Biochemistry

Introduction to Biochemistry

Biochemistry is the study of the chemical composition and reactions of living matter. It is fundamental to understanding the molecular basis of anatomy and physiology.

• Organic compounds: Contain carbon, are usually large, and are covalently bonded.

• Inorganic compounds: Include water, salts, and many acids and bases; do not contain carbon.

Water and Its Importance

Water is the most abundant inorganic compound in living cells and is essential for life due to its unique properties.

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

• High heat of vaporization: Evaporation requires significant energy, providing a cooling mechanism.

• Cushioning: Protects organs from physical trauma (e.g., cerebrospinal fluid cushions nervous system organs).

• Reactivity: Necessary for hydrolysis and dehydration synthesis reactions.

Salts

Salts are ionic compounds that dissociate in water, releasing ions that are vital for body functions.

• All ions are called electrolytes because they conduct electrical currents in solution.

• Important ions: Sodium, potassium, iron, copper.

• Salt balance is crucial for homeostasis.

Acids and Bases

Acids and bases are substances that dissociate in water to release ions, affecting pH and biological processes.

• Acids: Proton donors; release hydrogen ions (H+).

• Bases: Proton acceptors; pick up hydrogen ions (H+).

• When H+ ions are picked up, acidity is reduced.

• Important bases: Bicarbonate ion (HCO3-), ammonia (NH3).

pH: Acid-Base Concentration

pH is a measure of hydrogen ion concentration in a solution, indicating its acidity or alkalinity.

• pH scale: Ranges from 0 (acidic) to 14 (basic); pure water has a pH of 7.

• Each pH unit represents a tenfold difference in H+ concentration.

Formula:

Buffers

Buffers help maintain acid/base balance by resisting swings in pH.

• Convert strong acids/bases into weak ones.

• Example: Carbonic acid-bicarbonate system in blood.

Organic Compounds: Synthesis and Hydrolysis

Organic Molecules

Organic molecules contain carbon and are essential for life. They are synthesized and broken down by specific chemical reactions.

• Dehydration synthesis: Water is removed to form a covalent bond between monomers.

• Hydrolysis: Water is added to break covalent bonds between monomers.

Carbohydrates

Classification and Structure

Carbohydrates are organic molecules containing carbon, hydrogen, and oxygen in a 1:2:1 ratio. They are classified based on the number of sugar units.

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

• Disaccharides: Double sugars (e.g., sucrose, lactose, maltose).

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

Polysaccharides

• Starch: Storage form in plants.

• Glycogen: Storage form in animals, mainly in liver and muscle.

• Main function: Energy storage.

Lipids

Types and Functions

Lipids are diverse organic compounds, insoluble in water, and include fats, oils, and phospholipids.

• Triglycerides: Composed of three fatty acids bonded to a glycerol molecule; main function is energy storage.

• Saturated fatty acids: No double bonds; solid at room temperature (e.g., animal fats).

• Unsaturated fatty acids: One or more double bonds; liquid at room temperature (e.g., plant oils).

• Trans fats: Modified unsaturated fats; considered unhealthy.

• Phospholipids: Glycerol, two fatty acids, and a phosphate group; major component of cell membranes.

• Steroids: Four interlocking hydrocarbon rings; include cholesterol, steroid hormones.

• Eicosanoids: Derived from fatty acids; involved in inflammation and cell signaling.

Proteins

Structure and Function

Proteins are polymers of amino acids and perform a wide range of functions in the body.

• Contain C, H, O, N, and sometimes S and P.

• Joined by peptide bonds.

• Four levels of structure:

  • Primary: Sequence of amino acids.

  • Secondary: Alpha (α) helix and beta (β) pleated sheets.

  • Tertiary: 3D folding due to interactions among R groups.

  • Quaternary: Two or more polypeptides interacting.

Protein Denaturation

• Change in protein shape due to heat, acidity, alcohol, or heavy metals.

Enzymes

Function and Mechanism

Enzymes are globular proteins that act as biological catalysts, increasing the speed of chemical reactions without being consumed.

• Lower activation energy required for reactions.

• Highly specific for their substrates.

• Most are holoenzymes (protein + cofactor).

Three steps in enzyme action:

1. Substrate binds to enzyme's active site.

2. Substrate undergoes rearrangement.

3. Product is released.

Nucleic Acids

Structure and Types

Nucleic acids are the largest molecules in the body, composed of C, H, O, N, and P. They store and transmit genetic information.

• Polymers made of nucleotides (nitrogen base, pentose sugar, phosphate group).

• Two major types:

  • DNA (Deoxyribonucleic acid): Stores genetic information.

  • RNA (Ribonucleic acid): Involved in protein synthesis.

Summary Table: Major Biomolecules

Additional info: Some explanations and examples have been expanded for clarity and completeness, including the summary tables and formulas.