B2 photosynthesis Flashcards
Photosynthesis
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
Photosynthesis equation
Carbon dioxide + water }light+chlorophyll} glucose + oxygen
6CO2 + 6H2O } C6H12O6 + 6O2
Products are carbohydrates (if iodine added to leaf it would go blue/black)
Gas exchange in leaves
Leaves take in CO2 and release O2
History of photosynthesis
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
Glucose
Used for respiration
Transported by veins
Sucrose is also produced
The energy released is used for chemical reactions in cell eg.
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
Structure of a leaf
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
Inside the leaf
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
Upper epidermal tissue
Adaption- Thin and transparent waxy cuticle
Function- allows light to pass to the mesophyll to protect the leaf and stop water loss
Palisade mesophyll
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
Spongy mesophyll
Adaption-irregular shaped cells; many air spaces
Function- increases surface area for CO2 absorption;allows gases to diffuse
Lower epidermal tissue
Adaptions-many stomata;surrounded by guard cells
Functions-allow gases to diffuse;guard cells open and close stomata
Vascular bundles
Adaptions-contain xylem and phloem tubes
Functions-transport substances around the plant
Required practical- investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism such as pondweed
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
Limiting factor
A factor that runs out before the others so the experiment can not continue
Intense farming
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
Greenhouses
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
Hydroponics
Plants grown in nutrient-rich liquid medium,which can be formulated for the type of plant,supported on a material such as rock wool
Computer systems control conditions
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
Inverse square law
If the light distance is doubled, the light intensity decreases by the square of the distance
Diffusion
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
What increases the rate of diffusion
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
Transpiration
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
Transpiration rate is affected by
Temperature
Light availability
Wind
Humidity
Xylem
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
Phloem
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
Transpiration is important because…
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
Guard cells
Open and close to control the exchange of gases and water loss
Effect of adaptions
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
Marram grass adaptions
Has waxy cuticle
Rolled leaf
Stomata sunk in pits
Leaf hairs
Translocation
Transporting dissolved sugars made in the leaves around the plant
Root hair cells
Narrow structures with a large surface area.
Increase surface area for water absorption
Potometers
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
Different plants control water loss in different ways
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
