Chapter 3: The Cell and its Enviornment

Water

The universal solvent, which makes up 85% of living cells and can dissolve almost all substances needed for life.

Solutes

Substances dissolved in solvents, which together with solvents create a solution.

Plasma membrane

A double layer of phospholipid molecules embedded with globular proteins; a semi-permeable barrier that regulates molecular passage in and out of the cell.

Diffusion

The process by which solutes move naturally, either into or out of a cell, without requiring energy; includes passive transport.

Passive transport

The movement of molecules into a cell that requires no energy, often occurring through diffusion.

Active transport

The energy-requiring process of moving molecules from an area of low concentration to high concentration.

Osmosis

The passive diffusion of water molecules across a membrane.

Hypertonic

A solution that is more concentrated than another solution.

Hypotonic

A solution that is less concentrated than another solution.

Isotonic

A solution where the concentration is equal to another solution.