Chapter 2: Chemistry Comes Alive – Study Notes for Anatomy & Physiology I

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Chapter 2: Chemistry Comes Alive

Introduction

This chapter introduces the foundational chemical principles essential for understanding the structure and function of the human body. Key concepts include matter, energy, atomic structure, chemical bonds, and the biochemical molecules vital to life.

States of Matter

Solid: Definite shape and volume; particles are tightly packed.
Liquid: Definite volume but no fixed shape; particles move more freely than in solids.
Gas: No definite shape or volume; particles are far apart and move rapidly.

Forms of Energy

Chemical Energy: Stored in bonds of chemical substances (e.g., ATP).
Electrical Energy: Movement of charged particles (e.g., nerve impulses).
Mechanical Energy: Directly involved in moving matter (e.g., muscle contraction).
Radiant/Electromagnetic Energy: Travels in waves (e.g., light, X-rays).

Atoms and Elements

Atom: Smallest unit of an element retaining its properties.
Element: Substance that cannot be broken down by ordinary chemical means; defined by number of protons.
Major Elements in the Body: Oxygen, carbon, hydrogen, nitrogen.

Structure of Atoms

Nucleus: Contains protons (+) and neutrons (0).
Electrons (-): Orbit the nucleus in energy shells.
Atomic Number: Number of protons.
Mass Number: Protons + neutrons.

Identifying Elements

Each element is identified by its atomic number and symbol (e.g., H for hydrogen).

Radioisotopes

Isotopes: Atoms of the same element with different numbers of neutrons.
Radioisotopes: Unstable isotopes that emit radiation as they decay.
Applications: Used in medical imaging and cancer treatment.

Combining Matter: Mixtures and Compounds

Mixture: Physical combination of substances; components retain their properties (e.g., air, blood plasma).
Compound: Chemical combination of two or more elements in fixed proportions; properties differ from individual elements (e.g., H2O).

Chemical Bonds and Their Characteristics

Ionic Bonds: Transfer of electrons from one atom to another, forming ions (e.g., NaCl).
Covalent Bonds: Sharing of electrons between atoms (e.g., O2).
Hydrogen Bonds: Weak attraction between a hydrogen atom and an electronegative atom (important in water and DNA structure).

Chemical Reactions

Synthesis (Anabolic) Reactions: Atoms or molecules combine to form larger, more complex molecules.
Decomposition (Catabolic) Reactions: Molecule is broken down into smaller molecules or atoms.
Exchange (Displacement) Reactions: Bonds are both made and broken; atoms are exchanged between reactants.

Rate of Chemical Reactions

Influenced by temperature, concentration, particle size, and catalysts (enzymes).
Enzymes: Biological catalysts that speed up reactions by lowering activation energy.

Organic vs. Inorganic Compounds

Organic Compounds: Contain carbon; include carbohydrates, lipids, proteins, nucleic acids.
Inorganic Compounds: Do not contain carbon (exceptions: CO2, CO); include water, salts, acids, bases.

Acids, Bases, and Salts

Acids: Release H+ ions in solution; proton donors.
Bases: Accept H+ ions; proton acceptors (often release OH-).
Salts: Ionic compounds formed from acid-base reactions.

pH Scale

Measures hydrogen ion concentration.
Scale: 0 (most acidic) to 14 (most basic); 7 is neutral.

Buffers

Substances that minimize changes in pH by accepting or donating H+ ions.
Important for maintaining homeostasis in body fluids.

Carbohydrates

Monosaccharides: Simple sugars (e.g., glucose).
Disaccharides: Two monosaccharides joined (e.g., sucrose).
Polysaccharides: Long chains of monosaccharides (e.g., glycogen, starch).
Function: Primary energy source for cells.

Lipids

Types: Triglycerides (fats), phospholipids, steroids.
Functions: Energy storage, cell membrane structure, hormones.

Proteins

Amino Acids: Building blocks of proteins; 20 types.
Peptide Bonds: Covalent bonds linking amino acids.
Levels of Structure: Primary (sequence), secondary (alpha-helix, beta-sheet), tertiary (3D folding), quaternary (multiple polypeptides).
Fibrous Proteins: Structural (e.g., collagen).
Globular Proteins: Functional (e.g., enzymes, antibodies).

Protein Denaturation

Loss of protein structure (and function) due to changes in pH, temperature, or chemicals.

Nucleic Acids

DNA: Genetic material; double helix; bases A, T, C, G.
RNA: Single-stranded; bases A, U, C, G; involved in protein synthesis.

ATP (Adenosine Triphosphate)

Main energy currency of the cell.
Energy released when phosphate bonds are broken.

Summary Table: Organic vs. Inorganic Compounds

Property	Organic Compounds	Inorganic Compounds
Contains Carbon	Yes (usually)	No (few exceptions)
Examples	Carbohydrates, lipids, proteins, nucleic acids	Water, salts, acids, bases
Size/Complexity	Large, complex	Small, simple

Additional info: Some explanations and examples were expanded for clarity and completeness based on standard Anatomy & Physiology textbooks.