Photosynthesis (11) Flashcards
(40 cards)
Where does the light-independent reaction occur?
stroma
Where does the light-dependent reaction occur?
thylakoids
What is the role of light in photoionisation?
- Chlorophyll molecules absorb energy from photons of light
- 2 electrons are ‘excited’ (raised to a higher energy level) causing them to be lost from the chlorophyll
What are the 7 stages of the light-dependent reaction?
1) Chlorophyll molecules absorb energy from photons of light
2) 2 electrons are ‘excited’ (raised to a higher energy level) causing them to be lost from the chlorophyll
3) electrons released from chlorophyll move down series of carrier proteins embedded in thylakoid membrane
4) undergo series of redox reactions which releases energy at decreasing energy levels
5) energy used to join ADP and Pi to form ATP
6) photolysis of water produces oxygen, electrons and protons
7) NADP reduced by electrons and hydrogen
How is a proton concentration gradient established during chemiosmosis?
some energy released from ETC is coupled to the active transport of hydrogen ions from stroma to thylakoid space
How does chemiosmosis produce ATP during the LDR?
hydrogen ions move down concentration gradient from thylakoid space to stroma via the channel protein ATP synthase
What are the 3 main stages of the calvin cycle?
1) carbon fixation
2) reduction
3) regeneration
What is the role of ATP synthase?
catalyses reaction between ADP + Pi to form ATP
What is the role of chlorophyll in photolysis?
- absorbs light energy
- loses electrons
- accepts electrons from water
What is the role of light in photolysis?
light energy splits water molecules
What is the equation for photolysis of water?
2 H2O — 4H+ + 4e- + O2
What happens to the 4 hydrogen ions from photolysis of water?
- move out of thylakoid space via ATP synthase
- used to reduce NADP
What happens to the 4 electrons from photolysis of water?
replace electrons lost from chlorophyll
What happens to the oxygen from photolysis of water?
used for respiration or diffuses out of leaf as waste gas
What is the equation for reducing NADP?
NADP + 2H+ + 2e- > NADPH
Where is NADP reduced?
stroma
What catalyses the reaction for reducing NADP?
dehydrogenase enzymes
What do dehydrogenase enzymes do?
catalyses reaction to reduce NADP
Where are the 2 hydrogen ions from for reducing NADP?
from photolysis of water
What do the 2 electrons in reducing NADP do?
act as final electron acceptor in ETC
What are the 6 steps of the light-independent reaction?
1) CO2 enters leaf through stomata + combines with RuBP, catalysed by rubisco
2) forms unstable 6C compound that breaks down into 2 GP (3C compound)
3) 2 GP is reduced to 2 triose phosphate using 2 NADPH and energy from 2 ATP
4) forms 2 NADP and 2 ADP
5) 5/6 carbons from triose phosphate forms compound RuP
6) RuBP is regenerated from RuP using energy from 1 ATP
What happens to 1carbon from TP?
leaves cycle and is converted into useful organic molecules e.g. glucose
What is the role of ATP in the LIR?
reduction of GP to triose phosphate
provides phosphate group to convert RuP to RuBP
What is the role of NADPH in LIR?
this coenzyme transports electrons needed for reduction of GP to triose phosphate
