Photosynthesis

Question 1

Describe the process of cyclic photo phosphorylation

Answer 1

Involves only photosystem 1
Light is absorbed by photosystem 1 by accessory pigments and passed on to the primary pigment
An electron in the chlorophyll mol is excited to a higher energy level and emitted from the chlorophyll mol(photo activation)
Passed on to the ETC
ATP synthesized from ADP and pi by chemiosmosis
Electron is passed back to chlorophyll mol
ATP then passes to the LI reactions

Question 2

Describe non cyclic photo phosphorylation

Answer 2

Both photosystems involved
Light is absorbed by both photosystems
And excited electrons are emitted from the primary pigments of both reaction centers
These electrons are absorbed by electron acceptors and passed on to the ETC leaving the photosystems positively charged
The primary pigment of PS1 absorbs electrons from photosystem2 from photolysis
PS11 has water splitting enzyme water is broken down to 2 protons 2 electrons and 1/2 an O2 mol which is given off as waste
The protons and electrons combine with NADP to give reduced NADP
Reduced NADP is then passed on to the LIR

Question 3

What does the hill reaction investigate

Answer 3

Effect of light intensity or of light wave length on rate of photosynthesis

Question 4

What are the indicators that can be used to demonstrate the hill reaction

Answer 4

DCPIP which becomes reduced and changes colour from blue to Colourless
Fe3+

Question 5

Outline the steps of the LIR

Answer 5

▪️Rubisco catalyses combination of CO2 with RuBP(5C) to form an unstable intermediate(6C)
▪️which then splits in to 2 GP(3C)
▪️GP in presence of ATP and reduced NADP is reduced in to 2 TP (3C)
▪️some of the TP is used to make molecules such as glucose,lipids and amino acids
▪️the rest of TP is used to regenerate RuBP

Question 6

How is the structure of chloroplast adapted to carry out its function

Answer 6

Membranes of grana provide a large surface area which holds pigments ,enzymes and electron carriers
Pigment mol are arranged in light harvesting clusters for efficient light absorption
Membranes of grana hold ATP synthase for atp synthesis by chemiosmosis

Question 7

What are the external factors affecting the rate of photosynthesis

Answer 7

Light intensity,wave length,temperature,CO2 concentration

Question 8

How do u calculate the Rf value

Answer 8

Rf=distance travelled by pigment spot/distance travelled by solvent

Question 9

Describe the structure of a choloroplast

Answer 9

Starch grains
70s ribosomes
3-10um in diameter
Each cholorplast is surrounded by an envelope of 2 phospholipid mem
Stroma which is the ground substance
Flattened fluid filled sacs which are thylakoids
Stacks are called grana
Contains enyzmes such as rubsico for calvin cycle

Question 10

Explain the role of NADP in photosynthesis

Answer 10

On thylakoid mem
From photsystems in stroma
In light dependent reaction NADP becomes reduced by accepting 2 electrons and 1 proton
Co enzyme
Carries protons and high energy electrons
Becomes regenerated

Question 11

Describe the structure of photosystems

Answer 11

2 photosystems
Both are similar except 2 has the water splitting enzyme
Both in non cyclic
1 in cyclic only
Anatannea complex which consists of primary pigments
Primary pigment is reaction center
Exist on thylakoid membranes