1.2 Photosynthesis

Question 1

What type of reaction is photosynthesis

Answer 1

Endothermic

Question 1

What 2 reactants are needed for photosynthesis

Answer 1

Carbon dioxide and water

Question 2

What are the 2 products of photosynthesis

Answer 2

Glucose and oxygen

Question 3

learn the word and symbol equation for photosynthesis

Answer 3

Carbon dioxide + water ——> glucose + oxygen
(chlorophyll and light go above and below arrow)

Question 4

Formula of glucose

Answer 4

C6H12O6

Question 5

What are the layers of the leaf from top to bottom

Answer 5

Waxy cuticle
Upper epidermis
Palisade (mesophyll) layer
Spongy (mesophyll) layer
Lower epidermis - with stomata and guard cells

Question 6

Where is the main site of photosynthesis in leaf

Answer 6

Palisade layer

Question 7

How is the palisade layer adapted for photosynthesis

Answer 7

Cells contain many chloroplasts
Cells sit upright so can pack more in
Near upper surface

Question 8

How does carbon dioxide reach the palisade layer

Answer 8

Enters in through the stomata - passes along the air spaces in the spongy layer and enters cell in palisade layer

Question 9

How does water reach the palisade layer

Answer 9

Water enters through roots
travels up Xylem vessels in stem and enters leaf in veins

Question 10

How to test leaf for starch

Answer 10

Destarch plant in dark cupboard for 48hrs
expose to light
remove leaf and boil in water
then boil in ethanol
wash leaf
spread out and add iodine
if starch present turns blue black

Question 11

If a leaf is partially covered in card which part of the leaf will have starch

Answer 11

The part of leaf that is exposed will have starch - turn blue black
the part covered in card will stay yellow brown showing light needed for photosynthesis

Question 12

Another experiment may be to count bubbles of oxygen produced. You can then work out rate of photosynthesis.
What other measurement would you need to take to work out rate

Answer 12

Time - need to know rate which is number of bubbles/time

Question 13

In the experiment measuring rate of photosynthesis by counting bubbles- why is a transparent glass shield put between lamp and experiment

Answer 13

So light passes through but the temperature does not change (from heat of lamp)

Question 14

How can you change light intensity in an experiment

Answer 14

Move the lamp further away from plant

Question 15

What is meant by limiting factor

Answer 15

A factor that will prevent photosynthesis happening at its highest rate

Question 16

What are the 3 main limiting factors of photosynthesis

Answer 16

Carbon dioxide
Light intensity
Temperature

Question 17

On the graph showing light intensity against rate of photosynthesis - the graph initially increases and then levels out. What is the initial limiting factor?

Answer 17

The light intensity
- as the light intensity increased initially the rate also increases so this shows that light was slowing down photosynthesis at this stage

Question 18

On the graph showing light intensity against rate of photosynthesis - the graph initially increases and then levels out. What is the limiting factor when the graph levels out

Answer 18

No longer light as even though light intensity still incresing the rate is staying the same.
Other factors such as temperature or carbon dioxide now limitin

Question 19

What happens to the rate of photosynthesis if the temperature increases too much

Answer 19

The rate of photosynthesis decreases because enzymes for the reaction are now destroyed (denatured)

Question 20

What is the name of the indicator that shows changes to carbon dioxide levels

Answer 20

Hydrogen Carbonate indicator

Question 21

If rate of photosynthesis is greater than rate of respiration what colour does the hydrogen carbonate turn and why

Answer 21

Goes from Red to Purple
Carbon dioxide levels are going down (as used in photosynthesis) at a greater rate than Carbon dioxide being made in respiration

Question 22

If the rate of photosynthesis is the same as rate of respiraiton what is this known as
What time of the day is this most likely to occur

Answer 22

Compensation point
happens at sunrise and sunset

Question 23

What colour will hydrogen carbonate turn at the compensation point

Answer 23

It will remain red - levels of carbon dioxide balanced as rate at which carbon dioxide produced in respiration = rate at which carbon dioxide is used in photosynthesis

Question 24

What is glucose used for in plants

Answer 24

Stored as starch
Use in respiration
Converted to amino acids and used to make protein
converted to fats
converted to celluose for cell walls

Question 25

If rate of photosynthesis is less than rate of respiration what colour does the hydrogen carbonate turn and why

Answer 25

Red to Yellow
Rate of carbon dioxide being produced during respiration is greater than being used during photosynthesis