2.5 Biological molecules Flashcards
What is the plasma membrane?
The outer boundary of a cell that controls the movement of substances in and out of the cell.
What molecules does the plasma membrane allow through?
Very small molecules -> simply diffuse through he cell.
Some substances dissolve in the lipid bilayer + pass through.
Other substances pass through protein channels or carrier proteins.
What is the function of the plasma membrane?
Separate from outside.
Regulate transport in + out.
Cell communication.
Who proposed the fluid mosaic model?
Singer and Nicolson.
Proposed model that allowed passage of molecules.
Proposed that fabric of membrane consisted of phospholipid bilayer with proteins floating in it.
What is outside the membrane
Glycocalyx -> formed from carbohydrate chains attached to glycolipids or glycoproteins in the membrane.
What is simple diffusion?
Simple diffusion is the passive movement (doesn’t require ATP) of molecules from an area of higher concentration to an area of lower concentration.
What is facilitated diffusion?
Facilitated diffusion is the passive movement of molecules across a cell membrane (from high to low concentration) with the help of transport proteins.
How does temperature affect the rate of diffusion?
Temperature affects the rate of diffusion by increasing the kinetic energy of particles, causing them to move faster and collide more frequently, which results in faster rate of diffusion. Conversely, as they lose heat their rate of diffusion will slow down.
How does diffusion distance affect rate of diffusion?
the thicker the membrane across which molecules have to diffuse, the slower the rate of diffusion.
How does surface area affect the rate of diffusion?
The larger the surface area the more diffusion takes place. Cells specialised for diffusion have microvilli to increase their surface area.
How does size of diffusing molecule affect the rate of diffusion?
Smaller molecules diffuse faster than larger molecules.
How does the concentration affect the rate of diffusion?
The steeper the gradient, the faster diffusion takes place.
What is osmosis?
Osmosis is the movement of water molecules from an area of lower solute concentration to an area of higher solute concentration across a semi-permeable membrane.
What are the effects of osmosis on plant and animal cells?
Hypertonic, Isotonic, Hypotonic.
What does a hypertonic do to a plant/animal cell?
When cells are out into a solution with a lower water potential than inside the cell (hypertonic), water moves out the cell. Animal cells will shrink or crenate. The plasma membrane of plant cells comes away from the cell wall (plasmolysis)
