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: The cell's genetic material.

Types of Cells

Eukaryotic Cells

• Characterized by having organelles including a nucleus.
• Found in more complex organisms like plants and animals.

Prokaryotic Cells

• Lack a nucleus and membrane-enclosed organelles.
• Genetic material is not contained within a nucleus.
• Typically unicellular organisms, such as bacteria.

Organelles and Their Functions

Nucleus

• Serves as the control center of the cell.
• Contains DNA, which dictates the cell's functions.
• Includes chromatin (uncondensed DNA) and chromosomes (condensed DNA during cell division).
• Contains nucleolus, where ribosomes are made.

Ribosomes

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

Endoplasmic Reticulum (ER)

• Rough ER: Has ribosomes attached.
• Smooth ER: Lacks ribosomes.
• Transports materials, particularly proteins.

Golgi Apparatus

• Receives proteins and customizes them (e.g., folding, adding lipids/carbohydrates).

Vacuoles

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

Lysosomes

• Contain enzymes for breaking down damaged or worn-out cell parts ("garbage collectors").

Mitochondria

• Known as the powerhouse of the cell.
• Produces ATP through cellular respiration.
• More prevalent in cells that require more energy.

Cytoskeleton

• Maintains cell shape.
• Composed of microfilaments (protein) and microtubules (hollow tubes).

Chloroplasts (in plant cells)

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

Cell Wall (in plant cells)

• Provides additional support and protection outside the cell membrane.

Unique Structures in Some Cells

Cilia

• Microscopic hair-like projections.
• Found in the respiratory tract; help trap and expel inhaled particles.

Flagella

• Tail-like structures for movement.
• Found in some bacteria and in human sperm cells.

Summary

• Eukaryotic Cells: Found in plants and animals; have a nucleus and membrane-enclosed organelles.
• Prokaryotic Cells: Unicellular organisms lacking a nucleus.
• All cells share a cell membrane, cytoplasm, and genetic material.
• Chloroplasts are unique to plant cells, but mitochondria are present in both plant and animal cells.