Nutrition (plants) Pg20-24

Question 1

What is photosynthesis

Answer 1

Photosynthesis is the process that produces ‘food’ in plants, the ‘food’ it produces is glucose.

Question 2

Where does photosynthesis occur

Answer 2

In the leaves of all green plants. Photosynthesis happens inside the chloroplasts, which are found in leaf cells and in other green parts of a plant.

Question 3

What do chloroplasts contain

Answer 3

Chloroplasts contain a green pigment called chlorophyll, which absorbs sunlight and uses its energy to convert carbon dioxide and water into glucose, oxygen is also produced

Question 4

What is the word equation for photosynthesis

Answer 4

carbon dioxide + water —light and chlorophyll—> glucose + oxygen

Question 5

What is the chemical equation for photosynthesis

Answer 5

6CO2 + 6H2O —light and chlorophyll—> C6H12O6 + 6O2

Question 6

Why is photosynthesis and important process

Answer 6

It converts light energy to chemical energy, which is stored in the glucose. This chemical energy is released when glucose is broken down during respiration

Question 7

Name all the parts of the leaf starting with the upper waxy cuticle and going downwards.

Answer 7

upper waxy cuticle, upper epidermis, palisade mesophyll, spongy mesophyll, vascular bundle, lower epidermis and bottom waxy cuticle

Question 8

what is the structure of the leaf adapted for

Answer 8

photosynthesis and gas exchange

Question 9

How are leaves adapted for photosynthesis

Answer 9

• Leaves are broad so there is a larger surface area exposed to light
• Most of the chloroplasts are found in the palisade layer, this is so they are near the top of the leaf where they can get the most light
• The upper epidermis is transparent so that the light can pass through it to the palisade layer
  -Leaves have a network of vascular bundles. These are the transparent vessels xylem and phloem. They deliver water and other nutrients to every part of the leaf and take away the glucose produced by photosynthesis. They also help to support the leaf structure
• The waxy cuticle helps to prevent water loss by evaporation
• The adaptations of leaves for efficient gas exchange also make photosynthesis more efficient e.g. the lower epidermis is full of stomata which allows carbon dioxide to diffuse directly into the leaf

Question 10

What are the 3 important limiting factors that affect photosynthesis

Answer 10

light intensity, carbon dioxide concentration, temperature

Question 11

what is a limiting factor in photosynthesis

Answer 11

something which stops photosynthesis from happening any faster. Limiting factors depend on environmental conditions

Question 12

How is light intensity a limiting factor of photosynthesis

Answer 12

• If the light intensity is increased, the rate of photosynthesis increases steadily, but only up to a certain point.
• beyond that, it won’t make a difference because then it will either be temperature or carbon dioxide concentrations which is now the limiting factor, so the graph flattens out

Question 13

How is carbon dioxide concentration a limiting factor of photosynthesis

Answer 13

• increasing the carbon dioxide concentration will increase the rate of photosynthesis but only up to a certain point. The graph will flatten out showing that carbon dioxide concentration is no longer the limiting factor
• as long as light intensity and carbon concentration is in plentiful supply then the limiting factor must be temperature

Question 14

How is temperature a limiting factor of photosynthesis

Answer 14

• as temperature increases, rate of photosynthesis increases as well up to a point
• If the temperature is too high (+45 degrees (C)) the plant’s enzymes denatures so the rate of photosynthesis will rapidly decrease.
• usually temperature is the limiting factor

Question 15

How do you test a leaf for starch

Answer 15

• start by dunking a leaf in boiling water (hold with forceps for safety). This stops any chemical reactions taking place in the leaf.
• Now put the leaf in a boiling tube with some ethanol and heat it in a electric water bath until it boils (not with Bunsen burner because ethanol is highly flammable), this gets rid of any chlorophyll and makes the leaf a white-ish colour
• Finally, rinse the leaf in cold water and add a few drops of iodine solution. If the starch is present the leaf will turn from browny-orange to blue-black.

Question 16

How do you test if chlorophyll is needed for photosynthesis

Answer 16

• Take a variegated leaf (white and green leaf, only the green leaf has chlorophyll) and record which bits are green and which bits are white
• expose the leaf in the light so starch is produced
• dunk in boiling water with forceps so no more chemical reactions happen
• put leaf in a boiling tube with ethanol and hear it in a electrical water bath until it boils ( not Bunsen burner as ethanol is flammable)
• rinse leaf in cold water and put a few drops of iodine solution on it. Only the green bit of the variegated plant will turn blue black and the white bits will remain browny-orange as only the green bits produce starch as it contains chlorophyll

Question 17

How do you test if carbon dioxide is needed for photosynthesis

Answer 17

• contain the leaf with a sealed bell jar and make sure that a light source is pointing to the leaf
• put some soda lime in a bowl with the leaf.
• the soda lime will absorb all the carbon dioxide out of the air in the jar
• if you leave the plant in their for a while and then test it for starch, it will remain browny-orange as no starch has been made in the leaf which means that carbon dioxide is needed for photosynthesis

Question 18

How do you test if light is needed for photosynthesis

Answer 18

• put a plant in a dark room for 48 hours, so that the plant has used up its starch store
• test the plant for starch
• it will not turn blue-black and stay browny-orange to show that starch has not been produced as their is no light.

Question 19

How do you show the rate of photosynthesis

Answer 19

rate of which oxygen is produced
- add water to the test tube
- add pondweed in the test tube
- add sodium hydrogencarbonate in the water to show that it has enough carbon dioxide. sodium hydrogencarbonate releases carbon dioxide in the solution
- add a gas syringe so measure oxygen produced
- a source of white light is placed a specific distance away from the pondweed
- leave the pondweed to photosynthesise for a set period of time
- measure the amount of oxygen produced using the gas syringe
- this experiment can also be used to show how light intensity affects rate of photosynthesis (place light source at different distances from the pondweed)

Question 20

What 4 important minerals do plants need for growth

Answer 20

Nitrates, phosphates, potassium and small amounts of magnesium

Question 21

Why do plants need nitrates

Answer 21

plants need nitrates to make amino acids and proteins, these are needed for cell growth.

Question 22

What will happen if a plant does not have enough nitrates

Answer 22

The plant will be stunted and older leaves will turn yellow

Question 23

Why do plants need phosphates

Answer 23

plants need phosphates for making DNA and cell membranes and they are needed for respiration and growth

Question 24

What will happen if a plant does not have enough phosphates

Answer 24

They will have poor root growth and their older leaves are purple

Question 25

Why do plants need potassium

Answer 25

To help the enzymes needed for photosynthesis and respiration

Question 26

What will happen if a plant does not have enough potassium

Answer 26

Poor flowered and fruit growth and discoloured leaves

Question 27

Why do plants need small amounts of magnesium

Answer 27

Required to make chlorophyll in the leaves

Question 28

What will happen if a plant does not get enough magnesium

Answer 28

They will have yellow leaves