Chapter 2: The Chemistry of Life

Anatomy & Physiology I

Chemistry

The study of matter and energy.

Matter

Anything that has mass and occupies space, composed of elements.

Energy

Power to do work.

Elements

Simplest form of matter. Periodic table of elements—lists all known elements.

Octet Rule

elements with atomic number less than 20 have their outermost shell hold up to eight electrons.

Kinetic energy

Stored energy.

Potential energy

The potential for more energy to be gain.

Isotopes

varieties of an element that differ only in the number of neutrons; different atomic mass.

Radioisotopes

unstable isotopes that decay and give off radiation in a process called radioactivity.

Intense radiation can be ionizing (ionizing radiation)

Examples: UV radiation, X-rays, alpha particles, beta particles, gamma rays.

ejects electrons, destroys molecules, creates free radicals—cause genetic mutations and cancer.

Some radioisotopes have scientific and medical uses, what are they?

-Dating fossils (carbon-14)
-Diagnostic imaging; Cancer treatment
-Power supply for implants such as cardiac pacemakers

An ion is….

a charged particle with unequal number of protons and electrons.

Ionization

transfer of electrons from one atom to another.

Anion

net negative charge due to gain of electrons.

Cation

net positive charge due to loss of electrons.

Ions with opposite charges are….

attracted to each other.

Electrolytes

Examples: Calcium chloride, Sodium chloride, Potassium chloride.

substances that ionize in water.

Molecule

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

Compound

molecule composed of two or more different elements.

Kinds of chemical bonds….

(Attractive forces holding atoms together.)

-Covalent bonds

-Ionic bonds

-Hydrogen bonds

Single covalent bond

nuclei share 1 pair of electrons.

Double covalent bond

nuclei share 2 pairs of electrons.

Cation

a positively charged ion.

Anion

a negatively charged ion.

Water is _____ of body weight?

50 to 75%

Solvency

ability to dissolve other chemicals.

Hydrophilic

substances dissolve in water; are
polarized or charged. Likes water.

Hydrophobic

substances do not dissolve in water; are nonpolar or neutral. Does not like water.

Adhesion

tendency of one substance to cling to another.
Water adheres to membranes reducing friction around organs.

Cohesion

tendency of molecules from same substance to cling to each other.

-Water is very cohesive due to its hydrogen bonds

Water has the ability of what?

(Certain type of stability for water)

Thermal stability due to high heat capacity, it doesn’t increase temperature really fast or very slow.

Chemical reactivity

ability to participate in chemical reactions.

Acid

◦ Any molecule that releases hydrogen ions (H+)
◦ Increases hydrogen ion concentration in solutions

Base

◦ Any molecule that can accept hydrogen ions (H+) or releases OH-
◦ Decreases hydrogen ion concentration in solutions

pH Scale

A measure of hydrogen ion concentration.

Human Blood is a pH of?

7.4

Buffers….

-Minimize pH change
-Help maintain stable pH in body fluids

The body’s most important buffer pairs….

Carbonic acid and bicarbonate.

Synthesis Reaction or Dehydration synthesis

(Chemical reaction)

formation of a large molecule out of smaller molecules.

Decomposition Reaction or Hydrolysis

(Chemical reaction)

formation of smaller molecules out of a large molecule.

Organic compounds are molecules that contain a carbon backbone, essential for life and forming the basis of four major biological macromolecules:

Carbohydrates, lipids, proteins, and nucleic acids.

These macromolecules are polymers, meaning….

They are large chains built from smaller repeating units called monomers.

Monosaccharides are the simplest carbohydrates, what are they?

Glucose, galactose, and fructose.

Disaccharides are….

sugars made of two covalently bonded monosaccharides.

Three important disaccharides….

Sucrose (table sugar)—glucose + fructose

Lactose (milk sugar)—glucose + galactose

Maltose (sugar in grain products)—glucose + glucose

Oligosaccharides are….

short chains of 3 or more monosaccharides.

