Cell membrane

Fluid Mosaic model

fluid = parts of the membrane (except for the phospholipids) can easily move

mosaic = membrane looks like a pattern of lipids and proteins

Selectively permeable

The membrane has this characteristic, meaning some molecules can pass through and others cannot.

Phospholipids

The main component of the lipid bilayer. They have a phosphate, hydrophilic, polar head and a lipid, hydrophobic, nonpolar tail. The heads face the outside and inside of the cell, and the tails face each other inside the membrane.

Integral proteins

Membrane-spanning proteins that help let certain substances that cannot pass through the lipid bilayer into the cell.

Peripheral proteins

Protiens that sit on the border of the cell membrane.

Glycoproteins

Proteins that have carbohydrate chains that act as markers to identify cells.

Concentration gradient

The difference in density/amount of particles of a substance between two separate areas.

Passive transport

Transport of molecules down a concentration gradient (high to low). Requires no energy.

Diffusion

Movement of molecules from high to low concentrations directly through the membrane.

Facilitated diffusion

Movement of molecules from high to low concentrations using transport proteins.

Aquaporins

Channel proteins used to transport water.

Osmosis

The diffusion of water across a membrane through aquaporins.

Hypertonic

When the outisde of a cell has more solute and less water than the inside. The water from the cell moves to the outside. The cell shrivels.

Hypotonic

When the outside of a cell has less solute and more water than the inside. The water from the outside moves into the cell. The cell swells.

Isotonic

When the solute concentrations are equal on both sides. Water moves equally in both directions.

Active transport

Movement of molecules from low to high concentrations. Requires energy in the form of ATP.

Protein pump

Uses energy to push molecules against their concentration gradient during active transport.

Endocytosis

Cell taking materials in through active transport. Two types: phagocytosis and pinocytosis.

Pinocytosis

“Cell drinking” —> vesicles form around liquids/very small particles for the cell to ingest.

Phagocytosis

“cell eating” —> large particles are taken into the cell using this process.

Exocytosis

The cell gets rid of particles by fusing a membrane with the cell membrane.

Ion channels

Membrane-spanning proteins specifically designed to transport ions.