Chapter 2: Biochemistry Foundations in Anatomy & Physiology

Learning Objectives

• Compare and contrast organic and inorganic molecules.

• Explain the importance of water and its properties.

• Identify the three chemical elements that generally compose biological macromolecules.

• Describe the role of dehydration synthesis and hydrolysis in forming and breaking down organic molecules.

• Describe the building blocks, general structure, and biological functions of carbohydrates, lipids, proteins, and nucleic acids.

• Explain the role of ATP in cell metabolism.

Compounds in the Body

Inorganic Compounds

Inorganic compounds do not contain carbon as their main element. They play essential roles in physiological processes.

• Examples:

  • Water (H2O)

  • Acids and bases

  • Salts

• Exceptions: Some inorganic compounds may contain carbon, such as CO2 and bicarbonate.

Organic Compounds

Organic compounds always contain carbon and hydrogen, and often oxygen and nitrogen. They form the basis of biological macromolecules.

• Examples: Carbohydrates, lipids, proteins, nucleic acids

Water

Properties and Functions

Water is the most abundant inorganic compound in the human body, accounting for 60–80% of cell volume. Its unique properties make it vital for life.

• High heat capacity: Absorbs and releases large amounts of heat with minimal temperature change.

• High heat of vaporization: Requires significant energy to change from liquid to gas, aiding in cooling (e.g., sweating).

• Polar solvent: Dissolves ionic and polar substances, facilitating chemical reactions and transport.

• Reactivity: Participates in chemical reactions, such as hydrolysis and dehydration synthesis.

• Cushioning: Protects organs and tissues by absorbing shock.

Examples and Applications

• Water acts as a lubricant in body cavities.

• It is a major component of blood, cytoplasm, and interstitial fluid.

Biological Macromolecules

General Features

• Composed of repeating subunits called monomers.

• Formed by polymerization (joining monomers into polymers).

• Four main types: Carbohydrates, Lipids, Proteins, Nucleic Acids.

Polymer Formation and Breakdown

• Dehydration synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Carbohydrates

Elements and Structure

• Composed of C, H, O; general formula:

Functions

• Main source of energy for cells

• Some provide structural support (e.g., cellulose in plants)

Classification

• Monosaccharides: Simple sugars (e.g., glucose, fructose, galactose)

• Disaccharides: Two monosaccharides joined (e.g., sucrose, lactose, maltose)

• Polysaccharides: Long chains of monosaccharides (e.g., glycogen, starch, cellulose)

Examples and Applications

• Glucose: Main energy source for most cells; stored as glycogen in liver and muscle.

• Glycogen: Storage form of glucose in animals.

Lipids

Elements and Structure

• Composed of C, H, O (less O than carbohydrates)

• Nonpolar, hydrophobic molecules

Types of Lipids

• Fatty acids: Saturated (no double bonds), monounsaturated (one double bond), polyunsaturated (multiple double bonds)

• Triglycerides: Three fatty acids + glycerol

• Phospholipids: Amphipathic molecules (hydrophilic head, hydrophobic tail); major component of cell membranes

• Steroids: Four fused carbon rings (e.g., cholesterol, hormones)

Functions

• Energy storage

• Insulation and protection

• Cell membrane structure

• Hormone production

Proteins

Elements and Structure

• Composed of C, H, O, N (sometimes S)

• Monomers: Amino acids

• Linked by peptide bonds via dehydration synthesis

Levels of Protein Structure

• Primary: Sequence of amino acids

• Secondary: Alpha helix or beta pleated sheet (hydrogen bonding)

• Tertiary: 3D folding due to side chain interactions

• Quaternary: Multiple polypeptide chains joined

Functions

• Structural support (e.g., collagen, keratin)

• Enzymes/catalysts

• Transport (e.g., hemoglobin)

• Communication (e.g., hormones)

• Defense (e.g., antibodies)

Denaturation

• Loss of protein structure due to heat, pH changes, or chemicals

• Usually reversible if normal conditions are restored

Nucleic Acids

Elements and Structure

• Composed of C, H, O, N, P

• Monomers: Nucleotides (phosphate group, sugar, nitrogenous base)

Types

• DNA: Stores genetic information

• RNA: Transfers genetic information and helps in protein synthesis

ATP (Adenosine Triphosphate)

• Main energy currency of the cell

• Composed of adenine, ribose, and three phosphate groups

• Energy released by breaking phosphate bonds via hydrolysis:

Summary Table: Major Biomolecules

Key Terms and Concepts

• Monomer: Smallest repeating unit in a polymer

• Polymer: Large molecule made of monomers

• Dehydration synthesis: Reaction joining monomers by removing water

• Hydrolysis: Reaction breaking polymers by adding water

• Enzyme: Protein that speeds up chemical reactions

• ATP: Energy molecule for cellular processes

Additional info: Some context and explanations have been expanded for clarity and completeness, including definitions, examples, and academic context for each biomolecule.