Nutrition (Plants)

Question 1

Definition of photosynthesis

Answer 1

converting light energy into chemical energy

Question 2

Equation for photosynthesis

Answer 2

carbon dioxide + water –> glucose + oxygen

Question 3

Leaf test for starch

Answer 3

• dunk the leaf in boiling water for about 30s
• put the leaf into a boiling tube with ethanol (turn off the bunsen burner, highly flammable)
• heat in a water bath, ethanol turns green
• rinse the leaf in cold water
• test with iodine solution if starch is present

Question 4

Photosynthesis test (for chlorophyll)

Answer 4

• test with a variegated leaf (green + white)
• test for starch
• the green part will turn blue-black
• suggests that chlorophyll is needed for photosynthesis to produce starch

Question 5

Photosynthesis test (for CO2)

Answer 5

• in a sealed bell jar, add soda lime
• the soda lime absorbs CO2
• test for starch
• the leaf won’t turn blue-black
• suggests that CO2 is needed for photosynthesis to produce starch

Question 6

Rate of photosynthesis (oxygen production)

Answer 6

• pondweed with light at different distances
• the closer the light, the faster the rate

Question 7

Adaptation of a leaf for photosynthesis

Answer 7

• air spaces (faster diffusion, less dense)
• palisade mesophyll (lots of chloroplast, capture more sunlight)
• upper epidermis (allows light to enter, transparent)
• stoma (allows CO2 to enter)
• large surface area (absorbs more light)
• thin ( speeds up diffusion)

Question 8

What does the waxy cuticle do?

Answer 8

waterproofs the leaf, reduces water loss from evaporation

Question 9

What does the upper epidermis do?

Answer 9

protects the leaf from pathogens, transparent, so light can pass through to the palisade layer

Question 10

What does the palisade mesophyll do?

Answer 10

lots of chloroplasts for photosynthesis

Question 11

What does the spongy mesophyll do?

Answer 11

allows gas exchange, has air spaces for quick diffusion

Question 12

What does the xylem do?

Answer 12

brings water in, transport water and minerals

Question 13

What does the phloem do?

Answer 13

transport glucose

Question 14

What mineral irons is needed for plant growth?

Answer 14

• nitrate, phosphate, potassium, magnesium (a little bit)

Question 15

What makes up the vascular bundle?

Answer 15

the xylem and phloem

Question 16

What does the stomata do?

Answer 16

allow CO2 in by diffusion, allow oxygen out, controlled by guard cells

Question 17

What does the lower epidermis do?

Answer 17

protective layer for the cells, has stomata

Question 18

Why is nitrate needed for plant growth?

Answer 18

• use = to make amino acids and protein, DNA, chlorophyll, others
• effect = cell growth, nutrients, chlorophyll
• symptom = stunted (smaller), older leaves turn yellow, poor flower growth

Question 19

Why is phosphate needed for plant growth?

Answer 19

• use = to make DNA & cell membrane
• effect = respiration, growth, photosynthesis
• symptom = poor root growth, older leaves are purple/yellow, smaller plant

Question 20

Why is magnesium needed for plant growth?

Answer 20

• use = to make chlorophyll
• effect = photosynthesis
  symptom = yellow leaves

Question 21

Why is potassium needed for plant growth?

Answer 21

• use = to help enzymes
• effect = photosynthesis, respiration, growth, energy
• symptom = poor flower and fruit growth, discoloured leaves (yellow, purple, brown)

Question 22

Factors affecting the rate of photosynthesis

Answer 22

• light intensity = increasing light, increases rate, until a certain point (plato)
• carbon dioxide = increasing CO2 levels, increases rate, until a certain point (plato)
• temperature = increasing temperature, increases rate, until the enzymes denature

Question 23

What is a limiting factor?

Answer 23

something that stops photosynthesis from happening faster

Question 24

What happens to the rate of photosynthesis as light intensity increases and why?

Answer 24

• as light intensity increases, the rate of photosynthesis increases
• more stomata open at higher intensity, so more CO2 can enter the leaf, until a certain point

Question 25

What happens to the rate of photosynthesis as CO2 increases and why?

Answer 25

• as CO2 increases, the rate of photosynthesis increases
• more CO2 is needed for photosynthesis (reactant), until a certain point

Question 26

What happens to the rate of photosynthesis as temperature increases and why?

Answer 26

• as temperature increases, the rate of photosynthesis increases
• there is a greater kinetic energy, up to the optimum temperature
• if the temperatures are too high, enzymes start to denature, active site is damaged and no reaction can occur