Biology Semester 1: DNA and Proteins

DNA and Proteins

• Cell Theory:

  • All organisms are made of one or more cells.
  • The cell is the fundamental unit of life.
  • Cells arise only through division from preexisting cells.

• Basics of Cells:

  • Cells are the smallest units of life.
  • Cells are enclosed by a cell membrane.
  • They can reproduce, respond to environmental stimuli, and transform energy.
  • DNA is stored in the nucleus, varying by cell type.

Prokaryotic vs Eukaryotic Cells

• Characteristics:

  • Prokaryotic cells lack a nucleus and membrane-bound organelles.
  • Eukaryotic cells are more complex, larger (10-100 μm), and can be unicellular or multicellular.
  • Both cell types share:
    • Membrane enclosure
    • DNA as genetic material
    • Common metabolic pathways

• Prokaryotic Cells:

  • Size: 1-5 μm, typically unicellular.
  • Comprise bacteria and cyanobacteria.
  • Enclosed by plasma membrane and a rigid cell wall.
  • Have a single loop of double-stranded DNA with plasmids.
  • Include short projections (pili) and longer projections (flagella) aiding movement.

• Eukaryotic Cells:

  • More organized with specialized functions.
  • Comprised of various organelles with distinct roles ranging from chemical manufacture to energy processing.

Organelles and Their Functions

• Manufacture of Chemicals:

  • Organelles like the nucleus, ribosomes, and Golgi apparatus produce nucleic acids and proteins.

• Breakdown of Materials:

  • Lysosomes and vacuoles are responsible for the breakdown of materials, including foreign substances.

• Energy Processing:

  • Mitochondria and chloroplasts are involved in respiration and photosynthesis, respectively.

• Support and Communication:

  • Structures like the cytoskeleton, cell walls, and membrane surfaces support cell movement and communication.

Evolution of Organelles

• Some organelles, specifically mitochondria and chloroplasts, contain their own DNA, which is double-stranded and circular.
• A theory suggests they evolved from prokaryotic ancestors.

Structure and Function of DNA

• DNA contains the genetic code.
• It replicates to pass genetic information.
• Provides instructions for protein synthesis, crucial for building organisms and catalyzing biochemical reactions.

History of DNA Discovery

• Friedrich Miescher (1869):
  • Isolated nuclein from pus cells, rich in phosphorus; later known as nucleic acid.
• Rosalind Franklin (1952):
  • Contributed to understanding DNA structure through X-ray diffraction.
• Watson and Crick:
  • Proposed the double helix structure of DNA, further defining its role as genetic material.

This quiz covers the foundational concepts in Biology related to DNA structure and function as well as cell theory. It highlights the essential principles that govern cellular life and the significance of cells as basic units of life. Test your knowledge on these critical themes in biology and their implications for living organisms.