Chapter 6 - Lipids, Membrane, and the First Cells

Lipids

Molecules that store energy, act as signals, serve as pigments, form coatings, and serve in cellular processes.

Hydrophobic

Not soluble in water; describes nonpolar substances.

Amphipathic

Molecules that contain both hydrophobic and hydrophilic elements.

Phospholipid

A lipid consisting of a glycerol backbone, two fatty acids, and a phosphate group; crucial for forming cell membranes.

Selective Permeability

The property of cellular membranes that allows certain substances to pass through while blocking others.

Saturated Fatty Acids

Fatty acids that contain only single C—C bonds, solid at room temperature.

Unsaturated Fatty Acids

Fatty acids containing one or more double bonds; liquid at room temperature due to kinks in the structure.

Osmosis

The diffusion of water across a selectively permeable membrane from a region of low solute concentration to a region of high solute concentration.

Diffusion

The process of solutes moving from an area of higher concentration to an area of lower concentration.

Facilitated Diffusion

The process by which specific molecules pass through a membrane via a channel or carrier protein without energy expenditure.

Transmembrane Proteins

Integral proteins that span the membrane and are involved in transporting molecules across the membrane.

Hydrocarbon Chains

Long chains of carbon and hydrogen found in lipids, influencing their properties like fluidity and permeability.

Ester Linkages

Bonds formed between glycerol and fatty acids in fats, important for their structure.

Fluid-Mosaic Model

A model describing the cellular membrane as a mosaic of various components, including phospholipids and proteins, that move freely.

Active Transport

The movement of molecules against their concentration gradient, requiring energy in the form of ATP.

Channel Proteins

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

Carrier Proteins

Proteins that change shape to transport substances across a membrane during facilitated diffusion.

Sodium-Potassium Pump

A type of active transport mechanism that pumps sodium out of the cell and potassium into the cell, maintaining gradients.

Micelle

A structure formed by phospholipids in solution, where the hydrophobic tails face inward and the hydrophilic heads face outward.

Glycerol

A three-carbon alcohol that forms the backbone of triglycerides and phospholipids.

Hydrophilic

Water-attracting; describes substances that interact well with water.

Chemical Gradient

A difference in the concentration of a substance across a space, leading to movement toward equilibrium.