Nutrition And Transport Of Plants

Question 1

What is photosynthesis?

Answer 1

• it is a process in which light energy is absorbed by chlorophyll and converted into chemical energy
• plants are able to synthesis their food through the process of photosynthesis

Question 2

What is the equation of photosynthesis?

Answer 2

Carbon dioxide+ water— (light energy, chlorophyll)—> glucose+ oxygen +water

Question 3

What are the factors necessary for photosynthesis?

Answer 3

• sunlight
  -chlorophyll
• carbon dioxide
• suitable temperature
• water

Question 4

Why is suitable temperature one of the factors necessary for photosynthesis?

Answer 4

Enzymes are involved in photosynthesis and at high temperatures, the enzyme will denature which causes a lower rate of photosynthesis, whereas at a low temperature the enzymes are inactive which also causes a low rate of photosynthesis

Question 5

what test to use to find out if photosynthesis occurred

Answer 5

• test for starch (test with iodine)
• all glucose made formed during photosynthesis is derived from carbon dioxide
• excess glucose made is converted to starch(starch formation is not part of the process of photosynthesis)
• In darkness, starch is converted back to glucose. glucose is used up during respiration to release energy

Question 6

before using a plant in a photosynthetic experiment the plant must be destarched first. why?

Answer 6

to make sure that starch is not present at the start of the experiment so that the starch tested at the end of the experiment is made only during the duration of the experiment

Question 7

to destarch a plant, put the plant in darkness for two days. why?

Answer 7

it is to ensure that all stored starch before the experiment in the plant is converted to glucose for respiration and used up in 48 hours so that the starch found at the end of the experiment was made during the experiment

Question 8

what must you do when conducting a photosynthetic experiment

Answer 8

put the plant in a dark room to detarch a plant before conducting an experiment

starch broken down to glucose needed for respiration in plants

Question 9

test for starch in leaves

Question 10

part 1: why do you need to place the leaf in boiling water

part 2: why is it necessary to put the leaf in alcohol

part 3: why must you place the leaf in hot water again

Answer 10

part 1: ->to denature the enzymes that breaks down starch
->heat destroys cell membrane, making it permeable for the iodine solution to enter the cells
->to weaken the cell wall, so that iodine solution can penetrate the cell much faster later on

part 2: alcohol, an organic solvent, dissolves and removes green chlorophyll from the leaf so that any color changes can be observed clearly

part 3: this softens the leaf as the leaf will be very brittle to handle after treatment with alcohol

Question 11

is sunlight necessary for photosynthesis (refer to notes experiment)

Answer 11

only the parts exposed to sunlight will be stained blue-black, thus, sunlight is necessary for photosynthesis

• black paper-> no light-> no photosynthesis-> glucose not made-> starch absent
• parts exposed to sunlight-> photosynthesis occurs-> glucose made-> glucose converted to starch

Question 12

is chlorophyll necessary for photosynthesis (refer to notes experiment)

Answer 12

only the parts of a variegated leaf containing chlorophyll will manufacture starch and be stained blue-black. thus, chlorophyll is necessary for photosynthesis

Question 13

is carbon dioxide necessary for photosynthesis (refer to the notes experiment)

Answer 13

observation:
-> leaf from the experiment set-up remains brown (without co2)
-> leaf from the control set-up turn blue-black (with co2)

the iodine turns blue-black for the leaf exposed to air with carbon dioxide. thus, carbon dioxide is necessary for photosynthesis

Question 14

what are limiting factors

Answer 14

a factor that directly affects or limits a process if its quantity or concentration is altered is called a limiting factor

Question 15

what are the factors that limits the rate of photosynthesis

Answer 15

• light intensity
• carbon dioxide
• temperature

Question 16

how does temperature affect the rate of photosynthesis

Answer 16

• at low temperature, rate of photosynthesis is low as enzymes are less active at low temperature.
• rate of photosynthesis increases as enzymes become more active at higher temperatures
• rate of photosynthesis is maximum as enzymes are most active at this temperature
• rate of photosynthesis slows down as enzymes are denatured

Question 17

effect of light intensity on the rate of photosynthesis (refer to notes experiment)

Answer 17

rate of bubbling increases as the distance of the lamp from the plant decrease (observation)

Question 18

effects of co2 concentration on the rate of photosynthesis

Answer 18

rate of bubbling increases as the concentration of sodium hydrogencarbonate solution( produces co2 for the plant) is increases (observation)

Question 19

effects of temperature on the rate of photosynthesis

Answer 19

rate of bubbling increases as the temperature increases (observation)

Question 20

importance of photosynthesis

Answer 20

• plants are he producers in food chains. the chemical energy stored in plants is transferred to other organisms through feeding
• it helps to purify the air by removing carbon dioxide from the atmosphere and releasing oxygen into the atmosphere as a by-product
  -coal formed from trees provides a source of fuel.

Question 21

external feature of a leaf

Answer 21

• the lamina or leaf blade has a larger surface area to maximise absorption of sunlight. it allows rapid diffusion of carbon dioxide to reach the inner cell of the leaf
• the petiole positions the lamina for maximum absorption of sunlight and gaseous exchange.
• xylem vessels in the veins allow transport of water and mineral salts to the cells in the lamina
• phloem vessels in the veins transport manufactured food from the leaves to other parts of the plant
  -leaves are usually arranged in a regular pattern around the stem. this is to ensure that leaves are not blocking one another from sunlight and that each leaf receives optimum amount of light