Cell Biology Lecture Notes

Introduction to Cells

• All living organisms consist of cells.
• Types of cells in the body:
  • Bone cells
  • Cartilage cells
  • Blood cells
  • Muscle cells
  • Nerve cells

Classification of Cells

1. Eukaryotic Cells

• Characteristics:
  • Have a double membrane-bound nucleus containing DNA.
  • Contain large, complex, membrane-bound organelles:
    • Mitochondria
    • Rough and smooth endoplasmic reticulum
    • Golgi complex
    • Chloroplasts (in plant cells)
  • Generally larger than prokaryotic cells.
  • Mostly multicellular, but some are unicellular (e.g., amoebas, paramecium, yeast).
  • DNA Structure:
    • DNA forms tightly bound and organized chromosomes in the nucleus.
  • Reproduction:
    • Mostly sexual reproduction with offspring having genetic material from both parents.

2. Prokaryotic Cells

• Characteristics:
  • Lack a nucleus; DNA found in a nucleoid.
  • Do not have membrane-bound organelles.
  • Smaller in size than eukaryotic cells.
  • Always unicellular organisms (e.g., bacteria and archaea).
  • DNA Structure:
    • Single loop of stable chromosomal DNA in the nucleoid.
  • Reproduction:
    • Asexual reproduction through binary fission, producing clone offspring.
• Metabolic Rate:
  • Larger surface area to volume ratio, resulting in higher metabolic and growth rates, and shorter generation times.

Similarities between Eukaryotic and Prokaryotic Cells

• Ribosomes: Present in both, but larger and more complex in eukaryotic cells.
• Cell Membrane:
  • Composed of phospholipids and proteins.
  • Acts as a barrier and selective gateway for materials.
• DNA: Provides genetic material for cell function and offspring inheritance, though structure varies.
• Cytoplasm:
  • Eukaryotic: Everything inside the cell but outside the nucleus.
  • Prokaryotic: Everything inside the cell membrane.
• Cytosol: Gel-like part of the cytoplasm where many metabolic processes occur.

Evolutionary Context

• Prokaryotes were the earliest life forms on Earth.
• Eukaryotes evolved later through evolutionary processes.

These notes summarize the key differences, similarities, and functions of eukaryotic and prokaryotic cells, providing a foundational understanding of cell biology.