Polysaccharides are….

long chains of monosaccharides (~50 or more).

Three important polysaccharides….

Glycogen—energy storage in cells (ex. liver, muscle, brain)

Starch—energy storage in plants; digestible by humans

Cellulose—structural molecule in plants: fiber for humans (indigestible)

Lipids

Hydrophobic organic molecules with a high ratio of hydrogen to oxygen.

Five primary types of lipids in the human body….

• Fatty acids

• Triglycerides

• Phospholipids

• Eicosanoids

• Steroids

Fatty Acids, the two types are….

Saturated fatty acids and Unsaturated fatty acids.

Saturated fatty acids….

Solid at room temperature.
• Single bonds between carbons; saturated with hydrogen
• Animal fats

Unsaturated fatty acids….

Liquid at room temperature.
• Double bond between one or more neighboring carbons
• Oils: monounsaturated fat (e.g., olive oil);
polyunsaturated fat (e.g., canola oil).
• Mostly from plant origin

Proteins have three to four levels of complexity:

Insulin
Collagen
Globular proteins; muscular filaments Hemoglobin

Triglycerides

Each fatty acid covalently bonded to the oxygen atoms of the –OH groups of the
glycerol molecule.

The negative effects of artificial trans fats….

Trans fats, formed from partially hydrogenated oils, resists enzymatic breakdown in the human body, remain in circulation longer, deposits in the arteries; thus, raises the risk of heart disease.

Phospholipids

• Cell membrane structure: Bilayer

• Hydrophobic and hydrophilic regions, the head being hydrophilic, and the tail being hydrophobic.

Cholesterol is the “parent” (backbone)….

steroid from which other steroids are synthesized.

- Important for nervous system function and structural integrity of all cell membranes.

Other steroids include….

Cortisol, progesterone, estrogens, testosterone, and bile acids

Polymer of amino acids joined by peptide
bonds….

Oligopeptides (10 to15 amino acids)

Polypeptides (larger than 15 amino acids)

Amino acids have a central carbon with three attachments….

◦ Amino group (-NH2)
◦ Carboxyl group (–COOH)
◦ R (radical) group

Proteins have three to four levels of complexity:

a) Primary structure, ex. Insulin

b) Secondary structure, ex. Collagen

c) Tertiary structure, ex. Globular proteins; muscular filaments

d) Quaternary structure, ex. Hemoglobin

Proteins Shape referred to as their….

Conformation

Conformation is….

• Unique; crucial to function

• Proteins can reversibly change conformation to affect function

• Important examples seen in muscle contraction, enzyme catalysis, membrane channel opening, and so on.

Denaturation is….

Extreme conformational change that destroys function.

What can cause permanent (irreversible) denaturation?

Extreme heat or pH.

Enzymes….

Proteins that function as biological catalysts.
◦ Enzymes act on one or more substrates
◦ Speed up chemical reaction by lowering the activation energy
◦ Permit reactions to occur rapidly at body temperature
◦ Enzymes are not used up in reactions, and are reused.

Enzymatic Reactions….

Temperature, pH and other factors can change enzyme shape and function
• Optimum pH
• Salivary amylase works best at pH 7.0
• Pepsin in stomach works best at pH 2.0

Temperature optimum for human enzymes is usually near body temperature of?

(37°C) or (98°F)

Nucleic Acids….

(Polymers of nucleotides)

• DNA (deoxyribonucleic acid)
• RNA (ribonucleic acid)

DNA (deoxyribonucleic acid)….

• Contains millions of nucleotides

• Constitutes genes involved in protein synthesis

• Stays in the nucleus

• 2 strands

RNA (ribonucleic acid)….

• 70 to 10,000 nucleotides long

• Carries out genetic instruction (encoded in DNA) for synthesizing proteins

• Can leave the nucleus

• 1 strand