plant structures and their functions Flashcards
paper 1
where does photosynthesis take place
the leaves, more specifically the chloroplasts
what is the job of chloroplasts
they contain a pigment called chlorophyll that absorbs light, making plants green
how do chlorophyll perform photosynthesis
they absorb light in little packets of energy and uses the energy to convert carbon dioxide and water
what is the word equation for photosynthesis
carbon dioxide + water —(light)— glucose + oxygen
what is the symbol equation for photosynthesis
6CO2 + 6H2O → C6H12O6 + 6O2.
what type of reaction is photosynthesis and why
endothermic as energy is taken from the surroundings by chloroplasts
what are the 5 things plants need glucose for
- cellular respiration
- make cellulose
- make starch
- making amino acids
- make oils/fats
what is cellulose
a complex carbohydrate made by glucose to strengthen cell walls
what is starch and why do plants need it
a compact version of glucose, used as a long term energy source for when photosynthesis is not happening, its good because its insoluble so will not draw in water
why do plants need to make amino acids from glucose
they combine glucose and nitrate ions to make proteins
what are the 4 factors affecting photosynthesis
- light intensity
- temperature
- carbon dioxide
- chlorophyll
how does chlorophyll affect the rate of photosynthesis
chlorophyll is a pigment that absorbs light energy and different amounts of chlorophyll means the plant cannot absorb the required amount
what does the term plateaued mean on a graph
the rate stops increasing as another factor is in affect
how does temperature affect the rate of photosynthesis
it initially rises as enzymes can work quickly and molecules move faster, but past the optimum temperature, the enzymes begin to denature and the rate begins to drop
how can farmers artificially make light intensity, co2 and temperature
- in cold climates, they put crops in light houses to trap sun’s heat to increase temperature or lamps
- they might pump co2 into the greenhouse or use a paraffin heater which makes heat and co2
- fertiliser to ensure correct minerals
- pesticides to kill unwanted bugs
what is translocation
the movement of sugars around a plant
what are phloem tubes
long stacks of phloem cells sugars pass through
what direction can phloem cells transport materials
up or down
what are the pores in a phloem cell
gaps which enable to movement of cell sap
what are xylem tubes
long columns of xylems, which don’t have ends, effectively making one long hollow tube
what material are xylem cells strengthened by
lignin
what do xylem tubes do
transport water and mineral ions from the roots up the stem into the leaves
how does water constantly move up the plant
there is constantly water molecules in the xylem column, and when water is evaporated in the leaves (TRANSPIRATION), one moves up into its place (TRANSPIRATION STREAM)
what is transpiration
water in the leaves evaporating
what is the transpiration stream
the constant stream of water molecules up a xylem tube
what are the 4 factors affecting the rate of transpiration
- light intensity
- temperature
- air flow
- humidity
how does light intensity affect the rate of transpiration
the brighter the light intensity, the more photosynthesis taking place meaning stomata are open, leading more water to evaporate and a higher rate
how does temperature affect the rate of transpiration
when it is warm, the water molecules have more energy so more likely to evaporate, increasing the rate
how does air flow affect the rate of transpiration
because of the constant flow of water inside the leaf, the concentration gradient will be larger in the leaf than outside, so it is easy for the water to leave the leaf, when the air flow is high (windy) the water will quickly be blown away, keeping the concentration gradient high, increasing the rate
what is humidity
a measure of how much water vapour is in the air
how does humidity affect the rate of transpiration
the more humid it is, the lower the rate as there is a decrease in the concentration gradient, as there is a lot of water outside the plant, meaning less water will diffuse out and the rate will decrease
