Eukaryotic Cell Organelles: Structure and Function
Cellular Components and Organelles
- Ribosomes and membrane-bound organelles: Each is devoted to a specific function. The nucleus, composed of genetic material surrounded by a membrane, is a specialized organelle.
- Cytoskeleton: A network of filaments and microtubules designed to maintain cellular shape and facilitate cell movement.
| Organelle | Structure | Function |
|---|---|---|
| Endoplasmic Reticulum (ER) Rough ER (RER) & Smooth ER (SER) | Complex network of tubules and vesicles. RER contains ribosomes; SER does not. | Produces and distributes substances (RER: proteins; SER: lipids). |
| Golgi Apparatus (Dictyosome) | Set of flat sacs stacked parallel to one another. | Secretes substances within vesicles. |
| Lysosomes | Spherical tiny vesicles containing digestive enzymes. | Digests organic matter acquired from the environment. |
| Vacuoles | Bags containing various substances. | Stores different cellular substances. |
Energy Organelles
These organelles produce the energy required for cellular processes. They possess two membranes—a smooth external membrane and a folded internal membrane containing specific enzymes. They contain their own DNA, allowing them to reproduce independently:
- Mitochondria: Produce energy from organic molecules via cellular respiration. Found in all eukaryotic cells.
- Chloroplasts: Produce organic molecules from inorganic matter and light energy via photosynthesis. Found in autotrophic eukaryotic organisms (plants and algae).
Motion Structures
Cells move using cytoplasm viscosity changes (pseudopods) or via flagella and cilia.
- Pseudopods: Cytoplasm elongations caused by viscosity changes, driven by cytoskeleton proteins.
- Cilia and Flagella: Mobile organelles attached to the cell membrane, consisting of a basal corpuscle and a microtubule-based structure.
- Centrosome: Composed of two perpendicular cylinders called centrioles (each made of nine sets of three microtubules). It regulates cilia, flagella, and chromosome movement during cell division.
The Nucleus
The nucleus is a specialized organelle. In eukaryotic cells, the genetic material is enclosed within a double membrane, forming the nucleus.