A & P Ch. 2 The Chemistry of Life

Chemistry

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

Atomic mass

protons + neutrons

Atomic number

number of protons

Atomic symbol

1 or 2 letters

Valence shell

determines reactivity; bonding properties

Octet Rule

elements with atomic number ≤ 20 have their outermost shell hold up to eight electrons

When are atoms most stable?

when their outermost shell is full

• atoms will interact with other atoms to fill their outermost shell

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

Ionizing radiation

Intense radiation can be ionizing - ejects electrons,
destroys molecules, creates free radicals—cause genetic mutations and cancer (Ex. UV radiation, X rays, gamma rays)

Ion

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

Electrolytes

substances that ionize in water.
◦ Ex: Calcium chloride, Sodium
chloride, Potassium chloride

Molecule

composed of two or more atoms united by a chemical bond

Compound

molecule composed of two or more different elements

Chemical bonds

Attractive forces holding atoms together

Types of bonds

1. Covalent

2. Ionic

3. Hydrogen

Ionic bonds

attractive force between oppositely charged ions (Ex. NaCl)

Covalent bonds

atoms share one or more pairs of electrons; strongest bond

Single covalent bond

nuclei share 1 pair of electron

Double covalent bond

nuclei share 2 pairs of electrons

Nonpolar covalent bonds

electrons are shared equally (Ex. carbon atoms bonding together)

Polar covalent bonds

electrons shared unequally (Ex. hydrogen bonding with oxygen)

Hydrogen bonds

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

Solvency

ability to dissolve other chemicals

Hydrophilic

substance dissolve in water; are polarized or charged

Hydrophobic

substances don’t dissolve in water; nonpolar or neutral

Adhesion

tendency of one substance to cling to another

Cohesion

tendency of molecules from same substance to cling to each other

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

• Acidic pH < 7

• Neutral pH = 7

• Basic pH > 7

Buffers

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

Synthesis Reaction or Dehydration synthesis

formation of a large molecule out of smaller molecules

Decomposition Reaction or Hydrolysis

formation of smaller molecules out of a large molecule

Organic compounds

Compounds containing carbon as backbone

Macromolecules

polymers

Four categories of organic compounds

1. Carbohydrates

2. Lipids

3. Proteins

4. Nucleic acids

Carbohydrates

Hydrophilic organic molecules; source of energy (ATP)

Monosaccharides

Simplest form of carbohydrates (Ex. glucose, galactose, fructose)

Disaccharides

sugars made of 2 covalently bonded monosaccharides (Ex. sucrose, lactose, maltose)

Oligosaccharides

short chain of 3 or more monosaccarides

Polysaccharides

long chain of monosaccharides (50 or more) Ex. glycogen, starch, cellulose

Lipids

Hydrophobic; high ratio of hydrogen to oxygen

• long term energy storage

• insulation from environment

• component of cell membrane

• building block of certain hormones

Types of lipids

1. Fatty acids

2. Triglycerides

3. Phospholipids

4. Eicosanoids

5. Steroids

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 (Olive oil)

• Mostly from plant origin

Triglycerides

Trans - fats

• hydrogenated fats

• margarine, some peanut butter

Resists enzymatic breakdown in the human body, remain in circulation longer, deposits in the arteries; raises the risk of heart disease

Phospholipids

Cell membrane structure: bilayer

Hydrophilic (head) and Hydrophobic (tails) regions

Steroids

Cholesterol: “parent” (backbone) steroid from which other steroids are
synthesized

Important for nervous system function

Other Ex. cortisol, progesterone, estrogens, testosterone, bile acids

Proteins

Polymer of amino acids joined by peptide bonds

Oligopeptides

10-15 amino acids

Polypeptides

more than 15 amino acids

Proteins have 3-4 levels of complexity- Primary Structure

Sequence of amino acids joined by peptide bonds (Insulin)

Proteins have 3-4 levels of complexity- Secondary Structure

Alpha helix or beta sheet form by hydrogen bonding (Collagen)

Proteins have 3-4 levels of complexity- Tertiary Structure

A single polypeptide chain folded and coiled by interactions among R groups and between R groups and surrounding water (Globular proteins; muscular filaments)

Proteins have 3-4 levels of complexity- Quaternary Structure

Association of 2 or more polypeptide chains with each other (Hemoglobin)

Denaturation

extreme conformational change that destroys function (like extreme heat or pH)

Enzymes

Proteins that function as biological catalysts

• Enzymes act on 1 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

What can change enzyme shape and function?

Temperature and pH

Nucleic Acids

Polymers of nucleotides

• DNA (double strand)

  contains millions of nucleotides

• RNA (single strand)

  70 to 10,000 nucleotides long

  carries out genetic instruction for synthesizing proteins