KEY WORDS

MEANING

ATOMS

pages 11-13

atoms

The units of matter that form all chemical substances. Atoms have no electric charge because the number of protons in the nucleus equals the number of electrons outside the nucleus.

chemical element

Each type of atom is a chemical element. There are over 100 chemical elements. 24 are essential for human life. 4 account for 99% of the atoms in the body. They are hydrogen (63%), oxygen (26%), carbon (9%) and nitrogen (1%). (Table 2-1).

protons

Subatomic particle with one positive charge. Confined to the atomic nucleus. About 1800 times heavier than electron. (Fig 2-1).

neutrons

Subatomic particle with no charge. Confined to the atomic nucleus. About same mass as proton.

electrons

Subatomic particle with one negative charge. Electrons revolve in orbits of various distances around atomic nucleus.

atomic nucleus

See above.

major elements in the body

hydrogen, oxygen, carbon, nitrogen.

atomic weight

A scale that indicates an atom's mass relative to other atoms. It is based on assigning the carbon atom a value of 12. The atomic weight is about equal to the number of protons and neutrons. Hydrogen has an atomic weight of about 1 (has 1 proton, no neutrons).

gram atomic mass

The amount of the element in grams that is equal to the numeric value of the atomic weight. 1 gram atomic mass contains the same number of atoms (6.02 x 10²³).

trace elements

There are 13 trace elements essential for growth and function. Iron is one of them. (less than 0.01% of atoms in the body). (Table 2-1).

mineral elements

There are 7 essential mineral elements. They are the most abundant substances dissolved in the intracellular and extracellular fluid. For example, sodium (Na), chloride (Cl) and potassium (K) are essential for nerve conduction. (0.7% of atoms in the body). (Table 2-1).

MOLECULES

page 13

molecule

Two or more atoms bonded together.

covalent bond

The strongest chemical bond between atoms. Formed when the electron in the outer orbit of each atom is shared between two atoms. (Fig. 2-1).

molecular shape

Molecules are not rigid structures. Atoms can axially rotate around covalent bonds. (Fig. 2-3).

IONS

pages 13-15

ion

An atom which has gained or lost one or more electrons. It is then positively or negatively charged. ie. Na+, Cl-.

electrolytes

Ions are also called electrolytes when dissolved in water because of their ability to carry electric charge. ie NaCl (table salt) dissolves to Na+ and Cl-. (Fig. 2-5).

cations

Positively charged ions.

anions

Negatively charged ions.

carboxyl group

R-COOH (a commonly encountered group of atoms that undergoes ionization to R-COO- and H+).

amino group

NH₂ (a commonly encountered group of atoms that undergoes ionization to NH₃+).

page 15

Electrons orbiting around a nucleus occupy regions called orbitals. Each orbital can hold two electrons. Atoms are most stable when each orbital is occupied by two electrons of opposite spin.

An atom containing a single atom in its outermost shell is called a free radical, as are molecules containing such atoms. Typically, free radicals exist for only brief periods.

Important ones are:

superoxide anion: O₂-

hydroxyl radical: OH

nitric oxide: NO

The dot next to the atomic symbol indicates it is a free radical. They can have important roles in normal and abnormal cellular functions.

KEY WORDS

MEANING

POLAR MOLECULES

pages 15-17

polar covalent bond

Covalent bonds in which electrons are not shared equally between two atoms but instead reside closer to one atom of the pair. This atom has a slight negative charge while the other atom which has partly lost the electron has a slight positive charge. (Fig. 2-4).

hydroxyl group

R-OH (A polar covalent bond in which the oxygen is slightly negative and the hydrogen slightly positive.

polar molecules

Molecules containing significant numbers of polar bonds or ionized groups. ie R-OH. (Table 2-4).

nonpolar molecules

Molecules composed mainly of electrically neutral covalent bonds. ie C-C and C-H. (Table 2-4).

hydrogen bond

Weak bond due to electrical attraction between hydrogen in one polarized bond and oxygen or nitrogen in another. (Fig. 2-4).

hydrolysis

Break down of molecules by reaction with water.

SOLUTIONS

pages 17-20

solutes

Substances dissolved in a liquid. ie. Salt (NaCl) in salt water.

solvents

The liquid in which the substance is dissolved. ie. Water in salt water.

solution

Solutes dissolve in a solvent to form a solution.

hydrophilic

water loving: ionized or polarized groups will react with water and dissolve. (Fig. 2-5).

hydrophobic

water fearing: electrically neutral covalent bonds will not react with water. These are primarily carbon and hydrogen. Fat and oil are examples.

amphipathic

molecules with polar and non-polar ends. (Fig. 2-6).

concentration

The amount of solute present in a unit volume of solution. Usually expressed as grams per liter or moles per liter. 1 liter = 1.06 quarts.

molecular weight

The sum of the atomic weights of all the atoms in the molecule. Methane CH₄ has a molecular weight of

12 + 4 = 16. Glucose C₆H₁₂O₆ has a molecular weight of 6 X 12 + 12 X 1 + 6 X 16 = 180.

mole

The amount of the compound in grams equal to the molecular weight. One mole of glucose weighs 180 grams. 1 mole/l glucose = 1 M glucose = 180 grams/l. (l=liter)

acid

Molecules that release hydrogen in solution.

base

Substances that can accept a hydrogen ion.

strong acid

Acids which are 100% ionized in solution (ie. HCl).

