Unit 2

Question 1

chemical bonds

Answer 1

Attractions between atoms that hold atoms and molecules together. There are three major types of chemical bonds that are important in biology: i) covalent, ii) ionic, and iii) hydrogen bonds. Covalent bonds occur when two atoms share electrons. Ionic bonds occur when two oppositely charged ions stick together.

Question 2

covalent bonds

Answer 2

Covalent bonds represent the sharing of the electrons (negatively charged subatomic particles between atoms). The number of covalent bonds that can form is dictated by the number of unpaired electrons in the outer valence shell of the atom.

Question 3

electronegativity

Answer 3

The tendancy of an atom to hold shared electrons more close to its nucleus. Atoms like oxygen have a high electronegativity. This means when oxygen forms a covalent bond with an atom of lower electronegativity, the shared electrons will stay closer to the oxygen atom than to the other atom. Strongly electronegative atoms bonded to weakly electronegative hydrogen atoms, in a molecule, result in hydrogen bonding. The most important strongly electronegative elements in biological systems are oxygen and nitrogen.

Question 4

hydrogen bonds

Answer 4

Hydrogen bond (H-bond) is an interaction between a partially positive hydrogen atom and a partially negative atom with an unshared (lone) pair of electrons. In order for hydrogen to have a sufficient partial positive charge, hydrogen must be covalently attached to a very electronegative atom (O, N, P). A partially negative atom with a lone pair of electrons must also be a highly electronegative atom like oxygen or nitrogen.

Question 5

ionic bonds

Answer 5

An attractive force generated by the interactions between ions of opposite charges. An ionic bond forms due to an attraction between a positive and a negative ion. No electron sharing occurs in the ionic bond. In the formation of an ionic bond, electrons are said to be transferred from one atom to another.

Question 6

electron

Answer 6

Negatively charged subatomic particle that occupies shells surrounding the nucleus and has a mass that is so small it is considered to be zero.

Question 7

neutron

Answer 7

Subatomic particle with a neutral charge that is contained in the nucleus and has a mass of approximately 1 atomic mass unit.

Question 8

proton

Answer 8

A positively charged subatomic particle that is contained in the nucleus and has a mass of approximately 1 atomic mass unit.

Question 9

adhesion

Answer 9

The attraction of water molecules to molecules other than water. Capillary action (in which water will spontaneously climb up the walls of a tube without pumping) is a result of the adhesion of water molecules with the surface of a tube containing the water.

Question 10

cohesion

Answer 10

Describes a property of matter in which particles tend to stick together. Liquid water is cohesive and forms spherical droplets because of its hydrogen bonds, which attract the individual water molecules to each other.

Question 11

hydrophilic

Answer 11

Hydrophilic (from Greek meaning “water-loving”) refers to molecules that are water soluble. Hydrophilic molecules contain polar functional groups that can form hydrogen bonds or ionic bonds with water.

Question 12

hydrophobic

Answer 12

Hydrophobic, or water-fearing, molecules do not interact with water and are characterized by a complete lack of electronegative atoms. In aqueous solutions, the hydrophobic molecules are driven together to the exclusion of water.

Question 13

surface tension

Answer 13

The capacity of a liquid’s surface to resist being ruptured when placed under tension or stress.

Question 14

solute

Answer 14

Component of a solution that is present in the smallest quantity and which dissolves in a solvent.

Question 15

solutions

Answer 15

Homogeneous mixtures of solvent and solute.

Question 16

solvent

Answer 16

Component of a solution that is present in the greatest quantity and in which something else is dissolved.

Question 17

amino acids

Answer 17

A small organic molecule with the structure of an amino group, a carboxylic acid group, and an “R” group, which are all bonded to a single central carbon atom. The difference between the “R” group is what distinguishes one amino acid from another. Amino acids are the building blocks of proteins.

Question 18

biological macromolecules

Answer 18

Relatively large (“macro”) molecules made by living organisms from smaller molecular building blocks. There are four classes of biological macromolecules: proteins, lipids, nucleic acids and polysaccharides/complex sugars. For example, starch is a biological macromolecule made by plants from smaller subunits, glucose; all proteins are made of amino acids, and nucleic acids are made from nucleotides.

Question 19

carbohydrates

Answer 19

The extracellular surface of the cell membrane is decorated with carbohydrate groups attached to lipids and proteins. These short carbohydrates play a role in giving a cell its identity (i.e., distinguishing self from non-self) and are the distinguishing factor in human blood types.

Question 20

fats

Answer 20

A type of lipid composed of glycerol and saturated fatty acids; typically solid at room temperature.

