Chapter 2

Basic Chemistry and States of Matter

Introduction to Chemistry in Anatomy & Physiology

Chemistry is the study of matter and its interactions, which is foundational for understanding physiological processes. Matter exists in three states: solid, liquid, and gas.

• Atom: The smallest unit of matter that retains original properties.

• Subatomic particles: Even smaller structures that make up atoms.

Elements in the Human Body

Major, Mineral, and Trace Elements

The human body is composed of four major elements, along with several minerals and trace elements.

• Major elements: Hydrogen, Oxygen, Carbon, Nitrogen

• Mineral elements: 7 types (e.g., calcium, potassium)

• Trace elements: 13 types (e.g., iron, zinc)

Biochemistry: Organic and Inorganic Compounds

Classification of Compounds

Biochemistry studies the chemical processes within living organisms. Compounds are classified as inorganic or organic based on their structure.

• Inorganic compounds: Generally do not contain carbon bonded to hydrogen; includes water, acids, bases, and salts.

• Organic compounds: Contain carbon bonded to hydrogen; includes carbohydrates, lipids, proteins, and nucleic acids.

Water and Its Biological Importance

Properties and Functions of Water

Water (H2O) makes up 60–80% of the mass of the human body and serves as the medium for metabolic reactions.

• Transports chemicals

• Absorbs and transports heat

• Cushions and protects body structures

• Dissolves solutes that are hydrophilic (water-loving)

• Does not dissolve solutes that are hydrophobic (water-hating)

Acids, Bases, and pH

Definitions and Biological Relevance

Acids and bases are substances that affect the hydrogen ion concentration in solutions, influencing pH and biological processes.

• Acids: Release hydrogen ions (H+) in solution. Example: $\mathrm{HCl} \rightarrow \mathrm{H}^+ + \mathrm{Cl}^-$

• Bases (Alkali): Accept hydrogen ions or release hydroxide ions (OH-).

• pH Scale: Measures hydrogen ion concentration; pure water is neutral at pH 7.

• Solutions below pH 7 are acidic; above pH 7 are basic.

• Buffers: Chemicals that resist changes in pH.

Salts and Electrolytes

Role in Physiology

Salts dissociate in water to form cations and anions called electrolytes, which are essential for conducting electrical currents and metabolism.

• Important for nerve and muscle function

• Examples: Sodium chloride (NaCl), potassium chloride (KCl)

Organic Compounds: Carbohydrates, Lipids, Proteins, Nucleic Acids

Monomers and Polymers

Organic compounds are built from monomers that join to form polymers, each with specific biological functions.

• Carbohydrates: Monomers are monosaccharides (e.g., glucose, fructose). Disaccharides (e.g., sucrose) are formed from two monosaccharides. Polysaccharides (e.g., starch, glycogen) are long chains of monosaccharides.

• Lipids: Hydrophobic molecules including fats and oils. Fatty acids are lipid monomers; can be saturated (solid at room temperature) or unsaturated (liquid at room temperature).

• Triglycerides: Most common lipid in the body, used for energy storage.

• Steroids: Four-ring hydrocarbon structure; cholesterol is a major component of cell membranes.

• Proteins: Made of amino acids (21 types); involved in structure, movement, defense, and regulation.

• Nucleic acids: Built from nucleotides; include DNA and RNA.

Fatty Acids: Types and Health Implications

Classification and Effects

Fatty acids are classified based on their chemical structure and health effects.

• Omega-3 fatty acids: Found in fish oil; beneficial for cardiovascular health.

• Saturated fats: Found in animal products; excessive consumption linked to heart disease.

• Trans fats: Artificially produced; associated with increased risk of heart disease.

Proteins: Structure and Function

Macromolecules and Denaturation

Proteins are essential macromolecules with diverse functions in the body. Their structure is sensitive to environmental changes.

• Made of carbon, hydrogen, oxygen, nitrogen, and other elements

• Monomers are called amino acids

• Functions: Enzymes, structural roles, movement, defense, receptors, hormones

• Protein denaturation: Loss of protein structure due to heat, pH changes, or chemicals; disrupts function

Enzyme Deficiencies

Examples and Effects

Enzyme deficiencies can lead to serious metabolic disorders.

• Tay-Sachs Disease: Deficiency of hexosaminidase; gangliosides accumulate in neurons, leading to early death.

• Severe Combined Immunodeficiency Syndrome (SCIDs): May be due to adenosine deaminase deficiency; affects immune system function.

• Phenylketonuria: Deficiency of phenylalanine hydroxylase; leads to accumulation of phenylalanine, causing neurological issues.

Nucleic Acids: DNA and RNA

Structure and Function

Nucleic acids store and transmit genetic information. They are built from nucleotides, each consisting of a nitrogenous base, a five-carbon sugar, and a phosphate group.

• DNA (Deoxyribonucleic Acid): Double helix structure; bases include adenine, thymine, guanine, cytosine. Base pairing: A=T, G≡C.

• RNA (Ribonucleic Acid): Single strand; contains uracil instead of thymine, pairs A=U. RNA can move between nucleus and cytosol and is critical for making proteins.

Adenosine Triphosphate (ATP)

Energy Currency of the Cell

ATP stores and transfers energy within cells, enabling metabolic reactions.

• Energy is released when ATP is hydrolyzed to ADP and phosphate.

• Synthesized from ADP and phosphate using energy from glucose oxidation.

• ATP production requires oxygen; why we breathe air.

• Equation: $\mathrm{ATP} \rightarrow \mathrm{ADP} + \mathrm{P_i} + \text{energy}$

Table: Comparison of Major Organic Compounds

Compound Type	Monomer	Main Function	Example
Carbohydrates	Monosaccharide	Energy source, structure	Glucose, starch
Lipids	Fatty acid	Energy storage, cell membrane	Triglyceride, cholesterol
Proteins	Amino acid	Structure, enzymes, movement	Hemoglobin, actin
Nucleic Acids	Nucleotide	Genetic information	DNA, RNA

Additional info: Some context and definitions were expanded for clarity and completeness, including examples of mineral and trace elements, and the ATP equation.