Cell Biology Lecture Notes

Introduction to 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

• Eukaryotic Cells:
  • Have organelles including a nucleus.
  • Found in plants and animals.
  • More advanced and complex.
• Prokaryotic Cells:
  • No nucleus or membrane-enclosed organelles.
  • Genetic material not contained within a nucleus.
  • Always unicellular (e.g., bacteria).

Organelles and Their Functions

Nucleus

• Known as the control center of the cell.
• Contains DNA or genetic material.
• Chromatin: Tangled form of DNA found inside the nuclear membrane.
• Chromosomes: Condensed DNA structures for cell division.
• Nucleolus: Structure where ribosomes are made.

Ribosomes

• Synthesize proteins.
• Float in cytoplasm or attach to the endoplasmic reticulum (ER).

Endoplasmic Reticulum (ER)

• Rough ER: Has ribosomes attached.
• Smooth ER: No ribosomes.
• Functions as a passageway for transporting materials like proteins.

Golgi Apparatus

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

Vacuoles

• Sac-like structures for storage (e.g., water in plant cells).

Lysosomes

• Garbage collectors that break down cellular debris using enzymes.

Mitochondria

• Powerhouse of the cell.
• Produce ATP during cellular respiration.
• Cells needing more energy have more mitochondria.

Cytoskeleton

• Maintains cell shape.
• Includes microfilaments and microtubules.

Chloroplasts (in plants)

• Site of photosynthesis.
• Contains chlorophyll, a green pigment.

Cell Wall (in plants)

• Provides shape, support, and protection.
• Absent in animal cells.

Unique Structures in Certain Cells

• Cilia: Microscopic, hair-like projections in respiratory tract cells; help trap particles.
• Flagella: Tail-like structures aiding cell movement (e.g., sperm cells and some bacteria).

Summary

• Eukaryotic cells: Plant and animal cells with nucleus and organelles.
• Prokaryotic cells: Unicellular organisms without a nucleus.
• All cells have a cell membrane, cytoplasm, and DNA.
• Plant cells have chloroplasts; both plant and animal cells have mitochondria.