Photosynthesis

Question 1

Define photosynthesis

Answer 1

A metabolic pathway that converts light energy into chemical energy for synthesis of carbohydrate

Question 2

What is the cytosol of the chloroplast called and give 2 suspensions

Answer 2

Stroma - free ribosomes and starch granules

Question 3

What makes up the envelope of the chloroplast

Answer 3

Inner and outer membrane
Intermembrane space

Question 4

How is the main structure in chloroplasts arranged

Answer 4

Thylakoid membranes form thylakoids - they stack forming grana

Question 5

Where is the chlorophyll stored

Answer 5

In the thylakoid membranes

Question 6

How long are chloroplasts

Answer 6

7micrometers

Question 7

Where are the chloroplasts found in leaves

Answer 7

In the mesophyll

Question 8

Where does visible light range in the electromagnetic spectrum

Answer 8

380nm - 750nm

Question 9

What are substances that absorb visible light called

Answer 9

Pigments

Question 10

What light works best for chlorophyll a in terms of photosynthesis

Answer 10

Violet-blue and red

Question 11

What colour is chlorophyll a and b (what type of pigment is b)

Answer 11

a - Blue green
b - Olive green + accessory

Question 12

What is the role of carotenoids

Answer 12

Dissipate light that would damage the chlorophyll

Question 13

What happens when light is shone on an isolated chlorophyll molecule (3)

Answer 13

Molecule moves from a ground state to unstable excited state
Falling back to ground state gives off heat and photons
This causes molecule to fluoresce

Question 14

When chlorophyll is not isolated and light is shone - what happens to the photons and heat given off

Answer 14

It is converted into chemical energy

Question 15

what are photosystems made up of (RCC + LHC)

Answer 15

Reaction centre complex
Light harvesting complex

Question 16

What does the reaction centre complex contain

Answer 16

a pair of chlorophyll a molecules

Question 17

What makes up the light harvesting complexes

Answer 17

Pigments bound to proteins

Question 18

Outline the general process of photons ending up as electrons with the primary electron acceptor

Answer 18

Pigments in LHC absorb photon and pass electron between pigments - electron is then transferred to special chlorophyll a molecules which then pass it to primary electron acceptor

Question 19

What are the products of the linear flow of electrons in the light dependent cycle

Answer 19

ATP, NADPH and O2

Question 20

What are the chlorophyll a molecules in the reaction complex centre in PSII called

Answer 20

P680

Question 21

How does P680 become reduced after transferring its electron to the primary electron acceptor

Answer 21

P680+ oxidises H2O to form O2

Question 22

What complex makes up the ETC from PSII to PSI

Answer 22

Cytochrome complex

Question 23

What does the passing down of the electrons in the ETC cause

Answer 23

A release of energy which drives the creation of a proton gradient across the thylakoid membrane

Question 24

What are the chlorophyll a molecules in the reaction complex centre in PSI called

Answer 24

P700

Question 25

How does P700 become reduced after transferring its electron to the primary electron acceptor

Answer 25

P700+ accepts electron passed down the ETC from PSII

Question 26

Where do the electrons from PSII's go

Answer 26

Down a secondary ETC to ferredoxin (Fd)

Question 27

Once the electrons reach Fd in the second ETC what do they do

Answer 27

Reduce NADP+ to NADPH

Question 28

What PS does the cyclic electron flow involve and what is produced

Answer 28

PSI and ATP

Question 29

What is the advantage of cyclic electron flow

Answer 29

Photoprotection

Question 30

Outline the cyclic electron flow - starting with Fd - what is produced

Answer 30

Electrons cycle back from Fd to the PSI reaction complex centre via the ETC producing ATP

Question 31

What is the general function of the Calvin cycle

Answer 31

To reduce CO2 to sugar using ATP and NADPH

Question 32

How many turns of the Calvin cycle is needed to form a glucose molecule

Answer 32

6

Question 33

What are the 3 general stages in the Calvin cycle

Answer 33

Carbon fixation Reduction Regeneration

Question 34

What is the first and immediate second step in the Calvin cycle - enzyme?

Answer 34

CO2 is joined to ribulose bisphosphate to form an unstable 6C sugar catalysed by RuBISCO 6C intermediate splits into 2 molecules of 3-phosphoglycerate

Question 35

How is ATP used in the 1st step of the 2 step reduction process of the Calvin cycle

Answer 35

ATP converted to ADP and each 3-phosphoglycerate becomes 1,3-bisphosphoglycerate

Question 36

What is the second step in the reduction stage of the Calvin cycle

Answer 36

NADPH reduces 1,3-bisphosphoglycerate to G3P

Question 37

If 6 G3Ps are produced how many leave the Calvin cycle and what happens to them

Answer 37

1 - forms glucose and other organic compounds

Question 38

What is regenerated during the regeneration step of the Calvin cycle and what is formed as a biproduct

Answer 38

5 G3Ps become ribulose bisphosphate 3 molecules of ADP

Question 39

What is the advantage of photorespiration

Answer 39

Oxygen - oxidative damage

Question 40

Why would a plant carry out photorespiration

Answer 40

Hot and dry conditions so stomata have to remain closed to retain water

Question 41

How does the Calvin cycle differ in photorespiration

Answer 41

RuBISCO adds RuBP to oxygen instead of CO2 which forms a 2C compound

Question 42

What is carbon fixed to in C4 plants

Answer 42

A C4 compound

Question 43

What enzyme is used instead of RuBISCO in C4 plants - why is it advantageous

Answer 43

PEP carboxylase - has a high affinity for CO2 even in low CO2 conditions

Question 44

2 unique anatomical leaf features in C4 plants

Answer 44

Bundle sheath cells and Mesophyll cells

Question 45

What is the type of separation in CAM plants in comparison to C4 plants

Answer 45

C4 - structural / spatial separation CAM - Temporal separation

Question 46

What does the build up of acids do in CAM plants

Answer 46

They release CO2 to use in the Calvin cycle during the day when stomata are closed