Chapter 7 - Cellular Plasma Membrane “Wall”

Phospholipids

Amphipathic molecules with a hydrophilic head and hydrophobic tails, arranged into a biological membrane bilayer.

Fluid Mosaic Model

The physical structure of the plasma membrane, where lipids form the fluid structure and proteins form a mosaic.

Unsaturated Tails

Fatty acid tails with kinks that prevent phospholipids from packing tightly, keeping the membrane oily.

Saturated Tails

Fatty acid tails that pack more tightly and smoothly, like butter.

Cholesterol

A fluidity buffer in animal cells that restrains phospholipids at high temperatures and prevents tight packing at low temperatures.

Integral Proteins

Proteins that penetrate into the hydrophobic core (also called transmembrane proteins).

Peripheral Proteins

Proteins loosely bound to the surface and attached to integral proteins.

Transport Proteins

Proteins that move things across the membrane and can change shape.

Enzymatic Activity

Proteins functioning as enzymes with active sites to carry out metabolic reactions.

Signal Transduction

A process where a receptor protein binds to a signaling molecule, changes shape, and relays a message to the inside of the cell.

Cell Recognition

Proteins (glycoproteins) that form ID badges to identify cells.

Intercellular Joinings

Proteins hooking onto each other to form connections between cells.

Attachment to Cytoskeleton and Extracellular Matrix

Proteins giving shape and coordinating inside and outside cellular activities.

Mouse Cells vs. Human Cells Theory

An experiment where labeled membranes with different fluorescent dyes were fused, showing that proteins intermingle.

Selective Permeability

The property of the membrane acting as a gatekeeper, allowing small non-polar molecules through while stopping charged or polar molecules.

Passive Transport

Transport that takes no energy and is driven by diffusion down a concentration gradient.

Osmosis

The diffusion of free water across the membrane from low solute to high solute concentration.

Facilitated Diffusion

Passive transport that is assisted by transport proteins.

Aquaporins

Channel proteins that let in billions of water molecules.

Antiporter

A transport protein that simultaneously transports two different molecules in different directions.

Tonicity

The effect of all the water movement that happens from osmosis.

Hypotonic Solution

An environment where water rushes into the cell; ideal for plant cells where turgid pressure keeps them standing up.

Active Transport

Transport that moves things against their concentration gradient (low to high), requires ATP, and uses carrier protein pumps.

Sodium-Potassium Pump

A massive active transport pump in animal cells that uses a third of cellular energy to maintain high potassium and low sodium inside.

Electrochemical Gradient

The combined effect of voltage (membrane potential) and concentration gradients across the membrane.

Cotransport

When downhill diffusion powers the uphill diffusion of another substance.

Exocytosis

Bulk shipping out; an internal vesicle fuses with the membrane to release contents and add new membrane material.

Endocytosis

Bulk transport taking things in by pinching off pieces of the cell membrane to form a new vesicle.

Phagocytosis

"Cellular eating"; when a cell extends pseudopods to wrap around a large particle.

Pinocytosis

"Cellular drinking"; when a cell gulps tiny droplets of extracellular fluid.

Receptor-Mediated Endocytosis

Endocytosis where a membrane has receptors for a specific substance, pinching inward to form a vesicle when enough bind.

Familial Hypercholesterolemia

A condition caused by defective receptors where cholesterol cannot properly get in and out of cells.