SB6 Flashcards
What is the word equation for Photosynthesis
carbon dioxide + water → glucose + oxygen
uses light energy to react water and co2
What kind of reaction is photosynthesis
Endothermic
energy enters from the surrounding via light energy
How is temperature a factor of photosynthesis
(describe there relation)
Temperature - With an increase in temperature, the rate of photosynthesis
- if temp is too high enzymes will denature and the rate of photosynthesis wills low down
How is light intensity a factor of photosynthesis
(describe there relation)
Light Intensity - For most plants the higher the light intensity the faster the rate of reaction
- until something else become the limiting factor
How is Carbon dioxide concentration a factor of photosynthesis?
(describe there relation)
Carbon dioxide concentration - As the concentration of co2 increases so does the rate of reaction
- until something else become the limiting factor
What are photosynthetic organisms the main producer’s of?
- make there own food
- which is biomass
- they are producers
What is a limiting factor
variables that limit the rate of reaction in a chemical reaction
What is the inverse square law
- light intensity ⍺ 1/distance²
- L(New) = (L(orig) x D^2(orig) / D^2(new)
explain light intensity ⍺ 1/distance²
if you increase the distance from a light source, the light intensity increases
decrease the distance from the light source, increase the light intensity
What is the function of a root hair cell
- found on the outer surface of roots
- used to collect water and mineral ions via osmosis
how are water and mineral ions taken in by root hair cells
water - osmosis - takes no energy
mineral ions - active transport - uses energy
how the structure of the root hair cells is adapted to absorb water and mineral ions
- a large surface area to allow more water and mineral ions to be absorbed quickly
- thin cell walls
which allow for less diffusion distance making the osmosis much quicker
more mitochondria
energy to absorb mineral ion via active transport
What is transpiration and how does it occur?
- It is the process of water and mineral ions flowing into a root, up the stem and out of the leaves
- Occurs through xylem vessels, which are an unbroken chain of dead cells, by which water flows up due to weak forces of attraction between water molecules
- Water then evaporates from the xylem vessels in the leaves
What is translocation and how does it occur?
- This is the process of transporting sucrose to the entire plant
- It is done through companion cells pumping sucrose solution into our out of sieve cells, the increase pressure causing the sucrose to flow
How is a xylem adapted to take water to the leaves of the plant
- Upon formation, a chemical called lignin is deposited which cause the cells to die
- We say that these dead cells have become lignified
- They become hollow and are joined end to end to form a continuous tube so water and mineral ions can move through
- Lignin is deposited in spirals which helps the cells withstand the pressure of from the movement of water
How is a phloem adapted to transporting sucrose around the plant?
- Contain companion cells, which continuously pump sucrose in or out of sieve cells
- Sieve tube, which contains pores for sucrose solution to be pumped
- Holes in the end of cell walls allow liquids to flow from one sieve cell to the next
- Small amount of cytoplasm, so there’s more space for liquids
What is a stomata and how does it aid gas exchange?
- Open pore in a leaf, that allow gases to diffuse into or out of them
- They are controlled by guard cells, which open and close them
- During the daytime, water flows into the guard cells, allowing them to be rigid and open the stomata, for gas to exchange and photosynthesis to occur whilst it’s light
- At night, water flows out of the guard cells, resulting in them losing rigidity and so the stomata shuts, to prevent excess water loss
Why do leaves often have a large surface area?
- So they contain more chloroplasts, for more light energy to be trapped by chlorophyll
- This increases rate of photosynthesis
Why are leaves thin?
- Reduces distance that gas has to diffuse, increasing rate of photosynthesis
Why are there irregularly shaped spongy cells in a leaf?
- Creates air spaces, helping to allow gases to easily diffuse inside
What is the role of the epidermis cells?
- Hold the leaf together and protect cells inside
- Transparent, to allow light o pass through for photosynthesis
What is the role of a waxy cuticle?
- Helps to prevent water loss, as well as stops microorganisms entering leaf
How does wind affect rate of transpiration?
- Increases
- Moves water molecules away from stomata
How does low humidity affect rate of transpiration?
- Increases
- Less water vapour in air
How does high temperatures affect rate of transpiration?
- Increases
- Particles have more energy, so diffuse faster
How does greater light intensity affect rate of transpiration?
- Increases
- Makes stomata wider
How are conifers adapted to cold weather?
- Needle-shaped, with a smaller surface area and very thick cuticle to reduce water loss
- Shape reduces wind resistance
- Shape also means they collect less snow
- How are cacti adapted to hot weather?
- Hairs to trap water vapour leaving
- Spines instead of leaves, to minimise surface area. They also protect from predators
- Stomata open at night
- Thick cuticle
- Shallow, wide roots to absorb water as soon as it rains
What is phototropism?
- Response to light by growing towards or away from it
- Plant shoots are positively phototrophic, so they grow towards it
- Roots are negatively phototrophic
What is the role of the hormone ‘auxins’ in phototropism?
- Produced in the tips of shoots
- Cause elongation of cells
- Move to shaded side of shoot, causing the soot to bend towards the light source
What is gravitropism?
- Growth response to gravity
- In roots, positive gravitropism occurs, causing them to grow downwards
- In shoots, negative gravitropism occurs, causing it to grow upwards
What are the role of auxins in gravitropism?
- In shoots, they move downwards by gravity, increase cell elongation upwards
- In roots, they are pulled downwards by gravity and inhibit cell elongation upwards
What are the commercial uses of auxins?
- Weed killers, by causing uncontrollable growth in broad-leaved plants
- Rooting powders, allowing roots to develop quickly
What are the commercial uses of gibberellins?
- Artificially germinate
- Sprayed to overcome phototropism, to force plants to produce flowers
- Prevents seed formation when sprayed, to produce seedless fruits
- Produces bigger fruits
What are the commercial uses of ethene?
- Transported when unripe, before being ripened when needed using ethene gas
