Biology Chapter on Elements and Macromolecules

Common Elements in Cells

• Major elements include carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur (CHONPS).
• These elements are essential for forming the structures and functions of biological molecules.

Classes of Macromolecules

• Four main classes: carbohydrates, lipids, proteins, and nucleic acids.
• Corresponding monomers:
  • Carbohydrates: monosaccharides (e.g., glucose)
  • Lipids: fatty acids and glycerol
  • Proteins: amino acids
  • Nucleic acids: nucleotides

Electronegativity and Bond Types

• Electronegativity refers to an atom’s ability to attract electrons in a chemical bond.
• Differences in electronegativity determine bond types:
  • Nonpolar covalent bonds: difference of 0 to 0.4 (e.g., H₂)
  • Polar covalent bonds: difference of 0.5 to 1.7 (e.g., H₂O)
  • Ionic bonds: difference greater than 1.7 (e.g., NaCl)

Behavior of Molecules in Water

• Nonpolar covalent molecules (e.g., oils) do not mix with water; they are hydrophobic, meaning they repel water.
• Polar covalent molecules (e.g., sugars and salts) dissolve in water due to interaction with water molecules, classified as hydrophilic.

Hydrophobic vs. Hydrophilic Molecules

• Hydrophobic molecules are typically nonpolar and do not interact well with water, avoiding it.
• Hydrophilic molecules are polar or ionic, allowing them to form hydrogen bonds with water.

Water Molecule Structure

• Water (H₂O) consists of two hydrogen atoms and one oxygen atom connected by covalent bonds.
• Hydrogen bonds occur between water molecules, resulting in unique properties like cohesion and surface tension.

Contrast of Bond Types

• Covalent bonds: electrons are shared between atoms; strong and stable.
• Ionic bonds: transfer of electrons between atoms leads to electrostatic attraction; usually form between metals and nonmetals.
• Hydrogen bonds: weak attraction between a hydrogen atom bonded to an electronegative atom and another electronegative atom; important in biological structures.

Explore the fundamental elements crucial for life and their relationship to biological macromolecules in this quiz. Test your knowledge of electronegativity, bond types, and the behavior of these molecules in water. Perfect for students delving into cellular biology and biochemistry.