Cell Membrane Structure and Transport Mechanisms: Key Concepts and Definitions

Selective Permeability

Membranes allow some substances to freely cross, while limiting the transport of others, this property is referred to as __.

Integral Membrane Proteins

Proteins that span the cell membrane, protruding into both the extracellular and intracellular space, are referred to as __.

Peripheral Membrane Proteins

Proteins that are associated with cell membranes, but not actually embedded within, are called __.

Diffusion

__ refers to the tendency of molecules to fill the volume available to them, driven by random molecular motion.

Osmosis

__ is the term for diffusion of water across a membrane.

Osmoregulation

Multicellular organisms invest a great deal of energy in maintaining the appropriate tonicity (solute content) of the extracellular environment. This is called __.

Hypertonic

An extracellular environment with a higher solute concentration than the cell is described as being __ to the cell.

Hypotonic

An extracellular environment with a lower solute concentration than the cell is described as being __ to the cell.

Isotonic

An extracellular environment with a solute concentration equal to that of the cell is described as being __ to the cell.

Passive

__ transport involves the diffusion of a substance down a concentration gradient with no further investment of cellular energy require.

Active

__ transport involves the movement of a substance against its concentration gradient with an input of cellular energy required, frequently in the form of ATP hydrolysis.

Sodium potassium pump

__ is a membrane transport protein that maintains a strong concentration gradient of sodium and potassium ions on opposite sides of the cell membrane, using the energy of ATP hydrolysis to do so.

Cotransporter

A membrane transport protein that moves one substance against its concentration gradient, using the energy provided by moving another substance down its concentration gradient is referred to as a __.

Endocytosis

The general term for transport of large molecules across the membrane into the cell by means of vesicles is __.

Exocytosis

The general term that describes the transport of bulky large molecules, like secreted proteins, across the membrane and out of the cell is __.

Membrane Potential

A difference in electrical charge across the cell membrane is called __.

Channel

A protein that forms a pore in the membrane through which a specific small molecule can flow down its concentration gradient into or out of the cell is called a __ protein.

Carrier

A protein that undergoes a shape change to move a specific small molecule down its concentration gradient into or out of the cell is called a __ protein.

Diffusion

Movement of small, non-polar molecules like carbon dioxide and oxygen across the membrane occurs by a process called __.

Facilitated Diffusion

Movement of small polar molecules across the membrane down their concentration gradient with the help of membrane proteins is referred to as __.

Fluid mosaics

Cellular membranes are composed of many different types of lipids and proteins that are not covalently bonded to one another, and therefore can move laterally. Because of these properties, membranes are described as being ____ _______ (two words).

Cotransport

____ describes the process by which two or more substances are moved across the cell membrane in the same direction, at the same time, by the same protein.