Question 21

glucose

Answer 21

A simple carbohydrate (monosaccharide) with the chemical formula of C6H12O6. This is the primary product (output) of photosynthesis and the primary reactant (input) of cellular respiration

Question 22

hydrophilic

Answer 22

Hydrophilic (from Greek meaning “water-loving”) refers to molecules that are water soluble. Hydrophilic molecules contain polar functional groups that can form hydrogen bonds or ionic bonds with water.

Question 23

hydrophobic

Answer 23

Hydrophobic, or water-fearing, molecules do not interact with water and are characterized by a complete lack of electronegative atoms. In aqueous solutions, the hydrophobic molecules are driven together to the exclusion of water.

Question 24

inorganic molecules

Answer 24

Simple molecules not found in living things. They may contain carbon or hydrogen, but not both. Examples include CO2, N2, O2.

Question 25

lipids

Answer 25

Organic marcromolecules that are largely nonpolar (electrons are evenly distributed among atoms in a molecule) and as a result are hydrophobic (“water-fearing”). Lipids perform many functions in the cell including storage of energy for long-term use in the form of fats, insulation from the environment, and building blocks for hormones. Lipids include fats, oils, waxes, phospholipids, and steroids.

Question 26

monomer

Answer 26

A small organic molecule that may bind chemically to other molecules to form a polymer. A monomer is a repeating structural unit of a polymer. For example, glucose is a monomer that makes up polysaccharide starch, and amino acids are monomers that make up proteins.

Question 27

monosaccharide

Answer 27

A simple sugar (carbohydrate) containing carbon, hydrogen, and oxygen atoms in a 1:2:1 ratio respectively. Some common monosaccharides are glucose, fructose, and ribose.

Question 28

oils

Answer 28

A type of lipid composed of glycerol and unsaturated fatty acids; typically liquid at room temperature.

Question 29

organic molecules

Answer 29

Molecules containing a carbon atom that is covalently bonded to a hydrogen atom (C-H bonds). Many organic molecules also contain oxygen, nitrogen, or sulfur. All living organisms are composed of four major classes of large carbon-containing molecules: proteins, carbohydrates, lipids, and nucleic acids. The term organic is in common use these days. For example, you can buy organically grown tomatoes or clothes made from organically grown cotton. In these cases, organic refers to the way the tomatoes and cotton were grown — without the use of man-made pesticides or fertilizers, and nurtured only by natural substances. Here, organic is used to denote a natural process. You can see then that the word organic is used in two different ways. Be careful not to confuse the two. It can also be said that organic molecules (such as carbon-containing proteins, carbohydrates, lipids, and nucleic acids) are natural molecules. But not all naturally occurring molecules contain carbon, such as, water and common table salt. Are water and salt naturally occurring? Yes. But are they organic? No, because they are not built from carbon.

Question 30

phospholipids

Answer 30

A molecule consisting of a glycerol bonded to a phosphate group (hydrophilic head) and two fatty acids (hydrophobic tail).

Question 31

polymer

Answer 31

These are large molecules consisting of repeating structural units, or monomers, connected by covalent chemical bonds.

Question 32

polysaccharide

Answer 32

A carbohydrate (e.g., starch, cellulose, or glycogen) that consists of long chains of monosaccharides bonded together. Often used for energy storage and structural support by organisms.

Question 33

proteins

Answer 33

An organic macromolecule consisting of folded chains of amino acids. Proteins play a key role both structurally and functionally. Enzymes are proteins, and catalyze all of the chemical reactions in the cell.

Question 34

protein folding

Answer 34

The final 3-dimensional shape of proteins that results from interactions between the amino acids in the protein.

Question 35

steroids

Answer 35

A type of lipid composed of a common carbon ring structure. Examples include testosterone and cholesterol.

Question 36

waxes

Answer 36

Nonpolar lipids that form protective layers on plants and animals. Waxes are the simplest lipids in nature, consisting of two long hydrocarbon chains linked in the middle by an ester group.

Question 37

nucleotide

Answer 37

A specific region in the cytoplasm of a prokaryotic cell where genetic material (DNA) is stored.

Question 38

RNA: ribonucleic acid

Answer 38

The nucleic acid composed of nucleotides in a single strand whose primary function is protein synthesis.

Question 39

nucleic acid

Answer 39

Organic macromolecules, built from nucleotides, that carry out two main functions in the cell: storage of genetic information and synthesis of proteins. DNA and RNA are both nucleic acids.

Question 40

acetyl coA

Answer 40

A two-carbon molecule that is an intermediate product between glycolysis and the Krebs cycle in cellular respiration. Pyruvate from glycolysis is broken down into acetyl coA, which enters the Krebs cycle and is further broken down.