Lecture Notes: Introduction to Cell Biology

Overview of Cells

• Cells are the smallest living units of an organism.
• Common Features of All Cells:
  • Cell Membrane: Separates the inside of the cell from its environment.
  • Cytoplasm: Jelly-like fluid inside the cell.
  • DNA: Genetic material of the cell.

Categories of Cells

1. Eukaryotic Cells

   • Have organelles, including a nucleus.
   • More advanced and complex.
   • Found in plants and animals.

2. Prokaryotic Cells

   • No nucleus or membrane-enclosed organelles.
   • Genetic material not contained in a nucleus.
   • Always unicellular (e.g., bacteria).

Organelles and Their Functions

• Organelles are specialized parts of a cell with unique functions.

The Nucleus

• Control Center: Contains DNA.
• Chromatin: Tangled, spread-out form of DNA inside the nuclear membrane.
• Chromosomes: Condensed DNA structures formed when a cell is ready to divide.
• Nucleolus: Produces ribosomes.

Ribosomes

• Synthesize proteins.
• Located in the cytoplasm or attached to the endoplasmic reticulum (ER).

Endoplasmic Reticulum (ER)

• Rough ER: Has ribosomes, involved in protein synthesis.
• Smooth ER: Lacks ribosomes.
• Transports materials like proteins.

Golgi Apparatus

• Customizes proteins by folding them or adding materials such as lipids or carbohydrates.

Vacuoles

• Sac-like structures for storage.
• Central Vacuole in plants stores water.

Lysosomes

• "Garbage collectors" that break down old cell parts with enzymes.

Mitochondria

• Powerhouse of the cell; creates ATP via cellular respiration.
• More abundant in cells needing more energy.

Cytoskeleton

• Maintains cell shape.
• Composed of microfilaments (proteins) and microtubules (hollow tubes).

Chloroplasts

• Found in photoautotrophic organisms (e.g., plants).
• Site of photosynthesis; contains chlorophyll.

Additional Cell Structures

• Cell Wall: Provides shape and protection; only in plant cells.
• Cilia: Hair-like projections for movement and trapping particles.
• Flagella: Tail-like structures for movement; present in some bacteria and human sperm cells.

Summary

• Eukaryotic cells have a nucleus and organelles; found in plants and animals.
• Prokaryotic cells are unicellular without a nucleus or membrane-bound organelles.
• All cells share certain features: a cell membrane, cytoplasm, and genetic material.
• Plant cells have chloroplasts, and both plant and animal cells have mitochondria.