Chapter 4 - Cellular Transport

phospholipid

A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail.

equilibrium

A state of balance among the components of a system. This is the end result of diffusion.

cholesterol

A steroid that forms an essential component of animal cell membranes and helps to regulate the fluidity of the membrane. It is also a precursor to many important steroids.

phagocytosis

A type of endocytosis in which a cell ingests an extracellular solid and digests it.

pinocytosis

A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.

carrier protein

A type of transport proteins that moves substances across the membrane by changing shape. Can be used in both active and passive transport.

endocytosis

Active transport process of moving substances into a cell via formation of new vesicles from the plasma membrane. There are two types pinocytosis and phagocytosis.

exocytosis

Active transport process of moving substances/waste out of a cell via vesicles from the Golgi Apparatus.

isotonic

Describes a solution whose solute concentration is equal to the solute concentration inside a cell. Cells placed in this solution will remain the same size as water flows in and out equally.

diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

marker protein

Protein in the cell membrane that identifies the type of cell. Examples are antigens on the surface of red blood cells that identify ABO blood type.

channel protein

Protein with a pore that allows specific ions or other polar molecules to pass through the membrane.

transport protein

Proteins embedded in the membrane that allow molecules that cannot pass through the cell membrane (too large or polar) to pass through. Examples are ion channels and carrier proteins.

receptor protein

Proteins that transmit information in and out of cells. They allow communication between cells. Examples of proteins that receive neurotransmitters.

Passive transport

Requires NO energy, Movement of molecules from high to low concentration, Moves with the concentration gradient. There are two types - simple diffusion and facilitated diffusion.

active transport

The movement of a substance across a biological membrane against its concentration or electrochemical gradient with the help of energy input and specific transport proteins.

hypertonic

When comparing two solutions, the solution with the higher concentration of solute(s) and thus less free water molecules. Cells placed in this solution will shrink as water moves out of the cell.

hypotonic

When comparing two solutions, the solution with the lesser concentration of solute(s) and thus more free water molecules. Cells placed in this solution will swell as water moves into the cell.

sodium-potassium pump

a carrier protein that uses ATP to actively transport 3 sodium (Na+) ions out of a cell and 2 potassium (K+) ions into the cell

concentration

the amount of substance in a given volume or space

osmosis

the diffusion of water through a semi-permeable membrane