Plasma Membrane & Diffusion

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Extracellular fluid

Extracellular fluid

Fluid present outside of the cells of a multicellular organism.

Intracellular fluid

Fluid present inside of the cell.

Net Movement

When the flow of solute particle moving in one direction is bigger than the flow of solute particles moving in the opposite direction.

Name of the Model of the Plasma Membrane

Fluid Mosaic Model

Roles of the Plasma Membrane

• Movement of substances in and out of the cell.

• Providing structural support.

• Facilitating cell communication.

Phospholipid Bilayer

Quite fluid, with proteins flowing within it. Glycoproteins, glycolipids, and cholesterol are also apart of membrane structure.

Glycoproteins

Have an important role in cellular recognition and immune responses. They help stabilise the membrane structure.

Glycolipids

Act as surface receptors and stabilise the membrane.

Cholesterol

Makes the membrane more stable.

What can pass through the plasma membrane? (Hydrophobic or hydrophilic)

Hydrophobic molecules, eg: wateralcoholoxygen

What cannot pass through the plasma membrane? (Hydrophobic or hydrophilic)

Hydrophilic molecules, eg: ionslarge molecules

4 Types of Diffusion

Simple diffusion, Facilitated diffusion, Osmosis, Active transport

Simple diffusion

The net movement of a substance from a region of high concentration to a region of low concentration. Movement occurs down a concentration gradient, passive process.

Factors affecting rate of diffusion

• Distance

• Concentration gradient

• Physical barriers

• Surface area

Facilitated Diffusion

When a protein channel and/or carrier is used to help pass proteins through the membrane.

Protein Channel

A channel in membrane that some substances need to move through protein instead of passing straight through.

Protein Carrier

A carrier that is supplied in addition to a protein channel, in order to pass through the membrane.

Hypertonic Solution

The solution has a higher concentration of solute than the cell or solution that it is being compared to.

Hypotonic Solution

The solution has the lower concentration of solute as the cell or solution it is being compared to.

Isotonic Solution

The solution has the same concentration of solute as the cell or solution it is being compared to.

Osmosis

The movement of water from a dilute solution to a more concentrated one.

Dilute

A solution with a low concentration of solute, more water molecules than the solute.

Why do cells need osmosis?

It is how they gain water, making them turgid. (swollen, full)

Active Transport

Substances are moved across a membrane against a concentration gradient. It is an active process as it requires energy (ATP). Used to pump substances in or out of the cell with specific protein carrier molecules.