AP bio 9-12 cell transport

Lipid Bilayer

A two-layered structure of the cell membrane made up of lipids with hydrophilic heads pointing outward toward the aqueous environment and hydrophobic tails oriented inward away from water.

Transport Protein

A membrane protein that moves molecules across the cell membrane.

Receptor Protein

A molecule that binds to a signaling molecule and triggers a response in a target cell.

Integral Membrane Protein

A protein that is permanently associated with the cell membrane and cannot be separated from the membrane experimentally without destroying the membrane itself.

Peripheral Membrane Protein

A protein that is temporarily associated with the lipid bilayer or with integral membrane proteins through weak noncovalent interactions.

Glycolipid

A carbohydrate that is covalently linked to a lipid.

Glycoprotein

A carbohydrate that is covalently linked to a protein.

Fluid Mosaic Model

A model proposing that the lipid bilayer is a dynamic structure that allows molecules to move laterally within the membrane and is a mosaic, or mixture, of several components, including lipids, proteins, and carbohydrates

Concentration Gradient

A difference in concentration of a substance, with regions of higher and lower concentration.

Passive Transport

The movement of molecules across a cell membrane by diffusion.

Facilitated Diffusion

Diffusion across a cell membrane through a transmembrane protein, such as a channel or carrier.

Channel Protein

A transport protein with a passage that allows the movement of molecules through it.

Carrier Protein

A transport protein that facilitates movement of molecules across a cell membrane.

Aquaporin

A channel protein that allows water to cross the cell membrane more readily than by diffusing through the lipid bilayer.

Active Transport

The movement of substances across a cell membrane against a concentration gradient requiring an input of energy.

Exocytosis

The process in which a vesicle fuses with the cell membrane and empties its contents into the extracellular space or delivers proteins to the cell membrane.

Endocytosis

The process in which a vesicle buds off from the cell membrane, bringing material from outside the cell into that vesicle, which can then fuse with other membranes.

Solute

A dissolved molecule such as the ions, amino acids, and sugars often found in a solvent such as water.

Molarity

The amount of a solute in a volume of solution, expressed as moles of a solute per liter of solution. Also called molar concentration.

Osmosis

The net movement of a solvent, such as water, across a selectively permeable membrane toward the side of higher solute concentration.

Water Potential

A parameter that combines all the physical and chemical factors that influence the movement of water, such as pressure, osmosis, and gravity; water moves from regions of higher water potential to regions of lower water potential.

Osmotic Pressure

The pressure needed to prevent water from moving from one solution into another by osmosis.

Tonicity

A measure of osmotic pressure; the higher the osmotic pressure, the higher the tonicity.

Hypertonic

Describes a solution having a higher solute concentration (lower water potential) than another solution.

Hypotonic

Describes a solution having a lower solute concentration (higher water potential) than another solution.

Isotonic

Describes a solution having the same solute concentration (same water potential) as another solution.

Contractile Vacuole

An organelle in some protists that actively takes up and expels water that enters the cell by osmosis.

Pressure Potential

The effect of pressure in the movement of water.

Osmoregulation

The regulation of water and solute levels to control osmotic pressure.

Symbiosis

A close interaction that has evolved between species that live together, often interdependently.

Endosymbiosis

A symbiosis in which one partner lives within the other.