Biochemistry Overview

Introduction to Biochemistry

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

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

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

Water and Its Biological Importance

Properties of Water

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

• High heat capacity: Absorbs and releases heat with little temperature change, helping maintain stable internal conditions.

• High heat of vaporization: Large amounts of heat are needed to evaporate water, allowing for effective cooling (e.g., sweating).

• Reactivity: Involved in hydrolysis and dehydration synthesis reactions.

• Cushioning: Protects organs by providing a fluid cushion.

Polar Solvent Properties

Water is a universal solvent, dissolving and dissociating ionic substances and forming hydration layers around charged molecules.

• Major transport medium in the body.

Salts, Acids, and Bases

Salts

Salts are ionic compounds that dissociate into ions in water, forming electrolytes that conduct electrical currents.

• Important ions: Sodium (Na+), Potassium (K+), Calcium (Ca2+), Zinc (Zn2+), Copper (Cu2+).

• Vital for nerve impulses, muscle contractions, oxygen transport, and enzyme activity.

• Ionic balance is crucial for homeostasis.

Acids and Bases

Acids and bases are electrolytes that dissociate in water.

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

• Bases: Proton acceptors; pick up hydrogen ions or release hydroxide ions (OH−).

pH Scale

The pH scale measures the concentration of hydrogen ions in a solution.

• Acidic solutions: pH < 7

• Neutral solutions: pH = 7

• Alkaline (basic) solutions: pH > 7

Formula:

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

Buffers

Buffers help maintain pH stability in the body by converting strong acids or bases into weak ones.

• Important buffer system: Carbonic acid–bicarbonate system (blood).

Organic Compounds: Synthesis and Hydrolysis

Macromolecules and Monomers

Organic molecules contain carbon and are synthesized by dehydration synthesis, forming covalent bonds between monomers and releasing water.

• Dehydration synthesis: Monomers join, water is released.

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

Carbohydrates

Classification and Structure

Carbohydrates include sugars and starches, composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio.

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

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

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

Classification Table

Isomers

Isomers have the same molecular formula but different structures, resulting in different chemical properties.

Polysaccharides

• Starch: Storage form in plants.

• Glycogen: Storage form in animals (liver and muscles).

If glycogen stores are filled, excess glucose is converted to fat.

Lipids

Types and Functions

Lipids contain carbon, hydrogen, and oxygen, and sometimes phosphorus. They are insoluble in water and serve as energy storage, insulation, and protection.

• Triglycerides: Composed of three fatty acids bonded to glycerol by dehydration synthesis.

• Phospholipids: Modified triglycerides with a phosphate group; major component of cell membranes.

• Steroids: Four interlocking hydrocarbon rings; cholesterol is the most important steroid.

• Eicosanoids: Derived from fatty acids; include prostaglandins involved in inflammation and other processes.

Saturated vs. Unsaturated Fatty Acids

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

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

• Trans fats: Modified unsaturated fats; associated with health risks.

• Omega-3 fatty acids: Heart-healthy fats.

Proteins

Structure and Function

Proteins are made from 20 types of amino acids, each containing an amine group and an acid group. Amino acids are joined by peptide bonds to form polypeptides.

• Primary structure: Linear sequence of amino acids.

• Secondary structure: Alpha helix and beta sheet formations.

• Tertiary structure: Folding due to interactions among R groups.

• Quaternary structure: Multiple polypeptides interacting.

Protein Structure Table

Fibrous vs. Globular Proteins

• Fibrous proteins: Structural, provide support and strength (e.g., collagen).

• Globular proteins: Functional, involved in transport, enzymes, and immune response.

Enzymes and Enzyme Action

Enzyme Function

Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy.

• Each enzyme acts on a specific substrate.

• Enzyme action involves three steps: substrate binding, transition state formation, and product release.

Example: Digestive enzymes break down food molecules for absorption.

Nucleic Acids

DNA and RNA

Nucleic acids store and transmit genetic information. DNA and RNA are polymers of nucleotides.

• DNA: Double-stranded, contains genetic instructions.

• RNA: Single-stranded, involved in protein synthesis.

Summary Table: Major Biological Molecules

Additional info: These notes expand on the original bullet points with academic context, definitions, and examples to provide a comprehensive study guide for biochemistry in Anatomy & Physiology.