Cell Biology Lecture Notes

Overview of Cells

• Cells are the smallest living units of organisms.
• All cells share three common components:
  • 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

Eukaryotic Cells

• Definition: More advanced, complex cells with organelles.
• Examples: Cells found in plants and animals.
• Characteristics:
  • Contains a nucleus.
  • Membrane-enclosed organelles.

Prokaryotic Cells

• Definition: Simpler cells without a nucleus or membrane-enclosed organelles.
• Examples: Unicellular organisms like bacteria.
• Characteristics:
  • Genetic material is not contained within a nucleus.
  • Always unicellular.

Organelles

• Definition: Specialized structures within a cell that perform unique functions.

Nucleus

• Function: Control center of the cell containing DNA.
  • Chromatin: Tangled form of DNA in the nucleus.
  • Chromosomes: Condensed DNA structures during cell division.
  • Nucleolus: Site where ribosomes are produced.

Ribosomes

• Function: Synthesizing proteins.
  • Can be free-floating in cytoplasm or attached to the endoplasmic reticulum (ER).

Endoplasmic Reticulum (ER)

• Types:
  • Rough ER: Has ribosomes attached and is involved in protein synthesis.
  • Smooth ER: Lacks ribosomes and is involved in the synthesis of lipids and detoxification.
• Function: Membrane enclosed passageway for transporting materials.

Golgi Apparatus (Golgi Body)

• Function: Modifies, sorts, and packages proteins for use in the cell.
  • Customize proteins by folding them and adding materials (lipids/carbohydrates).

Vacuoles

• Function: Sac-like structures that store materials.
  • In plant cells, the central vacuole stores water.

Lysosomes

• Function: Garbage collectors that break down damaged or worn-out cell parts.
  • Contains enzymes for breakdown of cellular debris.

Mitochondria

• Function: Powerhouse of the cell; site of cellular respiration.
  • Produces ATP molecules for energy.
  • More mitochondria in cells that require more energy.

Cytoskeleton

• Function: Maintains cell shape.
• Composed of:
  • Microfilaments: Thread-like proteins.
  • Microtubules: Thin, hollow tubes.

Chloroplasts

• Function: Site of photosynthesis in plant cells.
  • Contains chlorophyll, which gives it a green color.

Cell Wall

• Function: Provides shape, support, and protection for plant cells.
• Characteristic: Animal cells do not have a cell wall.

Unique Cell Features

• Cilia: Microscopic hair-like projections that help trap particles in the respiratory tract.
• Flagella: Tail-like structures that help some cells (e.g., sperm) move.

Summary

• Eukaryotic Cells: Have a nucleus and membrane-enclosed organelles (includes plant and animal cells).
• Prokaryotic Cells: Unicellular organisms without a nucleus or organelles.
• All cells have a cell membrane, cytoplasm, and genetic material.
• Both plant and animal cells have mitochondria, but only plant cells have chloroplasts.