Photosynthesis

Question 1

What is meant by an organic compound?

Answer 1

A compound that contains carbon.

Question 2

What is meant by an inorganic compound?

Answer 2

A compound that does not contain carbon.

Question 3

What are the redox reactions?

Answer 3

Oxidation is Loss

Reduction is Gain

Question 4

What are co-enzymes?

Answer 4

Non-protein molecules that help enzymes to work by transferring other molecules around.

Question 5

What is phosphorylation?

Answer 5

Adding a phosphate.

Question 6

What is photophosphorylation?

Answer 6

Using light energy to add a phosphate.

Question 7

What is photolysis?

Answer 7

Using light energy to split a molecule.

Question 8

What is an electron transfer chain?

Answer 8

When electrons flow through proteins (Electron carriers) in a membrane.

Question 9

What is a proton?

Answer 9

A hydrogen ion (H+).

Question 10

What is the word equation for photosynthesis?

Answer 10

Carbon dioxide + Water = Glucose + Oxygen.

Question 11

What is the symbol equation for photosynthesis?

Answer 11

6CO2 + 6H2O = C6H12O6 + 6O2.

Question 12

Where does the light dependent reaction occur?

Answer 12

Membrane of the thylakoid.

Question 13

What happens during the light dependent reaction?

Answer 13

Light energy is used to make ATP and reduced NADP (NADPH).

Question 14

Where does the light independent reaction take place?

Answer 14

The stroma.

Question 15

What happens during the light independent reaction?

Answer 15

Products of the LDR are used to make useful organic compounds.

Question 16

What is another name for the light independent reaction?

Answer 16

The Calvin cycle.

Question 17

What happens during the light dependent reaction?

Answer 17

• Photosynthetic pigments (e.g. chlorophyll) absorb light energy.
• This excites an electron, causing it to leave the chlorophyll (photoionisation).
• The electron moves along the electron transfer chain.
• The electron releases energy.
• This energy is used to join ADP+Pi to form ATP.
• NADP is reduced to form reduced NADP (NADPH).
• Photolysis of water makes protons (H+), electrons (e-) and oxygen.

Question 18

What happens during the light independent reaction?

Answer 18

• CO2 combines with ribulose bisphosphate (RuBP) catalysed by the enzyme rubisco.
• This makes two molecules of glycerine-3-phosphate (GP).
• Both GP molecules are reduced to form two molecules of triode phosphate (TP) by using 2xATP and 2xNADPH.
• Most TP is regenerated to form RuBP using energy from ATP.
• Some of the TP is converted into useful organic compounds (e.g. lipids).

Question 19

What are the main limiting factors of photosynthesis?

Answer 19

• Light intensity.
• CO2 concentration.
• Temperature.

Question 20

How is light intensity a limiting factor of photosynthesis?

Answer 20

• The higher the light intensity, the more energy there is for the LDR so the faster the rate of photosynthesis.
• However light needs to be the right wavelength (plants reflect green light and absorb red and blue).
• Different pigments absorb different wavelengths.

Question 21

How is CO2 a limiting factor of photosynthesis?

Answer 21

• CO2 is about 0.04% in the atmosphere.
• Optimum CO2 concentration is 0.4%.
• Above 0.4% CO2 has a negative effect on rate of photosynthesis.

Question 22

How is temperature a limiting factor of photosynthesis?

Answer 22

• Photosynthesis is controlled by enzymes.
• If you increase the temp you increase the rate of reaction up to the optimum temperature.
• Beyond the optimum temp, the rate decreases.
• high temp can cause stomata to close (less CO2, less use of Calvin cycle).