Essential Biomolecules: Structure, Function, and Chemical Bonds

Fundamentals of Biological Molecules and Bonds

Essential Elements and Molecular Formation

The primary elements that form biological molecules are often summarized by the acronym CHOMPS (Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur). Carbon (C) is highly versatile, forming the backbone of organic compounds.

Monomers, Polymers, and Reactions

• Monomers: The smallest units of organic compounds.
• Polymers: Large molecules formed by repeating monomer units (M + M = Polymer + H₂O).
• Polymerization: The process of forming polymers.
• Dehydration Synthesis: A reaction where monomers join to form a polymer, releasing a water molecule (H₂O).
• Hydrolysis: A reaction that breaks down a polymer by adding a water molecule.

Chemical Bonds and Essential Elements

Molecules are groups of more than one element. The human body primarily contains: C, H, O, N, Cl, Na, P, Fe, Ca, S, Mg, K.

• Covalent Bonds: Found in molecules (e.g., organic compounds).
• Ionic Bonds: Found in salts. While ionic bonds are generally stronger in a dry state, covalent bonds are often stronger in aqueous solutions (like water).

The Role of Water (H₂O)

Water is essential due to its unique properties:

• It retains heat effectively.
• It acts as a lubricant.
• It participates in chemical reactions.
• It forms crucial Hydrogen bonds.

Essential Molecules: Nutrients and Metabolites

• Nutrients: Essential molecules that cannot be synthesized by the body (must be obtained through diet).
• Metabolites: Molecules synthesized by the body.

Vitamins and Minerals are required nutrients. They often function as enzyme co-factors and can be classified as either water-soluble or fat-soluble.

The Four Major Macromolecules

1. Carbohydrates

The basic unit is glucose. Carbohydrates follow the general ratio C:H:O = 1:2:1.

Types of Carbohydrates

• Monosaccharides (Simple Sugars): Glucose.
• Disaccharides (Two Monomers):
  • Sucrose (Glucose + Fructose)
  • Lactose (Galactose + Glucose)
  • Maltose (Glucose + Glucose)
• Polysaccharides (Complex Polymers): Starch, Glycogen, Cellulose.

2. Lipids (Fats)

The basic unit is the triglyceride. Lipids contain Carbon, Hydrogen, and Oxygen (C:H:O ratio is 1:2:?, with much less oxygen than carbohydrates).

Lipids are crucial for:

• Forming essential structures in cells (e.g., membranes).
• Storing energy efficiently.
• Providing waterproofing.

A triglyceride is formed from three fatty acids and one glycerol molecule. Examples include oils, fats, steroids (like cholesterol, estrogen, and testosterone).

3. Proteins

The basic unit is the amino acid. Proteins are formed of long chains of amino acids and contain Carbon, Hydrogen, Oxygen, and Nitrogen (CHON).

Enzymes are a primary example of proteins.

Protein Structure Classification

Proteins are classified based on their complexity:

1. Primary Structure: The particular number and sequence of amino acids in the chain.
2. Secondary Structure: Local folding patterns, such as alpha-helices and beta-sheets (turns and folds).
3. Tertiary Structure: The overall three-dimensional shape resulting from irregular loops and interactions.
4. Quaternary Structure: The arrangement of multiple tertiary subunits (lots of tertiary structures combined).

Biological Functions of Proteins

1. Catalytic Function: All chemical reactions are catalyzed by enzymes, which lower the activation energy required for the reaction to proceed.
2. Transport and Storage:
   • Hemoglobin: Transports oxygen (O₂) in erythrocytes (red blood cells).
   • Myoglobin: Carries and stores oxygen in muscles.
   • Albumin: Transports free fatty acids in the blood.
   • Transferrin: Transports iron (Fe) in the blood.
3. Coordinated Motion: Actin and myosin are contractile proteins essential for muscle movement.
4. Defense:
   • Clotting Proteins: Prevent bleeding.
   • Immunoglobulins (Antibodies): Protect against infections.

Reaction speed is increased by higher temperature, smaller particle size, and higher reactant concentration.

4. Nucleic Acids

The basic unit is the nucleotide. Nucleic acids are chains of nucleotides and contain Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus (CHONP).

DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid) are the primary nucleic acids.

Nucleotide Components

Each nucleotide consists of three parts:

1. A Sugar (Deoxyribose or Ribose)
2. A Phosphate Group
3. A Nitrogenous Base:
   • Adenine (A)
   • Guanine (G)
   • Cytosine (C)
   • Thymine (T) - Found only in DNA
   • Uracil (U) - Found only in RNA