Lecture 2

What is an element?

A substance that cannot be broken down into simpler substances.

What is an atom?

A building block of matter.

What is a molecule?

Two or more atoms chemically bonded together.

What is a synthesis reaction?

Two or more atoms, ions, or molecules combine to form a larger, more complex molecule.

What is the general equation for a synthesis reaction?

A + B → AB

What is an example of a synthesis reaction in the body?

Growth and repair.

What is a decomposition reaction?

A complex molecule breaks down into simpler, smaller molecules, atoms, or ions.

What is the general equation for a decomposition reaction?

AB → A + B

What is an example of a decomposition reaction in the body?

Digestion.

What is a reversible reaction?

A reaction in which synthesis and decomposition occur in opposite directions.

What symbol represents a reversible reaction?

Two arrows pointing in opposite directions.

What does a longer arrow indicate in a reversible reaction?

The favored direction of the reaction.

What do equal-length arrows indicate in a reversible reaction?

Chemical equilibrium.

What is the outermost electron shell called?

The valence shell.

Why is the valence shell important?

It is where electrons interact to form chemical bonds.

What is the octet rule or Rule of Eights?

Atoms tend to become stable when their outermost shell contains eight electrons.

What is the exception to the octet rule for the first electron shell?

The first shell can hold a maximum of two electrons.

Why are inert elements chemically stable?

Their outermost electron shells are complete.

Why are reactive elements able to form chemical bonds?

Their outermost electron shells are incomplete.

What do reactive atoms do to become more stable?

Gain, lose, or share electrons.

What are the three types of chemical bonds discussed in the notes?

Ionic, covalent, and hydrogen bonds.

What is an ionic bond?

An attraction between oppositely charged ions formed after electrons are transferred.

What happens to electrons during ionic bond formation?

Electrons are transferred from one atom to another.

What is an ion?

An atom or group of atoms that has gained or lost electrons and carries an electrical charge.

What is a cation?

A positively charged ion formed by losing electrons.

What is an anion?

A negatively charged ion formed by gaining electrons.

Is Na+ a cation or anion?

Cation because it has a positive charge.

Is Cl- a cation or anion?

Anion because it has a negative charge.

What is a covalent bond?

A chemical bond formed when atoms share electrons.

What is a single covalent bond?

A bond in which two atoms share one pair of electrons.

What is a double covalent bond?

A bond in which two atoms share two pairs of electrons.

What is a nonpolar covalent bond?

A covalent bond in which electrons are shared equally or nearly equally.

What is a polar covalent bond?

A covalent bond in which electrons are shared unequally.

What happens when electrons are shared unequally in a molecule?

Partial positive and partial negative poles can form.

Is water an example of a polar or nonpolar molecule?

Polar.

What molecule is shown as an example of nonpolar covalent bonding?

Carbon dioxide (CO2).

What is a hydrogen bond?

A weak attraction between a partially positive hydrogen atom and a partially negative region of another atom.

What is the role of hydrogen bonds between water molecules?

They help hold water molecules together.

How do ionic, covalent, and hydrogen bonds differ?

Ionic bonds involve electron transfer and attraction between ions; covalent bonds involve electron sharing; hydrogen bonds involve attraction between partial charges.

What is an inorganic compound?

A compound that generally lacks carbon; carbon dioxide is an exception to this simplified distinction.

What are the four inorganic substance categories listed in the notes?

Water, salts, acids, and bases.

What is an organic compound?

A carbon-containing compound; the major biological examples include carbohydrates, lipids, proteins, and nucleic acids.

What are the four major categories of organic compounds?

Carbohydrates, lipids, proteins, and nucleic acids.

What is the most abundant inorganic compound in the body?

Water.

What are the four vital properties of water listed in the notes?

High heat capacity, polarity and solvent properties, chemical reactivity, and cushioning or lubrication.

What does high heat capacity mean?

Water can absorb or release large amounts of heat before its temperature changes significantly.

Why is water's high heat capacity important for the body?

It helps prevent sudden changes in body temperature.

What is a solvent?

A substance that dissolves another substance.

Why is water considered an excellent solvent?

Its polarity allows it to dissolve many ionic and polar substances.

Why is water's solvent property important?

