5.1 Photosynthesis

Question 1

heat stress decreases the light-dependent reaction

explain why this leads too a decrease in the light independent reaction

Answer 1

less atp formed in light dependent reaction

therefore less reduced NADP formed in light independent reaction

Question 2

why does chloroplast contain more than 1 pigment

Answer 2

different pigments absorbs different wavelengths of light to maximise the absorbtion of light across different wavelengths

Question 3

where does light DEPENDENT reaction occur

Answer 3

the thylakoid

Question 4

give 2 uses of hexose sugars inside plant cells

Answer 4

conversion into starch for storage
converstion into cellulose for cell walls

Question 5

explain how ATP is created from the light dependent reaction (5)

Answer 5

electrons are excited by light and move to a higher energy level
electrons move to electron transport chain
electrons loose energy along electron transport chain
energy lost used to synthase ATP from ADP + Pi

Question 6

adaptations of chloroplast for light harvesting

Answer 6

GRANA/THYLAKOID have a large surface area for attatchment for chlorophyll and enzymes (light dependent)

stroma fluid has enzyme in it for light independent

a network of proteins in the grana hold the chlorophyll in precise position to allow max absorbtion of light

chloroplast have their own DNA and ribosomes so can quickly make any proteins it needs

Question 7

describe the role of the electron transport chain in the light independent reaction

Answer 7

electron tranport chain accepts excited electrons from chlorophyll
electrons lose energy along chain
atp is produced
from ADP + Pi
reduced NADP formed
when electrons and hydrogen combine with NADP
hydrogen from photolysis

Question 8

in the light - independent reaction of photosynthesis the carbon in carbon dioxide becomes triose phosphate
describe how (5)

Answer 8

Carbon dioxide combines RuBP
to produce two glycerate 3-phosphate

then reduced to triose phosphate
by NADP and energy from ATP

Question 9

describe how crop plants use light energy during the light dependent reaction

Answer 9

light energy excites electrons in chlorophyll allowing them to move out of chlorophyll

electrons travel down electron transport chain and loose energy

lost energy catalyses ATP and Pi to form ATP

photolysis of water produces hydrogen, electrons and oxygen

NADP reduced by Hydrogen

Question 10

Adaptations of the leaf

Answer 10

LARGE SURFACE AREA to capture as much sunlight as possible

VERY THIN so that light is absorbed in the first few mm for a short diffusion pathway

NETWORK OF XYLEM to bring water

MANY STOMATA for gas exchange

MINIMISING OVERLAPPING to avoid shadowing leaves