Cell Transport1. What is the purpose of the cell

membrane? 2. Why would we need to regulate

what goes in and out of the cell?3. What are some things that

might need to be transported into or out of the cell?

Structure of the Plasma Membrane

o Phospholipid Bilayer: two layers of lipids with a phosphate head• Phosphate head is hydrophilic• Lipid tail is hydrophobic • There is a watery environment inside and

outside the cell, so the phosphate heads align towards the water.

o Proteins – passageways through the plasma membrane • Some act as cell markers, others as channels

ProteinsCarbohydrate Chains

Phosphate HeadProtein Channel

Lipid Tail

Structure of the Plasma Membrane (cont)The plasma membrane is

selectively permeable – only certain substances are allowed to pass through it.

Types of Cell Transport

PASSIVE TRANSPORT ACTIVE TRANSPORT Movement of a

substance through a cell’s membrane without using any energy

Moves from high concentration to low concentration

Three types : diffusion, osmosis and facilitative diffusion

Movement of a substance through a cell’s membrane using any energy

Moves from low concentration to high concentration

Two types : endocytosis and exocytosis

 

PASSIVE TRANSPORT

1. Diffusion

the movement of particles through the plasma membrane from an area of high concentration to an area of low concentrationoConcentration - the amount of solute in a solution  • Solution – mixture of solutes and solvents• Solute – substance dissolved in another substance• Solvent – a substance that does the dissolving

oDiffusion will occur until equilibrium is reached (the concentration of the substance is the same)

o Example: in lungs, oxygen diffuses into the bloodstream because there is less oxygen in the bloodstream

2. Facilitated Diffusion

the transport of specific particles through a membrane by a channel protein.

3. Osmosis

the diffusion of water molecules through a selectively permeable membrane from an area of high water concentration to an area of low water concentration

Isotonic Solution – the concentration of solutes is the same inside and outside of the cell

The cell and environment are at equilibrium

Hypotonic solution – the solution with the higher solvent (water) content

Water moves into the cell and the cell will swell

Hypertonic solution – the solution with the higher solute concentration

Water moves out of the cell and the cell will shrink

ACTIVE TRANSPORT

1. Endosytosis

process by which a large macromolecule enters a cell. Extracellular vesicle fuses with the plasma membrane, the membrane pinches inward, the vesicle is transported into the cell.

◦Two types: Pinocytosis – engulfing a liquid (cell

drinking) Phagocytosis – engulfing another cell or

organic matter (cell eating)

Endocytosis

2. Exosytosis

large macromolecule leaving a cell. Intracellular vesicles migrate to the plasma membrane, fuse with it, and release the contents out into the cell

Exocytosis