S3IPBio_Notes_Movement of Substances

Cell Membrane

A boundary that separates the cell contents from the external environment, maintaining a constant internal environment.

Fluid Mosaic Model

A model describing the structure of cell membranes, where phospholipids move freely and proteins are embedded within the bilayer.

Phospholipids

Molecules that form the bilayer of cell membranes, consisting of hydrophilic heads and hydrophobic tails.

Passive Transport

Movement of substances across a membrane without energy, including simple diffusion, facilitated diffusion, and osmosis.

Simple Diffusion

The net movement of substances from a region of higher concentration to a region of lower concentration without energy.

Facilitated Diffusion

Movement of hydrophilic substances across a membrane with the help of transport proteins, down a concentration gradient.

Osmosis

The net movement of water molecules across a selectively permeable membrane from a region of less negative water potential to more negative water potential.

Active Transport

The movement of substances against a concentration gradient, requiring energy, often involving protein pumps.

Bulk Transport

The process of transporting large substances into or out of the cell, including endocytosis and exocytosis.

Endocytosis

The process of taking large substances into the cell by invagination of the cell membrane.

Exocytosis

The process of transporting large substances out of the cell, involving the fusion of vesicles with the cell membrane.

Turgor Pressure

The pressure exerted by the cell wall against the contents of a plant cell, maintaining its shape and firmness.

Isotonic Solution

A solution with the same water potential as the cytoplasm, resulting in no net movement of water.

Hypertonic Solution

A solution with a more negative water potential than the cytoplasm, causing water to move out of the cell.

Hypotonic Solution

A solution with a less negative water potential than the cytoplasm, leading to water moving into the cell.

Glycoproteins

Proteins with carbohydrate chains that aid in cell recognition and signaling.

Glycolipids

Lipids with carbohydrate chains that contribute to cell recognition and adhesion.

Cholesterol

A molecule interspersed within the phospholipid bilayer that regulates membrane fluidity.

Aquaporins

Channel proteins that facilitate the transport of water molecules across the cell membrane.

Concentration Gradient

The difference in concentration of a substance across a space, driving diffusion processes.