Chapter 7: Types of transport, diffusion, osmosis, membrane permeability

Integral Proteins:

Membrane proteins that penetrate deep into or span across the hydrophobic core of the lipid bilayer.

Peripheral Proteins

Membrane proteins bound loosely to the inner or outer surfaces of the membrane, often attached to integral proteins or the cytoskeleton.

Cholesterol

A steroid molecule embedded within the phospholipid bilayer that functions as a temperature buffer to stabilize membrane fluidity.

Glycoproteins & Glycolipids

Proteins or lipids bound to short carbohydrate chains on the outer surface of the cell membrane, serving primarily as cellular recognition markers ("ID tags").

Passive Transport

The movement of substances across a cell membrane down their concentration gradient without requiring cellular energy (ATP).

Concentration Gradient

A region along which the density or concentration of a chemical substance increases or decreases.

Simple Diffusion

The passive movement of small, nonpolar solute molecules directly through the lipid bilayer from high concentration to low concentration.

Facilitated Diffusion

The passive transport of polar molecules or charged ions across a membrane down their concentration gradient via specific transport proteins.

Osmosis

The diffusion of free water molecules across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Hypertonic Solution

A surrounding solution with a higher solute concentration compared to the inside of a cell, causing water to flow out of the cell.

Hypotonic Solution

A surrounding solution with a lower solute concentration compared to the inside of a cell, causing water to flow into the cell.

Isotonic Solution

A surrounding solution with an equal solute concentration compared to the inside of a cell, resulting in no net movement of water.

Plasmolysis

The phenomenon in plant cells placed in a hypertonic environment where the cytoplasm shrivels and the plasma membrane pulls away from the cell wall.

Turgid

The firm, healthy state of a plant cell when swollen with water from being in a hypotonic environment.

Crenation

The shriveling of an animal cell (such as a red blood cell) due to water loss in a hypertonic solution.

Lysis

The rupturing or bursting of a cell (especially an animal cell) caused by excess water intake in a hypotonic solution.

Aquaporin

A specialized channel protein in the plasma membrane that specifically facilitates the rapid movement of water molecules across the membrane.

Active Transport

The movement of a substance across a cell membrane against its concentration gradient, requiring transport proteins and cellular energy (ATP).

Sodium-Potassium Pump (Na+/K+) Pump

A primary active transport protein that uses ATP to pump 3 sodium ions out of the cell and 2 potassium ions into the cell against their concentration gradients.

Bulk Transport

The energy-requiring movement of large molecules, macromolecules, or large particles across the plasma membrane enclosed within vesicles.

Exocytosis

The cellular process where intracellular vesicles fuse with the plasma membrane to secrete or release materials out of the cell.

Endocytosis

The cellular process where the plasma membrane invaginates to engulf external materials and form new vesicles inside the cell.

Phagocytosis

A type of endocytosis ("cell eating") in which large solid particles, such as microbes or cellular debris, are engulfed by a cell.

Pinocytosis

A type of endocytosis ("cell drinking") in which droplets of extracellular fluid and dissolved solutes are non-specifically taken up by vesicles.

Receptor-Mediated Endocytosis

A highly specific type of endocytosis where target molecules (ligands) bind to surface receptors before the cell engulfs them.