Transport across cell membranes Flashcards
What is diffusion?
The net movement of particles from an area of higher concentration to an area of low concentration
- Diffusion is a passive process
What is meant by facilitated diffusion?
Large or charged particles diffuse through carrier proteins or channel proteins - speeding up the process
- Higher to a lower concentration gradient and a passive process
How do carrier proteins enable large molecules to move across the membrane?
- Large molecule attaches to a carrier protein in the membrane
- Protein changes shape
- Releases the molecule on the opposite side of the membrane
How do channel proteins enable large molecules to move across the membrane?
- Channel proteins form pores in the membrane for charged particles to diffuse through
- Different channels (sodium channel) facilitate the diffusion of different charged particles
What 3 factors affect the rate of simple diffusion?
- The concentration gradient, higher it is the faster the rate of diffusion
- The thickness of the exchange surface, thinner the exchange surface the shorter the diffusion distance
- The surface area, larger the surface area the faster the rate of diffusion
What 2 factors affect the rate of facilitated diffusion?
- Concentration gradient, higher the concentration gradient faster the rate of facilitated diffusion
- Number of channel/carrier proteins, faster the rate of facilitated diffusion
What is osmosis?
Diffusion of water molecules across a partially permeable membrane from an area of higher water potential to an area of lower water potential
What 3 factors affect the rate of osmosis?
- The water potential gradient, higher water potential gradient faster the rate of osmosis
- Thickness of the exchange surface, thinner surface faster rate of osmosis
- Surface area, larger surface area faster rate of osmosis
What is active transport?
Moves solutes from a low to a high concentration, requiring ATP
What is meant by co-transporters?
A type of carrier protein
- Bind two molecules at a time
- Concentration gradient of one molecules is used yo move the other molecule against its own concentration gradient
- E.g. sodium ions and glucose
What 3 factors affect the rate of active transport?
- Speed of individual carrier proteins
- Number of carrier proteins present
- The rate of respiration/availability of ATP