Photosynthesis in plants

Question 1

What is the word and balanced equation for photosynthesis?

Answer 1

Carbon dioxide + water ———-> oxygen + glucose

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

Question 2

How does temperature affect photosynthesis?

Answer 2

• Increase in temperature, increase in rate of photosynthesis
• As the reaction is controlled by enzymes, this trend only continues up to a certain temperature, until the enzymes begin to denature and rate of reaction decreases.

Question 3

How does light intensity affect photosynthesis?

Answer 3

• Higher light intensity, rate of photosynthesis increases
• As distance between light and plant increases, light intensity decreases.

Question 4

How does CO₂ concentration affect photosynthesis?

Answer 4

• CO₂ is also needed to make glucose.
• As the concentration increases, the rate of reaction increases.

Question 5

Describe the waxy cuticle

Answer 5

Helps to reduce water loss by evaporation and is a protective layer found at the top of the leaf

Question 6

Describe the upper epidermis

Answer 6

Very thin and transparent in order to let light in to the palisade mesophyll.

Question 7

Describe the palisade mesophyll

Answer 7

Contains lots of chloroplasts so that photosynthesis can happen rapidly

Question 8

Describe the spongey mesophyll

Answer 8

Have lots of air spaces to allow gases to diffuse in and out of cells faster, as it increases the SA:V ratio

Question 9

Describe the lower epidermis

Answer 9

Contains guard cells and stomata

Question 10

Describe the guard cell

Answer 10

Kidney-shaped cells that open and close the stomata by absorbing or losing water. When lots of water is available, the cells fill and open stomata

Question 11

Describe stomata

Answer 11

Where gas exchange and loss of water by evaporation takes place - opens during the day and closes at night.

Question 12

What is magnesium required for?

Answer 12

• Chlorophyll production
• Deficiency: causes leaves to turn yellow

Question 13

What is nitrate required for?

Answer 13

• Produce amino acids
• Deficiency: causes stunted growth and leaves turn yellow

Question 14

Describe an experiment to test leaves for starch

Answer 14

1. Start by dunking the leaf in boiling water. This stops any chemical reactions happening inside the leaf.
2. Put the leaf in a boiling tube with some ethanol and heat it in an electric water bath until it boils - this gets rid of any chlorophyll and makes the leaf a white-ish colour
3. Finally, rinse the leaf in cold water and add a few drops of iodine. solution - if starch is present, the leaf will turn blue-black

Question 15

Describe the experiment of evolution of oxygen from a water plant.

Answer 15

1. A source of white light is placed at a specific distance from the pondweed
2. The pondweed is left to photosynthesise for a set amount of time. As it photosynthesises, the oxygen realised will collect in the capillary tube.
3. At the end of the experiment, the syringe is used to draw the gas bubble in the tube up alongside a ruler and the length of the gas bubble is measured.
4. Temperature and time pondweed is left to photosynthesise remains controlled.
5. Experiment is then repeated with the light source place at different distances from the pondweed