B2 Cell Transport Flashcards
What is diffusion?
The net movement of particles from an area of high concentration to an area of low concentration along a concentration gradient
3 factors that affect the rate of diffusion
Concentration gradient
Temperature
Membrane surface area
How are villi adapted for exchanging substances?
Long and thin (increases surface area)
One cell thick membrane ( short diffusion pathway)
Good blood supply ( maintains a steep concentration gradient)
How are the lungs adapted for efficient gas exchange?
Alveoli for a large surface area
Moist membranes to increase the rate of diffusion
Good blood supply to maintain a steep concentration gradient
How are fish gills adapted for efficient gas exchange?
Large surface area for gases to diffuse across
Thin layer of cells for a short diffusion pathway
Good blood supply to maintain a steep concentration gradient
What is osmosis?
It is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
Give one example of osmosis in a plant
When water moves from the soil into the root hair cell
What is active transport?
It is the movement of particles against a concentration gradient- from a dilute solution to a more concentrated solution- using energy from respiration
Why is active transport needed in plant roots?
Because the concentration of mineral ions in the soil is lower than inside the root hair cells and the mineral ions must move against the concentration gradient to enter the root hair cells
What is the purpose of active transport in the small intestine?
So that the sugars can be absorbed when the concentration of sugar in the small intestine is lower than the concentration of sugar in the blood
Explain the movement of particles in diffusion
The particles move down the concentration gradient- from an area of high concentration to an area of low concentration
Explain the movement of particles in osmosis
The water moves from an area of lower solute concentration to an area of higher solute concentration
Explain the movement of particles in active transport
The particles move against the concentration gradient- from an area of low concentration to an area of high concentration
What three factors affect the rate of diffusion?
Difference in concentration
Temperature
Surface Area of the membrane
How does the difference in concentration affect the rate of diffusion?
The steeper the concentration gradient the faster the rate of diffusion
How does the temperature affect the rate of diffusion?
The higher the temperature, the faster the rate of diffusion
How does the surface area of the membrane affect the rate of diffusion?
The larger the membrane surface area, the faster the rate of diffusion
Why do single-celled organisms have a large surface area- to-volume ratio?
To allow enough molecules to be transported across their cell membranes to meet their needs
When do exchange surfaces warm the most efficient?
When they have…
A large surface area
A thin membrane
A good blood supply
What is the effect of osmosis on animal cells?
Animal cells don’t have a cell wall so it will change size and shape when put into solutions that are at a different concentration to the cell contents
What could happen to red blood cells during osmosis?
Lose water
Shrink
Gain answer
Swell
Burst in a more dilute solution
When cells lose or gain too much water by osmosis they don’t function efficiently so what must happen to avoid this?
Blood plasma and tissue fluid must be kept within strict limits
What is the effect of osmosis on plant cells in pure water?
In pure water, the plant cells contents (the cytoplasm and vacuole) push against the cell wall and the cell becomes turgid
What do turgid cells do to the plant cell?
Turgid cells are swollen and firm and this allows the plant to be healthy and stand upright
What is the effect of osmosis on plant cells in concentrated solutions?
If a plant does not get sufficient water, the cells will be surrounded by a more concentrated solution. This causes the cell contents to lose water by osmosis they shrink and pull away from the cell wall and the cell becomes flaccid
What do flaccid cells do?
It makes the plant wilt
