Photosynthesis

Question 1

What is the balanced equation for photosynthesis?

Answer 1

6H2O + 6CO2 —> C6H12O6 + 6O2

Question 2

What is photosynthesis?

Answer 2

A series of enzyme catalysed reactions that synthesise organic molecules like glucose. Other take olace in the chloroplast

Question 3

What is oxidation?

Answer 3

Loss of electrons, gain of oxygen

Question 4

What is reduction?

Answer 4

Gain of electrons, loss of oxygen

Question 5

What factors can increase photosynthesis due to its enzymes?

Answer 5

Increased temperature
Increased KE
More enzyme substrate complexes being formed

Question 6

How are thylakoids beneficial for photosynthesis?

Answer 6

The light dependent reaction occurs in thylakoids, as it contains electron transport proteins and chlorophyll to absorb light energy

Question 7

Why are grana useful in photosynthesis?

Answer 7

They increase the surface area so can absorb more light energy for the light dependent reaction

Question 8

What is the role of the stroma in photosynthesis?

Answer 8

It contains enzymes used for the light dependent reactions

Question 9

What is the role of starch grains?

Answer 9

They store excess carbohydrtaes made in photosynthesis

Question 10

Where does the light dependent reaction take place?

Answer 10

In the thylakoid

Question 11

Explain what happens during the light dependent reaction

Answer 11

• chlorophyll absorb light energy, a pair of electrons gain energy and become excited, so leave the chlorophyll. This reduces the chlorophyll. This is PHOTIONISATION.
• PHOTOLYSIS occurs in the stroma, where water is split into hydrogen ions, electrons and oxygen.
• the pair of electrons pass through electron carrier proteins and undergo a series of redox reactions. This releases energy that is used to pump the hydrogen ions through the thylakoid membrane to create a conc. gradient between the stroma and thylakoid lumen
• the hydrogen ions then travel from the lumen ro the stroma through ATP synthase down the conc. gradient. This causes PHOSPHORYLATION (ADP + Pi —> ATP)
• the pair of electrons and hydrogen ions are added to NADP to make reduced NADP.

Question 12

What is photoplysis?

Answer 12

Where LIGHT INDUCES the splitting of water into hydrogen ions, electrons and oxygen. H+ is used to reduce NADP, and electrons replace those lost in the chlorophyll

Question 13

What photoionisation?

Answer 13

When the chlorophyll absorbe light and loses electrons

Question 14

What is photophosphorylation?

Answer 14

Where LIGHT ENERGY is used to combine ADP with Pi to form ATP, using a hydrogen concentration gradient

Question 15

What is chemiosmosis?

Answer 15

Energy released from electrons in the electron transport chain are used to actively transport H+ from the stroma into the thylakoid lumen.
Creates a conc. gradient
The H+ diffuse down gradient through ATP synthase, which causes photophosphorylation

Question 16

How are the light dependent and independent reaction linked?

Answer 16

The light independent reaction rewuores ATP and reduced NADP that is produced during the light dependent reaction.

Question 17

Where does the light independent reaction take place?

Answer 17

In the stroma lf the chloroplast.

Question 18

What enzyme is used in the light independent reaction?

Answer 18

Rubisco

Question 19

Explain the process of the light independent reaction

Answer 19

Carbon dioxide combines with a five carbon molecule (RuBP) to produce two molecules of GP. This reaction is catalysed by rubisco
ATP and reduced NADP are used to reduce the molecules of GP to triose phosphate.
The ATP provides the energy necessary for this reaction. The reduced NADP provides the hydrogen, and becomes NADP.
1/6 of the tripse phosphate is converted into glucose
5/6 is used to regenerate RuBP

Question 20

State four limiting factors of photosynthesis

Answer 20

Carbon dioxide conc.
Light intensity
Temperature
Water availability

Question 21

How does light intesnsity affect the rate of photosynthesis?

Answer 21

It provides energy to excite electrons, sl they leave the chlorophyll to ultimately make ATP.

Question 22

How does carbon dioxide conc. affect the rate of photosynthesis?

Answer 22

It provides carbon to produce two molecules of GP, to ultimately make glucose

Question 23

How does temperature affect the rate of photosynthesis?

Answer 23

It provides kinetic energy

Question 24

How does water availability affect the rate of photosynthesis?

Answer 24

It releases H+ ions during photolysis, which are used to reduce NADP and in chemiosmosis

Question 25

What are benefits of producing crops in a commercial glasshouse?

Answer 25

Higher yield
Crops can be grown out of season, so provides better economic return
Plants can be grown in places they would not normally grow

Question 26

How do glass houses increase yield?

Answer 26

They allow farmers to controll limiting factors
This increases the rate of photosynthesis, to increase carbohydrates made
Therefpre more energy is available for growth, which increases yield.

Question 27

Suggest how to comtrol light intensity, carbon dioxide concentration and temperature in a glasshouse.

Answer 27

Light- artificial lighting, using specifoc wavelengths.
CO2- use paraffin heaters, pump carbon dipxide into the glasshouse
Temp- ventilation, glass stops heat escaping, use heating mechsnisms snd thermometres

Question 28

How could high temperatures lower the rate of photosynthesis?

Answer 28

High temperatures increase water loss by transpiration
Excessive water loss causes plants to close stomata to limit water loss
Carbon dipxide can therefore not enter the leaves, so photosynthesis decreases

Question 29

How can water availability be increased in a glasshouse?

Answer 29

Using a humidifier- increases water vapour inside glasshouse
Decreases water potential gradient between leaves and air
So less water diffuses out the spongy mesophyll, leading to less transpiration