Biochemistry Foundations for Anatomy & Physiology

Biochemistry: The Chemical Basis of Life

Introduction to Biochemistry

Biochemistry is the study of the chemical composition and reactions that occur in living matter. It is foundational for understanding physiological processes in the human body.

• Organic Compounds: Molecules containing carbon, typically found in living organisms (e.g., carbohydrates, lipids, proteins, nucleic acids).

• Inorganic Compounds: Molecules that generally do not contain carbon (e.g., water, salts, acids, bases).

Inorganic Compounds in Physiology

Water

Water is the most important inorganic molecule for life, making up the majority of cell mass and serving as a universal solvent.

• Properties:

  • High heat capacity: absorbs and releases heat slowly.

  • High heat of vaporization: requires much energy to change from liquid to gas.

  • Polar solvent: dissolves ionic and polar substances.

  • Reactivity: involved in hydrolysis and dehydration synthesis reactions.

  • Cushioning: protects organs from physical trauma.

• Example: Water's polarity allows it to dissolve salts and transport nutrients in blood.

Salts

Salts are ionic compounds that dissociate in water to form electrolytes, which are essential for nerve impulse transmission and muscle contraction.

• Ionic Compounds: Composed of cations and anions held together by ionic bonds.

• Dissociation in Water: Salts separate into ions when dissolved, enabling electrical conductivity.

• Common Salts in the Body: Sodium chloride (NaCl), potassium chloride (KCl), calcium phosphates.

Acid and Base Chemistry

Acids and bases are substances that release hydrogen ions (H+) or hydroxide ions (OH-) in solution, respectively. They are crucial for maintaining the body's pH balance.

• Dissociation of Water: $\mathrm{H_2O \rightleftharpoons H^+ + OH^-}$

• Acids: Proton donors that increase H+ concentration (e.g., HCl).

• Bases: Proton acceptors that decrease H+ concentration (e.g., NaOH).

Acid-Base Definitions

	Acid	Base
Arrhenius	Produces H+ in water	Produces OH- in water
Bronsted-Lowry	Proton donor	Proton acceptor
Lewis	Electron pair acceptor	Electron pair donor

pH and Buffers

The pH scale measures the concentration of hydrogen ions in a solution, ranging from 0 (acidic) to 14 (basic). The body tightly regulates pH, primarily through the lungs and kidneys.

• Buffers: Substances that minimize changes in pH by binding or releasing H+ (e.g., bicarbonate buffer system).

• Strong Acids/Bases: Completely dissociate in water (e.g., HCl, NaOH).

• Weak Acids/Bases: Partially dissociate (e.g., acetic acid, ammonia).

Organic Compounds in Physiology

Carbohydrates

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, serving as the primary energy source for cells.

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

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

• Polysaccharides: Long chains of monosaccharides (e.g., glycogen for storage, cellulose for structure).

Carbohydrate Reactions

• Dehydration Synthesis: Formation of a covalent bond with the removal of water.

• Hydrolysis: Breaking of a covalent bond with the addition of water.

Lipids

Lipids are hydrophobic organic molecules, including fats, oils, and steroids, important for energy storage, insulation, and cell membrane structure.

• Triglycerides: Composed of glycerol and three fatty acids.

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

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

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

• Steroids: Four fused carbon rings; includes cholesterol, hormones.

• Eicosanoids: Derived from arachidonic acid; involved in inflammation and immunity.

Proteins

Structure and Function

Proteins are polymers of amino acids that perform a vast array of functions, including catalysis, structure, transport, and regulation.

• Levels of Protein Structure:

  1. Primary: Amino acid sequence

  2. Secondary: Alpha helices and beta sheets

  3. Tertiary: 3D folding of a single polypeptide

  4. Quaternary: Association of multiple polypeptides

• Peptide Bonds: Covalent bonds linking amino acids.

Protein Functions

• Structural: Collagen, keratin

• Enzymatic: Catalyze biochemical reactions

• Transport: Hemoglobin, membrane channels

• Regulatory: Hormones, receptors

• Defensive: Antibodies

Enzymes

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

• Characteristics:

  • Highly specific for substrates

  • Not consumed in the reaction

  • Activity can be regulated

• Mechanism: Substrate binds to active site, reaction occurs, products are released.

Nucleic Acids

DNA and RNA

Nucleic acids store and transmit genetic information. DNA and RNA differ in structure and function.

Characteristic	DNA	RNA
Major cellular site	Nucleus	Cytoplasm
Major function	Genetic blueprint	Protein synthesis
Structure	Double helix	Single strand
Sugar	Deoxyribose	Ribose
Bases	A, T, C, G	A, U, C, G

Structure of DNA and RNA

• Monomer: Nucleotide (phosphate group, sugar, nitrogenous base)

• Base Pairing in DNA: Adenine (A) pairs with Thymine (T), Cytosine (C) pairs with Guanine (G)

• Base Pairing in RNA: Adenine (A) pairs with Uracil (U), Cytosine (C) pairs with Guanine (G)

Additional info: The notes are structured as an outline with supporting diagrams and tables, suitable for a college-level Anatomy & Physiology course. Some details were inferred and expanded for completeness and clarity.