Chapter 2 test review:
5. Explain whether CO2 (O-C-O) is an ionic or covalent compound. Why does this arrangement
satisfy all atoms involved?
CO2 is a covalent compound because it is composed of carbon and oxygen, which are both
non- metals and they share their electrons. When electrons are shared, each atom will contain 8
electrons in the outer shell. This allows for all the atoms of the compound to become stable and
have a completed outer shell.
6. Of what significance is the shape of molecules in organisms?
The shape of all organic molecules is necessary to the structural and functional roles they play
in living things.
7. Explain why water is a polar molecule. What does the polarity and shape of water have to do
with its ability to form hydrogen bonds?
Water is a polar molecule because it is composed of slightly negative oxygen with two slightly
positive hydrogens, thus the sharing of electrons is unequal.
8. Name five properties of water, and relate them to the structure of water, including its polarity
and hydrogen bonding between molecules.
a) Water has a high heat capacity: hydrogen bonds that link water molecules together help
water absorb heat without a great change in temperature.
b) Water has a high heat of evaporation: hydrogen bonds must be broken before water boils
c) Water is a solvent: In solutions, the slightly positive hydrogens of water attracts the
negative ions ( ex. Cl-) and the slightly negative oxygen of water attracts positive ions ( ex. Na+)
d) Water molecules are cohesive and adhesive; Cohesion: ability of water molecules to cling
to each other due to hydrogen bonding, Adhesion:ability of water molecules to cling to other
polar surfaces
e) Frozen water is less dense than liquid water; As liquid water cools, molecules come closer
together, and below temperatures of 4 degrees celcius, there is only vibrational movement and
the hydrogen bonding becomes more rigid but more open ( water expands)
9. On the pH scale, which numbers indicate a solution is acidic? Basic? Neutral?
7 is neutral. Numbers below 7 are more and more acidic as they tend towards 1 and numbers
above 7 are more and more basic as they tend towards 14.
10. What are buffers, and why are they important to life?
Buffers are chemicals that keep pH within normal limits. Buffers resist pH changes because
they can take up excess hydrogen ions or hydroxide ions. Buffers are important to life because
they help keep the blood in living things their normal pH, which is 7.4. Without these buffers, low
pH and high pH in living organism's blood can cause situations in which proteins cannot
function.
Chapter 3 test review:
3. What biomolecules are monomers of the polymers studied in this chapter? How do
monomers join to produce polymers, and how are polymers broken down to monomers?
Monosaccharides are monomers of carbohydrates; fatty acids, glycerol are monomers of lipids
; nucleotides are monomers of nucleic acids; amino acids are monomers of proteins. Polymers
are produced during dehydration reactions and then they are broken down to monomers
thought hydrolysis reactions.
4. Name several monosaccharides, disaccharides, and polysaccharides, and give a function of
each. How are these molecules structurally distinguishable?
Monosaccharides: Glucose, Fructose ---> Ready energy ( ex. cellular fuel for all living things)
Disaccharides: Maltose, Sucrose, lactose ----> sucrose is a sweetener for our foods; table sugar
Polysaccharides: Starch, Glycogen----->glycogen is stored in bodies of animals until needed.
These molecules differ in the number of sugar molecules they contain. Monosaccharides are
simple sugars ( one sugar molecule), disaccharides are two monosaccharides combined, and
polysaccharides are considered to have more than one sugar molecule.
5. What is the difference between a saturated and an unsaturated fatty acid? Explain the
structure of a fat molecule by stating its components and how they join together.
Saturated fats do not have double bonds. Unsaturated fats have double bonds between
carbons, which cause the kink in the chain, and they are liquid at room temperature. A fat
molecule consists of three fatty acids and a glycerol group, which have been joined together in
the dehydration reaction.
6. How does the structure of a phospholipid differ from that of a fat? How do phospholipids form
a bilayer in the presence water?
A phospholipid contains 2 fatty acids, a glycerol group, a phosphate group, and a functional
group. In the presence of water, the hydrophilic heads face the water medium of the cells, while
the hydrophobic tails project inwards to each other.
8. Draw the structure of an amino acid and a peptide, pointing out the peptide bond.
9. Discuss the four possible levels of protein structure, and relate each level to particular
bonding patterns.
Primary Structure: Sequence of amino acids that join by peptide bonds
Secondary Structure : Hydrogen bonding between amino acids cause the polypeptide to form
an alpha
helix or a pleated sheet.
Tertiary Structure: Due to covalent bonding between R groups of polypeptide to give it a
globular shape.
Quaternary Structure: Two or more polypeptides join to form a single protein.
10. How do nucleotides bond to form nucleic acids? State and explain several differences
between the structure of DNA and that of RNA.
Nucleotides bond through complementary base pairing (A with T, C with G). DNA contains the
sugar deoxyribose while RNA contains the sugar ribose. DNA contains adenine, cytosine,
guanine, and thymine, while RNA contains adenine, guanine, cytosine, and uracil. DNA is
double stranded and RNA is single stranded. DNA is in the form of a helix and RNA is not.
11. Discuss the structure and function of ATP.
ATP is composed of adenosine and three phosphate groups. ATP provides energy for all sorts
of organism functions.