5.2.1

Question 1

What is an autotrophic organism?

Answer 1

An organism that is able to photosynthesise, such as plants and algae

Question 2

What are heterotrophic organisms?

Answer 2

Organisms that obtain complex organic molecules by eating other organisms

Question 3

What is the overall equation of photosynthesis?

Answer 3

6CO2 + 6H2O -> C6H12O6 + 6O2

Question 4

Where does photosynthesis take place?

Answer 4

The chloroplasts

Question 5

How are chloroplasts adapted to their function?

Answer 5

They have an inner membrane with transport proteins, many grana consisting of many thylakoids, photosynthetic pigments, proteins embedded in the grana, fluid-filled stroma, chloroplast DNA an ribosomes

Question 6

How does the inner membrane with transport proteins aid the chloroplast?

Answer 6

It allows for transport of molecules into and out of the chloroplast. It controls what enters and exits

Question 7

How do the grana aid the chloroplast?

Answer 7

This is where the light-dependent stage of photosynthesis takes place. They also contain lipids which help support the electron transport chain. They also contain ATP synthase

Question 8

How do the photosynthetic pigments aid the chloroplast?

Answer 8

They absorb different wavelengths of light, allowing for more energy to be taken in for photosynthesis

Question 9

How do the proteins embedded in the grana aid the chloroplast?

Answer 9

They catalyse reactions. They also hold pigments in place. Some of the proteins are also used as electron carriers

Question 10

How does the stroma aid the chloroplast?

Answer 10

It is a site of chemical reactions, containing the enzymes for the light independent stage

Question 11

How do the chloroplast DNA and RNA aid the chloroplast?

Answer 11

They allow for rapid synthesis of proteins required for photosynthesis

Question 12

What is the light harvesting system?

Answer 12

It is composed of numerous secondary pigments and proteins

Question 13

What is the function of the light harvesting system?

Answer 13

To absorb, or harvest, light energy of different wavelengths and transfer this quickly to the reaction centre.

Question 14

What pigment is located in the reaction centre?

Answer 14

Chlorophyll a

Question 15

What happens in reaction centre?

Answer 15

The reactions involved in photosynthesis take place

Question 16

What are the light harvesting system and the reaction centre collectively known as?

Answer 16

A photosystem

Question 17

What are the two stages of photosynthesis?

Answer 17

Light dependent stage and light independent stage

Question 18

How many photosystems are involved in non-cyclic photophosphorylation?

Answer 18

2, PSII and PSI, or PS680 and PS700

Question 19

What does the light absorbed by the photosystems do?

Answer 19

Excite electrons at the reaction centres

Question 20

Where do the excited electrons go?

Answer 20

The excited electrons are released from the reaction centre of PSII and are passed to an electron transport chain. ATP is produced by the process of chemiosmosis

Question 21

What is chemiosmosis?

Answer 21

The diffusion of H+ ions from a region of high concentration to a region of low concentration through a partially permeable membrane. The movement of the protons releases energy that is used in the synthesis of ATP from ADP and a Pi

Question 22

How are the electrons lost by PSII replaced?

Answer 22

They are replaced by electrons produced by the process of photolysis

Question 23

What is photolysis?

Answer 23

Light energy from the sun causes water molecules to split into hydrogen ions, electrons, and oxygen molecules

Question 24

Where do the excited electrons eventually reach?

Answer 24

The electrons leaving the electron transport chain following PSI are accepted, along with a hydrogen ion, by the coenzyme NADP, forming reduced NADP

Question 25

Where does the light-independent stage of photosynthesis take place?

Answer 25

The stroma of the chloroplast

Question 26

How does the calvin cycle start?

Answer 26

Carbon dioxide enters the intercellular spaces within the spongy mesophyll og leaves by diffusion. It diffuses into the cells and into the stroma, where it combines with ribulate bisphosphate.

Question 27

What is the binding of CO2 and RuBP called?

Answer 27

Carbon fixation

Question 28

What catalyses the carbon fixation?

Answer 28

RuBisCO, and produces an unstable 6 carbon intermediate

Question 29

What does the unstable 6 carbon intermediate do?

Answer 29

It breaks down into two 2 glycerate 3-phosphate (GP) molecules

Question 30

What happens when GP receives a hydrogen and energy?

Answer 30

It forms TP, triose phosphate

Question 31

What is the majority of TP used for?

Answer 31

Regeneration of RuBP so that the calvin cycle can continue

Question 32

How many turns of the calvin cycle are there for 1 glucose molecule to be produced?

Answer 32

6, as 6 CO2 molecules must enter the calvin cycle. This means 12 TPs are produced, 2 of those being used to create the glucose molecule, while the other 10 are used to create 6 RuBP molecules

Question 33

What are the factors affecting photosynthesis?

Answer 33

- Light intensity - Carbon dioxide concentration - Temperature

Question 34

Why is carbon dioxide concentration a factor?

Answer 34

Carbon dioxide is needed as a source of carbon for the carbon fixation in the Calvin cycle

Question 34

Why is light intensity a factor?

Answer 34

Light is needed as an energy source. As light intensity increases, ATP and reduced NADP are produced at a higher rate

Question 35

Why is temperature a factor?

Answer 35

Temperature affects the rate of enzyme controlled reactions. As temperature increases, the rate of enzyme activity increases until the point at which the proteins denature.

Question 36

What is the effect of reducing light intensity on the Calvin cycle?

Answer 36

Reducing light intensity reduces the rate of the light-dependent stage of photosynthesis. This reduces the quantity of ATP and reduced NADP produced. ATP and reduced NADP are needed to convert GP to TP. This means concentration of GP will increase while concentrations of TP and RuBP will decrease

Question 37

What is the effect of CO2 and temperature on the calvin cycle?

Answer 37

At very low temperatures and very high temperatures, the concentrations of TP, GP and RuBP will all be low. Low CO2 concentrations would decrease the concentrations of GP and TP. However, the concentration of RuBP will increase, as it is being formed but not used up