Bio paper 1 only (book 2 - 1,2,3,4,5,6,7,8)

Question 1

Photosystem?

Answer 1

Funnel shaped collection of accessory pigments with a reaction centre

Question 2

Where does the light dependent stage happen?

Answer 2

On the thylakoid membrane

Question 3

Where does light get trapped in?

Answer 3

In the grana - by the reaction centres

Question 4

Where does the light independent stage happen?

Answer 4

In the stroma

Question 5

What special features are in a chloroplast?

Answer 5

Circular loop of DNA, starch grains, 70s ribosomes

Question 6

What is the stroma?

Answer 6

The chloroplasts own cytoplasm - a jelly which carries enzymes for the light independent reaction and products from one place to another (within the chloroplast)

Question 7

What does a photosystem contain?

Answer 7

Chlorophyll a/b, carotenes, xanthophylls

Question 8

P700 vs P680?

Answer 8

P700 - PS1 (chlorophyll A has max WL absorption of 700nm)

P680 - PS2 (chlorophyll A has max WL absorption of 680nm)

Question 9

What are the accessory pigments?

Answer 9

Chlorophyll b, carotenes, xanthophylls

Question 10

Where are the photosystems/light-harvesting complexes found?

Answer 10

Embedded in the thylakoid membranes

Question 11

What is the LDS of photosynthesis?

Answer 11

The stage which occurs in the photosystems - within the thylakoid membrane

Question 12

7 stages of LDS?

Answer 12

1. Absorption of light by pigments in both photosystems
2. Conversion of light energy to chemical
3. Splitting of water to get protons and electrons
4. Production of O2
5. Use of energy to pump protons from the stroma into thylakoid spaces
6. Using a proton gradient to drive formation of ATP
7. Formation of reduced NADP

Question 13

What are the products of the LDS which go on to the LIS?

Answer 13

ATP and reduced NADP

Question 14

Where does photolysis of water happen?

Answer 14

In the thylakoid membrane

Question 15

Chemiosmosis?

Answer 15

The production of ATP using the flow of protons through ATP synthase enzymes (across the thylakoid membranes) in photosynthesis

Question 16

How do electrons leave the light harvesting complexes?

Answer 16

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)

Question 17

What is the energy used for, which is released by the electrons passing through the ETC?

Answer 17

It is used to actively move hydrogen ions from the stroma into thylakoid space (against conc gradient)

Question 18

In the ETC, how do the hydrogen ions return to the stroma?

Answer 18

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

Question 19

Why does a part of the ATP synthase protein spin, in the ETC?

Answer 19

So its active site can accept ADP and a Pi - this gets phosphorylated to form ATP

Question 20

Photophosphorylation?

Answer 20

When ATP is made using light energy

Question 21

What is the light independent stage of photosynthesis known as?

Answer 21

The Calvin cycle

Question 22

First stage in the Calvin kelvin cycle?

Answer 22

CO2 enters the plant via stomatal pores - it dissolves in water and diffuses into mesophyll cells - then into chloroplasts in those cells

Question 23

What is Rubisco’s role in the Calvin cycle - second stage?

Answer 23

The enzyme (Rubisco) combines CO2 with a 5C molecule RuBP

Question 24

Third stage of Calvin cycle involving unstable C6 molecule?

Answer 24

Unstable C6 molecule breaks down into two C3 GP molecules = carboxylation

Question 25

Stage four of the Calvin cycle - after C6 breakdown?

Answer 25

Both GP molecules are reduced by the addition of hydrogen from reduced NADP (which leaves the cycle in NADP form (oxidised again)), ATP is also phosphorylated into ADP and Pi - forming X2 TP 3C molecules

Question 26

What fraction of the two TP molecules are used in the fish stage of the Calvin cycle?

Answer 26

5/6ths of the TP is used to reform RuBP by another phosphorylation of ATP

Question 27

Where does the small fraction of TP (not used in the cycle) go to?

Answer 27

The 1/6th of TP goes to form hexose phosphates - forming either sucrose or starch cellulose