The Chemistry of Life
Human Anatomy and Physiology Study Notes
The Chemistry of Life
Importance of Chemistry in Anatomy and Physiology
The chemical level is the basic structural level of organization in the human body, composed of chemicals.
Example: Bones are strong due to minerals and collagen, which are chemical substances.
Chemistry serves as the foundation for all bodily functions and concepts in human physiology.
2.1 Atoms and Elements
Matter: Anything with mass that occupies space.
Chemistry: The study of matter and its interactions.
Atom: The smallest unit of matter that retains its properties.
Element: A substance made up of identical atoms that cannot be chemically broken down.
Atoms and Atomic Structure
Composition of Atoms: Atoms consist of three types of subatomic particles:
Protons: Positively charged particles located in the atomic nucleus.
Neutrons: Neutral particles slightly larger than protons, also found in the nucleus.
Electrons: Negatively charged particles that orbit the nucleus.
An atom is electrically neutral since the number of protons equals the number of electrons.
Variation exists in the number of neutrons, contributing to atomic mass, which is mainly derived from protons and neutrons (over 99.95%).
Electron Shells:
1st Shell: Holds 2 electrons.
2nd Shell: Holds 8 electrons.
3rd Shell: Can hold up to 18 electrons but is satisfied with 8 due to the stability provided by the octet rule.
Elements in the Periodic Table and the Human Body
Elements are defined by their atomic number (the number of protons).
The Periodic Table arranges elements by increasing atomic number and reflects repeating properties.
Chemical Symbols: Abbreviations for elements.
Main Elements in the Human Body:
Four major elements make up 96% of the body's mass:
Oxygen (O) = 65%
Carbon (C) = 18%
Hydrogen (H) = 10%
Nitrogen (N) = 3%
Seven Mineral Elements contribute less than 4%:
Sodium (Na), Potassium (K), Calcium (Ca), Chlorine (Cl), Magnesium (Mg), Phosphorus (P), Sulfur (S).
Trace Elements (13 total), including Iron (Fe), Copper (Cu), Iodine (I), Zinc (Zn), play vital roles in bodily functions.
Isotopes and Radioactivity
Mass Number: Total of protons and neutrons; represented at the top left of an element symbol.
Isotope: Atoms with the same number of protons but a different number of neutrons.
Example: Hydrogen has three isotopes:
Protium (Hydrogen-1): 0 neutrons.
Deuterium (Hydrogen-2): 1 neutron.
Tritium (Hydrogen-3): 2 neutrons.
Radioisotopes: Unstable isotopes that release energy as radiation; utilized in nuclear medicine.
Nuclear Medicine
Cancer Radiation Therapy: Uses radiation to target and kill cancer cells.
Radiotracers: Injected into patients; detected and analyzed using cameras to examine cell and organ activity.
Iodine-131: Used for treatment of thyroid disorders, specifically to destroy cancerous thyroid cells.
2.2 Matter Combined: Mixtures and Chemical Bonds
Mixtures
Mixture: Physical intermixing of atoms from two or more elements without altering their chemical nature; components can be separated physically.
Types of Mixtures:
Suspensions: Visible large particles that settle out (e.g., sand in water).
Colloids: Small particles, not visible, that remain dispersed (e.g., milk).
Solutions: One substance (solute) dissolves in another (solvent) and appears translucent (e.g., sugar in water).
Chemical Bonds
Chemical Bonds: Attractiveness between atoms that forms molecules or compounds.
Molecule: Formed when two or more atoms of the same element bond.
Compound: Formed when two or more different elements bond.
Macromolecules: Very large compounds composed of many atoms.
Valence Electrons: Electrons in the outermost shell, responsible for forming bonds.
Atoms tend to follow the Octet Rule, striving for 8 valence electrons for stability, with exceptions for those with 5 or fewer electrons (following the Duet Rule).
Ions and Ionic Bonds
Ionic Bond: Electrical transfer of electrons between a metal and nonmetal.
When an atom loses or gains electrons, it becomes charged, forming ions:
Cation: Positively charged ion.
Anion: Negatively charged ion.
Oppositely charged ions attract and form compounds known as salts.
Covalent Bonds
Covalent Bond: Formed by sharing electrons between nonmetals; strongest type of bond.
Atoms can share:
Single Bond: 1 electron pair.
Double Bond: 2 electron pairs.
Triple Bond: 3 electron pairs.
Nonpolar Covalent Bond: Electrons shared equally (e.g., same element or specific arrangements prevent unequal sharing).
Polar Covalent Bond: Electrons shared unequally, leading to partial charges:
More protons in an atom equate to higher electronegativity.
Dipoles: Molecules with partially positive and negative ends.
Hydrogen Bonds
Hydrogen Bonds: Weak attractions between partially positive and negative ends of polar covalent molecules.
Important for surface tension and interactions in water.
2.3 Chemical Notation
Chemical Reaction: Occurs when bonding is formed, broken, or rearranged; includes electron transfer.
Chemical Notation: Symbols represent reactions.
Reactants: Original substances undergoing change (left side of equation).
Products: Substances produced (right side of equation).
Reversible Reactions: Can proceed in either direction, shown with two opposing arrows.
Irreversible Reactions: Proceed from reactants to products, shown with a single arrow.
Energy and Chemical Reactions
Energy: Capacity to do work; crucial for chemical reactions.
Potential Energy: Stored energy available to do work.
Kinetic Energy: Energy in motion.
Types of Energy:
Chemical Energy: Energy in chemical bonds.
Electrical Energy: Movement of charged ions.
Mechanical Energy: Direct transfer from one object to another.
