Photosynthesis & Adaptations of Leaves - Bioenergetics

Question 1

What type of reaction is photosynthesis?

Answer 1

Endothermic

Question 2

What is the word equation for photosynthesis?

Answer 2

Carbon dioxide + water → Glucose + Oxygen

Question 3

What is the symbol equation for photosynthesis?

Answer 3

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Question 4

What are the 5 uses of glucose?

Answer 4

• To make cellulose for the cell wall
• To make starch - stored in the cells to break down when photosynthesis doesn’t happen, insoluble, compact
• Cellular respiration
• Make amino acids by glucose combining with nitrate ions from soil
• Make lipids - store for energy for later

Question 5

What adaptations do leaves have to maximise photosynthesis?

Answer 5

• Large surface area
• Thin shape
• Lots of stomata
• Xylem and Phloem
• Long, narrow upper mesophyll cells with chloroplasts
• Waxy, waterproof cuticle

Question 6

What does a large surface area do?

Answer 6

Allows them to absorb as much light as possible

Question 7

What does having a thin shape do?

Answer 7

Short distance for carbon dioxide and oxygen to diffuse + most light is absorbed within the first few milimetres of the leaf

Question 8

What does having lots of stomata do?

Answer 8

Allow more gas exchange

Question 9

What does having a xylem an phloem do?

Answer 9

• Xylem brings water to the leaf for photosynthesis
• Phloem transports sugars produced in photosynthesis

Question 10

What does having a long, narrow upper mesophyll cells with chloroplasts do?

Answer 10

More chloroplasts means more sunlight absorbed

Question 11

What does having a waxy, waterproof cuticle do?

Answer 11

Cuts down water lost by evaporation and protects against parisitic fungi

Question 12

Order of the leaf structure top to bottom

Answer 12

1. Upper epidermis
2. Palisade mesophyll
3. Spongy mesophyll
4. Gaurd cells
5. Stomata
6. Lower epidermis

Question 13

Required Practical 6: Rate of Photosynthesis, why is an LED light used as the light source? What can we do if we want to use normal light?

Answer 13

• LED doesn’t change the temperature which is a factor that affects photosynthesis
• If you want to use normal light, have a beaker of water in front of the light so it absorbs the heat

Question 14

Required Practical Method

Answer 14

1. Fill boiling tube with with sodium hydrogen carbonate solution (will encourage pondweed to photosynthesise)
2. Put pondweed, cut end of pondweed in water
   3.Put boiling tube 10cm away (using ruler)
3. Let the pondweed adjust to lighting
4. Count number of bubbles from the cut end
5. Repeat and calculate the mean
6. Increase distance by 10 cm and make a graph

Question 15

Required Practical variables

Answer 15

Independant: Light intensity/Distance between boiling tube and light
Dependant: How light intensity affects the rate of photosynthesis
Controlled: Age of pondweed/ Volume of sodium hydrogen carbonate

Question 16

What is the inverse square law formula?

Answer 16

light intensity∝ 1/distance(d)²

∝ = proportional

Question 17

What is the inverse square law?

Answer 17

Light intensity decreases in proportion to the square of the distance

Question 18

Inverse Square Law = What would the light intensity be if you halved the distance?

Answer 18

4 times greater

Question 19

Inverse Square Law = What would the light intensity be if you third the distance?

Answer 19

9 times greater

Question 20

Inverse Square Law = What would the light intensity be if you double the distance?

Answer 20

4 times smaller

Question 21

Inverse Square Law = What would the light intensity be if you treble the distance?

Answer 21

9 times smaller

Question 22

What do greenhouses do?

Answer 22

Trap the Sun’s heat to make sure temp doesnt become limiting

Question 23

What if the temp gets too hot in greenhouses?

Answer 23

Use shades and ventiliation

Question 24

How to increase CO2 in greenhouse?

Answer 24

Paraffin heaters burn paraffin, it makes co2 as a by-product

Question 25

Why should greenhouses be enclosed?

Answer 25

Keeps pests away, diseases

Question 26

What can the farmer do to provide minerals for healthy growth?

Answer 26

Add fertiliser

Question 27

Factors that affect photosynthesis

Answer 27

CO2, temperature, light intensity, conc of chlorophyll

Question 28

Invserse law formula

Answer 28

intensity of light decreases proportionally to the square of the distance from its source.