topic 5 (photosynthesis) Flashcards
(39 cards)
what is photosynthesis?
the process where energy from light is used to make glucose from water and carbon dioxide
what is the word equation for photosynthesis?
carbon dioxide + water = glucose + oxygen
what is the chemical equation for photosynthesis?
6CO2+6H2O=C6H12O6+6O2
where does photosynthesis take place?
in the chloroplasts of plant cells
what is a chloroplast?
flattened organelle surrounded by a double membrane
what do thylakoid membranes stack to form?
grana
what are grana linked by?
lamellae
what photosynthetic pigments do chloroplasts contain?
chlorophyll a
chlorophyll b
carotene
what is a photosynthetic pigment?
coloured substances that absorb the light energy needed for photosynthesis
where are photosynthetic pigments found?
in the thylakoid membranes attached to proteins
what is a photosynthetic pigment attached to a protein called?
photosystem
what wavelength does photosystem I best absorb light at?
700nm
what wavelength does photosystem II best absorb light at?
680nm
what is the stroma?
gel like substance containing enzymes, sugars and organic acids
what happens to carbohydrates produced by photosynthesis that are not used straight away?
stored as starch grains in the stroma
what are the two stages of photosynthesis?
light dependent reaction
light independent reaction
where does the light dependent reaction occur?
in the thylakoid membranes
what is the energy in the light dependent reaction used by?
making ATP
making reduced NADP
photolysis
what are the two types of photophosphorylation in the light dependent reaction?
non cyclic and cyclic
what are the stages of non cyclic photophosphorylation?
light energy is absorbed by PSII
light energy excites electrons in chlorophyll
electrons move to a higher energy level
high energy electrons released from chlorophyll move down the electron transport chain to PSI
excited electrons from chlorophyll leave PSII to move down the electron transport chain (but these must be replaced)
light energy splits water into protons, electrons and oxygen during photolysis
excited electrons lose energy as they move down the electron transport chain
energy used to transport protons into the thylakoid so it has a higher concentration of protons than the stroma= proton gradient
protons move down their concentration gradient into the stroma via ATP synthase, which synthesises ATP
light energy absorbed by PSI excites the electrons to a higher energy level
electrons transferred to NADP with a proton from the stroma to produce reduced NADP
what happens in cyclic photophosphorylation?
only uses PSI
electrons from chlorophyll passed back to PSI by electron carriers
electrons recycled and repeatedly flow through PSI
produces small amounts of ATP
where does the light independent reaction occur?
in the stroma
what are the stages of the light independent reaction?
CO2 enters the leaf via the stomata and diffuses into the stroma
combined with ribulose bisphosphate, catalysed by the enzyme rubisco
produces unstable 6C compound- broken down into 2 3 carbon compounds= glycerate 3 phosphate
hydrolysis of ATP ,and H+ ions from reduced NADP, provides energy to change glycerate 3 phosphate into triose phosphate
some converted into useful organic compounds, some continues in the Calvin Cycle to regenerate ribulose biphosphate
what useful organic substances do triose phosphate and glycerate 3 phosphate make?
carbohydrates
lipids
amino acids
