B2 photosynthesis

Question 1

Photosynthesis

Answer 1

Is the chemical reaction that plants use to produce glucose (food)
Reactants are:
Carbon dioxide (absorbed through leaves)
Water (absorbed through roots and transported to leaves)
Endothermic reaction

Question 2

Photosynthesis equation

Answer 2

Carbon dioxide + water }light+chlorophyll} glucose + oxygen
6CO2 + 6H2O } C6H12O6 + 6O2

Products are carbohydrates (if iodine added to leaf it would go blue/black)

Question 3

Gas exchange in leaves

Answer 3

Leaves take in CO2 and release O2

Question 4

History of photosynthesis

Answer 4

1600
Increase in the mass of a willow tree wasn’t just due to the soil
1771
Put a plant in glass container with a lit candle. Left it for 27 days and candle was still burning. Shows oxygen is present

Question 5

Glucose

Answer 5

Used for respiration
Transported by veins
Sucrose is also produced

Question 6

The energy released is used for chemical reactions in cell eg.

Answer 6

Building glucose into starch for storage
Building sugars into cellulose, which strengths cell walls
Combining sugars with nitrate ions and other minerals to make amino acids for protein synthesis
Building fats and oils for storage

Question 7

Structure of a leaf

Answer 7

Most leaves are:
Broad, with a large surface area for light to be absorbed
Thin, short diffusion distance
Vascular bundles, support leaf and transport water to leaf and glucose away from leaf

Question 8

Inside the leaf

Answer 8

Waxy cuticle,protect it
Upper Epidermal tissue, cover the leaf, letting light penetrate
Palisade mesophyll carries out photosynthesis, absorbs most light
Spongy mesophyll has air spaces for gas diffusion
Lower epidermal layer protects the underside of the leaf
Stoma allows gases to diffuse in and out of the leaf

Question 9

Upper epidermal tissue

Answer 9

Adaption- Thin and transparent waxy cuticle

Function- allows light to pass to the mesophyll to protect the leaf and stop water loss

Question 10

Palisade mesophyll

Answer 10

Adaption- regular shaped cells,arranged end on, near upper surface;most chloroplasts at the top of the cells
Function- absorb the maximum amount of light possible

Question 11

Spongy mesophyll

Answer 11

Adaption-irregular shaped cells; many air spaces

Function- increases surface area for CO2 absorption;allows gases to diffuse

Question 12

Lower epidermal tissue

Answer 12

Adaptions-many stomata;surrounded by guard cells

Functions-allow gases to diffuse;guard cells open and close stomata

Question 13

Vascular bundles

Answer 13

Adaptions-contain xylem and phloem tubes

Functions-transport substances around the plant

Question 14

Required practical- investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism such as pondweed

Answer 14

Photosynthesis produces glucose and oxygen
*Oxygen will be released as bubbles in water
Light energy is absorbed by chlorophyll found in the chloroplasts in the mesophyll cells
Photosynthesis can be limited by different factors
Plot data on a line graph

Question 15

Limiting factor

Answer 15

A factor that runs out before the others so the experiment can not continue

Question 16

Intense farming

Answer 16

Growing crops in greenhouses gives a larger yield for a given area. Conditions can be altered to increase the rate of photosynthesis. Protect plants from weather and animals

Question 17

Greenhouses

Answer 17

Sunlight heats up the inside of greenhouses, temp rises
CO2 can be increases to increase concentration of gas
Paraffin heaters used, as burn produce CO2. Increases temp
Watering systems, regular supply of water
Blinds, control amount of light
Humidifiers add moisture to the air

Question 18

Hydroponics

Answer 18

Plants grown in nutrient-rich liquid medium,which can be formulated for the type of plant,supported on a material such as rock wool

Question 19

Computer systems control conditions

Answer 19

Nutrients are monitored and concentrations adjusted as needed
Temp is controlled by sensors to within 0.1 degrees Celsius
Weather detection systems monitor external conditions and adjust vents and blinds to suit
Floors covered in white plastic to reflect light
The glass used has a low iron content to ensure maximum light levels and even the metal supports are as thin as possible
Special Lights are used to increase the hours of light. These are switched off for about 7 hours allowing plants to transport the glucose that has been made

Question 20

Inverse square law

Answer 20

If the light distance is doubled, the light intensity decreases by the square of the distance

Question 21

Diffusion

Answer 21

The net movement of particles from an area of high concentration to an area of low concentration through a partially permeable membrane until equilibrium is reached

Question 22

What increases the rate of diffusion

Answer 22

Increase surface area
Increase distance it has to travel
Increase concentration gradient
Wind, increase CO2 concentration gradient
High humidity, decrease concentration of water vapour between inside and outside, diffusion slows down

Question 23

Transpiration

Answer 23

Plants absorb water from soil through root hairs
Water passes up stem into the leaves
Water on spongy mesophyll evaporates
diffuses out of leaves via the stomata

Question 24

Transpiration rate is affected by

Answer 24

Temperature
Light availability
Wind
Humidity

Question 25

Xylem

Answer 25

Tissue carries water and minerals from the roots of the plant, especially to the leaves
Made from long cells with thick reinforced walls containing lignin
Making them strong
Cell walls are waterproof
Dead
1 way flow

Question 26

Phloem

Answer 26

Tissue transports dissolved sugars made in the leaves around the plant
Elongated thin walled
Living cells
End cells walls have sieve plates
2 way flow
Cytoplasm but no nucleus have companion cell next to it
Companion cell controls activity of phloem but doesn’t help with translocation

Question 27

Transpiration is important because…

Answer 27

Evaporation of water cools leaves
Water is a reactant in photosynthesis
Cells full of water support the plant
Water carries dissolved materials around the plant

Question 28

Guard cells

Answer 28

Open and close to control the exchange of gases and water loss

Question 29

Effect of adaptions

Answer 29

Disadvantage of stomata is while they are open for gas exchange water is lost
Broad thin leaves increase surface area so water has small distance to diffuse out of

Question 30

Marram grass adaptions

Answer 30

Has waxy cuticle
Rolled leaf
Stomata sunk in pits
Leaf hairs

Question 31

Translocation

Answer 31

Transporting dissolved sugars made in the leaves around the plant

Question 32

Root hair cells

Answer 32

Narrow structures with a large surface area.

Increase surface area for water absorption

Question 33

Potometers

Answer 33

Are used to measure the uptake of water by plants in different conditions. The movement of the air bubble in the tube shows how much water is taken up

Question 34

Different plants control water loss in different ways

Answer 34

Waxy cuticle- in hot environments it can be very thick
Stomata on underside- protected from environmental factors
Needle like,spiny or rolled up leaves
Stomata in pits on the leaf surface