7:3 Movement Through the Membrane

Cell Membrane

Every cell has a cell membrane Regulates what enters and leaves the cell. Provides protection & support The middle section is called a lipid bi-layer, a

double layer lipid sheet.

Lipid Bi-layer

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel

Lipid bilayer

Carbohydratechains

Diffusion

Liquids are present both in and out of the cell

The membrane monitors what enters or exits the cell

The cytoplasm has various solutes within it The concentration of a solution is the mass

of solute in a given volume (mass/volume) Diffusion is when molecules move from one

area of concentration to another (usually through a membrane)

Diffusion causes many substances to move across a cell membrane but does not require the cell to use energy!

Equilibrium is reached when the concentration of the solute is the same throughout a solution of a system.

HighConcentration

LowConcentration

CellMembrane

Proteinchannel

Osmosis

Osmosis is the diffusion of water through a selectively permeable membrane

Selectively permeable means the membrane allows certain substances to pass by and others not.

Osmosis allows water molecules to pass through a biological membrane easily.

Osmosis is the movement of water from an area of high concentration of water molecules to an area of low concentration of water molecules.

When a cell membrane does not allow substances in, it is said to be impermeable.

Water will move across a membrane until there is equilibrium.

Biological membranes are permeable to water, but impermeable to larger molecules such as sugar.

Membranes may be selectively permeable, allowing only substances of their choice into the cell.

When a cell is at equilibrium with the surrounding solution, the cell is isotonic.

Cell membranes are completely permeable to water, therefore, the environment the cell is exposed to can have a dramatic effect on the cell.

3 types of solutions:

Isotonic, Hypotonic and Hypertonic

Osmosis in cellsLet’s take a look!

Facilitated Diffusion

During facilitated diffusion, molecules such as glucose that cannot cross the cell membrane’s lipid bilayer directly move through protein channels instead.

Hundreds of different protein channels have been found that allow ions, sugars and salts to cross various membranes.

Active Transport

When materials move across a membrane AGAINST concentration differences.

Requires the input of energy

Some types of active transport move materials through the cell membrane.

Endocytosis – taking in through pockets of cell membrane (process is called phagocytosis)

Exocytosis – exits the cells via the membrane

7-4 The Diversity of Cellular Life

UNICELLULAR – one celled MULTICELLULAR – many cells Multicellular organisms have cell specialization.

They are specialized to perform specific functions within the organisms.

LEVELS OF ORGANIZATION IN AN ORGANISM:

Cells Tissues Organs Organ Systems Organism