passed to pair of chlorophyll a molecules in the reaction centre
- the excited electrons can each reduce an electron acceptor, and reduces NADP.
What is the Calvin Cycle?
the Light Independent Reaction for the uptake of CO2 and production of triose phosphate
what are the steps of the Calvin Cycle?
- uptake of CO2 by 5C ribulose biphosphate by the enzyme RuBisCO to form 2 glycerate-3-phosphates
- ATP and reduced NADP from LDR reduces glycerate-3-phosphate to triose phosphate
- ribulose biphosphate is regenerated
what happens to the electrons in the photolysis of water?
the electrons are removed to replace those lost by the chlorophyll a of the photosystem II
