Lecture 1C par 2

Chemical Reactions

• Definition: A chemical reaction is a process that involves the transformation of substances.

Key Components

• Reactants: These are the molecules or atoms that enter a chemical reaction.

  • Examples of reactants in a chemical equation are found on the flat end of the arrow in a reaction's representation.

• Products: The substances that remain after the reaction has occurred.

  • Products are represented on the pointy end of the arrow.

• Arrow Significance: The arrow in a chemical equation indicates the direction of the reaction and signifies a transformation, often read as "yields" rather than "equals."

  • Example: Instead of stating "oxygen plus oxygen equals O₂," it is written as:
  • O + O
    ightarrow O_2

Reaction Types

• Synthesis Reaction:

  • Definition: A reaction where smaller reactants combine to form a larger product.
  • Example: A + B
    ightarrow AB
  • Real-life Example: ext{Na} + ext{Cl}
    ightarrow ext{NaCl}
  • This shows sodium and chloride combining to form sodium chloride (table salt).

• Decomposition Reaction:

  • Definition: A process where a larger molecule breaks down into smaller components.
  • Example: CD
    ightarrow C + D

Solutions

• Definition of a Solution: A homogeneous mixture formed when a solute is dispersed in a solvent.
  • Solute: The substance that is dissolved (e.g., Kool-Aid powder).
  • Solvent: The medium that dissolves the solute (e.g., water).
  • The resulting mixture is known as the solution (e.g., Kool-Aid drink).

Isomers

• Definition: Isomers are molecules that share the same molecular formula but differ in the arrangement of atoms.
  • Example: Glucose and Fructose both have the formula $C<em>6H</em>{12}O_6$.
  • Glucose has a specific structure that differs from fructose, leading to variations in their properties despite having the same formula.
  • Additional Example: Galactose, which is also a form of $C<em>6H</em>{12}O_6$, illustrating that multiple isomers exist for one formula.

Biological Macromolecules

• Definition: Large, complex molecules with significant biological functions, typically consisting of carbon backbones.

Monomers and Polymers

• Monomers: The repeating units that make up macromolecules.
  • Analogy: Like freight cars on a train; individual cars represent monomers while the entire train represents the polymer.
• Polymers: Larger structures formed when monomers are linked together through covalent bonds.
  • Terminology:
  • Mono- means single.
  • Poly- means many.

Categories of Biological Macromolecules

1. Carbohydrates:

   • Monomer Unit: Monosaccharides (single sugar molecules).
     • Examples: Glucose, Fructose.
   • Functions:
     • Energy storage (short-term and long-term).
     • Structural components in cells.

2. Lipids:

   • Monomer Unit: Not defined by repeating units but includes molecules like fatty acids and glycerol.
   • Functions:
     • Energy storage.
     • Structural components of cell membranes.
     • Some lipids act as hormones.

3. Proteins:

   • Monomer Unit: Amino acids (20 different types).
   • Functions:
     • Structural roles, enzymatic functions, storage, protection, etc.

4. Nucleic Acids:

   • Monomer Unit: Nucleotides.
   • Functions:
     • Storage of genetic information (DNA).
     • Various functions in RNA (to be discussed later).

Carbohydrates - Detailed Overview

• Characteristics: Sweet and starchy properties.
• Monosaccharides: Cannot be further broken down; examples include:
  • Glucose
  • Fructose
  • Galactose
• Function: Fuel for cellular processes
  • Especially important for brain function.

Types of Carbohydrates

• Disaccharides: Formed from two monosaccharides bonded together.

  • Examples:
    • Lactose: Glucose + Galactose.
    • Sucrose: Fructose + Glucose.
    • Maltose: Glucose + Glucose.
  • Notable suffix: Many sugars end in "-ose."

• Polysaccharides: Larger molecules made from numerous monosaccharides, often referred to as complex carbohydrates.

  • Examples:
    • Starch: Energy storage in plants.
    • Glycogen: Energy storage form in animals; can be broken down into glucose when needed.
    • Cellulose: Also known as dietary fiber; aids in digestion but cannot be broken down by human enzymes.
    • Peptidoglycan: Structural carbohydrate in bacterial cell walls.
    • Chitin: Structural carbohydrate in fungal cell walls.

Reactions in Polymers

• Synthesis Reactions (Dehydration Reactions):

  • Process where monomers are linked together, releasing a molecule of water.
  • Example: ext{Monomer}1 + ext{Monomer}2
    ightarrow ext{Polymer} + H_2O

• Degradation Reactions (Hydrolysis Reactions):

  • Process where polymers are broken down into monomers; water is added.
  • Example: ext{Polymer} + H2O ightarrow ext{Monomer}1 + ext{Monomer}_2