3.2 photosynthesis

Question 1

what is the photosynthesis

Answer 1

the process by which carbohydrates are synthesised from carbon dioxide and water using light energy

Question 2

what is the main site of photosynthesis in plants

Answer 2

palisade mesophyll cells/ tissue

Question 3

what part of the lead has the most chloroplast

Answer 3

top part of the lead in the palisade cell

Question 4

label chloroplasts and

Question 5

where does photosynthesis take place

Answer 5

in chloroplasts

Question 6

what do chloroplasts contain

Answer 6

photosynthetic pigments which absorb light energy at particular wavelengths of light

Question 7

how are leaves adapted for photosynthesis

Answer 7

-spongy mesophyll, air spaces for gas exchange
-large SA (flat and thin)
- waxy cuticle (reduce water loss)
- thin, upper layer is transparent so light can penetrate through the leaf (short diffusion distance)

Question 8

how are chloroplasts adapted for photosynthesis

Answer 8

stacked thylakpids (increase SA)
move around to optimise light absorption
chloroplasts have many grana, large SA

Question 9

what is an energy transducer

Answer 9

something that changes energy from light into chemical energy

Question 10

why do plants look green

Answer 10

plants absorb light from all electromagnetic spectrum except for the colour green, it is reflected

Question 11

how can photosynthetic pigments be seoarated

Answer 11

using chromatography

Question 12

what is a photosynthetic pigment

Answer 12

a photosynthetic pigment is a chemical substance that is present in chloroplasts to absorb the light energy necessary for photosynthesis

Question 13

what are the 2 different groups of photosynthetic pigments

Answer 13

chlorophyll and carotenoids

Question 14

different chlorophylls
where are they present

Answer 14

chlorophyll a
chlorophyll b
they’re all green, found in green plants

Question 15

carotenoids

Answer 15

carotene (orange and in all plants)
xanthophyll (yellow and in most plants)

Question 16

what is the absorption spectrum

Answer 16

a graph to show the absorbance of different wavelengths of light by a pigment

Question 17

what is the action spectrum

Answer 17

a graph to show the rate of photosynthesis at different wavelengths of light

Question 18

where are photsysytems found

Answer 18

embedded in the thylakoid membrane

Question 19

explain how light harvesting works

Answer 19

energy from different wavelengths absorbed by an ‘antenna’ complex of an accessory pigment is ‘funneled down’ to a reaction centre

Question 20

example of accessory pigments

Answer 20

chlorophyll B/ carteroids

Question 21

where is the reaction centre found

Answer 21

at the base of the photosysten, it contains a pair of chlorophyll A molecules

Question 22

what does the antenna complex contain

Answer 22

many different light absorbing pigments

Question 23

puprose of the photosystem

Answer 23

to trap as much light energy as possible

Question 24

how many photosystems are there

Answer 24

2

Question 25

at what wavelength does chlrophyll A absorb light in photosystem 1 and 2

Answer 25

1. 700nm 2. 680 nm

Question 26

what is the light dependent stage

Answer 26

photophosphorylation

Question 27

what happens in the light dependent stage

Answer 27

electrons lost from the reaction centre pass along a chain of electron acceptors which power a hydrogen pump that carries a H+ ion from the stroma to the thylakoid lumen

Question 28

what is photophosphorylation

Answer 28

the addition of a phosphate group to ADP to form ATP using light energy

Question 29

2 types of phosphorylation

Answer 29

cyclic/non-cyclic

Question 30

what photosystem does cyclic phosphorylation involve

Answer 30

just photosystem 1

Question 31

explain cyclic phosphorylation

Answer 31

a photon of light hits photosystem 1, 2 electrons become excited, they pass to an electron acceptor, this is donated to the ETC which generates a proton gradient for chemiosmosis. the electrom is passed back to PS1.

Question 32

what is the purpose of the ETC generating energy cyclic phosphorylation

Answer 32

energy is needed so H+ ions go from stroma to the thylakoid lumen.

Question 33

non-cyclic photophosphorylation

Answer 33

an alternative pathway, both photosystems high energy electrons from PS1

Question 34

what does photolysis provide and what is it

Answer 34

provides an electron for PSII molecules of water absorb light energy and split to form electrons protons and oxygen

Question 35

what do the electrons from photolysis do

Answer 35

passed to PSII to replace those lost during non-cyclic photophosphorylation

Question 36

what do the protons from photolysis do

Answer 36

used to reduce NADP each NADP molecule picks up 2 protons and 2 electrons to become reduced

Question 37

what are the products of the light dependent stage

Answer 37

ATP and reduced NADP both are needed in the calvin cucle

Question 38

what is the light independent stage

Answer 38

the calvin cycle, it fixes carbon dioxide into glucose using ATP (from photophosphorylation) and reduced NADP

Question 39

where does the calvin cycle happen

Answer 39

stroma

Question 40

what controls the calvin cycle

Answer 40

enzymes

Question 41

3 stages of the calvin cycle

Answer 41

fixation reduction making glucose and regeneration of rubulose bisphosphate

Question 42

explain the first stage of the calvin cycle

Answer 42

carbon dioxide is taken up by 5C ribulose bisphosphate to form an unstable 6c molecule (catalysed by rubisco) this 6c molecule then dissociates into 2 glycerate 3 phosphate molecules

Question 43

explain the second stage of the calvin cycle

Answer 43

Glycerate 3 phosphate is reduced (gains 2H atoms) into triose phosphate using ATP NADP reduced goes to NADP (gives up H atoms)

Question 44

explain the third stage of the calvin cycle

Answer 44

5/6 of triose phosphate is used t make ribulose phosphate 1/6 of triose phosphate is used to mkae glucose (can be converted into fructose or sucrose and starch) ribulose phosphate is converted to RuBp using ATP (ADP+Pi)

Question 45

how many turns of the calvin cycle to make glucose

Answer 45

6

Question 46

mineral requirements for plants

Answer 46

**nitrogen**: for amino acid, protein production and chlorophyll production (deficience: reduced growth of organs and yellowing of the leaves (chlorosis)) ** magnesium**: essential for production of chlorophyll. deficiency:yellowing of leaves=chlorosis)

Question 47

3 limiting factors of photosynthesis

Answer 47

temperature, light intensity, CO2

Question 48

what is a limiting factor of photosynthesis

Answer 48

where if any of the factors become too low, rate of photosynthesis will decrease

Question 49

limiting factor: temperature

Answer 49

affects kinetic energy and therefore rates of transport and enzyme activity

Question 50

limiting factor: light intensity

Answer 50

light is needed to excite electrons in the photo system during the light dependent stages

Question 51

limiting factor: CO2

Answer 51

as concentration increases, the rate of the light independent reactions increase the rate of photosynthesis increases