1. Nucleus:
* Function: The control center of the cell, containing the cell's DNA in the form of chromosomes. It's responsible for:
* DNA replication: Copying the DNA for cell division.
* Transcription: Copying DNA into RNA.
* Ribosome synthesis: Produces ribosomes, which are essential for protein synthesis.
* Key Features: Surrounded by a double membrane (nuclear envelope) with pores allowing passage of molecules. Contains nucleolus where ribosomes are assembled.
2. Ribosomes:
* Function: The protein synthesis machinery of the cell, translating genetic code from mRNA into amino acid sequences to build proteins.
* Key Features: Found free in the cytoplasm or attached to the endoplasmic reticulum. Composed of ribosomal RNA (rRNA) and proteins.
3. Endoplasmic Reticulum (ER):
* Function: A network of interconnected membranes that plays a critical role in:
* Protein synthesis: Rough ER has ribosomes attached, producing proteins for secretion or use within other organelles.
* Lipid and steroid synthesis: Smooth ER lacks ribosomes and synthesizes lipids, steroids, and phospholipids.
* Detoxification: Smooth ER detoxifies harmful substances in the cell.
* Key Features: Extends throughout the cytoplasm. Rough ER has ribosomes attached to its surface, while smooth ER does not.
4. Golgi Apparatus:
* Function: A stack of flattened membrane-bound sacs (cisternae) that processes and packages proteins and lipids synthesized in the ER. It's involved in:
* Protein modification: Adds sugars, lipids, and other modifications to proteins.
* Sorting and packaging: Packages proteins and lipids into vesicles for transport to other organelles or for secretion.
* Key Features: Cis face receives proteins from the ER, and trans face releases packaged proteins in vesicles.
5. Lysosomes:
* Function: The "recycling center" of the cell, containing hydrolytic enzymes that break down waste materials, cellular debris, and engulfed bacteria or viruses.
* Key Features: Small, spherical organelles with a single membrane.
6. Mitochondria:
* Function: The powerhouse of the cell, responsible for cellular respiration, producing ATP (adenosine triphosphate) through the breakdown of glucose.
* Key Features: Double membrane-bound organelles with their own DNA and ribosomes. The inner membrane is folded into cristae, increasing its surface area for ATP production.
7. Peroxisomes:
* Function: Small, membrane-bound organelles that contain enzymes for various metabolic reactions, including:
* Lipid breakdown: Break down fatty acids.
* Detoxification: Remove harmful substances from the cell.
* Key Features: Contain oxidative enzymes, which produce hydrogen peroxide as a byproduct.
8. Vacuoles:
* Function: Large, fluid-filled sacs primarily involved in:
* Storage: Store water, nutrients, waste products, and pigments.
* Turgor pressure: Maintain cell shape in plants.
* Key Features: Larger and more prominent in plant cells than animal cells.
9. Cytoskeleton:
* Function: A network of protein fibers that provides structural support, facilitates movement, and aids in cell division.
* Key Features: Composed of three main types of filaments: microtubules, microfilaments, and intermediate filaments.
10. Centrioles:
* Function: Small, cylindrical structures involved in the formation of microtubules and the organization of spindle fibers during cell division.
* Key Features: Found only in animal cells.
Note: While these are the major organelles, other structures like the cell wall (in plants and fungi), cilia and flagella, and plastids (in plants) also play important roles in eukaryotic cells.
