Photosynthesis

Question 1

Light dependent reaction
Detailed

Answer 1

Chlorophyll absorbs light energy causing photoionisation: electrons are excited and leave the chlorophyll.
Electrons taken up by an electron carrier and is transferred along the electron transport chain in a series of redox reactions. Each new carrier is at a slightly lower energy level than the one before do electrons lose energy at each stage.
Some of this energy is used to combine an inorganic phosphate molecule with ADP to make ATP.

Question 2

LDR from markschemes

Question 3

Chemiosmotic theory

Answer 3

Protons are pumped from the stroma, across the thylakoids membrane into the thylakoid using protein carriers: proton pumps: ATP synthase.
The energy to drive this process comes from electrons released by photolysis of water
Photolysis of water also produces protons (further increases concentration in thylakoid)
Conc grad maintained
As protons pass through ATP synthase channels they cause changes to the enzyme structure which catalyses the combination of ADP with Pi to make ATP

Question 4

Photolysis of water

Answer 4

Chlorophyll molecules need electrons to replace the ones lost by photoionisation if they are to continue releasing electrons.
Water molecules are split up using light energy to yield these electrons and also protons and oxygen.
These protons pass through atp synthase and taken up by an electron carrier called NADP
NaDP is reeuced

Question 5

NADP or NAD in photosynthesis?

Answer 5

NADP (reduced to NADPH)

Question 6

Adaptation of thylakoid

Answer 6

Large surface area for attachment of chlorophyll, electron carriers and enzymes involved in the LDR

Question 7

Adaptations of grana

Answer 7

Selectively permeable allow establishment of proton gradient
Have atp synthase within them to catalyse reaction to form atp

Question 8

Adaptation of chloroplasts

Answer 8

Have dna and ribosomes can can quickly and easily manufacture proteins involved in LDR

Question 9

Light independent reaction
Detailed

Answer 9

In the stroma
CO2 reacts with 5 carbon RuBP, catalysed by rubisco
Produces 2 molecules of 3 carbon GP
NADPH reduces GP into TP using ATP
NADP reformed and goes back to LDR by accepting more protons
Some TP converted into organic substances (starch/ cellulose/ lipids/ amino acids etc)
Most TP used to regenerate RuBP using ATP from LDR

Question 10

LIR from mark schemes

Question 11

Adaptations of stroma/ chloroplasts for LIR

Answer 11

Fluid of stroma contains all enzymes needed
Surrounds grana so products of LDR rapidly diffuse into stroma
Contains dna and ribosomes

Question 12

Identify environmental factors that limit the rate of photosynthesis

Question 13

Chromatography experiment

Question 14

Investigating effect of naked factor on rate of dehydrogenase activity