Transport in cells Flashcards
Define diffusion.
The net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient across a semi-permeable membrane.
Name three substances which move by diffusion within animal cells.
- Oxygen 2. carbon dioxide in gas exchange, 3. Urea out of cells to be excreted from the body.
Name three factors which affect the rate of diffusion.
- The difference in concentrations (concentration gradient)
- Temperature
- Surface area of the membrane.
Does a single-celled organism have a high or low surface area:volume ratio?
High.
How do single-celled organisms get enough oxygen without having lungs?
Due to its small size, and therefore its high SA:vol, diffusion across its membrane allows sufficient gas exchange
Why do multicellular organisms tend to need exchange surfaces and transport systems?
Low SA:vol, therefore cannot rely on diffusion across cell membranes.
Name two common features that aid the exchange of substances in the small intestine, lungs and fish gills but also a plant roots and leaves.
- Large surface area, 2. Thin membrane to provide a short diffusion path.
Define osmosis.
The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
If an animal cell loses a lot of water, what happens?
It crenates (shrivels) and cellular reactions are slowed or stopped.
If an animal cell gains a lot of water, what happens?
It can lyse (burst) and die.
If a plant cell loses a lot of water, what happens?
It becomes plasmolysed (cell membrane shrinks away from the cell wall).
If a plant cell gains a lot of water, what happens?
It becomes turgid (cell membrane pushes up against the cell wall).
Define active transport.
The movement of substances from a low concentration to a high concentration (against a concentration gradient).
What two things does active transport require that diffusion doesn’t?
- A transport protein (found in the cell membrane)
- Energy.
From what reaction does the energy required for active transport come?
Respiration.
Where does active transport happen within a cell?
The mitochondria.
Give two examples of where active transport is used in Biology. (1 plant, 1 animal)
- Plant root hair cells absorbing mineral ions from the soil, 2. Glucose absorption from the small intestine into the blood.
Why does active transport require extra energy?
Goes against the concentration gradient.
