Molecular Movement and Membrane Transport

Ions: Atoms with a net charge.
- Cations: Positively charged ions.
- Anions: Negatively charged ions.

Phospholipid Structure:
- Composed of hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.
- Amphiphilic Properties: The molecule possesses both hydrophilic and hydrophobic regions, crucial for membrane formation.
Protein Structure: Integral and peripheral proteins play roles in transport, reception, and signaling.

Solution: A liquid mixture of two or more substances.
Solute: The substance being dissolved (e.g., salt).
Solvent: The dissolving medium (e.g., water).
- Water as "Solvent of Life": Its polarity allows it to dissolve many substances, including polar molecules and ions.

Definition: Movement of molecules along a concentration gradient, from areas of high to low concentration.
Factors Affecting Diffusion:
- Temperature: Higher temperatures increase kinetic energy, leading to faster diffusion.
- Phase: Diffusion occurs in gases and liquids.
Example: Simulation available at PhET Diffusion Simulation.

Definition: A special form of diffusion specifically for water, moving through aquaporins.
Direction of water movement:
- From high water concentration (low solute concentration) to low water concentration (high solute concentration).

Definition: Refers to the relative concentrations of dissolved solutes on either side of a cell membrane, which affects the movement of water.

Regulation of Material Movement: Cells control ion and molecule transport through the membrane.

Passive Transport:
- Relies on diffusion and the random movement of molecules without energy expenditure.
- Types:
- Simple Diffusion: Movement without assistance.
- Facilitated Diffusion: Involves specific molecules like carrier and channel proteins.
  - Carrier Proteins: Change shape to transport substances (e.g., uniporters, symporters, antiporters).
  - Channel Proteins: Form channels for substances, e.g., aquaporins for water.
Active Transport:
- Requires energy (ATP) to move substances against their concentration gradients.
- Types:
- Primary Active Transport: Directly uses ATP to move ions.
- Secondary Active Transport: Utilizes the electrochemical gradient established by primary active transport to move other substances.
- Transport Ports: Classified by
- Number of types of molecules transported (e.g., uniport, co-transport).
- Direction of transport (e.g., antiporter - opposite directions; symporter - same direction).

Fick's Law of Diffusion: Describes the diffusion rate proportional to the concentration gradient.
Osmolarity: Concentration of solute particles in a solution.
Electrochemical Gradient: A gradient that combines both the concentration gradient and the electrical gradient across a membrane, influencing the movement of ions.