Sb6 Flashcards
What is algae
A protist
Biomass
The materials in an organism
Why are plants producers in a food chain
Because they produce their own biomass and produce food for the rest of life on Earth
Photosynthesis equation
Carbon dioxide + water = glucose + oxygen
Where does photosynthesis occur
It occurs in chloroplast because they contain a green substance called chlorophyll that traps energy transferred by light
Is photosynthesis endothermic or exothermic
Endothermic
Why is photosynthesis an endothermic reaction
Because the products of photosynthesis have more energy than the reactants since energy enters by transfer of sunlight
What happens to the glucose after it’s made by photosynthesis
The glucose molecules linked together to form a polymer called starch. Which stays in the chloroplast until photosynthesis stops
What happens to the starch after photosynthesis stops
The starch is broken down into simpler substances and is moved into the cytoplasm and is used to make sucrose which is transported around the plant
What can sucrose be used to make
Starch in a storage organ
Other molecules like cellulose lipids or proteins
Glucose for respiration
Adaptations of leaves
They are broad and flat which gives them a large surface area which allows rate of reaction to be quicker
Palisade cells adaptations
They are near the top of the leaf and awful of chloroplasts so they can absorb a great deal of light
How are leaves adapted for carbon dioxide needs
They contain pores called stomata which allow carbon dioxide to diffuse into the leaf. They are opened and closed by guard cells.
How are guard cells specialised
In light water flows into guard cells making them rigid which opens the stomata. At night water flows out of the guard cells which lose their rigidity and the stomata shuts shuts
Why does photosynthesis happen slower at the top of a mountain
Because there are reduced concentrations of air molecules at the top of a mountain which reduces the rate of photosynthesis because the enzymes that help with photosynthesis work better at warmer temperatures so they don’t happen as quickly
Limiting factors
A factor that prevents a rate increasing as a limiting factor. In photosynthesis the limiting factors are
Carbon dioxide concentration
Temperature
Light intensity
Inverse square Law
Lnew = Lorig xD^2orig/ d2 new
Why do plants absorb water
To carry dissolved mineral ions
Keep cells rigid to reduce silting
Cools the leaves
Photosynthesis
Root hair cells adaptations
The root hairs provide a large surface area so water and mineral ions can be quickly absorbed
Have thin walls for quicker diffusion
What is used to transport mineral salts
Through active transport which uses carrier proteins
Transpiration
Flow of water into a root, up the stem and out of the leaves
Xylem process
Xylem vessels form small pipes from the roots to the leaves
The vessels have an unbroken chain of water because there are weak attraction forces between the molecules
It is kept going because the water diffuses out of the lead and more water evaporates fro the xylem inside the leaf
Factors that increase the rate of transpiration
Wind and low humidity means there’s less water outside so there’s a higher concentration gradient so transpiration is faster
Higher temperatures mean particles diffuse faster out of the leaves
Greater light intensity means stomata are wider so more transpiration
Xylem adaptations
They have a long empty vessel because they die and their top and bottom cell walls disintegrate this means water can move more easily
They have hard rings on lignin so the water pressure doesn’t burst them
Translocation
Transportation of sucrose
How do phloem do translocation?
Sucrose is transported in the sieve tubes of phloem tissue
Each sieve cell is connected by holes and sucrose solution flows through this
Companion cells pump sucrose into and out of the sieve cells. When it is being pumped, the pressure increases so sucrose flows up to shoots or down to storage organs
Epidermis cells
Form the outside of the leaf, hold the leaf tkfehter and protect cells inside
They are transparent so light can pass through them easily
Produce a waterproof waxy cuticle so water loss is prevented
Cuticles stop microorganisms from getting in
Adaptations for cold places to stop water loss
Deciduous trees lose their leaves
Pine trees have needle leaves which have a smaller surface area, which means less water loss
Conifers shape means they can withstand high winds
They have stomata in small pits so water vapid collects because there’s less exposure to reduces the rate of transpiration
Adaptations for hot weather
Thick cuticle to reduced water loss
Stomata open at night so carbon dioxide is taken in at night
Stimulus
Change in the environment causes a response in the organism
Phototropism
Phototropism is response to a stimulus of lights. Plants move towards the light so they are positively phototropic. When a shoot detects light coming from One Direction the auxins which are plant hormones move to the shaded side of the shoot so the shaded site elongates more which means that that shoot grows in the direction of the light
Gravitropism
 auxins are also found in a root tips. In the roots auxin causes cells to stop elongating and this causes grow towards the direction of gravity.
This is useful because it helps the roots to anchor a plan in place and to reach the water underground. In shoots they grow upwards so the oxygen is pulled down and therefore the shoot becomes longer. In roots they grow downwards so the auxins are pulled upwards which stops the cell elongating
Gibberellins in bananas
Gibberellins of plant hormone that helps seeds to germinate and grow roots and shoots. Ethan gas is used to help fruits ripen. So for example bananas will be picked on right so they can be shipped and then when the time is right they use Ethan to rapidly ripe in the banana so they’re ready for supermarkets
Selective weed killer is
These have artificial auxins in them to make the plants grow quickly which kills them. Selective weed killer is target plants with broad leaves like dandelions and weeds but not those with narrow leaves like wheat and grass so they can kill the weeds but don’t affect the crop
Auxins in rooting powders
Auctions in rooting powder is cause plant cuttings to develop a route to quickly. This means large numbers of identical plants can be produced quickly
Gibberellin uses
Gibberellins are naturally released to start germination. An excess use of gibberellins can make seeds germinate without periods of darkness. Gibberellins can cause fruits to be produced without seeds and they can be used to make a bigger fruits
Photoperiodism
The response of an organism to the number of daylight hours in a day. This means some plants will flower at certain times but gibberellins can override this to make them grow quicker
