Photosynthesis Flashcards
Definition of wavelength
The distance from peak to peak and is measured in nanomaters.
Definition of primary pigment
Chlorophyll A, found in reaction centre, absorbs light energy and excites 2 electrons.
Definition of accessory pigments
Absorbs different wavelength of light, passes energy down to primary pigment / reaction centre.
Describe thylakoids in chloroplasts.
They contain photosynthetic pigment. Chlorphyll found on its membrane which traps light energy.
Describe grana in chloroplasts
Stack of thylakoids, where the light dependent reaction occurs.
Describe stroma in chloroplasts
Fluid-filled chlorphyll matrix where the light independent reaction reaction occurs.
Explain what an absorption spectrum graph represents.
The wavelength of light energy that is absorbed by the different pigments.
Explain what an action spectrum graph represents.
The relative effectiveness of different wavelengths on photosynthesis.
Definition of oxidation
Loss of electrons and/or hydrogens.
Definition of reduction
Gain of electrons and/or hydrogens.
Definition of an electron carrier
A protein molecule that transfers electrons in the ETC.
Definition of photolysis
Splitting water into protons, electrons and oxygen, using light energy.
Definition of photophosphorylation
Addition of a phosphate molecule, using light energy.
Definition of photoionisation
Molecules absorb light energy exciting electrons to leave the molecules.
Describe the light dependent reaction (7 points)
- Chlorophyll absorbs light energy.
- Excites electrons out of chlorophyll / photosystem.
- Electrons move along the electron trnapsort chain releasing energy.
- Energy is used to join ADP and Pi to from ATP by chemiosmosis.
- Photolysis of water produces protons, electrons and oxygen.
- NADP reduced by electrons/hydrogen.
- Oxygen is released as waste gas. ATP and red NADP go to light independent reaction.
Describe the light dependent reaction (7 points)
- Chlorophyll absorbs light energy.
- Excites electrons out of chlorophyll / photosystem.
- Electrons move along the electron trnapsort chain releasing energy.
- Energy is used to join ADP and Pi to from ATP by chemiosmosis.
- Photolysis of water produces protons, electrons and oxygen.
- NADP reduced by electrons/hydrogen.
- Oxygen is released as waste gas. ATP and red NADP go to light independent reaction.
Describe chemiosmosis (5 points)
- Energy is released as electrons pass along the ETC in the thylakoid membrane.
- Energy is used to pump protons from the photolysis of water from the stroma into the intermembranal space.
- Proton graident is established.
- Protons flood from intermembranal space to stroma down concentration gradient.
- Causes ATP synthase to smash ADP and Pi to form ATP.
Describe the light independent reaction (6 points)
- Carbon dioxide combines with ribulose bisphosphate (RuBP).
- Produces an unstable 6C which breaks into twoglycerate phosphate molecules.
- Glycerate phosphate reduced to triose phosphate.
- Using reduced NADP and energy from ATP produced in light dependent stage.
- Triose phosphate converted to glucose.
- Or regenerated into ribulose bisphosphate (RuBP).
Write out the pathway taken by carbon dioxide from the atmosphere into the chloroplast (6 points)
- Diffuse through the stomata.
- Diffuse through the spongy mesophyll.
- Dissolves in water around palisade cells.
- Diffuses through palisade membrane.
- Diffuses through palisade cytoplasm.
- Diffuses through chloroplast envelope into the stroma.
Definition of a limiting factor
The factors that presents in the lowest amount (and therefore the one that limits the rate of the overall reaction).
Which stage of photosynthesis is the most affected by temperature?
Light independent as it is enzyme-controlled.
Describe and explain the effect of temperature on the rate on photosynthesis.
Increase in kinetic energy, increased collisions between active site of RuBisCO and CO2. More enzyme-substrate complexes, more enzyme product complexes form, so more GP formed.
Increase in kinetic energy break hydrogen bonds in tertiary structure and changes shape of active site of RuBisCO. Active site is no longer complementary to CO2. Less enzyme substarte complexes, less enzyme product complexes.
Which stage of photosynthesis is affected by concentration of CO2?
Light independent as CO2 is the substrate for the reaction.
Explain how carbon dioxide affects the rate of photosynthesis.
Increasing the concentration means more substrate available. More collisions. More enzyme substrate complexes and enzyme-product complexes. More GP produced.
Which stage of photosynthesis will be most affected by light intensity?
Light dependent.
Describe and explain the effect of light intensity on the rate of photosynthesis.
As light intensity increases, rate of photosynthesis also increases. Directly proportional.
As light intensity increases, the rate of photosynthesis plateaus. Another limiting factor is limiting the rate, e.g. temperature, carbon dioxide concentration.
