Exam 1
BIOL 222
1) At what temperature is water at its densest?
A) 0°C
B) 4°C
C) 32°C
D) 100°C
E) 212°C
2) The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called?
A) a covalent bond
B) a hydrogen bond
C) an ionic bond
D) ahydroneutral bond
E) a hydrophobic bond
3) Which of the following indicates the number of protons in the nucleus of an atom?
A) atomic mass
B) atomic weight
C) atomic number
D) mass weight
E) mass number
4) If the pH of a solution is decreased from 9 to 8, it means that the
A) concentration of H+ has decreased
B) concentration of H+ has increased
C) concentration of H+has not changed
D) concentration of OH- has decreased
E) Both B and D are correct.
5) Which above is a functional group that helps stabilize proteins by forming covalent bond cross-links between non-adjacent monomers in folding protein molecules?
6) About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter?
A) carbon, sodium, chlorine, nitrogen
B) carbon, sulfur, phosphorus, hydrogen
C) oxygen, hydrogen, calcium, sodium
D) carbon, oxygen, sulfur, calcium
E) carbon, hydrogen, nitrogen, oxygen
7) What is the chemical reaction by which cells make polymers from monomers?
A) catabolism
B) hydrolysis
C) dehydration synthesis
D) ionic bonding of monomers
E) atomic fusion
The following question is based on the figure below, a solute atom surrounded by a hydration shell of water.
8) Based on your knowledge of the polarity of water molecules, the solute atom is most likely
A) positively charged
B) negatively charged
C) without charge
D) hydrophobic
E) nonpolar
9) The mass number of an element can be easily approximated by adding together the number of ______in an atom of that element.
A) neutrons and electrons
B) protons and neutrons
C) protons and electrons
D) energy levels
E) isotopes
10) Which drawing depicts the electron configuration of oxygen (8O – atomic # = 8)?
11) The two molecules shown above are best described as
A) optical isomers
B) radioactive isotopes
C) structural isomers
D) nonradioactive isotopes
E) geometric isomers
12) In a water molecule, two hydrogen atoms are bonded to a single oxygen atom by
A) hydrogen bonds
B) nonpolar covalent bonds
C) polar covalent bonds
D) ionic bonds
E) van der Waals interactions
13) A new organism is discovered in the forests of Costa Rica. Scientists there determine that the polypeptide sequence of hemoglobin from the new organism has 72 amino acid differences from humans, 65 differences from a gibbon, 49 differences from a rat, and 5 differences from a frog. These data suggest that the new organism
A) is more closely related to humans than to frogs
B) is more closely related to frogs than to humans
C) may have evolved from gibbons but not rats
D) is more closely related to humans than to rats
E) may have evolved from rats but not from humans and gibbons
14) In the methane molecule shown here, bonds have formed that include both the s orbital valence electrons of the hydrogen atoms and the p orbital valence electrons of the carbon. The electrons in these bonds are said to have
A) double orbitals
B) separate orbitals
C) complex orbitals
D) hybrid orbitals
E) reduced orbitals
15) A group of molecular biologists is trying to synthesize a new artificial compound to mimic the effects of a known hormone that influences sexual behavior. They have turned to you for advice. Which of the following compounds is most likely to mimic the effects of the hormone?
A) a compound with the same number of carbon atoms as the hormone
B) a compound with the same molecular mass as the hormone
C) a compound with the same three-dimensional shape as part of the hormone
D) a compound with the same number of orbital electrons as the hormone
E) a compound with the same number of hydrogen and nitrogen atoms as the hormone
16) What is the difference between covalent bonds and ionic bonds?
A) Covalent bonds involve the sharing of protons between atoms, and ionic bonds involve the sharing of electrons between atoms
B) Covalent bonds involve the sharing of neutrons between atoms, and ionic bonds involve the sharing of electrons between atoms
C) Covalent bonds involve the sharing of electrons between atoms, and ionic bonds involve the electrical attraction between atoms
D) Covalent bonds involve the sharing of protons between atoms, and ionic bonds involve the sharing of neutrons between atoms
E) Covalent bonds involve the transfer of electrons between atoms, and ionic bonds involve the sharing of neutrons between atoms
17) How many molecules of glucose (C6H12O6 molecular mass =180 daltons) would be present in one mole of glucose?
