Lecture Notes: Cell Membranes and Transport
Introduction
- Cells are like nightclubs: selectively permeable.
- Allow necessary substances in, expel unneeded ones.
- Importance: Cell communication and regulation.
Types of Transport
Passive Transport
- Definition: Movement without energy.
- Examples:
- Oxygen and water use passive transport.
- Diffusion: Movement from high to low concentration.
- Osmosis: Diffusion of water across a membrane.
- Isotonic, Hypertonic, Hypotonic:
- Isotonic: Equal concentration inside and outside.
- Hypertonic: Higher concentration inside.
- Hypotonic: Lower concentration inside.
Active Transport
- Definition: Requires energy (ATP) to move substances.
- Example: Sodium-potassium pump.
- Vital for energy-demanding cells like muscle and brain cells.
- ATP (Adenosine Tri-Phosphate):
- The energy currency of the cell.
- Used to power transport proteins.
Transport Mechanisms
Channel Proteins
- Allow substances like water and ions to pass without energy.
- Aquaporins: Specific channels for water.
Sodium-Potassium Pump
- Discovery: Jens Christian Skou in the 1950s.
- Works against concentration and electrochemical gradients.
- Involves pumping out sodium and bringing in potassium.
- Essential for nerve function.
Vesicular Transport (Cytosis)
- Definition: Active transport using vesicles.
- Types:
- Exocytosis: Transport materials out of the cell.
- Endocytosis: Transport materials into the cell.
- Phagocytosis: "Devouring cell action" for large particles.
- Pinocytosis: "Drinking action" for dissolved substances.
- Receptor-Mediated Endocytosis: Specific molecules are absorbed based on receptors.
Conclusion
- Cell transport is crucial for maintaining homeostasis.
- Different mechanisms ensure cells acquire nutrients and expel waste efficiently.
- Engage with additional resources for deeper understanding.
Review and Further Questions:
- Visit linked resources for detailed explanations.
- Engage with community and instructors for clarifications.