Cell Biology Lecture Notes

Overview of Cells

• Cells are the smallest living units of an organism.
• 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: The cell's genetic material.

Categories of Cells

• Eukaryotic Cells

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

• Prokaryotic Cells

  • Lack a nucleus or membrane-enclosed organelles.
  • Genetic material is not contained within a nucleus.
  • Unicellular organisms, e.g., bacteria.

Organelles and Their Functions

Nucleus

• Known as the control center of the cell.
• Contains DNA, which dictates cell function.
• Chromatin: Spread-out form of DNA inside the nuclear membrane.
• Chromosomes: Condensed DNA structures during cell division.
• Nucleolus: Site where ribosomes are made.

Ribosomes

• Synthesize or make proteins.
• Can be free-floating in the cytoplasm or attached to the Endoplasmic Reticulum (ER).

Endoplasmic Reticulum (ER)

• Rough ER: Has ribosomes attached.
• Smooth ER: Lacks ribosomes.
• Acts as a passageway for material transport.
• Proteins and materials emerge in vesicles and are sent to the Golgi apparatus.

Golgi Apparatus (Golgi Body)

• Customizes proteins into usable shapes or adds lipids/carbohydrates.

Vacuoles

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

Lysosomes

• Function as garbage collectors.
• Break down damaged or worn-out cell parts using enzymes.

Mitochondria

• Known as the powerhouse of the cell.
• Conduct cellular respiration to make ATP.
• Cells with higher energy needs have more mitochondria.

Cytoskeleton

• Maintains the cell's shape.
• Composed of microfilaments and microtubules.

Chloroplasts (in plants)

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

Cell Wall (in plants)

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

Special Structures in Some Cells

• Cilia: Microscopic hair-like projections in the respiratory tract, helps trap particles and expel them.
• Flagella: Tail-like structures aiding movement, found 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 organelles, e.g., bacteria.
• All cells share cell membrane, cytoplasm, and DNA.
• Mitochondria are present in both plant and animal cells, while chloroplasts are only in plant cells.