Biochemistry Foundations for Anatomy & Physiology

Biochemistry in Anatomy & Physiology

Introduction to Biochemistry

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

• Organic Compounds: Molecules containing carbon, typically found in living organisms. Examples include carbohydrates, lipids, proteins, and nucleic acids.

• Inorganic Compounds: Molecules that generally do not contain carbon. Water, salts, acids, and bases are key inorganic compounds in the body.

Water and Inorganic Compounds

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

  • High heat of vaporization

  • Polar solvent properties

  • Reactivity (in hydrolysis and dehydration reactions)

  • Cushioning (protects organs)

Salts

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

• Ionic Compounds: Formed from the attraction between positively and negatively charged ions.

• Dissociation in Water: Salts separate into their component ions when dissolved in water.

• Common Salts in the Body: Sodium chloride (NaCl), potassium chloride (KCl), calcium phosphate (Ca3(PO4)2).

Acid and Base Chemistry

Acids and bases are substances that can donate or accept protons (H+), affecting the body's pH balance.

• Dissociation of Water: Water can dissociate into hydrogen ions (H+) and hydroxide ions (OH-).

• Acids: Proton donors that increase H+ concentration in solution.

• Bases: Proton acceptors that decrease H+ concentration.

Acid-Base Definitions Table

	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. The body maintains a narrow pH range (7.35–7.45) using buffers, lungs, and kidneys.

• Buffers: Substances that minimize changes in pH by absorbing or releasing H+ ions.

• Strong Acids/Bases: Completely dissociate in water, causing significant pH changes.

• Weak Acids/Bases: Partially dissociate, providing more gradual pH changes.

Organic Compounds

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).

Dehydration Synthesis: Formation of larger molecules by removing water.

Hydrolysis: Breakdown of molecules by adding water.

Lipids

Lipids are hydrophobic molecules 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.

  • Unsaturated Fats: One or more double bonds; liquid at room temperature.

• Phospholipids: Modified triglycerides with a phosphate group; major component of cell 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 in the body, including catalysis, structure, transport, and regulation.

• Levels of Protein Structure:

  • Primary: Sequence of amino acids.

  • Secondary: Alpha helices and beta sheets formed by hydrogen bonding.

  • Tertiary: 3D folding due to side chain interactions.

  • Quaternary: Association of multiple polypeptide chains.

• Peptide Bonds: Covalent bonds linking amino acids.

Protein Functions

• Structural: Collagen, keratin

• Enzymatic: Catalyze biochemical reactions

• Transport: Hemoglobin, membrane channels

• Regulatory: Hormones, growth factors

• Defensive: Antibodies

Enzymes

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

• Specificity: Each enzyme acts on a specific substrate.

• Reusability: Enzymes are not consumed in reactions.

• Regulation: Enzyme activity can be modulated by inhibitors or activators.

Enzyme Action Equation:

$E + S \rightleftharpoons ES \rightarrow E + P$

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

Nucleic Acids

DNA and RNA

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

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)

DNA Double Helix Equation:

$\text{DNA}: \text{A} = \text{T}, \text{C} = \text{G}$

Summary: Understanding the chemical basis of life is essential for comprehending physiological processes in anatomy and physiology. Biochemistry provides the foundation for topics such as metabolism, cell structure, and genetic inheritance.