chap 3- Movement in and out of cells Flashcards
Diffusion
net movement of particles from their region of higher concentration to their region of lower concentration down their concentration gradient
Where does the energy for diffusion come from?
Where does the energy for diffusion come from?
Why is diffusion important?
- Many life processes depend on it:
-Oxygen entering the blood from lungs - Glucose and amino acids pass from the gut to the blood
-Plants absorb CO2 into leaves
How do substances enter cells?
- By diffusion through the cell membrane
How can diffusion speed be increased in some organisms?
-Reduced diffusion distances: Shorter distance = faster diffusion
* Concentration gradients kept high: Equilibrium is not reached so diffusion continues
* Large surface area for diffusion to take place across cell membranes
osmosis
the net movement of water molecules from their region of higher water potential to their region of a lower potential gradient down their concentration gradient through a partially permeable membrane
How does water enter cells?
- By osmosis through the cell membrane
How does osmosis affect plant and animal cells differently?
- Plant cells not permanently damaged
- Cell walls give plant cell support
- Animal cells permanently damaged
- Animal cells shrink with water loss and burst if swell too much
What is plasmolysis?
- When too much water moves out of a plant cell the cell contents shrink
- This pulls the cell membrane away from the cell wall
What is the result of putting plant tissue in a high concentration solution?
- Plant cells have higher water potential
- Water lost from the plant into the solution
- Plant cells become flaccid
If plant tissue is placed in a dilute solution
- Plant cells have lower water potential
- Water enters plant through osmosis
- Plant cells become more turgid
Plants are supported by
- Water pressure inside cells pushing outwards
- Water pressure acts against inelastic cell wall - turgor pressure
Define active transport
net movement of molecules from their region of lower concentration to their region of higher concentration against the concentration gradient using energy from respiration with the help of carrier proteins
Where is active transport useful?
- Can move molecules up a concentration gradient
- E.g. Uptake of ions in to root cells, uptake of glucose in kidney tubules
Describe how active transport occurs
- Protein carriers are found in the cell membrane
- Carrier recognises particle to transport
- Particle transported across membrane by carrier protein using energy
- Particle released in to cell
- Carrier protein returns to surface membrane
