Chapter 2: The Chemistry of Life - Atoms, Molecules, and Organic Compounds

What is a chemical element?

The simplest form of matter to have unique chemical properties.

How many naturally occurring elements are there?

98 naturally occurring elements.

Which six elements account for 98.5% of the body's weight?

Oxygen, hydrogen, carbon, nitrogen, calcium, and phosphorus.

What are minerals?

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

What is the role of minerals in the body?

They contribute to body structures, enable enzyme function, and are vital to nerve and muscle function.

What is the nucleus of an atom composed of?

Protons and neutrons.

What charge do protons have?

A positive electrical charge.

What is the atomic number of an element?

The total number of protons in the nucleus.

What are valence electrons?

Electrons in the outermost shell that determine chemical bonding properties.

What is the octet rule?

Atoms tend to react in ways that produce an outer shell with 8 electrons.

What are isotopes?

Varieties of elements that differ in the number of neutrons.

What are radioisotopes?

Unstable isotopes that decay into stable isotopes, giving off radiation.

What is an ion?

A charged particle with unequal numbers of protons and electrons.

What is the difference between an anion and a cation?

An anion has a negative charge; a cation has a positive charge.

What are electrolytes?

Salts that ionize in water, forming solutions that can conduct electricity.

What is a molecule?

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

What is a compound?

A molecule composed of two or more different elements.

What is a covalent bond?

A bond formed by the sharing of electrons between two atoms.

What is a hydrogen bond?

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

What is the significance of water in the body?

Water constitutes 50% to 75% of the body and has properties that support life, such as solvency and cohesion.

What is solvency?

The ability to dissolve other chemicals; water is often called the universal solvent.

What is adhesion?

The tendency of one substance to cling to another.

What is cohesion?

The tendency of a substance to cling to itself.

What is a hydration sphere?

The structure formed when water molecules surround and separate ions in solution.

What are free radicals?

Chemical particles with an unusual number of electrons.

What is the molecular weight of a compound?

The sum of the atomic weights of its atoms.

What are isomers?

Molecules with the same molecular formula but different arrangements of atoms.

What are van der Waals forces?

Weak, brief attractions between neutral atoms caused by random fluctuations in electron orbits.

What property of water allows it to form a surface film?

Surface tension

What is the significance of water's high heat capacity?

It allows water to absorb energy without changing state, providing thermal stability.

How many calories are required to raise the temperature of one gram of water by one degree Celsius?

One calorie

How many calories can be lost in the evaporation of 1 gram of perspiration?

580 calories

What is a solution?

A mixture of solute particles (under 1 nm) and a solvent, usually water.

What is a colloid?

A mixture with larger particles (1 to 100 nm) that scatter light and remain mixed.

What is a suspension?

A mixture with large particles (over 100 nm) that do not remain mixed and can separate upon standing.

What is an emulsion?

A suspension of one liquid in another, such as oil and vinegar.

What does concentration measure?

The amount of solute in a given volume of solution.

What is molarity?

The number of moles of a solute per liter of solution.

What is an acid?

A proton donor that releases H+ in water.

What is a base?

A proton acceptor.

What is the pH range of human blood and tissues?

7.35-7.45

What are buffers?

Chemical solutions that resist changes in pH.

What is a chemical reaction?

A process where a covalent or ionic bond is formed or broken.

What are the three classifications of chemical reactions?

Decomposition, synthesis, and exchange reactions.

What is catabolism?

Decomposition reactions that release energy, known as exergonic reactions.

What is anabolism?

Synthesis reactions that require energy input, known as endergonic reactions.

What is metabolism?

All the chemical reactions that take place in the body.

What is organic chemistry?

The study of compounds of carbon.

What are the four main classes of organic molecules?

Carbohydrates, lipids, proteins, and nucleic acids.

What is a polymer?

A molecule made up of a long chain of monomers.

What is dehydration synthesis?

The process of joining monomers to form a polymer by removing water.

What is hydrolysis?

The process of breaking down a polymer by adding water.

What is a carbohydrate?

A hydrophilic organic molecule with the general formula (CH2O)n.

What are monosaccharides?

The simplest carbohydrates, including glucose, fructose, and galactose.

What is glycogen?

A branched, energy-storage polysaccharide produced by liver and muscle cells.

What is cellulose?

A structural polysaccharide made by plants that cannot be broken down in the human body.

What is a moiety in conjugated molecules?

Each type of component in a conjugated molecule.

What are lipids?

Hydrophobic molecules usually composed only of carbon, hydrogen, and oxygen, with a high ratio of hydrogen to oxygen.

Why do lipids have more calories per gram than carbohydrates?

Lipids are less oxidized than carbohydrates.

What defines a saturated fatty acid?

A fatty acid that has as much hydrogen as it can carry.

What is an unsaturated fatty acid?

A fatty acid that has some carbons joined by double covalent bonds.

What is a triglyceride?

A molecule consisting of three fatty acids bonded to glycerol.

What are phospholipids?

Similar to neutral fats, but have a phosphate group instead of one fatty acid.

What is the amphiphilic nature of phospholipids?

Phospholipids have hydrophobic tails and a hydrophilic head.

What are eicosanoids?

20-carbon compounds derived from arachidonic acid with hormone-like functions.

What is the parent steroid from which all others are synthesized?

Cholesterol.

What is the primary function of fats?

Energy storage, thermal insulation, and cushioning vital organs.

What is a protein?

A polymer of amino acids.

What is a peptide?

A molecule composed of two or more amino acids joined by peptide bonds.

What is the primary structure of a protein?

The amino acid sequence held together by covalent bonds.

What is denaturation in proteins?

A usually irreversible change in conformation due to extreme changes in pH or temperature.

What are enzymes?

Proteins that function as biological catalysts.

What is the role of cofactors in enzyme function?

They are nonprotein molecules that assist enzymes in catalyzing reactions.

What is adenosine triphosphate (ATP)?

The body's most important energy-transfer molecule.

What are nucleotides?

Organic compounds consisting of a nitrogenous base, a monosaccharide, and one or more phosphate groups.

What is the function of DNA?

To store genetic information.

What is the function of RNA?

To play roles in genetics and protein synthesis.

What is the difference between oligopeptides and polypeptides?

Oligopeptides have fewer than 10-15 amino acids; polypeptides have 50 or more.

What is the secondary structure of a protein?

A shape held together by hydrogen bonds between non-adjacent amino acids.

What is tertiary structure in proteins?

The further bending and folding of a protein resulting from interactions of R groups.

What is quaternary structure in proteins?

The association of two or more polypeptide chains by non-covalent forces.

What is the significance of the R group in amino acids?

It varies and determines the properties of each amino acid.

What is the function of proteins in cell adhesion?

Proteins bind cells to each other.

What is the role of enzymes in metabolic pathways?

Each step in a metabolic pathway is catalyzed by a different enzyme.