1.2 Photosynthesis

Question 1

Photosynthesis is an endothermic reaction. What does this mean

Answer 1

Takes in energy (from the sun)

Question 2

What part of the plant cell is needed for photosynthesis

Answer 2

Chloroplasts

Question 3

What is the green pigment in chloroplasts called

Answer 3

Chlorophyll

Question 4

What is the word equation for photosynthesis

Answer 4

Carbon Dioxide + Water ——-> Glucose + Oxygen

Question 5

What 2 things are needed to allow photosynthesis to happen (what do you write above and below the arrow on the word equation)

Answer 5

Chlorophyll
Light energy

Question 6

How is a broad leaf a good adaptation for photosynthesis

Answer 6

Gives a large surface area to trap light

Question 7

Where in the leaf does most photosynthesis occur

Answer 7

Palisade layer

Question 8

How is the palisade layer a good adaptation for photosynthesis

Answer 8

The cells are packed with chloroplasts to trap light
The layer is near the top of the leaf to catch as much light as possible
The cells sit upright and are long and rectangular - more cells packed into the layer

Question 9

How do gases enter and leave the leaf

Answer 9

Through the stomata on the lower epidermis

Question 10

Why does the spongy layer have large air spaces

Answer 10

tTo allow rapid gasous exchange

Question 11

How do you test for starch and what is the colour change

Answer 11

Add iodine
Turns from yellow brown to blue black

Question 12

How do you test a leaf for starch

Answer 12

Heat leaf in boiling water
Add leaf to a test tube of ethanol and heat in water bath
Wash leaf in water
Spread leaf and cover with iodine

Question 13

What is the purpose of boiling the leaf in water

Answer 13

To stop chemical reactions and weaken cell wall

Question 14

What is the purpose of heating the leaf in a test tube of ethanol

Answer 14

To remove the green chlorophyll

Question 15

Why do you wash the leaf after it has been in the ethanol

Answer 15

The leaf is brittle so washing it softens the leaf

Question 16

Another way to test a leaf is to count the number of bubbles produced. What gas is present in the bubbles

Answer 16

Oxygen

Question 17

How would you measure the rate of photosynthesis using the bubbles produced by the plant

Answer 17

Count number of bubbles over a period of time
Then calculate rate = bubbles per min

Question 18

What factors can limit the rate of photosynthesis

Answer 18

LIght intensity
Carbon dioxide concentration
Temperature

Question 19

How do plants use the glucose produced in photosynthesis

Answer 19

Store as starch
use in respiration for energy
Convert glucose to amino acids to make proteins for growth
Convert to cellulose for cell walls
Convert to fats and oils for storage

Question 20

On a limiting factors graph describe what shape the graph would be and what it means

Answer 20

The line graph will initially rise up and then level out
It rises due to the factor on x axis being the limiting factor - as this factor increases e.g. light intensity the rate of photosynthesis increases.
The graph levels out as the factor on the x axis is no longer a limiting factor but one of the other 2 factors is now.

Question 21

In an experiment to compare the rate of photosynthesis and the rate of respiration. What is the indicator used

Answer 21

Hydrogen carbonate

Question 22

What does hydrogen carbonate detect

Answer 22

Changing levels of carbon dioxide
Turns red to purple if carbon dixoide levels decrease
Turns red to yellow if carbon dioxide levels increase

Question 23

In an experiment of a plant under light the hydrogen carbonate turns from red to purple. What does this mean

Answer 23

This means that the level of Carbon dioxide has decreased.
The rate of photosynthesis (uses carbon dixoide) is greater than the rate of respiration (produces carbon dioxide)

Question 24

In an experiment of a plant in hydrogen carbonate the hydrogen carbonate stays red. What are the light conditions that cause this and what does it mean

Answer 24

The light conditons - low light intensity eg. sunrise/sunset
stays red as the rate of photosynthesis = rate of respiration
This is called the compensation point

Question 25

In an experiment plant in dark and the hydrogen carbonate turned yellow What does this mean

Answer 25

The rate of respiration (Carbon dioxide produced) is greater than rate of photosynthesis.
As no light no photosynthesis occurred