It allows chemical reactions to occur and helps transport nutrients, wastes, and gases in blood.

What does chemical reactivity mean as a property of water?

Water participates as a reactant in chemical reactions such as digestion.

What is the cushioning and lubricating function of water?

It protects organs and reduces friction between moving structures.

What are three examples of water providing cushioning or lubrication?

Cerebrospinal fluid, amniotic fluid, and synovial fluid.

What is a salt?

An ionic compound composed of positively charged cations and negatively charged anions.

What happens when sodium chloride dissolves in water?

Water pulls the salt apart into Na+ and Cl- ions.

What is an electrolyte?

A substance that produces ions in solution and allows electrical current to be conducted.

Why are salts considered electrolytes when dissolved in water?

They separate into charged ions that can conduct electricity.

What is an acid?

A substance that releases hydrogen ions (H+) in water.

What is a base?

A substance that releases hydroxide ions (OH-) in water.

What does the pH scale measure?

The relative concentration of hydrogen ions in a solution.

What is the range of the standard pH scale?

0 to 14.

What pH is neutral?

7.

What pH is acidic?

Below 7.

What pH is basic or alkaline?

Above 7.

Does a lower pH mean a higher or lower hydrogen ion concentration?

A higher hydrogen ion concentration.

Does a higher pH mean a higher or lower hydrogen ion concentration?

A lower hydrogen ion concentration.

How much does hydrogen ion concentration change for each difference of one pH unit?

Tenfold.

What is the normal pH range of human blood?

Approximately 7.35 to 7.45.

Is normal blood slightly acidic, neutral, or slightly alkaline?

Slightly alkaline.

What is a buffer?

A substance or system that resists changes in pH when acids or bases are added.

What is a polymer?

A large chain-like molecule made of many similar or repeating units called monomers.

What is a monomer?

A small building-block molecule that can join with other monomers to form a larger molecule.

What is dehydration synthesis?

A reaction that joins smaller molecules together by removing water.

What is the general equation for dehydration synthesis?

Monomer + monomer → larger molecule + H2O.

What is hydrolysis?

A reaction that breaks a larger molecule into smaller units by adding water.

What is the general equation for hydrolysis?

Larger molecule + H2O → smaller molecules.

Which process builds polymers: dehydration synthesis or hydrolysis?

Dehydration synthesis.

Which process breaks polymers apart: dehydration synthesis or hydrolysis?

Hydrolysis.

What happens to carbohydrates during dehydration synthesis?

Simple sugars join together while water is removed.

What happens to carbohydrates during hydrolysis?

Larger carbohydrates break into smaller sugars when water is added.

What happens to proteins during dehydration synthesis?

Amino acids join together through peptide bonds while water is removed.

What happens to proteins during hydrolysis?

Peptide bonds are broken with the addition of water, producing smaller peptides or amino acids.

What elements are found in carbohydrates?

Carbon, hydrogen, and oxygen.

What is the main function of carbohydrates in the body?

They provide a readily available source of energy for cells.

What are the building blocks of carbohydrates?

Monosaccharides or simple sugars.

What is a monosaccharide?

A single simple sugar.

Which examples of monosaccharides are listed in the notes?

Glucose, fructose, ribose, and deoxyribose.

What is a disaccharide?

Two monosaccharides joined together.

Which examples of disaccharides are listed in the notes?

Lactose, sucrose, and maltose.

What is a polysaccharide?

A long chain of linked simple sugars.

Which examples of polysaccharides are listed in the notes?

Starch and glycogen.

What is the monomer of glycogen?

Glucose.

What is the main role of glycogen?

Storage of glucose for later energy use.

What are the major lipid categories covered in the notes?

Triglycerides, phospholipids, and steroids.

What elements are found in lipids?

Carbon, hydrogen, and oxygen.

Are lipids soluble or insoluble in water?

Generally insoluble in water.

What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids have no carbon-carbon double bonds; unsaturated fatty acids have one or more carbon-carbon double bonds.

What is the typical shape of a saturated fatty acid chain?

A relatively straight chain that can pack closely together.

What is the typical shape of an unsaturated fatty acid chain?

A chain that may have bends or kinks caused by double bonds.

What is the typical state of saturated fats at room temperature?

Solid.