Bio – week 4 – lecture 1 – 24/3/25 – Membrane structure:
Chromosome = molecule of DNA in a cell
The solute can dissolve in a solvent making = a solution e.g. salt dissolved in water.
Molecular motion in liquids:
Molecules in a liquid or solution are always in motion. They move randomly throughout the
liquid or solution.
Diffusion: molecules that begin near one another will tend to separate over time. This is
called diffusion. (random movement of particles) -> diffusion is
main way molecules get from one place to another within a cell.
- Each solute particle is moving at random when introduced
into liquid just randomly moving around (spreading out).
e.g. food dye in water.
Membrane fluidity:
- Phospholipids in membrane move throughout membrane (wont leave membrane but
can move around it) –> 1 second to move to other side of membrane. But rare for
phospholipid to move to opposite site of membrane.
Reasons why fluidity is important:
1. Fluidity helps small molecules cross the membrane -> molecule such as oxygen
entering cell by wriggling through phospholipids.
2. Helps molecules move around throughout the membrane -> proteins need to move
to find the desired protein to bind to.
3. Helps proteins in the membrane undergo conformational change. -> enzymes need
to change shape and move and hence membrane needs to be fluid for this to occur.
4. Helps entire membrane to change shape as cell changes shape.
Fluid mosaic:
- Fluid = As cell changes shape the cell membrane conforms to the shape of the cell
Chromosome = molecule of DNA in a cell
The solute can dissolve in a solvent making = a solution e.g. salt dissolved in water.
Molecular motion in liquids:
Molecules in a liquid or solution are always in motion. They move randomly throughout the
liquid or solution.
Diffusion: molecules that begin near one another will tend to separate over time. This is
called diffusion. (random movement of particles) -> diffusion is
main way molecules get from one place to another within a cell.
- Each solute particle is moving at random when introduced
into liquid just randomly moving around (spreading out).
e.g. food dye in water.
Membrane fluidity:
- Phospholipids in membrane move throughout membrane (wont leave membrane but
can move around it) –> 1 second to move to other side of membrane. But rare for
phospholipid to move to opposite site of membrane.
Reasons why fluidity is important:
1. Fluidity helps small molecules cross the membrane -> molecule such as oxygen
entering cell by wriggling through phospholipids.
2. Helps molecules move around throughout the membrane -> proteins need to move
to find the desired protein to bind to.
3. Helps proteins in the membrane undergo conformational change. -> enzymes need
to change shape and move and hence membrane needs to be fluid for this to occur.
4. Helps entire membrane to change shape as cell changes shape.
Fluid mosaic:
- Fluid = As cell changes shape the cell membrane conforms to the shape of the cell
