Comprehensive Biology: Chemistry of Life, Molecules, and Cell Functions

Biochemistry

The study of the molecules that compose living organisms.

Chemical Element

The simplest form of matter to have unique chemical properties.

Atomic Number

Number of protons in the nucleus of an atom.

Periodic Table

Arranges elements by atomic number and represents them as 1-2 letter symbols.

Naturally Occurring Elements

91 elements that are found in nature.

Most Abundant Elements in Humans

6 elements that make up 98.5% of body weight: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.

Trace Elements

Elements present in minute amounts that play vital roles in the body.

Minerals

Inorganic elements extracted from soil by plants and passed up the food chain to humans.

Body Weight Contribution of Minerals

4% of body weight, mostly calcium and phosphorus.

Atom

The smallest unit of matter.

Nucleus

Center of an atom, composed of protons and neutrons.

Protons

Particles with a single (+) charge and a mass of 1 atomic mass unit (amu).

Neutrons

Particles with no charge and a mass of 1 atomic mass unit (amu).

Electrons

Particles with a single (−) charge and very low mass, found in concentric clouds surrounding the nucleus.

Atomic Mass

Approximate total number of protons and neutrons in an atom.

Valence Electrons

Electrons in the outermost shell that determine the chemical bonding properties of an atom.

Isotopes

Varieties of an element that differ only in the number of neutrons and therefore in atomic mass.

Ion

A charged particle (atom or molecule) with an unequal number of protons and electrons.

Ionization

Transfer of electrons from one atom to another.

Anion

A particle that has a net negative charge due to the gain of electrons.

Cation

A particle that has a net positive charge due to the loss of electrons.

Ions with Opposite Charges

Attracted to each other.

Salts

Electrically neutral compounds of cations and anions; readily dissociate in water into ions and act as electrolytes.

Electrolytes

Substances that ionize in water and form solutions capable of conducting electric current.

Functions of electrolytes

Chemical reactivity, osmotic effects, electrical excitability of nerve and muscle.

Electrolyte balance

One of the most important considerations in patient care; imbalances can lead to coma or cardiac arrest.

Free radicals

Unstable, highly reactive particles with an unusual number of electrons.

Production of free radicals

Produced by normal metabolic reactions, radiation, certain chemicals.

Effects of free radicals

Trigger reactions that destroy molecules, and can cause cancer, death of heart tissue, and aging.

Example of a free radical

Superoxide anion.

Antioxidants

Chemicals that neutralize free radicals.

Example of an antioxidant

Superoxide dismutase (SOD) is an antioxidant enzyme that converts superoxide anion into oxygen and hydrogen peroxide.

Dietary antioxidants

Selenium, vitamin E, vitamin C, and carotenoids are antioxidants obtained through the diet.

Molecule

Particle composed of two or more atoms united by a chemical bond.

Compound

Molecule composed of two or more different elements.

Molecular formula

Represents a compound by identifying constituent elements and how many atoms of each are present.

Ionic bonds

Attraction of a cation to an anion.

Example of ionic bond

Sodium and chloride ions bond to form sodium chloride.

Covalent bonds

Atoms share one or more pairs of electrons.

Single covalent bond

Nuclei share 1 pair of electrons.

Double covalent bond

Nuclei share 2 pairs of electrons.

Nonpolar covalent bond

Electrons are shared equally; example: carbon atoms bonding together.

Polar covalent bond

Electrons shared unequally; example: hydrogen bonding with oxygen, electrons spend more time by oxygen.

Hydrogen bond

A weak attraction between a slightly positive hydrogen atom in one molecule and a slightly negative oxygen or nitrogen atom in another atom.

Importance of hydrogen bonds

Relatively weak bonds, but very important to physiology; water molecules are attracted to each other by hydrogen bonds.

Body fluids

Complex mixtures of chemicals.

Mixtures

Consist of substances that are physically blended but not chemically combined; each substance retains its own chemical properties.

