Chapter 2 - Photosynthesis

Question 1

Where does PS take place in the plants?

Answer 1

The green parts (chlorophyll is present)

Question 2

What does chlorophyll do during PS ?

Answer 2

Traps the energy from the suns light.

Question 3

Is photosynthesis exo/endothermic ?

Answer 3

endothermic

Question 4

What is the waste product produced by PS?

Answer 4

oxygen

Question 5

What is the word equation for PS?

Answer 5

light energy
carbon dioxide + water——————->glucose + oxygen
chlorophyll

Question 6

What is the balanced symbol equation for PS?

Answer 6

6CO(2) +6H(2)O —–> C(6)H(12)O(6) +6O(2)

Question 7

Give three uses for glucose in a plant.

Answer 7

1: Respiration
2: Storage - many plants convert it into starch and oils for storage

3:Useful substances - glucose can be turned into cellulose, chlorophyll and protein.

Question 8

List the steps taken to carry out the starch test for a leaf.

Answer 8

1: Place leaf in boiling water for 30 seconds
2: Place leaf in boiling ethanol (to remove the chlorophyll)
3: then place back into water to stop leaf drying out.
4: Place on white tile and add iodine

If starch is present it will go from yellow-brown to blue-black.

Question 9

Why and how do you destarch a plant ?

Answer 9

Leave in a dark cupboard for 2 days. Starch already in the leaf will be used up before you carry out the experiment.

Question 10

How do you show light and chlorophyll is needed in PS?

Answer 10

1: Destarch the plant
2;Test the leaf for starch (if negative continue)
3:Cover one part of the leaf with foil
4:Place the plant in bright light for several hours
5:Test leaf for starch. Make drawing of leaf after the test.

Question 11

How do you show carbon dioxide is needed for PS?

Answer 11

Get one leaf from a plant and place it in a conical flask with water in it. Get another leaf and place it in one with sodium hydroxide (removes CO2 from the plant). Test both leaves for starch and the one in water should test positive while the one in sodium hydroxide should test negative.

Question 12

How will changing the light intensity change the rate of PS?

Answer 12

The higher the light intensity the higher the rate of PS.

Question 13

What are the factors affecting PS?

Answer 13

Carbon dioxide availability
Light intensity
Water
Temperature

Question 14

What is the term used to describe the best level for the reaction ?

Answer 14

Optimum level

Question 15

If one factor of PS is in short supply it is known as …….

Answer 15

a limiting factor ( the rate of PS is determined by the factor that is in the shortest supply)

Question 16

What two processes are leaves adapted for ?

Answer 16

Light absorption

Gas exchange

Question 17

What is a mesophytic leaf?

Answer 17

a typical unspecialised leaf

Question 18

How is a leaf adapted for light absorption?

Answer 18

• short distance between upper and lower surfaces.
• large surface area
• thin transparent cuticle, reduces water loss while letting light to enter into the leaf
• epidermis lacks chloroplasts to allow light in.
• many chloroplasts rich in chlorphyll
• regular structure of the palisade mesophyll, allows many cells rich in chloroplasts to be near the surface of the cell.

Question 19

How is a mesophytic leaf adapted for gas exchange ?

Answer 19

• the intercellular air spaces in the spongy mesophyll allow CO2 in and O2 out.
• stomata, which allow gases to enter and leave the leaf. Each stomata is surrounded by two guard cells that regulate the opening and closing of the stoma.

Question 20

What is need and what is the waste product for plant respiration ?

Answer 20

O2 is needed and CO2 is produced as a waste product.

Question 21

Explain what happens at night regarding the movement of gasses in a leaf.

Answer 21

At night there is no light for photosynthesis so only respiration occurs. Therefore O2 will enter the leaf and CO2 will leave.

Question 22

Explain what happens in the day regarding the movement of gasses in a leaf.

Answer 22

Both processes will take place. When light intensity is high the level of PS exceeds the level of respiration so CO2 enters the leaf and O2 exits the leaf.

Question 23

What is known by the term compensation point ?

Answer 23

There will be times during the day when the light intensity is low. This causes PS to occur very slowly. At these points , usually dawn and dusk the rates of Ps and respiration are equal and there will be no overall or net gas exchange.

Question 24

Describe the colour change of hydrogencarbonate indicator.

Answer 24

bright red - normal conc
yellow - increased conc
purple - lowered conc