Respiration and photosynthesis

Question 1

What is the structure of a chloroplast

Answer 1

Chloroplast envelope- this is the outer and inner membrane and it’s function is to keep the reactants for photosynthesis close to their reaction site
Thylakoids- the green pigment chlorophyll is found in thylakoids they are the site of the light dependent reaction of photosynthesis
Grana - they are stacks of thylakoids
Lamellae - they join the grana together maintaining a working distance between the grana for maximum function as efficiently as possible

Question 2

What is a photo system

Answer 2

A photo system is a combination of the protein and the pigment in the thylakoid membrane

Question 3

What is the stroma

Answer 3

It’s a gel like substance contained within the inner membrane. It contains enzymes, sugars etc for the light dependent reaction

Question 4

What wavelengths of light can a plant best absorb

Answer 4

Blue and red light

Question 5

What does the action spectrum show

Answer 5

It shows the volume of oxygen produced

Question 6

Why do most plants appear green

Answer 6

Because the green wavelength isn’t being absorbed as much so it is being reflected

Question 7

What is the compensation point

Answer 7

Where the rate of photosynthesis and respiration are equal

Question 8

Why do plants have several pigments

Answer 8

It allows the plant to absorb more of the light in a wider range of wavelengths than a single pigment would be able to

Question 9

What is phosphorylation

Answer 9

This is when phosphate is added to a molecule

Question 10

What is photolysis

Answer 10

This is the splitting of water molecules using light

Question 11

What is light energy used for when it is absorbed by the photosynthetic pigments

Answer 11

It’s used to:

• add a phosphate group to ADP to form ATP
• Form reduced NADP

Question 12

What are ATP and reduced NADP used for in the light dependent reaction

Answer 12

ATP is used to provide energy for the Calvin cycle and reduced NADP transfers hydrogen to the Calvin cycle

Question 13

What happens to water when light hits the plant

Answer 13

Water is oxidised to form protons (H+), electrons and oxygen which is mostly lost through the stomata but some is used for aerobic respiration

Question 14

What is photophosphorylation

Answer 14

Adding a phosphate group to a molecule using light energy

Question 15

What is a coenzyme

Answer 15

A molecule (e.g NADP) that aids the function of an enzyme

Question 16

What are the 4 stages of non cyclic photophosphorylation

Answer 16

Stage 1
- light energy is absorbed by photsystem II
- The light energy excites electrons in the chlorophyll
- the electrons move to a higher energy level
- they move along the electron transport chain to photosytem I
Stage 2
- as excited electrons leave PSII they must be replaced
- light energy splits water into protons, electrons and oxygen
Stage 3
-the excited electrons lose energy as they pass the electron transport chain this energy is used to produce ATP from ADP and Pi
Stage 4
-Light energy is absorbed by PSI which excites the electrons again to an even higher energy level
- finally the electrons are transferred to NADP to form reduced NADP

Question 17

What is chemiosmosis

Answer 17

The process where movement of protons across a membrane generates atp

Question 18

What happens in the process of cyclic photophosphorylation

Answer 18

• The electrons go back to PSI instead of NADP this means that electrons are recycled and can repeatedly flow through PSI
• this produces a little bit of atp but no oxygen or reduced NADP

Question 19

Where does the Calvin cycle take place in the chloroplast

Answer 19

The stroma

Question 20

What is the first stage of the Calvin cycle

Answer 20

• Carbon dioxide is combined with ribulose bisphosphate (RuBP) to form two molecules of glycerate 3 phosphate (GP)
• Carbon dioxide combines with RuBP and the carbon dioxide is said to be fixed so this is carbon fixation
• this reaction is catalysed by the enzyme rubisco

Question 21

What is the second stage of the Calvin cycle

Answer 21

• atp from the light dependent stage provides energy for the 3 carbon compound GP to be reduced into GALP another 3 carbon compound
• this reduction requires h+ ions which come from reduced NADP
• reduced NADP is then recycled to oxidised NADP
• GALP then gets converted into different useful compounds

Question 22

What is the third stage of the Calvin cycle

Answer 22

• 5 of the 6 GALP produced in the cycle are used to regenerate RuBP to continue the Calvin cycle
• this regenerating requires ATP

Question 23

What are the products of the Calvin cycle

Answer 23

Carbs, lipids, proteins and nucleic acids

Question 24

How are carbs formed from the Calvin cycle

Answer 24

Two GALP molecules are joined together which is known as gluconeogensis

Question 25

How are lipids formed from the Calvin cycle

Answer 25

They are made using glycerol and fatty acids

Question 26

How are nucleic acids formed from the Calvin cycle

Answer 26

The sugar in the RNA is made using GALP and phosphates taken in by the root hairs aid this process

Question 27

What are the limiting factors for photosynthesis

Answer 27

Temp, light intensity and carbon dioxide concentration