B8 - photosynthesis

Question 1

What is the word equation for photosynthesis?

Answer 1

Carbon dioxide + water —sunlight-> glucose + oxygen

Question 2

What is the symbol equation for photosynthesis?

Answer 2

CO2 + H2O —> C6H12O6 + O2

Question 3

How is a leaf adapted for photosynthesis?

Answer 3

-A transparent upper epidermis – this allows light to pass through.
-Waxy cuticle – decreases water loss from the leaf through evaporation.
-Broad leaves – increase the surface area of the leaf so there is more exposure to sunlight.
-Chloroplasts located near the top in the palisade mesophyll layer – this is so they can get the most light as this is where most of the plant’s photosynthesis takes place.
-Stomata (holes on the lower surface) – allow the movement of Carbon Dioxide and Oxygen into and out of the leaf as well as water vapour.
-Air spaces – increase surface area for gas exchange and allow gases to move more easily.
-Vascular bundles (xylem and phloem) – help transport water and sugars.

Question 4

Is photosynthesis endo or exothermic?

Answer 4

Endothermic as energy is required in the form of light for the reaction to occur.

Question 5

What are 3 possible limiting factors in photosynthesis.

Answer 5

• light intensity
• CO2 concentration
• temperature

Question 6

What is the most common limiting factor of photosynthesis?

Answer 6

CO2 concentration

Question 7

Write the method for working out the rate of photosynthesis of a certain leaf.

Answer 7

-Set up the apparatus as in the diagram.

-making sure to measure the starting volume on the measuring cylinder, start a timer and leave the pond weed over night.

• after 24 hours come back and note the change in volume of gas.

-Move the light 10 cm further back and repeat the process again.

-Repeat by moving the lamp away by 10 cm intervals until 50 cm is reached.

Question 8

Name some things we can’t control during the photosynthesis practical.

Answer 8

Pondweed (measured length but…)=
-different thicknesses
-different number of leaves
-different number of chloroplasts
-different plants
Temperature
-heat absorbent barrier
-consider denaturation
Light bulb
-age of bulb
-light intensity
-sunlight from windows
-time of year completed

Question 9

Describe the method for testing for starch in a leaf.

Answer 9

1) place a leaf in boiling water for about 1 min to remove waxy cuticle
2)place the leaf into a test tube of ethanol and replace back into hot water for 10 mins
3)spread leaf out onto white tile and cover with iodine
4)return leaf to hot water for about a minute

Question 10

During the leaf starch test why did we