Plasma Membranes And Transport Processes Flashcards
What is water potential?
The pressure exerted by water molecules as they collide with the membrane or container.
What is water potential measured in?
Pascals or kilopascals
What is the water potential of pure water?
0
What does it mean if water potential is more negative?
The solution is more concentrated
Which way across a water potential gradient does water move?
From an area of higher water potential to an area of lower water potential. Continues until water potential is equal on both sides.
What is hydrostatic pressure?
When diffusion of water leads to an increase in the volume of the solution = increased pressure.
What is cytolysis?
When a cell bursts
What happens if an animal cell is placed in solution with a higher water potential than the cytoplasm?
Water will move into the cell via osmosis, increasing the hydrostatic pressure inside the cell. Cell surface membrane cannot stretch much and therefore bursts due to increased pressure.
What happens if an animal cell is placed in solution with a lower water potential than the cytoplasm of the cell?
The cell will lose water to the solution by osmosis down the water potential gradient. Reduces volume of the cell and cell surface membrane puckers ( crenation )
What happens if you put a plant cell in water?
If higher water potential outside;
Water enters by osmosis and increased hydrostatic pressure pushes the membrane against rigid cell walls. This pressure is called turgor. As pressure increases it resists the entry of further water and the cell is said to be turgid.
What happens when plant cells are placed in solution with a lower water potential than their own?
Water lost from cells by osmosis. Reduces volume of cytoplasm which pulls cell surface membrane away from the cell wall - cell has been plasmolysed.
What is active transport?
An energy requiring process that is the movement of ions from a region of lower concentration to higher concentrations.
What does active transport require?
Energy and carrier proteins.
Explain how transport can transport substances from outside the cells to inside the cell?
Molecule / ion binds to receptors in channel of carrier protein on outside of cell.
ATP binds to carrier protein and is hydrolysed into adp and phosphate.
Binding of phosphate to carrier protein causes protein to change shape and channel opens.
Molecule or ion released to inside of cell.
Phosphate molecule released from carrier protein and recombines with adp to form atp.
Carrier protein returns to original state.
What is bulk transport?
When large molecules such as enzymes, hormones and whole cells are too large to fit through channels or carrier proteins so they’re moved by bulk transport.
