Photosnythesis

Question 1

Structure of a chloroplast

Answer 1

Double membrane

Stroma (liquid) contains:
-thylakoid membrane
-70s ribosomes
-circular DNA
-starch granules/lipid droplets

Lamella - thylakoid linking grana

Grana - stacks of thylakoid

Question 2

Stages of photosynthesis

Answer 2

Light dependant reaction:
-thylakoid membrane of a chloroplast

-light independent reaction:
-stroma of a chloroplast

Question 3

Describe photoionisation in the LDR

Answer 3

Chlorophyll absorbs light energy which excites its electrons(higher energy level)

So electrons are released from chlorophyll which becomes positively charged

Question 4

What happens after the photoionisation

Answer 4

Electrons move along electron transfer energy chain (releasing energy)

This energy is used to actively pump protons (H) from storma into thylakoid

Protons(H) move by facilitated diffusion down electrochemical gradient into the stroma via atp synthase

Energy used to join ADP and Pi to form ATP (photophosphylation)

NADP accepts proton and an electron to become reduced NADP

Question 5

What is photolysis (LDR)

Answer 5

Water splits to produce H and electrons and oxygen
They replace the electrons lost in the chlorophyll
H2O-> 1/2O2 + 2e- + 2H+

Question 6

What is the light dependent reaction known as

Answer 6

The Calvin cycle

Question 7

Describe the Calvin cycle

Answer 7

1) Co2 reacts with Toulouse biophosphate (RuBP)
Catalysed by rubisco (enzyme)

2) this forms 2 glycerate 3-phosphate molecules (GP)

3) GP is reduced to triose phosphate
Using products from the LDR (reduced NADP and every from ATP)

4) some TP is converted to organic substances (glucose)

5) some TP is used to regenerate RuBP in the Calvin cycle (using energy from ATP)

Question 8

How does temp affect rate of photosynthesis

Answer 8

As temp increases rate increases
(Enzymes gain energy so more enzyme substrate complexes formed)

Above a optimum point, rate decreases as enzymes denature (H bonds break)

Question 9

How dose light intensity affect rate of photosynthesis

Answer 9

As light increases, rate increases
LDR increases (more phosphorylation)so more ATP and reduced NADP
Light independent increases as more GP reduced to TP

Above a intensity rate stops increasing

Question 10

How dose Co2 conc change photosynthesis

Answer 10

Rate increases when Co2 conc increases:
-light independent increase
-more Co2 to combine with RuBP to form GP
-to reduce TP
- so more RuBP/organic substances

Above a certain conc rate stops increasing