Cell Membranes

Vocabulary flashcards for Cell Membranes lecture.

Hydrophilic

Water-loving; carbohydrates; requisite for rapid transport/distribution

Hydrophobic

No hydrogen bonds; water-fearing; lipids (fats)

Cell (plasma) membrane

The barrier between intracellular and extracellular fluids, made of lipids, phospholipids, cholesterol, glycolipids, and proteins.

Glycocalyx

Layer of carbohydrates on the extracellular face of the membrane

Microvilli

Fingerlike projections to increase surface area

Membrane Proteins

Allow transport across the membrane, signaling, adhesion, identification, and enzymatic activity. Can be integral or peripheral.

Receptor

A protein that binds to chemical messengers such as hormones sent by other cells

Enzyme

An enzyme that breaks down a chemical messenger and terminates its effect

Channel

A channel protein that is constantly open and allows solutes to pass into and out of the cell.

Gated channel

A gate that opens and closes to allow solutes through only at certain times; many are also receptors.

Cell-identity marker

A glycoprotein acting as a cell-identity marker distinguishing the body's own cells from foreign cells.

Cell-adhesion molecule (CAM)

A cell-adhesion molecule (CAM) that binds one cell to another.

Diffusion

Solutes move randomly in solution from high concentration to low concentration until equilibrium is reached.

Protein Mediated Transport

Impermeable molecules can be moved using channels or carriers (transporters); proteins provide a suitable environment

Channels

Open when electricity activates (voltage gated channel) or when a substrate (molecule) binds and activates

Passive Transport

Passive transport mechanisms allow solutes to flow down their concentration gradients towards equilibrium. No energy expended.

Active Transport

Active transport mechanisms transport solutes UP their concentration gradients; energy dependent; creates/maintains concentration gradients

Types of Active Transport

ATP is used as the energy source, or a secondary ion gradient is used as the energy source (typically Na+)

Carriers vs Channels

Aids in the movement of solutes across the membrane, channels are fast, carriers are slow. Channels can only transport substance down their gradients; carriers can transport larger solutes and saturate.

Osmosis

The diffusion of water from low solute to high solute concentration.

Osmotic pressure

The force of water due to osmosis that depends on relative solute concentrations.

Osmotic Pressure

The force of water due to osmosis; terms to describe relative solute concentrations

Aquaporins

Channels that increase water permeability, important in urine formation

Vesicular Transport

An intracellular container, used to move/isolate molecules from the regular activity of the cell

Exocytosis

Vesicles move from the inside to the outside

Endocytosis

Bringing materials into the cell using membrane bound vesicles

Pinocytosis

Cells bring in small amounts of extracellular fluid by forming vesicles

Phagocytosis

Cells bring in large particles that it encounters; limited to specialized cells

Receptor mediated endocytosis

Receptors detect target molecules and bring them into the cell through endocytosis