Lipids, Membranes, & The First Cells

Flashcards covering key vocabulary from the lecture notes on lipids, membranes, and the first cells, including types of lipids, their structure, and membrane properties.

Lipids

A catchall term for hydrophobic, carbon-based molecules that are insoluble in water due to a high proportion of C-C or C-H bonds.

Hydrocarbons

Molecules composed solely of carbon and hydrogen atoms, forming nonpolar regions.

Fatty Acids

Lipids composed of a long nonpolar hydrocarbon tail and an acidic, hydrophilic carboxyl group, making them amphipathic.

Amphipathic

A characteristic of molecules possessing both hydrophilic (water-loving) and hydrophobic (water-fearing) regions.

Saturated Fatty Acids

Fatty acids where all carbon-carbon bonds are single bonds, allowing for a straight chain structure, typically solid at room temperature.

Unsaturated Fatty Acids

Fatty acids containing at least one carbon-carbon double bond, which creates a kink in the chain, typically liquid at room temperature.

Steroids

A type of lipid characterized by four carbon rings, a polar functional group, and a nonpolar hydrocarbon tail, serving as signaling molecules (hormones) and cell membrane components (e.g., cholesterol).

Triglycerides

Also known as fats or triacylglycerols, composed of a glycerol head group linked to three fatty acid tails, primarily serving as energy storage molecules.

Phospholipids

Amphipathic lipids consisting of a polar head group (glycerol linked to phosphate and a small organic molecule) and two nonpolar hydrocarbon tails, forming the primary components of cell membranes.

Micelles

Spherical structures spontaneously formed by single-chain fatty acids in water, where polar head groups interact with water and nonpolar tails associate internally.

Lipid Bilayers

Double-layered structures spontaneously formed by bulkier phospholipids in water, where polar heads face outward towards water and nonpolar tails form a hydrophobic interior, forming the basis of cell membranes.

Membrane Permeability

The ability of a solute to pass through a cell membrane, which acts as a selective barrier, allowing small, nonpolar molecules to diffuse freely, but restricting ions.

Factors Affecting Membrane Permeability

Temperature (higher increases), length of hydrocarbon tails (longer decreases), saturation of hydrocarbon tails (more saturated decreases), and cholesterol (reduces).

Cholesterol

A steroid component found in cell membranes that reduces the membrane's permeability.