Cell Biology Lecture Notes

Basic Characteristics of All Cells

• Smallest living units of an organism
• Common features in all cells:
  • Cell membrane: Separates inside of the cell from the environment
  • Cytoplasm: Jelly-like fluid inside the cell
  • DNA: Cell's genetic material

Categories of Cells

Eukaryotic Cells

• Have organelles including a nucleus
• More advanced and complex (e.g., plants, animals)

Prokaryotic Cells

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

Cell Organelles and Their Functions

Nucleus

• Control center of the cell
• Contains DNA (genetic material)
• DNA dictates cell functions and activities
• Chromatin: Tangled form of DNA inside nuclear membrane
• Chromosomes: Condensed DNA structures during cell division
• Nucleolus: Produces ribosomes

Ribosomes

• Synthesizes proteins
• Can be free-floating in cytoplasm or attached to the endoplasmic reticulum (ER)

Endoplasmic Reticulum (ER)

• Membrane-enclosed passageway for transporting materials
• Rough ER: Has ribosomes, involved in protein synthesis
• Smooth ER: No ribosomes, involved in lipid synthesis

Golgi Apparatus (Golgi Body)

• Receives, customizes, and packages proteins
• Modifies proteins by folding them or adding other materials (lipids, carbohydrates)

Vacuoles

• Sac-like structures for storage
• Plant cells: Central vacuole stores water

Lysosomes

• Garbage collectors: Digest worn-out cell parts
• Filled with enzymes that break down cellular debris

Mitochondria

• Powerhouse of the cell for both plant and animal cells
• Produces ATP via cellular respiration
• More mitochondria in cells requiring more energy

Cytoskeleton

• Maintains cell shape
• Includes microfilaments (protein threads) and microtubules (hollow tubes)

Chloroplasts (in Plant Cells)

• Organelle for photosynthesis
• Contains chlorophyll (green pigment)

Cell Wall (in Plant Cells)

• Provides shape, support, and protection
• Not found in animal cells

Unique Structures in Certain Cells

Cilia

• Found in respiratory tract cells
• Microscopic hair-like projections
• Move in waves to trap and expel inhaled particles

Flagella

• Found in some bacteria and sperm cells in humans
• Tail-like structure for movement

Summary

• Eukaryotic cells: Plant and animal cells with nucleus and organelles
• Prokaryotic cells: Unicellular organisms without nucleus and organelles
• Common features in all cells: cell membrane, cytoplasm, genetic material
• Plant cells have chloroplasts, but both plant and animal cells have mitochondria.