뒤로Chapter 2: Chemistry Comes Alive – Study Notes for Anatomy & Physiology
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Chapter 2: Chemistry Comes Alive
Introduction to Chemistry in Physiology
Chemistry forms the foundation for all physiological processes in the human body. Understanding the structure and behavior of matter and energy is essential for comprehending movement, digestion, nerve impulses, and more.
2.1 Matter and Energy
Matter
Matter is anything that has mass and occupies space.
States of matter:
Solid: Definite shape and volume.
Liquid: Changeable shape, definite volume.
Gas: Changeable shape and volume.
Energy
Energy is the capacity to do work or put matter into motion.
Forms of energy:
Kinetic energy: Energy in action.
Potential energy: Stored energy.
Chemical energy: Stored in bonds of chemical substances.
Electrical energy: Movement of charged particles.
Mechanical energy: Directly involved in moving matter.
Radiant energy: Travels in waves (e.g., light, X-rays).
Energy conversions are inefficient; some energy is lost as heat.
2.2 Atoms and Elements
Elements and Atoms
Elements are substances that cannot be broken down by ordinary chemical means.
Four elements make up 96% of the human body: Oxygen, Carbon, Hydrogen, Nitrogen.
Atoms are the smallest units of elements, retaining their properties.
Atomic Structure
Atoms consist of three subatomic particles:
Protons (p+): Positive charge, 1 amu, in nucleus.
Neutrons (n0): No charge, 1 amu, in nucleus.
Electrons (e-): Negative charge, ~0 amu, orbit nucleus.
Atomic Number, Mass Number, Isotopes
Atomic number: Number of protons in the nucleus.
Mass number: Total number of protons and neutrons.
Isotopes: Atoms of the same element with different numbers of neutrons.
Atomic weight: Average of mass numbers of all isotopes.
2.3 Combining Matter
Molecules, Compounds, and Mixtures
Molecule: Two or more atoms bonded together.
Compound: Molecule with two or more different kinds of atoms.
Mixtures: Physical combinations of substances; can be separated by physical means.
Types of mixtures:
Solutions: Homogeneous, solute particles do not settle out.
Colloids: Heterogeneous, larger particles, do not settle out, scatter light.
Suspensions: Heterogeneous, large particles, settle out.
2.4 Chemical Bonds
Role of Electrons in Bonding
Electrons occupy electron shells (energy levels) around the nucleus.
The valence shell is the outermost shell; electrons here are involved in bonding.
Octet rule: Atoms tend to gain, lose, or share electrons to achieve 8 in their valence shell (except H and He, which require 2).
Types of Chemical Bonds
Ionic bonds: Transfer of electrons from one atom to another, forming ions (cations and anions).
Covalent bonds: Sharing of electrons between atoms. Can be:
Nonpolar: Equal sharing (e.g., O2, CO2).
Polar: Unequal sharing, creating dipoles (e.g., H2O).
Hydrogen bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., between water molecules).
2.5 Chemical Reactions
Types of Chemical Reactions
Synthesis (Anabolic): Atoms or molecules combine to form larger molecules. Example: Protein synthesis from amino acids.
Decomposition (Catabolic): Molecules are broken down into smaller components. Example: Glycogen breakdown to glucose.
Exchange (Displacement): Bonds are both made and broken. Example: ATP transfers a phosphate to glucose.
2.6 Inorganic Compounds
Water
Most abundant inorganic compound in the body (60–80% of cell volume).
Properties:
High heat capacity and vaporization.
Polar solvent properties (dissolves ionic substances).
Reactivity (in hydrolysis and dehydration synthesis).
Cushioning (protects organs).
Salts
Ionic compounds that dissociate in water to form electrolytes (conduct electricity).
Vital for nerve impulse transmission, muscle contraction, and water balance.
Acids and Bases
Acids: Proton donors; release H+ ions.
Bases: Proton acceptors; release OH- ions.
pH scale: Measures H+ concentration; 0–6.99 acidic, 7 neutral, 7.01–14 basic.
Buffers: Resist changes in pH by releasing or binding H+ ions.
2.7 Organic Compounds: Synthesis and Hydrolysis
Organic molecules contain carbon (except CO2 and CO).
Major classes: Carbohydrates, lipids, proteins, nucleic acids.
Polymers are formed by dehydration synthesis (removal of water) and broken down by hydrolysis (addition of water).
2.8 Carbohydrates
Include sugars and starches; contain C, H, O in a 1:2:1 ratio.
Three classes:
Monosaccharides: Simple sugars (e.g., glucose, fructose, ribose).
Disaccharides: Two monosaccharides joined (e.g., sucrose, maltose, lactose).
Polysaccharides: Long chains of monosaccharides (e.g., glycogen, starch).
2.9 Lipids
Contain C, H, O (less O than carbohydrates), sometimes P; insoluble in water.
Main types:
Triglycerides: Glycerol + 3 fatty acids; energy storage, insulation, protection.
Phospholipids: Glycerol + 2 fatty acids + phosphate group; main component of cell membranes.
Steroids: Four interlocking rings; cholesterol is the most important.
Eicosanoids: Derived from arachidonic acid; involved in inflammation and other functions.
2.10 Proteins
Comprise 10–30% of cell mass; contain C, H, O, N, sometimes S and P.
Functions: Structural support, enzymes, movement, transport, communication, defense.
Polymers of amino acids linked by peptide bonds.
Four structural levels:
Primary: Sequence of amino acids.
Secondary: Alpha helices and beta sheets.
Tertiary: 3D folding of the polypeptide.
Quaternary: Multiple polypeptides together.
Denaturation: Loss of structure and function due to pH or temperature changes.
Enzymes: Biological catalysts that speed up reactions by lowering activation energy.
2.11 Nucleic Acids
Composed of C, H, O, N, P; largest molecules in the body.
Monomers: Nucleotides (nitrogen base, pentose sugar, phosphate group).
Two types:
DNA: Double helix, genetic blueprint, in nucleus.
RNA: Single strand, involved in protein synthesis, in cytoplasm.
2.12 ATP (Adenosine Triphosphate)
ATP is the energy currency of the cell.
Structure: Adenine, ribose, three phosphate groups.
Energy is released when phosphate bonds are broken (ATP → ADP → AMP).
