Science 10: Cellular Transport C 2.1-2.4

Study Notes

The Cell Membrane as a Gate Keeper
- Cells are open systems, allowing matter and energy exchange between themselves and the environment.
- The cell membrane regulates this exchange through selective permeability, maintaining internal balance (homeostasis).
Cell Membrane Structure: The Fluid Mosaic Model
- Composed of a phospholipid bilayer with phosphate groups on each surface, creating a double lipid layer.
- Proteins, some with attached carbohydrates, are interspersed throughout the membrane.
Forms of Cellular Transport
- Passive Transport: Utilizes kinetic energy of molecules without external energy input.
- Active Transport: Requires energy (ATP) for movement against concentration gradients.
Energy and Concentration Gradients
- Concentration gradient defines the difference in molecule concentration inside vs. outside the cell.
- Moving from high to low concentration requires no energy; moving from low to high concentration requires energy (ATP).
Types of Passive Transport
- Diffusion: Spontaneous movement of particles from high concentration to low concentration, continuing until equilibrium is reached.
- Can be accelerated by increasing temperature or agitation.
Diffusion & The Particle Model of Matter
- Particles have large spaces between them and are in constant motion, with the least attraction in gases and most in solids.
Osmosis
- Defined as the diffusion of water through a semi-permeable membrane.
- Water movement depends on the tonicity of solutions:
  - Isotonic: Equal concentration (no net water movement).
  - Hypotonic: Less solute than cell (water enters cell).
  - Hypertonic: More solute than cell (water exits cell).
Facilitated Diffusion
- Occurs for water-soluble substances needing assistance through protein channels or carrier proteins.
- Movement is still from higher to lower concentration.
Types of Active Transport
- Active Transport with Carrier Proteins: Moves molecules from low to high concentration using energy.
- Endocytosis and Exocytosis: Processes for transferring large molecules that cannot pass through the membrane. Both require ATP.
  - Endocytosis: Intake of substances via vesicle formation.
    - Phagocytosis: Engulfment of larger molecules.
    - Pinocytosis: Engulfment of liquids and dissolved substances.
Additional Notes
- Various classroom activities include demonstrations, workbook assignments, and simulations to enhance understanding.
- Students may complete flow charts summarizing material transport across membranes.

Description

This quiz covers key concepts from Science 10 regarding cellular transport and the role of the cell membrane as a selective barrier. Students will explore the fluid mosaic model and the importance of homeostasis in cellular function. Test your understanding of how cells interact with their surroundings through regulated exchanges.