Biochemistry Foundations for Anatomy & Physiology: Inorganic Compounds, Acids, Bases, and Buffers

Biochemistry in Anatomy & Physiology

Introduction to Biochemistry

Biochemistry is the study of the chemical composition and reactions of living matter. Understanding biochemistry is essential for comprehending the molecular basis of physiological processes in the human body.

• Organic compounds: Contain carbon, are usually large, and are covalently bonded. Examples include carbohydrates, fats, proteins, and nucleic acids.

• Inorganic compounds: Do not contain carbon (with some exceptions such as CO2 and CO). Examples include water, salts, acids, and bases.

Inorganic Compounds

Water

Water is the most abundant inorganic compound in living cells, accounting for 60%–80% of their volume. Its unique properties are vital for life.

• High heat capacity: Absorbs and releases heat slowly, helping to maintain stable body temperature.

• High heat of vaporization: Requires significant energy to change from liquid to gas, aiding in cooling mechanisms like sweating.

• Polar solvent properties: Dissolves ionic and polar substances, making it an excellent medium for biochemical reactions.

• Reactivity: Participates in many chemical reactions, including hydrolysis and dehydration synthesis.

• Cushioning: Protects organs by providing a resilient, shock-absorbing medium.

Salts

Salts are ionic compounds that dissociate into separate ions in water, excluding H+ and OH- ions.

• Cations: Positively charged ions.

• Anions: Negatively charged ions.

• Salts are essential for nerve impulse transmission, muscle contraction, and water balance.

Acids and Bases

Definitions and Properties

• Acids: Proton donors that release hydrogen ions (H+) in solution. Example: HCl → H+ + Cl-

• Bases: Proton acceptors that pick up H+ ions or release hydroxyl ions (OH-) in solution. Example: NaOH → Na+ + OH-

• Important acids: Hydrochloric acid (HCl), acetic acid (HC2H3O2), carbonic acid (H2CO3).

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

pH Scale

The pH scale measures the concentration of hydrogen ions [H+] in a solution, ranging from 0 (most acidic) to 14 (most basic). The scale is logarithmic, so each pH unit represents a tenfold difference in H+ concentration.

• Formula: $\text{pH} = -\log_{10}[\text{H}^+]$

• Example: A solution with pH 5 is 10 times more acidic than a solution with pH 6.

pH Value	Example Substance
0–1	1M Hydrochloric acid
2–3	Lemon juice, gastric juice
4–5	Wine, black coffee
6–7	Milk, blood (7.4)
8–9	Egg white, household bleach
10–11	Household ammonia
12–14	Oven cleaner, 1M sodium hydroxide

Buffers

Buffers are systems that resist abrupt changes in pH by releasing or binding hydrogen ions as needed. They are crucial for maintaining homeostasis in biological systems.

• Function: Convert strong acids or bases into weak ones, minimizing pH fluctuations.

• Example: The carbonic acid–bicarbonate buffer system in blood.

Buffer system equation:

$\mathrm{H_2CO_3} \rightleftharpoons \mathrm{HCO_3^-} + \mathrm{H^+}$

• If pH rises (becomes more basic), carbonic acid (H2CO3) releases H+ to lower pH.

• If pH falls (becomes more acidic), bicarbonate (HCO3-) binds H+ to raise pH.

Summary Table: Key Inorganic Compounds and Their Roles

Compound	Key Properties	Physiological Role
Water	High heat capacity, solvent, reactivity, cushioning	Medium for reactions, temperature regulation, protection
Salts	Ionic, dissociate in water	Nerve impulses, muscle contraction, fluid balance
Acids	Proton donors, increase [H+]	Digestion, metabolic reactions
Bases	Proton acceptors, release OH-	Neutralize acids, maintain pH
Buffers	Stabilize pH	Homeostasis, especially in blood

Additional info: The content above is foundational for understanding the chemical environment in which physiological processes occur, including enzyme activity, cellular metabolism, and homeostatic regulation.