Photosynthesis

Question 1

Photosynthesis definition

Answer 1

Photosynthesis is the process by which plants make their own food

Question 2

Photosynthesis Equation

Answer 2

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

Question 3

Experiment to test leaves for starch

Answer 3

1. Destarch leaf by placing in a dark room for 48hours
   Ensures that any starch detected is under conditions
2. Boil the leaf in water
   This kills the leaf by stopping all chemical reactions
3. Boil the leaf in ethanol
   Removes the green pigment so any colour change can be seen
4. Dip leaf in water
   This softens leaf after ethanol makes it brittle
5. Add iodine
   Detects starch. Yellow/brown-blue/black

Question 4

Other experiment test on leaves

Answer 4

Test for chlorophyll (variegated leaf)
Test for light (partially covered leaf)
Test for carbon dioxide (leave kept in air, treated with soda lime)

Question 5

Experiment to prove oxygen production in plants

Answer 5

A water plant, elodea, can be used to probe the production of oxygen. The gas collected will delight a glowing splint

Question 6

Affects of light intensity, temperature and carbon dioxide with photosynthesis

Answer 6

As light intensity increases so does the rate of photosynthesis as the pant absorbs the light. As it decreases so does the rate at which the bubbles are produced

At high temperatures the rate of photosynthesis will decrease

The higher the concentration of carbon dioxide the rate of photosynthesis increases
To stop warm temperatures from killing the plant, it is placed in a cool beaker of water

Question 7

How the products of photosynthesis are used

Answer 7

1. Growth
2. Storage
3. Respiration

Question 8

Balance between photosynthesis and respiration

Answer 8

It can be demonstrated by using bicarbonate indicator as it detects changes in the concentration of carbon dioxide.

Normal (0.04)- red/orange
Increased- yellow
Decreased- purple

Question 9

Compensation point

Answer 9

This is when the processes of photosynthesis and respiration balance. The carbon dioxide and water is used in photosynthesis.

Remember plants respire all the time and only photosynthesise when there is light.

Question 10

Chemical equation for photosynthesis

Answer 10

6CO2 + 6H2O ——> CH12O6 + 6O2

Question 11

Factors affecting the rate of photosynthesis

Answer 11

Carbon dioxide
> rate will decrease if carbon dioxide is in short supply as it is a reactant in the process

Light
> rate will increase if light intensity increased. Light energy drives the process

Temperature
> rate will decrease if temperature are low as the molecules are moving slower and less likely to collide.

Question 12

Palisade mesophyll

Answer 12

Tall thin cells packed with chloroplasts

Ideal for trapping Light

Question 13

Stomata

Answer 13

Tiny pores in the leaf that allows gases to enter and leave the leaf.
More on the lower surface than the upper
Carbon dioxide diffuses through stoma

Question 14

Guard cells

Answer 14

Sausage shaped cells that surround the stoma
Controls the size of the stomata in order to reduce water loss
Contain chlorophyll

Question 15

Waxy cuticle

Answer 15

Waxy transparent layer that reduces evaporation but allows light through
Coats both sides of the leaf

Question 16

Upper epidermis

Answer 16

A layer of thin cells that act as a protective layer

Question 17

Spongy mesophyll

Answer 17

Loosely packed cells with large air spaces between

Site of gas exchange (air spaces make diffusion of gases more efficient )

Question 18

Vein

Answer 18

Carries water and mineral up the roots where they are absorbed

Question 19

Benefits from the structure of a leaf

Answer 19

Flat surface
Creates more surface area for light to be absorbed

Thin
Light can get to the chloroplasts in short distance for carbon dioxide to diffuse

Low density
It can hold position which maximum light can be absorbed

Question 20

Uses of glucose in a plant

Answer 20

Can be converted into:
cellulose for cell wall
Amino acids for growth
Starch for storage
Lipids for energy