#biology #basicbiology #cellstructure

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Eukaryotic Cells

Eukaryotic cells are more complex and larger than prokaryotic cells. They have a true nucleus and membrane-bound organelles. The main components of a eukaryotic cell include:

1. Plasma Membrane

• Function: Regulates the movement of substances in and out of the cell.

• Composition: Phospholipid bilayer with embedded proteins.

2. Cytoplasm

• Function: Site of metabolic activities.

• Composition: Gel-like substance containing water, enzymes, nutrients, wastes, and gases.

3. Nucleus

• Function: Contains the cell's genetic material and controls cellular activities.

• Composition: Enclosed by the nuclear envelope, contains chromatin (DNA and proteins) and nucleolus (site of ribosome synthesis).

4. Ribosomes

• Function: Synthesize proteins.

• Composition: Made of RNA and proteins; can be free in the cytoplasm or attached to the endoplasmic reticulum.

5. Endoplasmic Reticulum (ER)

• Function: Synthesizes and processes proteins (rough ER) and lipids (smooth ER).

• Composition: Network of membranous tubules and sacs.

6. Golgi Apparatus

• Function: Modifies, sorts, and packages proteins and lipids for transport.

• Composition: Stacks of flattened membranous sacs.

7. Mitochondria

• Function: Produce ATP through cellular respiration.

• Composition: Double membrane, with the inner membrane folded into cristae.

8. Lysosomes

• Function: Digest and recycle cellular waste and foreign materials.

• Composition: Membrane-bound vesicles containing hydrolytic enzymes.

9. Peroxisomes

• Function: Break down fatty acids and detoxify harmful substances.

• Composition: Membrane-bound vesicles containing oxidative enzymes.

10. Cytoskeleton

• Function: Maintains cell shape, facilitates cell movement, and organizes cell components.

• Composition: Network of protein fibers (microfilaments, intermediate filaments, and microtubules).

11. Chloroplasts (in plant cells)

• Function: Conduct photosynthesis to convert light energy into chemical energy.

• Composition: Double membrane, with internal thylakoid membranes.

12. Cell Wall (in plant cells, fungi, and some protists):

• Function: Provides structural support and protection.

• Composition: Made of cellulose in plants, chitin in fungi, and various other substances in protists.

13. Vacuoles

• Function: Store nutrients, and waste products, and help maintain turgor pressure.

• Composition: Membrane-bound sacs, large central vacuole in plant cells.

Prokaryotic Cells

Prokaryotic cells are simpler and smaller than eukaryotic cells. They lack a true nucleus and membrane-bound organelles. The main components of a prokaryotic cell include:

1. Cell Wall

• Function: Provides structural support and protection.

• Composition: Made of peptidoglycan in bacteria; varies in archaea.

2. Plasma Membrane

• Function: Regulates the movement of substances in and out of the cell.

• Composition: Phospholipid bilayer with embedded proteins.

3. Cytoplasm

• Function: Site of metabolic activities.

• Composition: Gel-like substance containing water, enzymes, nutrients, wastes, and gases.

4. Ribosomes

• Function: Synthesize proteins.

• Composition: Made of RNA and proteins.

5. Nucleoid

• Function: Contains the cell's genetic material.

• Composition: Region in the cytoplasm where the DNA is located, not enclosed by a membrane.

6. Plasmids

• Function: Carry additional genetic information that can confer advantages such as antibiotic resistance.

• Composition: Small, circular DNA molecules.

7. Flagella and Pili

• Function: Movement (flagella) and attachment to surfaces or other cells (pili).

• Composition: Protein structures.