B2.2.1 Organelles as discrete subunits of cells that are adapted to perform specific functions Notes

Organelles Are Discrete Subunits of Cells Adapted to Specific Functions

1. Recall unit A:
   1. Mitochondria: Have folded inner membranes (cristae) to provide a large surface area for energy production.
   2. Nucleus: Double membrane for DNA protection and organization.

What Defines an Organelle?

1. Not everything in the cell is an organelle.
2. To qualify:
   1. It must be a distinct structure.
   2. It must perform a specific job.
3. True Organelles: Nucleus, mitochondria, ribosomes, vesicles.
4. Not Organelles: Cytoplasm (it’s a fluid), cytoskeleton (a network of fibers), and cell wall (outside the cell).

Organelles Are Either Membrane-Bound or Non-Membrane-Bound

Membrane-Bound Organelles

1. Surrounded by membranes to create compartments for specialized functions.
2. Key Adaptations:
   1. Isolation: Keeps processes like ATP production separate.
   2. Optimal conditions: Lysosomes maintain acidity.
   3. Selective exchange: Membranes like nuclear pores allow selective entry/exit.

Non-Membrane-Bound Organelles

1. Lack membranes and are made mostly of proteins or RNA.

Why Are Organelles Necessary?

Organelles are essential for compartmentalization, enabling cells to:

1. Increase Efficiency: Concentrates enzymes and substrates for faster reactions.
2. Protect the Cell: Contains harmful processes, such as digestion in lysosomes.
3. Specialize Functions: Maintains unique environments, like the oxygen-rich matrix of mitochondria.

Tools Of Science Have Helped Us Study Organelles

1. Advances in technology have enhanced our understanding of organelles:
   1. Ultracentrifugation: Separates organelles based on density for biochemical studies.
   2. Electron Microscopy: Provides detailed images to reveal organelle structures.