Biological membranes - Module 2

Active transport

The active movement of substances from a low concentration to a higher concentration (up their concentration gradient) with the use of energy in the form of ATP.

Amphipathic

A molecule with both hydrophobic and hydrophilic parts.

Cell lysis

The bursting of a cell, particularly after the uptake of too much water into an animal cell through osmosis.

Cholesterol

A mostly hydrophobic molecule that sits in the hydrophobic portion of the membrane and regulates membrane fluidity.

Crenation

The shrinking of a cell when placed in a hypertonic solution due to large amounts of water moving out of the cell through osmosis.

Endocytosis

The bulk uptake of substances into a cell by invagination of the membrane to form a vesicle trapping the substances inside the cell with the use of energy in the form of ATP.

Exocytosis

The bulk transport of substances out of a cell using a vesicle that fuses with the plasma membrane using energy in the form of ATP.

Facilitated diffusion

The net movement of substances from a high concentration to a lower concentration (down their concentration gradient) through transport proteins without the use of energy.

Fluid mosaic model

A model that describes membrane structure as a sea of mobile phospholipids studded with various proteins.

Hydrophilic

A molecule which is attracted to water.

Hydrophobic

A molecule which repels water.

Integral membrane protein

A type of protein bound to the membrane with strong interactions.

Osmosis

The net movement of water molecules across a partially permeable membrane from a region of high water potential to a region of lower water potential without the use of energy.

Peripheral membrane protein

A type of protein that is weakly bound to the surface of the membrane.

Phagocytosis

The ingestion of solid material (particularly pathogens and foreign material) by phagocytic cells.

Phospholipid

A type of lipid formed by the condensation of one molecule of glycerol, two molecules of fatty acid and a phosphate group.

Pinocytosis

The bulk uptake of liquids into the cell using energy in the form of ATP.

Plasmolysis

The effect produced by placing plant cells in a hypertonic solution causing the cell to shrivel from water loss, resulting in the membrane pulling away from the rigid cell wall.

Simple diffusion

The spreading out of substances from a high concentration to a lower concentration (down their concentration gradient) without the use of energy.

Turgid

A term used to describe a cell that is swollen due to large amounts of fluid uptake

Water potential

A measure of the tendency of water molecules to move from one area to another measured in kilopascals (kPa) and given the symbol Ψ.