Cellular Transport Overview

Cellular Transport Overview

• Cellular transport is the movement of substances into and out of cells.
• Two main types: passive and active transport.

Passive Transport

• Does not require energy (ATP).
• Movement of substances down a concentration gradient (from high to low concentration).
• Three types:
  • Diffusion: Movement of small, uncharged particles (e.g., oxygen, carbon dioxide, lipids) across a permeable membrane from high to low concentration, until equilibrium is reached. No energy required. Dynamic equilibrium occurs when there is continuous movement but no overall change.
  • Facilitated diffusion: Movement of large or charged particles (e.g., glucose, ions, some water) across a membrane through protein channels. No additional energy required. There are two types of proteins involved - channel proteins and carrier proteins.
  • Osmosis: Diffusion of water across a selectively permeable membrane from areas of high water concentration to areas of low water concentration.

Active Transport

• Requires energy (ATP).
• Movement of substances against a concentration gradient (from low to high concentration).
• Types:
  • Molecular Transport/Protein Pumps: Using ATP, protein pumps move molecules across a membrane against the concentration gradient (e.g., Sodium-Potassium Pump).
  • Bulk Transport: Moving large particles across the membrane via endocytosis (entering the cell) and exocytosis (exiting the cell).

Osmotic Solutions

• Isotonic: Solute and solvent concentrations are equal.
• Hypertonic: Higher concentration of solutes than the cell content.
• Hypotonic: Lower concentration of solutes than the cell content.

Key Concepts

• Cells need to take in nutrients, eliminate waste, and communicate with each other.
• The cell membrane controls which materials move in and out of the cell.