SB6 - Plant Structures And Their Functions Flashcards
How do plants and algae get energy
Trap energy transferred by the light from the sun
Energy transferred to glucose in photosynthesis - glucose and products made from it are stores of energy
What is biomass
The materials in an organism are its biomass
Plants and algae produce their own and so produce their own food
They are producers in food chains
What is photosynthesis simply
A series of chemical reactions catalysed by enzymes
Tell me the word equation for photosynthesis
Carbon dioxide and water = glucose and oxygen
Where does photosynthesis occur
In chloroplasts which contain a green substance called chlorophyll that traps energy transferred by light
What type of reaction is photosynthesis
Endothermic reaction as energy enters from its surroundings and so products have more energy than reactants
What happens to glucose molecules
Glucose molecules are linked to form a polymer starch - stays in chloroplasts until photosynthesis stops
Starch is broken down into simpler substances which move into cytoplasm to make sucrose
What can sucrose be used for
It’s another type of sugar molecule
Sucrose is transported around the plant and may be used to make:
- starch (in a storage organ such as potato)
- other molecules for the plant (such as cellulose, lipids, or proteins)
- glucose for respiration (to release energy)
Tell me about palisade cells
They are near the top of a Leaf packed with chloroplasts - adapted to allow leaf to absorb maximum light
Tell me about stomata
Leaves contain microscopic pores called stomata or singular stoma
They allow carbon dioxide to diffuse into the leaf
Allow oxygen producer escape into the air and as well as water vapour
Tell me about guard cells
The stomata are opened and closed by stomata
In the light, water flows into pairs of guard cells making them rigid
This opens the stoma
At night water flows out of the guard cells so they shut
Why are leaves thin
So carbon dioxide does not have to diffuse far into the leaf
What’s gas exchange
The flow of different gases into and out of a leaf eg carbon dioxide and oxygen
What’s reduced concentration of air molecules
Causes a lower rate of photosynthesis in high mountains
How can temperature affect rate of photosynthesis
The reactions in photosynthesis are catalysed by enzymes that work better in warmer conditions
What’s the limiting factor
The factor that prevents a rate increasing
Carbon dioxide concentration, temperature and light intensity can be limiting factors
The maximum rate of photosynthesis is controlled by the factor in shortest supply
What’s a linear relationship
Between two variables
What’s direct proportion
If line in graph goes through the origin - it shows the two variables are in proportion
As one increases the other one does too
What’s the inverse square law
Used to calculate new light intensity
1/new distance from light source ^2
What is water absorbed by plant roots also used for
Carrying dissolved mineral ions
Keeping cells rigid - otherwise they will wilt (stems and leaves will droop)
Cooling the leaves - when it evaporates from them
Photosynthesis
Tell me about root hair cells
The outer surfaces of many roots are covered with root hair cells
They are extensions to increase surface area so water and mineral ions can be quickly absorbed - also have thin walls so the flow of water into the cells is not slowed down
Tell me about osmosis and diffusion
Particles Constantly move in random directions and so particles in a fluid diffuse down a concentration gradient
This is diffusion inside plant roots as the cell walls have an open structure allowing water particles to diffuse towards the middle of the root
Water passes into the cytoplasm of root hair cells by osmosis
Tell me about active transport
Mineral salts are naturally occurring ionic compounds
Plants need the ions to from new substances
Eg nitrate ions are needed to make proteins
The concentration of ions in root hair cell is greater than in the soil
Proteins in the cell membrane pump the ions into the cell and so is an example of active transport
What’s transpiration
The evaporation of water from leaves keeps them cool and helps dissolved mineral ions move up the plant
The flow of water into a root up the stem and out of the leaves is transpiration
Tell me about xylem vessels
Xylem vessels form continuous pipes leading from a plants roots to its leaves
Inside the vessels is an unbroken chain of water due to weak forces of attraction between water molecules
Water is pulled up the xylem vessels in the stem as water evaporates from the xylem vessels in the leaves
As the water vapour diffuses out of s leaf, more evaporates from the xylem vessel inside the leaf
What makes diffusion faster
The bigger the difference between the concentrations makes it faster
What factors increase transpiration
But reduce concentration of water molecules outside the stomata
Wind moves water molecules away from the stomata
Low humidity means little water in the air
Higher temps so particles move faster and so will diffuse
Greater light intensity - makes stomata wider
Tell me about xylem
Xylem cells die and Thor top and bottom cell walls will disintegrate
To create long empty vessels so water can move easily
Why are xylem vessels rigid
Becuase they have thick side walls and rings of hard lignin and so water pressure inside the vessel does not burst or collapse on them
The rigid xylem vessels also help to support the plant
Tell me about phloem
Plants make sucrose and glucose and starch made in photosynthesis
Sucrose is translocated in the sieve tubes of the phloem tissue - the large central channel in each sieve cell is connected to its neighbours by holes, through which sucrose solution flows
What do companion cells do
They actively pump sucrose into or out of the sieve cells that form the sieve tubes
As sucrose is pumped into sieve tubes, the increased pressure causes the sucrose solution to flow up to growing shoots or down to storage organs
Why do leaves have large surface areas w
To collect enough light
The energy transferred by light is trapped by chlorophyll packed into discs inside chloroplasts
The energy is then transferred to glucose during photosynthesis
The chloroplasts in a cell can move yoward or away from the light - as protection from bright light
