Biology notes

Prokaryotes and Eukaryotes

• Prokaryotes: Organisms without a membrane-bound nucleus.

  • Include Bacteria and Archaea.

  • Typically unicellular with circular DNA and no organelles.

  • Size: 1-2 micrometers (µm).

• Eukaryotes: Organisms with a membrane-bound nucleus.

  • Include Fungi, Plantae (plants), and Animalia (animals).

  • Can be unicellular or multicellular with linear DNA.

  • Contain membrane-bound organelles (MBO).

Size Measurement

• Units of Measurement:

  • 1 meter (m) = 100 centimeters (cm)

  • 1 mm = 1000 micrometers (µm)

  • 1 µm = 1,000 nanometers (nm)

  • 1 nm = 10^-9 m.

Atoms and Bonds

• Atomic Structure:

  • Central nucleus containing protons (+) and neutrons (neutral).

  • Electrons (-) orbiting around the nucleus.

• Influence of Atoms:

  • Hydrogen (H) and Carbon (C) are common elements in biological molecules.

• Types of Bonds:

  • Ionic Bonds: Formed by the transfer of electrons (e.g., NaCl).

  • Covalent Bonds: Formed by the sharing of electrons.

    • Polar Covalent Bonds: Unequal sharing (e.g., between Oxygen (O) and Hydrogen (H)).

    • Non-polar Covalent Bonds: Equal sharing of electrons.

Electronegativity and Bond Formation

• Electronegativity: An atom's ability to attract electrons.

  • Higher electronegativity indicates stronger attraction (e.g., Oxygen more electronegative than Hydrogen).

• Polar Covalent Bond Formation:

  • When O and H bond, O becomes partially negative and H becomes partially positive.

  • Example of a condensation reaction: Water is removed to form a bond (dehydration synthesis).

• Hydrolysis: Process that breaks bonds between monomers by adding water.

Microorganisms Overview

• Archaea and Bacteria:

  • Typically smaller cells (1-2 micrometers).

  • These are essential organisms in various ecosystems.

Lipids

• Diversity of Lipids:

  • Lipids are hydrophobic (water-repellent) and amphipathic (contain both hydrophilic and hydrophobic parts).

  • Do not form polymers like carbohydrates or proteins.

• Types of Lipids:

  • Fats and Oils: Serve as long-term energy storage.

  • Phospholipids: Major components of cell membranes.

  • Steroids: Important components of plasma membranes, including hormones.

  • Waxes: Provide protection and prevent water loss (e.g., plant cuticles).