The Chemistry of Life

Question 1

Covalent bonds

Answer 1

The sharing of a pair of valence electrons by two atoms.

Question 2

Nonpolar covalent bond

Answer 2

In a covalent bond between two atoms of the same element, the electrons are shared equally because the two atoms have the same electronegativity - the tug-of-war is a standoff.

Question 3

Polar covalent bond

Answer 3

When one atom is bonded to a more electronegative atom, the electrons are not shared equally. Such bonds vary in their polarity, depending on the relative electronegativity of the two atoms. For example, the bonds between the oxygen and hydrogen atoms of a water molecule are quite polar.

Question 4

Ionic bonds

Answer 4

A chemical bond resulting from the attraction between oppositely charged ions.

Question 5

Molecule

Answer 5

Two or more atoms held together by covalent bonds

Question 6

Electron

Answer 6

A subatomic particle with a single negative electrical charge and a mass about 1/2000 that of a neutron or proton. One or more electrons move around the nucleus of an atom.

Question 7

Atom

Answer 7

The smallest unit of matter that retains the properties of an element.

Question 8

Element

Answer 8

A substance that cannot be broken down to other substances by chemical reactions

Question 9

Weak interactions

Answer 9

4 types
Ionic interactions
Hydrogen bonds
Van der Waals interactions 
Hydrophobic interactions

Important properties

1. They have a cumulative effect - individually they are weak, but together they provide reinforcing stability
2. They are reversible
3. They are transient

Question 10

Hydrogen bonds

Answer 10

The strongest of the weak interactions. The partial positive charge on a hydrogen atom that is covalently bonded to an electronegative atom allows the hydrogen to be attracted to a different electronegative atom nearby.
This noncovalent attraction between a hydrogen and an electronegative atom is called a hydrogen bond.

Question 11

Van der Waals interactions

Answer 11

Weak attractions between molecules or parts of molecules that result from transient local partial charges. Individually weak and occur only when atoms and molecules are very close together. When many such interactions occur simultaneously, however, they can be very powerful.

Question 12

Ionic interactions

Answer 12

When a salt (such as NaCl) is placed in solution, the strong ionic bonds that are present in the crystal NaCl are weakened as each of the ions become surrounded by a hydrogen shell.
Ionic interactions can exist between any two chemical groups that have opposite charges.

Question 13

Hydrophobic interactions

Answer 13

A type of weak chemical interaction caused when molecules that do not mix with water coalesce to exclude water.

Question 14

Hydrogen shell

Answer 14

The sphere of water molecules around each dissolved ion.

Question 15

Conformation

Answer 15

3D shape

Question 16

Macromolecule

Answer 16

A giant molecule formed by the joining of smaller molecules, usually by a dehydration reaction. Polysaccharides, proteins, and nucleic acids are macromolecles

Question 17

Monomer

Answer 17

The subunit that serves as the building block of a polymer

Question 18

Polymer

Answer 18

A long molecule consisting of many similar or identical monomers linked together by covalent bonds

Question 19

The building block principal

Answer 19

The mechanism by which all polymers are synthesised and broken down.
Key points:
The two ends of a biological polymer are always different, and the polymer is synthesised by step-wise addition of monomers
to one end.
Dehydration (also called condensation) reactions join monomers to form polymers.
Hydrolysis reactions break polymers down into monomers.
The joining of monomers is a process that requires an input of energy. This is accomplished by activating the monomers with energy before joining them together.
Special proteins called enzymes are used to carry out the dehydration and hydrolysis reactions. Without the correct enzymes, the reactions will not occur in the cell.

Question 20

Dehydration reaction

Answer 20

A chemical reaction in which two molecules become covalently bonded to each other with the removal of a water molecule

Question 21

Hydrolysis

Answer 21

A chemical reaction that breaks bonds between two molecules by the addition of water; functions in disassembly of polymers to monomers

Question 22

Nucleic acid

Answer 22

A polymer consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA.

Question 23

Nucleotide

Answer 23

The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and one or more phosphate groups.

Question 24

Protein

Answer 24

A biologically functional molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure.

Question 25

Amino acid

Answer 25

An organic molecule possessing both a carboxyl and an amino group. Amino acids serve as the monomers of polypeptides.

Question 26

Lipids

Answer 26

Varied in form and function. Not polymers or macromolecules. Hydrophobic. Include fats, phospholipids and steroids.

Question 27

Glycerol

Answer 27

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Question 28

Fatty acid

Answer 28

A carboxylic acid with a long carbon chain. Fatty acids vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form a fat molecule, also known as a triacylglycerol or triglyceride.

Question 29

Carbohydrate

Answer 29

A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides)

Question 30

Monosaccharide

Answer 30

The simplest carbohydrate, acting alone or serving as a monomer for disaccharides and polysaccharides. Also known as simple sugars, monosaccharides have molecular formulas that are generally some form of CH2O

Question 31

Polypeptide

Answer 31

A polymer of amino acids. Different from a protein which consists of one or more polypeptides folded into a specific conformation.