Lecture+5+Biomembranes+%2C+protein+membranes%2C+ions+and+molecules+transport+across+membranes++winter+2025

Phospholipids

Molecules consisting of a glycerol, two fatty acids, and a phosphate group, which spontaneously form bilayers in water.

Fluid Mosaic Model

A model describing the membrane structure as a dynamic mosaic of phospholipids and proteins.

Diffusion

The process by which substances move from an area of higher concentration to an area of lower concentration.

Osmosis

The movement of water across a semipermeable membrane from areas of low solute concentration to areas of high solute concentration.

Active Transport

The movement of ions or molecules across a membrane against a concentration gradient, requiring energy.

Passive Transport

The movement of substances across a membrane without the need for energy input, occurring along the concentration gradient.

Steroids

A class of lipids characterized by a bulky, four-ring structure, with varying functional groups.

Hydrophobic

Repelling water; lipids are primarily hydrophobic due to their nonpolar bonds.

Integral membrane proteins

Proteins that span the lipid bilayer, facilitating various functions such as transport.

Cholesterol

A lipid that stabilizes the fluidity of cell membranes and reduces permeability.

Sodium–Potassium Pump

An important protein that uses ATP to transport Na+ out of the cell and K+ into the cell against their concentration gradients.

Aquaporins

Channel proteins that facilitate the passive transport of water across cell membranes.

Lipids

Carbon-containing compounds that are hydrophobic and include fats, phospholipids, and steroids.

Micelles

Spherical aggregates of amphipathic molecules that are formed in aqueous environments.

Facilitated Diffusion

A form of passive transport where transmembrane proteins assist molecules in crossing the membrane.

Permeability

The ability of substances to pass through a membrane; influenced by factors such as lipid composition and temperature.

Macromolecules

Large complex molecules, including proteins, lipids, carbohydrates, and nucleic acids, that play vital roles in cells.