Water

Makes up 50 to 75% of body weight and is essential for life.

Solvency

Ability to dissolve other chemicals.

Universal solvent

Water is the universal solvent because it dissolves more substances than any other solvent.

Hydrophilic substances

Substances that dissolve in water; are polarized or charged.

Hydrophobic substances

Substances that do not dissolve in water; are nonpolar or neutral.

Hydration spheres

Water forms hydration spheres around each ion, allowing salts like NaCl to dissolve.

Adhesion

Tendency of one substance to cling to another.

Cohesion

Tendency of molecules of the same substance to cling to each other.

Chemical reactivity

Ability to participate in chemical reactions.

Thermal stability

Water stabilizes internal temperature; hydrogen bonds resist temperature increases.

Solution

Consists of particles called the solute mixed with a more abundant substance (usually water) called the solvent.

Solute

Can be gas, solid, or liquid that is mixed in a solution.

Colloids

Mixtures of protein and water that can change from liquid to gel state.

Suspension

Defined by particles too large to penetrate selectively permeable membranes and that separate on standing.

Emulsion

Suspension of one liquid in another, such as oil-and-vinegar salad dressing.

Acid

A proton donor; releases ions in water.

Base

A proton acceptor; accepts ions in water.

pH scale

Measures acidity based on the amount of hydrogen ions present.

Neutral pH

A pH of 7.0.

Acidic pH

A pH of less than 7.

Basic pH

A pH of greater than 7.

Buffers

Chemical solutions that resist changes in pH.

Normal pH of blood

The normal pH of blood is 7.4, which is crucial for physiological functions.

Energy

The capacity to do work.

Work

To do work means to move something, such as a muscle or a molecule.

Potential energy

Energy stored in an object, but not currently doing work; for example, water behind a dam.

Chemical energy

Potential energy in molecular bonds.

Free energy

Potential energy available in a system to do work.

Kinetic energy

Energy of motion, energy doing work.

Heat

Kinetic energy of molecular motion.

Electromagnetic energy

Kinetic energy of photons.

Electrical energy

Energy that has both potential and kinetic forms.

Chemical reaction

A process in which a covalent or ionic bond is formed or broken.

Chemical equation

A symbolic representation of the course of a chemical reaction.

Reactants

Substances on the left side of a chemical equation.

Products

Substances on the right side of a chemical equation.

Decomposition reactions

Reactions where a large molecule breaks down into two or more smaller ones, symbolized as AB → A + B.

Synthesis reactions

Reactions where two or more small molecules combine to form a larger one, symbolized as A + B → AB.

Exchange reactions

Reactions where two molecules exchange atoms or groups of atoms, symbolized as AB + CD → AC + BD.

Reversible reactions

Reactions that can proceed in either direction under different circumstances, symbolized with a double-headed arrow.

Law of mass action

The principle stating that the direction of a reversible reaction is determined by the relative abundance of substances on either side of the equation.

Equilibrium

A state reached when the ratio of products to reactants is stable.

Reaction rates

The speed at which a chemical reaction occurs, which increases when the concentration of reactants increases, temperature rises, or a catalyst is present.

Catalysts

Substances that increase the rate of a reaction without being consumed in the process.

Metabolism

All chemical reactions of the body, divided into catabolism and anabolism.

Catabolism

Energy-releasing (exergonic) decomposition reactions that break covalent bonds and produce smaller molecules.

Anabolism

Energy-storing (endergonic) synthesis reactions that require energy input.

Organic chemistry

The study of compounds containing carbon.

Macromolecules

Large organic molecules with high molecular weights, most of which are polymers.

Polymers

Molecules made of a repetitive series of identical or similar subunits called monomers.

Monomers

The identical or different subunits that make up polymers.

Dehydration synthesis

The process of covalently linking monomers together by removing a hydroxyl (-OH) group from one monomer and a hydrogen (-H) from another, producing water as a by-product.

Hydrolysis

The process of splitting a polymer into monomers by the addition of water.