weak acid

Acids only partially ionized in solution (ie.lactic acid).

acidity, pH

Acidity refers to the free hydrogen ion concentration in solution. The higher the hydrogen ion concentration the greater the acidity. pH is the negative logarithm to the base 10 of the hydrogen ion concentration.

pH = -log [H+]

A solution with [H+] of 10^-7 M has pH of 7. (neutral)

A solution with [H+] of 10^-5 M has pH of 5. (more acidic)

neutral solution

pH 7.0 (as in pure water)

acidic solution

pH lower than 7.0 (more than 10^-7 M hydrogen ion concentration)

alkaline solution

pH higher than 7.0 (extracellular body fluids about pH 7.4)

KEY WORDS

MEANING

CLASSES OF ORGANIC MOLECULES

Major categories are carbohydrates, lipids, proteins and nucleic acids. (Table 2-5).

pages 20-33

macromolecules, polymers

Large molecules composed of thousand of atoms. They are characterized by many carbon atoms, which have four sites for covalent bonding, resulting in long strings of atoms.

1. Carbohydrates

Composed of carbon, hydrogen and oxygen in the ratio C_nH_2nO_n

monosaccharides

Sugars with one ring. (Figs. 2-7, 2-8).

glucose

A 6 carbon monosaccharide. Blood sugar. Major sugar in blood. (Fig. 2-7).

pentoses

5 carbon sugars.

hexoses

6 carbon sugars. Pentoses and hexoses are the major monosaccharides in the body.

disaccharide

Carbohydrates compose of two monosaccharides.

sucrose

Table sugar. Disaccharide composed of glucose and fructose. (Fig. 2-9).

polysaccharide

Large polymer of many monosaccharides. (Fig. 2-10).

glycogen

A major polysaccharide in animal cells. Consists of many molecules of glucose. (Fig. 2-10).

2. Lipids

(Fig. 2-11)

Molecules composed mainly of hydrogen and carbon in neutral covalent bonds. Thus, lipids are nonpolar and insoluble in water.

fatty acid

Consists of a chain of carbon atoms with a carboxyl group at one end (-COOH).

saturated fatty acid

All carbons in the fatty acid chain are linked by single covalent bonds. All carbon sites are saturated.

unsaturated fatty acid

Contain one or more double bonds.

mono-unsaturated

One double bond is present.

polyunsaturated

More than one double bond is present.

triacylglycerols

The majority of lipids in the body. Formed by linking glycerol with three fatty acids.

glycerol

A 3 carbon carbohydrate.

phospholipids

Similar to triacylglycerols except the third hydroxyl of glycerol is linked to phosphate rather than a fatty acid.

steroids

These contain strings of carbon with attached hydrogens as other lipids do. However, the carbons are in rings. Steroids have a four ring structure to which side chains can be attached (Fig 2-12).

Examples: cholesterol, estrogen, testosterone.

3. Proteins

Polymers of amino acids. Proteins account for 50% of the organic nutrients of the body. They are critical to almost every physiological process.

amino acid

The subunits of protein. Amino acids have an amino group, a carboxyl group, and a side chain linked to a carbon atom (Figure 2-13).

amino acid side chain

There are 20 different side chains for the 20 different amino acids in the human body.

peptide bond

The bond formed between amino acids to form peptides. The peptide bond is between the carboxyl group of one amino acid and the amino group of another (Figure 2-14). In the process a molecule of water is released.

polypeptides

A sequence of amino acids formed by peptide bonds.

peptide

Amino acid chain of 50 or less amino acids. Proteins are considered to have 50 or more.

glycoprotein

Some proteins have sugars attached to the side chains. These are glycoproteins.

conformation ***

The three-dimensional shape of a molecule. (Figs. 2-15, 2-16, 2-19).

van der Waals forces

Very weak forces between hydrophobic regions of a molecule. Know Table 2-6, first 3 columns.

alpha helix

Helical shape to peptide chains caused by regularly spaced hydrogen bonds. (Fig. 2-18).

disulfide bond

A covalent bond between the sulfhydryl groups of two cysteine amino acids (Fig. 2-20). (Don't need to know).

4. Nucleic acids

Account for only 2% of body weight but are responsible for storage, expression and transmission of genetic information. Nucleic acids are vital to the continuation of life.

nucleotide

The subunits of DNA and RNA. A nucleotide contains 3 components: a phosphate group, a sugar and a purine or pyrimidine base. (Fig. 2-21).

DNA

deoxyribonucleic acid, contains the 5 carbon sugar, deoxyribose. DOUBLE STRANDED string of nucleotides. (Fig. 2-21).

RNA

ribonucleic acid, contains the 5 carbon sugar, ribose. SINGLE STRANDED string of nucleotides. (Fig. 2-21).

purine bases

adenine, guanine (have two rings). (Fig 2-22).

pyrimidine bases

cytosine, thymine (have one ring). Uracil instead of thymine in RNA. (Fig. 2-22).

DNA DOUBLE HELIX

Fig. 2-23. Two chains of nculeotides coiled around each other with the chains held together by hydrogen bonds between purine and pyrimidine bases.

hydrogen bonds between purine and pyrimidine bases

Bonds are: A-T (2 hydrogen bonds)

G-C (3 hydrogen bonds). (Fig. 2-23).

sugar-phosphate backbone

The "backbone" of the DNA molecule made up of alternating sugar (deoxyribose) and phosphate groups. (Fig. 2-22).