⭐️SB6- plant structures and their functions Flashcards
What is the store of energy for plants?
Glucose and substances made from glucose
What is a biomass?
The materials in an organism
What are plants and algae in the food chain and why?
They are producers as they produce their own biomass and so produce the food for almost all life of earth
What is photosynthesis and what is the word equation?
A series of chemical reactions catalysed by enzymes
Carbon dioxide + water -> glucose + oxygen
Where does photosynthesis occur?
In chloroplasts which contain chlorophyll which traps energy transferred by lights
What kind of reaction is photosynthesis ?
Endothermic because energy enters from the surroundings and the products of photosynthesis have more energy than the reactants
What are the steps in photosynthesis?
- Chlorophyll traps energy transferred by light
- Glucose molecules are made and link together to make the polymer starch
- Starch stays in chloroplasts until broken down into simpler substances
- These are transported unto the cytoplasm and used to make sucrose
- the sucrose can be transported around the plant to make substances
What is sucrose used to make in a plant?
- starch (in a storage organ like a potato)
- other molecules for the plant like cellulose, lipids or proteins
- glucose for respiration to release energy
How are leaves adapted to their function?
- broad and flat giving them a large surface area
- palisade cells are at the top of the leaf and are full of chloroplasts to allow the lead to absorb lots of light
- they are thin so CO2 doesn’t have far to diffuse before reaching cells
Why is there air spaces in a cross section of a leaf?
They provide a large surface area for cells to exchange gases with the air
What are stomata?
Microscopic pores that allow carbon dioxide to diffuse into the leaf and oxygen and water vapour to escape into the air
What do guard cells do?
Open and close the stomata
How do the guard cells work?
In the light, water flows into pairs of guard cells making them rigid and opening the stomata and at night, water flows out of the guard cells, they loose rigidity and the stomata shuts
Describe the structures of a guard cell
- Chloroplasts
- cell membrane
- vacuole
- thin cell wall on the outside
- thick cell wall on the inside by the stomata
- mitochondrion
Give an example a way of gas exchange in a leaf
The stomata
What is a limiting factor?
A factor that prevents a rate increasing
Give three limiting factors of photosynthesis
- CO2 concentration
- temperature
- light intensity
- amount of chlorophyll
What controls the maximum rate of photosynthesis?
The limiting factor in shortest supply
Where can you properly learn limiting factors?
Go on YouTube or use mygcsescience
On a graph,
What does it mean if the line is straight?
What does it mean if the line goes through the origin?
- There is a linear relationship between the two variables
- the two variables are in direct proportion
Inverse square law?
Watch a video / look through notes, Pearson active learn pg 127
Name what water absorbed by plant roots is used for
- carrying dissolved mineral ions
- keeping cells rigid
- cooling the leaves when water evaporates
- photosynthesis
What cells are roots covered with?
How are they adapted to their function?
Root hair cells
Adapted as:
-the ‘hairs’ are extensions of the cell that provide a large surface area so water and mineral ions can be quickly absorbed
-the ‘hairs’ also have thin cell walls so the flow of water into cells is not slowed down
What is diffusion?
Where particles in a fluid move from an area of high concentration to low conc
What is osmosis?
When solvent molecules diffuse through a semi permeable membrane from high to low concentrations
What is active transport?
Diffusion of particles agains the concentration gradient from low to high concentration and needs energy
To learn more about limiting factors
Watch a video or look in old exercise book
What is transpiration?
The flow of water into the root, up the stem and out of the leaves; it’s water in the xylem
What’s glucose for in a plant?
The create anything in a plant that’s made of carbon
Explain what’s happing inside xylem vessels
There is an unbroken chain of water when it’s flowing through due to weak forces of attraction between water molecules
What do the xylem vessels do?
Transports water and solutes from the roots to the leaves
How does water get transported out of the leaf via the xylem vessels
It gets pulled up the xylem vessels as water evaporates from the xylem in the leaves, as the water vapour diffuses out of the leaf, more water evaporates from the xylem inside the leaf
How is water able to diffuse out of the leaf?
Because the concentration difference of water vapour in the air spaces of the leaf is greater than outside it is water molecules are able to diffuse down the concentration gradient and out of the leaf
What process does the xylem help carry out
Transpiration
What does the phloem do?
Transports food from the leaves to the rest of the plant
What factors increase transpiration and why do they do this?
-Wind - moves water away from the stomata
Low humidity - little water vapour in the air
They increase transpiration as concentration of water molecules outside is reduced so there’s a bigger difference between concentrations increasing the gradient making it steeped
What other factors increase transpiration that don’t have anything to do with the concentration gradient?
