Diffusion And Osmosis Flashcards
What is diffusion and why is it needed in living cells
Diffusion is the movement of substance from HIGH to a LOW concentration (diffuses through cell membrane)
Living cells need to obtain oxygen,glucose and minerals from their surroundings and remove waste such as carbon dioxide
For diffusion there must be a high and low concentration
Why is there a low concentration of oxygen inside the cell and a high concentration outside the cell
Low concentration of oxygen inside the cell, it is being constantly used up for respiration
High concentration of oxygen outside the cell, oxygen is constantly being replaced
Describe the movement of particles in diffusion
Particles in diffusion move randomly
The net (overall) movement of particles is from high concentration to low
How can the rate of diffusion be increased
When the cell membranes surface is bigger
With bigger difference between concentrations
When particles have a shorter distance to travel
Osmosis
The diffusion of water from a dilute solution to a more concentrated solution through a partially permeable membrane
Water moves from a cell will a high concentration of water to a cell with a low concentration of water in each cell. It reaches an equilibrium and stops
The cell membranes allow movement of water for osmosis
Do they allow the movement of dissolved substances?
Cell membranes restrict the movement of dissolved substances
How is osmosis used in root hair cells
Water gradually moves from high concentration of water into lower concentration in the cell by osmosis along concentration gradient
The cell has a more concentrated solution so water from ground seeks to dilute it (osmosis)
What do plants use water for
Keeping leaves cool (via evaporation from leaves)
Transports minerals
Enables them to photosynthesise to produce glucose
Keep cells firm and keep plant rigid for support
Water is taken in via the roots
How are roots adapted to maximise this
The root hair cells increase surface area of the root- greater area for absorption
Explain how water is transported through the plant
Water is absorbed by root hair cells and travels through the plant to the leaves along a concentration gradient from an area if high concentration to low concentration
When water reaches the leaves how can it then be lost
When water reaches the leave sit can be lost by evaporation (transpiration) through stomata
What adaptions reduce water being lost through transpiration
Having a waxy cuticle on the surface
Having the majority of stomata on the lower surface of the leaf where they are less exposed to sunlight
Amount,position,size and distribution of stomata vary between plants depending on their environment which affects how much water they need
What is essential to maintain the support of plants
Plant cells have inelastic cell walls, preventing them from bursting from excess water entering. This contributes to turgidity
The water in the cells gives support
What will happen if there is not enough water in the soil
plants wilting
Stomata closes to prevent transpiration and diffusion so photosynthesis rate reduces
Lack of water inside cells causes them to become flaccid due to reduced turgor pressure
If cells lose a lot of pressure they may become plasmolysed, the inside of the cell contracts
What will happen if there is lots of water in the soil
Stomata open to allow transpiration and the diffusion of gases so photosynthesis rate increases
The plant cells will be full of water so the plant is turgid and erect
