Download Cell Transport Key Terms - Final

Cell Transport Key Terms
Active Transport: The movement of molecules across a membrane from low concentration to high
concentration (against its concentration gradient) with the input of chemical energy.
Cell Membrane: Phospholipid Bilayer, Hydrophilic Heads, Hydrophobic Tails, Proteins, Cholesterol
Endocytosis: The energy-using process by which cells absorb proteins (and other molecules) by
engulfing them.
Exocytosis: The energy-using process by which a cell directs the contents of vesicles out of the cell
membrane and into the extracellular space.
Facilitated Diffusion: The process by which molecules and ions are transported across the cell
membrane through channels in carrier proteins without the use of chemical energy.
Hydrophilic: Polar substances capable of interacting with water through hydrogen bonding.
Hydrophobic: Repulsion between water and nonpolar substances. (water fearing)
Hypertonic: Having a higher osmotic pressure than that of a specified solution.
Hypotonic: Having the lower osmotic pressure of two fluids.
Isotonic: Having the same osmotic pressure.
Osmosis: The spontaneous movement of solvent molecules through a partially permeable membrane
into a region of higher solute concentration.
Passive Transport: The movement of molecules across membranes from high concentration to low
concentration without an input of chemical energy. Three types of passive transport are Simple
Diffusion, Facilitated Diffusion, and Osmosis.
Phospholipid: A Phosphate Head with Diglyceride (2 Fatty Acid Chains) Tails
Selectively Permeable: To allow some molecules and ions through a membrane, but not all molecules
and ions.
Simple Diffusion: The process where a molecule passes through a membrane without the aid of an
integral membrane protein.
Suppose an animal or a plant cell is placed in a solution of sugar or salt in water:
1. If the medium is hypotonic — a dilute solution, with a higher water concentration than the cell
— the cell will gain water and swell up through osmosis.
2. If the medium is isotonic — a solution with exactly the same water concentration as the cell —
there will be no net movement of water across the cell membrane.
3. If the medium is hypertonic — a concentrated solution, with a lower water concentration than
the cell — the cell will lose water and shrink down by osmosis.