- Higher temps as particles move faster so diffuse faster
- greater light intensity as this makes the stomata wider
What are the adaptations of a xylem cell?
- Water can only move one way
- there are no cell walls between cells making a lint tube
- they have tiny pores allowing water and mineral ions to enter and exit the xylem vessels
- the dead cells in the middle have no cytoplasm so it forms a hollow tube for water
- have thick cell walls made of living to stand water pressure and can help support the plant
What is translocation?
The movement of sucrose through the phloem of a plant
What cells make up the phloem
The sieve tubes and companion cells
What do sieve cells do
They form a large channel in the phloem tissue where each cell is connected to its neighbour by holes through which sucrose flows through
What do companion cells do? How are they adapted?
They actively pump sucrose into or out of sieve cells that form the sieve tubes. They have a lot of mitochondria to produce the energy for active transport
Where does the phloem take the sucrose?
An increase of pressure causes it to flow up to growing shoots or roots or down into storage organs
What are the adaptations of the phloem?
- It’s got holes in the ends of the cell walls to allow liquid to flow from one sieve cell to the next
- there is only a small amount of cytoplasm and there’s no nucleus so more room for the central channel
- the sucrose can flow two ways depending on where it needs to be transported
Give the adaptations of leaves
- have a large surface area to collect enough light
- leaves are thin so CO2 doesn’t have far to diffuse before reaching photosynthesising cells
- sponges cells in the leaf are irregular shapes so create air spaces for gas to easily diffuse in and out of the leaf
- leaves have a waterproof waxy cuticle to help prevent water loss and to stop excess water and microorganisms getting in the leaf
- chloroplasts can move towards light or away
How do leaves trap energy?
- The energy transferred by light is trapped by chlorophyll packed into disks inside chloroplasts
- The energy is then transferred to glucose during photosynthesis
What do the epidermis cells do?
They form the outer layer of a leaf holding the leaf together and protecting the cells inside
what is a tropism? What does it mean if it’s positive or negative?
Responding to a stimulus by growing towards or away from it. Positive means it’s growing towards it and negative is growing away from it
What is phototropism?
A tropism by light
How are selective weed killers effective?
They contain artificial auxins to make plants grow uncontrollably so they die. This only effects plants with broad leaves so weeds and not those with narrow leaves like wheat and grass
How are rooting powders effective?
The auxins cause plant cuttings to develop roots quickly so large numbers of identical plants can be produced quickly using cuttings instead of growing plants from seed
What are gibberillins
They are plant hormones that are naturally released in a seed to start germination
How can gibberellins be used?
- to grow plants that usually need a period of cold and darkness before they germinate
- to produce seedless fruits that would usually produce a seed
- by spraying them on plants it can produce bigger fruits
What is photoperiodism? What is it used for? How do farmers deal with it?
The response of an organism to the number of daylight hours in a day.
-Some plants use it to flower at a certain time like when it’s not too cold and so farmers can override it by using gibberellins
How do fruit producers keep fruit unripened and for what reason?
By spraying the fruit with ethene ( a plant hormone gas) so that the fruit reaches the shop at just ripened condition. This is because fruits that aren’t ripe are easier to transport than ripe ones and ripe ones can be kept longer in storage without going off
What is the mesophyll in leaves
The collection of cells with space between for gas exchange
How are plants that live in cold and windy environments adapted?
- they are deciduous to prevent soil and water loss when frozen
- leaves are needle shaped so they collect less snow and so there’s less wind resistance
How are plants that live in dry and hot environments adapted?
- trap water vapour close to leaves to slow down rate of diffusion and reduce water loss
- covered in tiny hairs to trap water vapour
- stems store water
- transpiration increases
- guard cells become flaccid
What kind of tropisms are plant roots?
- negatively phototropic
- positively geotropic
- positively hydrotropic
What’s positive phototropism caused by?
Auxins (type plant hormones)
How do auxins control the growth of plant shoots towards the light?
- They are produced at the very tip of the shoot and move down it
- As auxins move down they move to the shaded part of the shoot when light is coming down on only one direction
- The auxins then cause cell elongation on the shaded side causing the plant to grow towards the light
How do auxins effect plant roots?
They have the opposite effect to plant shoots:
Auxins are pulled downwards in the roots to prevent cell elongation to anchor the plant in place and reach moisture underground
What equipment measures the rate of transpiration and how does it work?
A potometer
Works as air bubbles move along a tube as the plant loses water and the speed of bubbles gives the rate of transpiration
