Lecture Notes: Introduction to Cells

Key Characteristics of All Cells

• Cells are the smallest living units of an organism.
• Common features across all cell types:
  • 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 nucleus and membrane-enclosed organelles.
  • Found in plants and animals.
  • More advanced and complex.
• Prokaryotic Cells
  • No nucleus or membrane-enclosed organelles.
  • Genetic material is not contained within a nucleus.
  • Always unicellular, such as bacteria.

Organelles and Their Functions

• Organelles

  • Specialized parts of a cell with unique jobs.

• Nucleus

  • Control center of the cell.
  • Contains DNA, which controls cell function.
  • Includes chromatin and nucleolus (where ribosomes are made).

• Ribosomes

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

• Endoplasmic Reticulum (ER)

  • Rough ER: Has ribosomes.
  • Smooth ER: No ribosomes.
  • Transports materials like proteins.

• Golgi Apparatus/Body

  • Modifies and packages proteins.

• Vacuoles

  • Sac-like structures for storage.
  • Plant cells have a central vacuole for water storage.

• Lysosomes

  • Contain enzymes for breaking down waste.

• Mitochondria

  • Powerhouse of the cell, producing energy (ATP).
  • Present in both plant and animal cells.

• Cytoskeleton

  • Maintains cell shape.
  • Includes microfilaments and microtubules.

• Chloroplasts (in plant cells)

  • Site of photosynthesis, contains chlorophyll.

• Cell Wall (in plant cells)

  • Provides structure and protection.
  • Not found in animal cells.

Unique Structures and Features

• Cilia: Hair-like projections in the respiratory tract.

  • Help trap particles and expel them.

• Flagella: Tail-like structure for movement.

  • Present in some bacteria and sperm cells.

Summary

• Eukaryotic cells have a nucleus and organelles, while prokaryotic cells do not and are unicellular.
• All cells have a cell membrane, cytoplasm, and DNA.
• Both plant and animal cells have mitochondria, but only plant cells have chloroplasts.