Cell Membrane Structure & Function

Aquaporins

Integral membrane proteins that serve as channels for the transport of water molecules.

Pump Proteins

Proteins that use energy from ATP to move molecules across cell membranes against their concentration gradient.

Glycolipids

Lipids with carbohydrate chains attached, important for cell recognition and interaction.

Fluid Mosaic Model

A model describing the structure of cell membranes, where lipids and proteins can move laterally within the layer, giving the membrane a flexible nature.

Selective Permeability

The property of cell membranes that allows certain molecules to enter or exit the cell while restricting others.

Cholesterol

A lipid molecule within the cell membrane that modulates its fluidity and stability.

Endocytosis

The process by which cells engulf substances from the external environment by forming vesicles.

Exocytosis

The process by which cells expel materials to the external environment by vesicles fusing with the plasma membrane.

Gated Ion Channels

Ion channels that open or close in response to specific stimuli, such as neurotransmitters or changes in voltage.

Sodium-Potassium Pump

A type of pump protein that uses ATP to exchange sodium and potassium ions across the cell membrane, crucial for maintaining cell membrane potential.

Membrane Fluidity

The viscosity of the lipid bilayer, influenced by the composition of fatty acids and cholesterol, allowing for membrane flexibility and the movement of embedded proteins and lipids.

Micelle

A spherical structure formed by amphipathic molecules in aqueous solutions, with hydrophobic tails inward and hydrophilic heads outward.

Liposome

A vesicle formed by a lipid bilayer, often used in drug delivery systems.

Polar

A molecule with an uneven distribution of charge, resulting in regions with slight positive and negative charges. These molecules typically interact well with water (hydrophilic).

Non-polar

A molecule with an even distribution of charge, lacking distinct positive or negative poles. These molecules do not interact well with water (hydrophobic).

Ions

Atoms or molecules that have gained or lost one or more electrons, resulting in a net positive or negative charge. Typically hydrophilic and cannot pass through the lipid bilayer without assistance from transport proteins.

Concentration Gradient

The difference in the concentration of a substance between two regions. Molecules tend to move from an area of higher concentration to an area of lower concentration along the gradient.

Amphipathic

A molecule that has both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions. Phospholipids are amphipathic, with hydrophilic heads and hydrophobic tails.

Hydrocarbon Chain

A chain of carbon atoms bonded to hydrogen atoms. These chains are hydrophobic and make up the tails of phospholipids in the lipid bilayer.

Adenosine Triphosphate (ATP)

The primary energy carrying molecule in cells. ATP provides energy for many cellular processes, including active transport across membranes.

Viscosity

A liquid's resistance to flowing (related to its density)

Lipid Bilayer

A double layer of phospholipids that forms the basic structure of all cell membranes, with hydrophilic heads facing outward and hydrophobic tails facing inward.

Phospholipid

A lipid molecule with a hydrophilic phosphate head and two hydrophobic fatty acid tails, essential for forming cell membranes.

Hydrophobic

Water-repelling; describes the fatty acid tails of phospholipids that avoid water.

Hydrophilic

Water-attracting; describes the phosphate heads of phospholipids that interact with water.

Integral Proteins

Proteins embedded in the lipid bilayer, spanning one or both layers, and involved in various functions such as transport and cell signalling.

Peripheral Proteins

Proteins attached to the surface of the lipid bilayer, involved in various functions like cell signalling and maintaining cell shape.

Simple Diffusion

The passive movement of molecules from an area of higher concentration to an area of lower concentration directly through the lipid bilayer.

Osmosis

The passive movement of water molecules across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Facilitated Diffusion

The passive movement of molecules across cell membranes through protein channels or carriers, without energy expenditure.

Active Transport

The movement of molecules across a cell membrane against their concentration gradient, requiring energy from ATP.

Channel Proteins

Proteins that form pores in the membrane to allow specific ions or molecules to pass through by facilitated diffusion.

Glycoproteins

Proteins with carbohydrate chains attached, playing roles in cell recognition and signalling.