Membrane transport mechanisms Ultimate Study Guide

Solute

The substance that is dissolved in a solution.

Solvent

The substance that performs the dissolving and is present in the greater amount in a solution.

Passive Transport

Movement of substances across a membrane without using cellular energy.

Diffusion

The movement of molecules from an area of higher concentration to an area of lower concentration.

Facilitated Diffusion

Specialized passive transport involving the diffusion of molecules aided by membrane carrier proteins.

Osmosis

The movement of water molecules across a selectively permeable membrane towards an area of lower water concentration.

Isotonic Solution

A solution with the same solute concentration as the cytoplasm of a cell.

Hypertonic Solution

A solution with a higher solute concentration compared to the cytoplasm of a cell.

Hypotonic Solution

A solution with a lower solute concentration compared to the cytoplasm of a cell.

Active Transport

Physiological mechanism requiring cellular energy to move molecules against their concentration gradient.

Carrier-mediated Active Transport

Active transport through specialized transmembrane proteins that require energy.

Fixed Pore Theory

Proposes the existence of stationary pores formed by membrane proteins for transport.

Endocytosis

Process of taking extracellular material into a cell by engulfing it with the cell membrane.

Pinocytosis

Non-specific endocytosis of small droplets of extracellular fluid.

Phagocytosis

Endocytosis of large solid particles, forming a vacuole called a phagosome.

Exocytosis

Process of ejecting substances from a cell by fusing a cytoplasmic vacuole with the cell membrane.

Cyclosis

Active circular streaming of cytoplasm within a cell.

Surface Area to Volume Ratio

A critical factor limiting the maximum size of a cell, with implications for nutrient absorption and waste elimination.

Cell Division

The process required when a cell grows too large to maintain adequate surface area for nutrient uptake and waste removal.