A) 24
B) 342
C) 23 × 1014
D) 180 × 1014
E) 6.02 × 1023
18) A given solution contains 0.0001(10-4) moles of hydrogen ions [H+] per liter. Which of the following best describes this solution?
A) acidic: H+ acceptor
B) basic: H+ acceptor
C) basic: H+ donor
D) acidic: H+ donor
E) neutral
19) Which of the following solutions has the greatest concentration of hydroxyl ions [OH-]?
A) lemon juice at pH 2
B) vinegar at pH 3
C) tomato juice at pH 4
D) urine at pH 6
E) seawater at pH 8
20) Water's high specific heat is mainly a consequence of the
A) absorption and release of heat when hydrogen bonds break and form.
B) small size of the water molecules.
C) high specific heat of oxygen and hydrogen atoms.
D) fact that water is a poor heat conductor.
E) inability of water to dissipate heat into dry air.
21) How many electronsdoes carbon need in order to complete its valence shell?
A) 1
B) 2
C) 3
D) 4
E) 8
22) Why are hydrocarbons insoluble (hydrophobic) in water?
A) The majority of their bonds are polar covalent carbon-to-hydrogen linkages
B) The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages
C) They are hydrophilic
D) They exhibit considerable molecular complexity and diversity
E) They are heavier than water
23) Water molecules in a solution reach equilibrium between whole water molecules and dissociated water molecules where a hydrogen ion leaves one molecule and attaches to another. The two products of this are?
A) Water and hydrogen ions
B) Water and hydroxyl ions
C) Water and hydronium ions
D) Hydroxyl ions and oxygen gas
E) Hydroxyl and hydronium ions
24) Which is the best description of a carbonyl group?
A) an oxygen joined to a carbon by a single covalent bond
B) a nitrogen and two hydrogens joined to a carbon by covalent bonds
C) a carbon joined to two hydrogens by single covalent bonds
D) a sulfur and a hydrogen joined to a carbon by covalent bonds
E) an oxygen atom joined to a carbon by a double covalent bond
25) Which of the following contains nitrogen in addition to carbon, oxygen, and hydrogen?
A) an alcohol such as ethanol
B) a monosaccharide such as glucose
C) a steroid such as testosterone
D) an amino acid such as glycine
E) a hydrocarbon such as benzene
26) The molecule shown here could be described in chemical symbols as
A) CH4
B) H2O
C) C2H3
D) C4H4
E) CH2O
27) One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+). Thus,
H2CO3 HCO3- + H+
A response to a drop in blood pH would be…
A) a decrease in the concentration of H2CO3 and an increase in the concentration of HCO3-.
B) the concentration of hydroxide ions (OH-) to increase.
C) the concentration of bicarbonate ions (HCO3-) to increase.
D) the HCO3- to act as a base and remove excess H+ with the formation of H2CO3.
E) the HCO3- to act as an acid and remove excess H+ with the formation of H2CO3.
Use these diagrams for q’s 28 and 29.
28) Which molecule is an alcohol?
29) Which molecule has a carbonyl functional group in the form of a ketone?
30) Testosterone and estradiol (estrogen) are
A) nucleic acids
B) carbohydrates
C) steroids
D) phospholipids
E) proteins
31) Which of the following best summarizes the relationship between dehydration synthesis reactions and hydrolysis?
A) Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers
B) Macromolecular synthesis occurs through the removal of water and digestion occurs through the addition of water
C) Dehydration reactions can occur only after hydrolysis
D) Hydrolysis creates polymers, and dehydration reactions break down polymers
E) A and B are correct
32) One difference between carbon-12 and carbon-14 is that carbon-14 has
A) two more protons than carbon-12
B) two more electrons than carbon-12
C) two more neutrons than carbon-12
D) A and C only
E) B and C only
33) Why does ice float in liquid water?
