Organelles Are Discrete Subunits of Cells Adapted to Specific Functions
Definition
Organelles
Organelles are structures inside cells that perform specific jobs to keep the cell alive. Their form suits their function perfectly.
- Recall unit A:
- Mitochondria: Have folded inner membranes (cristae) to provide a large surface area for energy production.
- Nucleus: Double membrane for DNA protection and organization.
Organelles as a Factory:
- Nucleus: "Manager's office" – stores instructions (DNA).
- Ribosomes: "Assembly line workers" – build proteins.
- Mitochondria: "Powerhouse" – generates energy.
- Golgi Apparatus: "Shipping department" – packages and ships materials.
- Lysosomes: "Waste disposal" – breaks down waste.
- Vesicles: "Delivery trucks" – transport materials.
- Chloroplasts (plants only): "Solar panels" – convert sunlight into energy.
What Defines an Organelle?
- Not everything in the cell is an organelle.
- To qualify:
- It must be a distinct structure.
- It must perform a specific job.
- True Organelles: Nucleus, mitochondria, ribosomes, vesicles.
- Not Organelles: Cytoplasm (it’s a fluid), cytoskeleton (a network of fibers), and cell wall (outside the cell).
Acronyms to Remember Membrane-Bound Organelles: MEN Double Trouble
- M: Mitochondria
- E: Endoplasmic reticulum
- N: Nucleus
- Double Trouble: Double membrane structures (Nucleus, Mitochondria, Chloroplasts).
Organelles Are Either Membrane-Bound or Non-Membrane-Bound
Membrane-Bound Organelles
- Surrounded by membranes to create compartments for specialized functions.
- Key Adaptations:
- Isolation: Keeps processes like ATP production separate.
- Optimal conditions: Lysosomes maintain acidity.
- Selective exchange: Membranes like nuclear pores allow selective entry/exit.
