Photosynthesis Flashcards
Label the structure of chloroplast
See notes include
- granum
- lamella
- ribosomes
- stoma
- outer membrane
-inner membrane
- starch grain
- thylakoid
- lipid droplet
What photosynthetic pigments do plants contain
Chlorophyll ( a & b)
Carotenoid (b-carotene & xanthophyll)
explain why plant benefits from having pigments that absorb different wavelengths
E,g what does chlorophyll absorb
Each pigment absorbs slightly different wavelengths so having different pigments plants maximise the wavelengths of light they can absorb energy from
E.g chlorophyll absorbs blue and red wavelengths of visible light
Absorption spectrum shows…
% light of different wavelengths absorbed by isolated pigments
What type of light does chlorophyll absorb
Blue and red wavelengths
Action spectrum shows..
Rate of photosynthesis of plants exposed to different wavelengths of light
E.g. highest rates of photosynthesis stimulated by blue and red wavelengths of light
Def of photosystem
Light- harvesting cluster of pigment molecules in the thylakoid membrane
What is photosystem I and photosystem II?
Photosystem I
Reaction centre (cluster of pigment molecules) = chlorophyll A with peak absorption 700nm
Photosystem II
Reaction centre (cluster of pigment molecules) = chlorophyll A with peak absorption 680nm
Role of accessory pigments in photosystem
(Examples of pigments)
Accessory pigments (Chlorophyll A & B and carotenoids) pass energy from light to the chlorophyll A at the reaction centre for start of photosynthesis
Def of Photophosphorylation
The synthesis of ATP using energy harvested from light
The process of cyclic photophosphorylation (photosystem I)
(5 steps)
1) light energy excites electron from chlorophyll A in photosystem I
2) electron passes down electron transport chain (ETC) in the thylakoid membrane
3) energy lost from electron used to pump protons across membrane into thylakoid lumen
4) protons diffuse through ATP synthase & energy is used to synthesis ATP
5) electron returns to chlorophyll molecule
Compare photophosphorylation & oxidative phosphorylation
1) organelle
2) location of ETC
3) Location of high [H+]
4) source of high energy electrons
organelle
Photo) Chloroplast
OP) mitochondrion
location of electron transport chain
Photo) thylakoid membrane
OP) inner mitochondrion membrane
location of high H+ concentration
Photo) thylakoid lumen
OP) inter mitochondrion membrane
source of high energy electrons
Photo) chlorophyll A
OP) glucose
What does the light- dependent reaction of photosynthesis (non-cyclic phototphosphorylation) involve?
-both photo systems 1 & 2
- synthesis of ATP and reduced NADP
- the splitting of water (photolysis)
Process of photolysis
1) energy from light used to split water into
H2O —> 2H+. + 2e- + 1/2 O2
2) electrons from water replace electrons lost from chlorophyll a and PS2
Explain the differences between cyclic and non-cyclic photophosphorylation
Cyclic
- only photosystem 1 used
- exited electrons return to photosystem 1 to go through cycle again
- no photolysis
- only ATP produced
- produces steady supply of ATP in presence of sunlight
Non-cyclic
- photosystems 1 & 2 used
- exited electrons enter photosystem 1 to be picked up by NADP —> reduced NADP
- photolysis of water replenishes electrons lost to photosystem 1
- produces both NADPH and ATP
- allows for synthesis’s of organic molecules for long term energy