Bio paper 1 only (book 2 - 1,2,3,4,5,6,7,8) Flashcards
Photosystem?
Funnel shaped collection of accessory pigments with a reaction centre
Where does the light dependent stage happen?
On the thylakoid membrane
Where does light get trapped in?
In the grana - by the reaction centres
Where does the light independent stage happen?
In the stroma
What special features are in a chloroplast?
Circular loop of DNA, starch grains, 70s ribosomes
What is the stroma?
The chloroplasts own cytoplasm - a jelly which carries enzymes for the light independent reaction and products from one place to another (within the chloroplast)
What does a photosystem contain?
Chlorophyll a/b, carotenes, xanthophylls
P700 vs P680?
P700 - PS1 (chlorophyll A has max WL absorption of 700nm)
P680 - PS2 (chlorophyll A has max WL absorption of 680nm)
What are the accessory pigments?
Chlorophyll b, carotenes, xanthophylls
Where are the photosystems/light-harvesting complexes found?
Embedded in the thylakoid membranes
What is the LDS of photosynthesis?
The stage which occurs in the photosystems - within the thylakoid membrane
7 stages of LDS?
- Absorption of light by pigments in both photosystems
- Conversion of light energy to chemical
- Splitting of water to get protons and electrons
- Production of O2
- Use of energy to pump protons from the stroma into thylakoid spaces
- Using a proton gradient to drive formation of ATP
- Formation of reduced NADP
What are the products of the LDS which go on to the LIS?
ATP and reduced NADP
Where does photolysis of water happen?
In the thylakoid membrane
Chemiosmosis?
The production of ATP using the flow of protons through ATP synthase enzymes (across the thylakoid membranes) in photosynthesis
How do electrons leave the light harvesting complexes?
The light excites the electrons in P700 in the reaction centre of PS2 - electrons can then be accepted by an electron carrier (once they’ve left the photosystem)
What is the energy used for, which is released by the electrons passing through the ETC?
It is used to actively move hydrogen ions from the stroma into thylakoid space (against conc gradient)
In the ETC, how do the hydrogen ions return to the stroma?
The PH inside the stroma gets lower than the thylakoid space - forming an electrochemical gradient, this initiates the movement of the ions through ATP synthase complex
Why does a part of the ATP synthase protein spin, in the ETC?
So its active site can accept ADP and a Pi - this gets phosphorylated to form ATP
Photophosphorylation?
When ATP is made using light energy
What is the light independent stage of photosynthesis known as?
The Calvin cycle
First stage in the Calvin kelvin cycle?
CO2 enters the plant via stomatal pores - it dissolves in water and diffuses into mesophyll cells - then into chloroplasts in those cells
What is Rubisco’s role in the Calvin cycle - second stage?
The enzyme (Rubisco) combines CO2 with a 5C molecule RuBP
Third stage of Calvin cycle involving unstable C6 molecule?
Unstable C6 molecule breaks down into two C3 GP molecules = carboxylation
