Cell Biology Lecture

Introduction to Cells

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

Categories of Cells

Eukaryotic Cells

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

Prokaryotic Cells

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

Organelles and Their Functions

• Organelles: Specialized parts of a cell

Nucleus

• Control center of the cell
• Contains DNA (genetic material)
• Chromatin: Spreads out form of DNA inside nuclear membrane
• Chromosomes: Condensed DNA structures during cell division
• Nucleolus: Where ribosomes are made

Ribosomes

• Synthesize proteins
• Can be free in cytoplasm or attached to endoplasmic reticulum (ER)

Endoplasmic Reticulum (ER)

• Membrane-enclosed passageway for transporting materials
• Types of ER:
  • Rough ER: Has ribosomes attached
  • Smooth ER: No ribosomes attached

Golgi Apparatus (Golgi Body)

• Customizes proteins from ER
• Folds proteins into usable shapes
• Adds materials like lipids or carbohydrates

Vacuoles

• Sac-like structures storing different materials
• Central vacuole in plants stores water

Lysosomes

• Garbage collectors
• Filled with enzymes to break down cell debris

Mitochondria

• Powerhouse of the cell (both animal and plant cells)
• Perform cellular respiration to make ATP (energy)
• Cells requiring more energy have more mitochondria

Cytoskeleton

• Maintains cell shape
• Includes microfilaments (proteins) and microtubules (thin hollow tubes)

Chloroplasts

• Present in photoautotrophic organisms (like plants)
• Site of photosynthesis
• Contains chlorophyll (green pigment)

Cell Wall (Plant Cells)

• Outside the cell membrane
• Shapes, supports, and protects the cell
• Not present in animal cells

Unique Cellular Structures

• Cilia: Hair-like projections in respiratory tract (trap particles, aid in expulsion)
• Flagella: Tail-like structure aiding cell movement (e.g., sperm cells in humans, some bacteria)

Summary

• Eukaryotic cells: Plant and animal cells with a nucleus and organelles
• Prokaryotic cells: Unicellular with no nucleus or membrane-enclosed organelles
• All cells have a cell membrane, cytoplasm, and genetic material
• Plant cells have chloroplasts; both plant and animal cells have mitochondria