Reactions & Energy:
Endergonic Reactions: Require energy input; products contain more energy than reactants.
Exergonic Reactions: Release stored energy, making available for external use.
Homeostasis and Chemical Reactions
Types of Chemical Reactions in maintaining homeostasis:
Catabolic Reactions: Breakdown of larger substances into smaller ones (e.g., digestion).
Anabolic Reactions: Build new substances (e.g., tissue regeneration).
Exchange Reactions: Transfer atoms or electrons (e.g., metabolism).
Oxidation-Reduction Reactions (Redox Reactions): Focus on electron transfer:
Oxidation: Loss of electrons.
Reduction: Gain of electrons.
Reaction Rates and Enzymes
Activation Energy: Energy needed for a reaction to occur. Successful reactions need strong collisions of electrons.
Factors Affecting Reaction Rate:
Concentration: More reactants lead to more collisions.
Temperature: Increased temperature raises kinetic energy (with physiological limits).
Properties of Reactants: Size and phase affect the reaction rate (smaller and gaseous particles react faster).
Catalysts: Lower activation energy; biological catalysts are called Enzymes.
Enzymes
Enzymes: Proteins that accelerate reaction rates, reducing activation energy requirements.
Properties:
Specific for substrates and reactions by binding in active sites.
Do not alter the chemical reaction or get permanently changed in the process.
Increase reaction speeds significantly.
Mechanism of Action: Enzymes utilize the induced fit mechanism for substrate binding.
Enzyme Deficiencies
Tay-Sachs Disease: Deficiency of hexosaminidase affecting brain cells, leading to severe outcomes by age 3.
Severe Combined Immunodeficiency Syndrome (SCIDs): Deficiency of adenosine deaminase, resulting in almost complete immune system absence.
Phenylketonuria: Deficiency in phenylalanine hydroxylase causing severe health issues, manageable through dietary changes.
2.4 Inorganic Compounds: Water, Acids, Bases, and Salts
Inorganic Compounds: Do not contain carbon-hydrogen bonds (e.g., water, acids, bases, salts).
Organic Compounds: Contain carbon bonded to hydrogen.
Water
Comprises 50-65% of body mass. Properties include:
Absorbs heat without significant temperature changes.
Transports heat during phase changes (liquid to gas).
Provides cushioning to body structures.
Acts as a lubricant in bodily interactions.
Serves as the primary solvent in biological systems:
Hydrophilic solutes dissolve in water.
Hydrophobic solutes do not dissolve in water, such as uncharged nonpolar molecules.
Acids and Bases
Acids: Proton donors that increase hydrogen ion concentration in solutions.
Bases (Alkalis): Proton acceptors that decrease hydrogen ion concentration in solutions.
pH Scale: Measures hydrogen ion concentration, expressed as:
Pure water is neutral at pH 7; acidic below 7, basic above 7.
Buffers: Chemical systems that maintain stable pH levels, critical for physiological functions.
Salts and Electrolytes
Salts: Combinations of metal cations and nonmetal anions held by ionic bonds.
Electrolytes: Resulting ions in solution critical for physiological processes, including sodium, potassium, and calcium for various bodily functions.
2.5 Organic Compounds: Hydrocarbons and Structures
Hydrocarbons: Compounds composed of only carbon and hydrogen, forming the backbone of all organic compounds.
Monomers and Polymers:
Four major types of organic compounds: Carbohydrates, Lipids, Proteins, Nucleic Acids.
Monomers serve as building blocks for larger structures, termed polymers.
Dehydration Synthesis: Process linking monomers, water is produced.
Hydrolysis Reactions: Break polymers down by adding water.
Carbohydrates
Composed of carbon, hydrogen, and oxygen; typically in 1C:2H:1O ratio, often polar and hydrophilic.
Major roles in energy storage and structure.
Monosaccharides: Simple sugars, e.g., glucose. Key energy sources.
Disaccharides: Composed of 2 monosaccharides (e.g., sucrose). Formed via dehydration synthesis.
Polysaccharides: Long chains of monosaccharides (e.g., glycogen). In plants as starch, in animals as glycogen for energy storage.
Lipids
Composed of carbon and hydrogen; includes fats and oils, are nonpolar and hydrophobic.
Major types:
Fatty Acids:
Saturated: No double bonds, solid at room temperature.
Unsaturated: One or more double bonds, liquid at room temperature.
Triglycerides: Glycerol linked to three fatty acids, stored energy.
Phospholipids: Key components of cell membranes, have a hydrophilic head and hydrophobic tails.
Steroids: Four-ring structures like cholesterol, important for cellular structure and hormone production.
Proteins
Composed of carbon, hydrogen, nitrogen, oxygen; makes up ~20% body mass. Functions include structural roles, enzyme activity, cell signaling, etc.
Composed of amino acids (21 types) linked by peptide bonds.
Levels of protein structure include primary, secondary, tertiary, and quaternary structures contributing to its function.
Denaturation: Loss of protein shape from heat, pH changes, etc., leading to loss of function.
Nucleotides and Nucleic Acids
Composed of nucleotide subunits, contain nitrogenous bases (purines: adenine, guanine; pyrimidines: cytosine, thymine, uracil).
ATP: Energy currency of the cell, produced mainly from glucose catabolism; requires oxygen for replenishment.
DNA and RNA: Store and execute genetic information. DNA forms a double helix, RNA is single-stranded and involved in protein synthesis.
Summary of Organic Compounds
Provides insights into types, structures, and functions of various organic compounds in the body, including carbohydrates, lipids, proteins, and nucleic acids, along with their importance in physiological processes.