Biochemistry: The Chemical Basis of Life

Introduction to Biochemistry

Biochemistry is the field of science that bridges biology and chemistry, focusing on the study of the properties and activities of molecules in living organisms. It explores how molecular structure determines function and how chemical interactions underlie biological processes.

• Biological molecules include proteins, nucleic acids, carbohydrates, and lipids.

• These molecules are primarily composed of carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.

• Biochemistry explains how the arrangement of atoms in molecules determines their properties and roles in living systems.

Functional Groups and Linkages

Key Functional Groups in Biological Molecules

Functional groups are specific groups of atoms within molecules that have characteristic properties and reactivity. They are critical in determining the behavior of biological molecules.

• Hydroxyl group (-OH): Found in alcohols; increases solubility in water.

• Carbonyl group (C=O): Found in aldehydes and ketones; important in sugars.

• Carboxyl group (-COOH): Found in acids; acts as an acid by donating H+.

• Amino group (-NH2): Found in amino acids; acts as a base by accepting H+.

• Phosphate group (-PO42-): Found in nucleic acids and ATP; involved in energy transfer.

• Sulfhydryl group (-SH): Found in some amino acids; forms disulfide bonds in proteins.

Main Types of Biological Reactions

Condensation and Hydrolysis

Biological macromolecules are assembled and broken down by two main types of reactions:

• Condensation (Dehydration Synthesis): Joins monomers by removing water, forming covalent bonds.

• Hydrolysis: Breaks covalent bonds by adding water, splitting polymers into monomers.

Acids, Bases, and Buffers

Acids and bases are substances that donate or accept protons (H+), affecting the pH of biological systems. Buffers help maintain stable pH in cells and tissues.

• Acid: Substance that donates H+ ions (proton donor).

• Base: Substance that accepts H+ ions (proton acceptor).

• Buffer: A solution that resists changes in pH by absorbing or releasing H+ ions.

Formula:

Properties of Water

Importance of Water in Biology

Water is essential for life due to its unique chemical and physical properties, which arise from its molecular structure and hydrogen bonding.

• Cohesion: Water molecules stick together due to hydrogen bonding, aiding in transport in plants.

• Adhesion: Water molecules stick to other substances, important for capillary action.

• High specific heat: Water absorbs and releases heat slowly, stabilizing temperatures.

• High heat of vaporization: Evaporation of water cools organisms (e.g., sweating).

• Ice is less dense than liquid water: Ice floats, insulating aquatic environments.

• Solvent properties: Water dissolves many substances, facilitating chemical reactions.

Macromolecules: Structure and Function

Carbohydrates

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, typically in a 1:2:1 ratio. They serve as energy sources and structural components.

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

• Disaccharides: Two monosaccharides joined by a glycosidic bond (e.g., sucrose).

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

Example: Glycogen is a storage polysaccharide in animals; cellulose is a structural polysaccharide in plants.

Lipids

Lipids are hydrophobic molecules, including fats, oils, phospholipids, and steroids. They function in energy storage, membrane structure, and signaling.

• Triglycerides: Composed of glycerol and three fatty acids; main form of energy storage.

• Phospholipids: Major component of cell membranes; have hydrophilic heads and hydrophobic tails.

• Steroids: Four fused carbon rings; include cholesterol and hormones.

Proteins

Proteins are polymers of amino acids linked by peptide bonds. They perform a wide range of functions, including catalysis, transport, structure, and signaling.

• Amino acids: Building blocks of proteins; 20 standard types.

• Peptide bond: Covalent bond between amino acids formed by condensation.

• Levels of structure: Primary (sequence), secondary (alpha helix, beta sheet), tertiary (3D folding), quaternary (multiple polypeptides).

Example: Enzymes are proteins that catalyze biochemical reactions.

Nucleic Acids

Nucleic acids (DNA and RNA) store and transmit genetic information. They are polymers of nucleotides, each consisting of a sugar, phosphate group, and nitrogenous base.

• DNA: Double-stranded; stores genetic information.

• RNA: Single-stranded; involved in protein synthesis and gene regulation.

• Nucleotides: Adenine (A), Thymine (T), Guanine (G), Cytosine (C), and Uracil (U, in RNA).

Example: DNA replication ensures genetic continuity; RNA translates genetic code into proteins.

Summary Table: Major Classes of Biological Macromolecules

Enzymes and Metabolism

Enzyme Activity and Regulation

Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy. Their activity can be regulated by various factors.

• Active site: Region on the enzyme where the substrate binds.

• Substrate: The reactant molecule upon which an enzyme acts.

• Regulation: Enzyme activity can be controlled by inhibitors, activators, and environmental conditions (pH, temperature).

Formula:

Where E = enzyme, S = substrate, ES = enzyme-substrate complex, P = product.

Additional info:

• Some content was inferred and expanded for clarity and completeness, as the original notes were fragmented and partially illegible.

• Key terms and examples were added to ensure the notes are self-contained and suitable for exam preparation.