56 ■ CHAPTER 03 Chemistry of Life
THE QUESTIONS
The Basics
(^1) The atomic number of an atom is determined by the number of
in the atom.
(a) protons
(b) neutrons
(c) electrons
(d) electrons plus neutrons plus protons
(^2) The atomic mass number of an atom is determined by the sum
of the number of in the atom.
(a) protons plus electrons plus neutrons
(b) protons plus electrons
(c) neutrons plus electrons
(d) neutrons plus protons
(^3) Link each term with the correct definition.
ION
MATTER
SOLUTION
ELEMENT
CHEMICAL
COMPOUND
MOLECULE
ISOTOPE
POLYMER
ATOM
(^4) The partial negative charge at one end of a water molecule is
attracted to the partial positive charge of another water molecule.
What is this attraction called?
(a) a hydrogen bond
(b) a van der Waals interaction
(c) an ionic bond
(d) a covalent bond
(e) a hydrophilic bond
- The smallest subunit of an element.
- A molecule made up of repeating monomers.
- An atom that has gained or lost an electron.
- Consists of two or more atoms chemically
bonded together. - Consists entirely of atoms with the same
atomic number. - Anything that has mass and occupies space.
- Has the same atomic number but a different
atomic mass than its original element. - A molecule that contains atoms from two or
more different atoms. - A combination of a solvent and a solute.
(^5) Select the correct terms:
Proteins are (polymers / monomers) of amino acids. A common
carbohydrate is (sugar / fat). Nucleic acids are composed of
(nucleotides / DNA). Lipids (are / are not) polymers. All of these
organic molecules contain (carbon / nitrogen).
Challenge Yourself
(^6) You are asked to determine the classification of an unknown
biomolecule. You are told that it can be broken down into only
carbon, oxygen, and hydrogen atoms, and nothing else. Using your
knowledge of biomolecules and their components, identify which
of the following statements about your unknown sample are true.
(Select all that apply.)
(a) It is an organic compound.
(b) It contains amino acids.
(c) It contains sugar.
(d) It is a nucleic acid.
(e) It is a carbohydrate.
(^7) Explain why life on Earth is carbon-based rather than, for
example, hydrogen- or oxygen-based.
(^8) Why did Miller’s addition of hydrogen sulfide (H
2 S) to the
mixture of molecules in the spark discharge experiments increase
the number of amino acids he found?
Tr y Something New
(^9) In the accompanying figure, a carbon atom resides at each
unlabeled corner of the hexagons and wherever a “C” is shown.
Each “O” is an oxygen atom, and each “H” is a hydrogen atom.
What is this structure?
H
CH 2 OH
H
H
OH H
OH H OH
O
HO
H H
OH
CH 2 OH
H
OH H
O
O
H
(a) a fatty acid monomer(b) two simple sugar molecules linked together(c) a nucleotide polymer(d) a hydrocarbon ring polymer(e) an amino acid