A) The liquid water molecules have more kinetic energy and thus support the ice
B) The ionic bonds between the molecules in ice prevent the ice from sinking
C) Ice always has air bubbles that keep it afloat
D) Hydrogen bonds stabilize and keep the molecules of ice (water) farther apart than the water molecules of liquid water
E) The crystalline lattice of ice causes it to be more dense than liquid water
34) Humans can digest starch but not cellulose because
A) the monomer of starch is glucose, while the monomer of cellulose is galactose
B) humans have enzymes that can hydrolyze the alphaglycosidic linkages of starch but not the betaglycosidic linkages of cellulose
C) humans have enzymes that can hydrolyze the betaglycosidic linkages of starch but not the alphaglycosidic linkages of cellulose
D) humans harbor starch-digesting bacteria in the digestive tract
E) the monomer of starch is glucose, while the monomer of cellulose is maltose
35) Which of the following statements is false for lipids?
A) They are soluble in water
B) They are an important constituent of cell membranes
C) They contain more energy than proteins and carbohydrates
D) They are not true polymers
E) They include waxes and steroids
36) Which of the structures above contain(s) a carboxyl functional group?
A) A
B) B
C) C
D) C and E
E) none of the structures
37) The molecule shown above is a(n)
A) polysaccharide
B) polypeptide
C) saturated fatty acid
D) triacylglycerol
E) unsaturated fatty acid
38) There are 20 different amino acids. What makes one amino acid different from another?
A) different carboxyl groups attached to a carbon
B) different amino groups attached to a carbon
C) different side chains (R groups) attached to a carbon
D) different carbons
E) different asymmetric carbons
39) Which bond is the peptide bond joining the two amino acids?
40) What maintains the secondary structure of a protein?
A) peptide bonds
B) hydrogen bonds
C) disulfide bonds
D) ionic bonds
E) phosphodiester bonds
41) Enzymes are ______that function to ______the activation energy of chemical reactions.
A) catalytic proteins; lower
B) signaling proteins; lower
C) structural proteins; raise
D) catalytic proteins; raise
42) Altering which of the following levels of structural organization could change the function of a protein?
A) primary
B) secondary
C) tertiary
D) quaternary
E) all of the above
43) Which two functional groups are always found in amino acids?
A) ketone and aldehyde
B) carbonyl and carboxyl
C) phosphate and sulfhydryl
D) carboxyl and amino
E) hydroxyl and aldehyde
44) What is the term used for a protein molecule that assists in the proper folding of other proteins?
A) tertiary protein
B) chaperonin
C) enzyme protein
D) renaturing protein
E) denaturing protein
45) Which of the following descriptions best fits the class of molecules known as nucleotides?
A) a nitrogenous base and a phosphate group
B) a nitrogenous base and a pentose sugar
C) a phosphate group and an adenine or uracil
D) a nitrogenous base, a phosphate group, and a pentose sugar
E) a pentose sugar and a purine or pyrimidine
Essay Questions:
Choose TWO of the following and answer on a separate sheet of paper.
(5 pts ea.)
1. Provide the complete chemical reaction for the combination of carbon dioxide and water including ALL possible different products (bicarbonate buffer system). Explain how this reaction is affecting global ocean pH and the resultant problem for calcareous marine organisms(calcium carbonate shell builders).
2. Draw a table of the four classes of macromolecules including the type of monomer, polymer, and specific linkages for each. Describe the typical water affinities (hydrophilic/phobic) for each class. Provide an example molecule (name only, not formula) for each class of macromolecule. (Include lipids in this table in the manner discussed in class)
3. Describe the levels of structure for proteins and draw an example of each (may be crude). Include the types of molecular interactions responsible for the structure achieved. Provide the term for the loss of the final three-dimensional shape of a protein and three examples of conditions that may cause this.
4. Diagram a salt crystal in water showing, at the molecular level, how the salt is dissolved into solution. Be sure to include any charges involved along with specific interactions among the salt ions and water molecules. Include a label for the structure formed by water molecules and these ions.