photosynthesis

Question 1

Autotrophs

Answer 1

Organisms that generate their own organic matter through photosynthesis

Question 2

why are plant leaves green

Answer 2

because they reflect or transmit t green light, or they do not absorb wavelengths of green light

Question 3

adaptations of leaves for photosynthesis and explain how these help in photosynthesis

Answer 3

large surface area: helps to capture the maximum amount of light

thin: light is able to penetrate right through the leaf. also, it creates a short diffusion pathway for the diffusion of CO2

permeable: they have stomata, which allow carbon dioxide to diffuse into the leave

have air spaces:this allows carbon dioxide to diffuse into all the cells of the leaf

cuticle and epidermis are transparent, so light is able to pass through them easily to the chloroplasts.

Question 4

adaptations of palisade mesophyll cells for photosynthesis

Answer 4

large vacuole

they are cylindrical, elongated, and at right angles to the surface of the leaf. Due to this, light has to pass through the epidermal cells and only one palisade mesophyll cell before reaching the chloroplast.

contain a large number of chloroplasts, so the maximum amount of light can be trapped

Question 5

the function of the chloroplasts

Answer 5

to absorb light energy and convert it into chemical energy

Question 6

where are photosynthetic pigments found in the chloroplast

Answer 6

in the thylakoid membranes

Question 7

stacks of thylakoid membranes

Answer 7

grana/ granum

Question 8

where are chlorophylls found, what are they and what is their function

Answer 8

in the thylakoid membrane
green pigment that captures light for photosynthesis

Question 9

functions of starch and lipid droplets in chloroplasts

Answer 9

they store the products of photosynthesis

Question 10

function of the stroma

Answer 10

contains enzymes for photosynthesis

Question 11

the function of the outer membrane of the chloroplast

Answer 11

contains the contents of the stroma, like photosynthetic enzymes in the chloroplast, preventing them from mixing with the contents of the cytoplasm

Question 12

I am the site of the light-independent reactions

Answer 12

stroma

Question 13

I am the site of the light-dependent reactions

Answer 13

thylakoid membranes

Question 14

why are starch grains used as carbohydrate stores in the chloroplast

Answer 14

because starch does not affect the water potential as it is insoluble

Question 15

Why does the chloroplast have a double membrane

Answer 15

to control the movement of substances in and out of the chloroplast

Question 16

advantage of the leaves having more than one photosynthetic pigment

Answer 16

enables the leaves to absorb various wavelengths of light. So more light is absorbed overall if there are more pigments

Question 17

main photosynthetic pigments involved in harvesting light energy

Answer 17

chlorophyll a
chlorophyll b
carotenoids

Question 18

difference between chlorophyll a and chlorophyll b

Answer 18

chlorophyll a has a methyl group attached to it while chlorophyll b has a carbonyl group attached

Question 19

chromatography

Answer 19

a separation technique first used to separate pigments in plant leaves

Question 20

Rf value

Answer 20

the value that shows how far a component has traveled compared to the solvent front

Question 21

formula for Rf

Answer 21

distance moved by component/ distance moved by solvent front

Question 22

Plants take up minerals from the soil. These are combined with the products of the light-independent
stage to produce other molecules needed by the plant.
Give three examples of minerals taken up from the soil and state what molecules are produced when
each example combines with the products of the light-independent stage.

Answer 22

nitrates, to serve as a source of nitrogen for protein synthesis and the synthesis of nucleic acids

phosphate for the synthesis of phospholipids

magnesium for chlorophyll synthesis

Question 23

State why only some of the triose phosphate produced by the Calvin cycle can be used to produce
hexose phosphate.

Answer 23

Some TP is needed to regenerate more RUBP

Question 24

Diuron is a weed killer which is a very specific and sensitive inhibitor of photosynthesis. It blocks the
electron carrier binding site on photosystem II. This stops the electron flow from where it is generated, in
photosystem II, to the electron carrier. This reduces the ability of the plant to convert light energy into
chemical energy.
Diuron only blocks electron flow from photosystem II. It has no effect on photosystem I or other reactions
in photosynthesis, such as light absorption or carbon fixation in the Calvin cycle.
(a) Explain the effects of Diuron on non-cyclic photophosphorylation and why cyclic photophosphorylation
is not affected.

Answer 24

it stops electrons from being transferred from PSII to PSI

so NADP is not reduced to NADPH

Cyclic photophosphorylation only involves PS1

so it is not stopped as electrons are passed from PS1 and returned to PS1

Question 25

Use your knowledge of photosynthesis to explain the role of photosynthetic pigments in the
production of ATP.

Answer 25

Pigments in PSII absorb light energy

electrons excited emitted from the reaction center

used to power proton pumps to generate an electrochemical gradient

movement of protons through ATP synthase allows for ATP production

Question 26

in photosystem 1, what is the reaction centre called and why?

Answer 26

p700 because it contains a chlorophyll molecule with a maximum absorption at wavelength 700nm

Question 27

in photosystem 2, what is the reaction centre called and why

Answer 27

p680 because it contains a chlorophyll molecule with maximum absorption at wavelength 680nm