Download Answers to Exam 1 multiple choice, TF and short answer questions

Biol 205 Exam 1 TEST FORM A Spring 2008
NAME___________________________________
•
•
•
•
•
Fill out both sides of the Scantron Sheet.
On Side 2 be sure to indicate that you have TEST FORM A
The answers to Part I should be placed on the SCANTRON SHEET.
The answers to Part II should be written directly on the exam.
NO CALCULATORS OR CELL PHONES ALLOWED
Part I: Multiple choice Questions. 2 pts. each.
ONE POSSIBLE CORRECT ANSWER for questions 1-11
Answers shown in blue
1. A number of physiological changes occur when an animal hybernates. Its body temperature
drops and the membrane composition of its cells changes. To maintain membrane fluidity, the
lipid bilayers in a hybernating animal would show a(n) __________ in the amount of
unsaturated fatty acids and a(n) ____________ in the length of the hydrocarbon tails.
a. increase, increase
b. decrease, decrease
c. increase, decrease
d. decrease, increase
2. Which statement is incorrect with respect to passive transport facilitated by carrier proteins:
a. the movement of an individual solute can occur in either direction, but the net flow of solutes
is down the concentration gradient (from higher to lower)
b. the conformation change in the carrier that is required to move the solute across the
membrane is triggered by binding of the solute to a pocket in the protein
c. carrier transporters are very specific with respect to the solute that they transport
d. an energy source is not required
3. Custom genome sequencing is currently available for individuals who are willing and able to
ante up a considerable sum of money: ~$300,000. How much per base pair does this price
represent? Note: use the size of a single genome copy in this calculation. You do not need a
calculator to answer this question.
a. $1 b. 10 cents c. 1 cent d. 1/10 of a cent e. 1/100 of a cent
4. Which of the following would move through the lipid bilayer of a plasma membrane most
rapidly (unaided by transporters)?
a. O2
b. an amino acid
c. a nucleotide
d. K+
e. a very large hydrophobic molecule
5. A protein domain
1
a. is another term for the primary sequence of a protein.
b. refers to a subunit in a multi-subunit protein (i.e., one that has quaternary structure).
c. refers to the pattern of α-helices and β-sheets in particular parts of a protein.
d. is a segment of a protein that can fold independently of the rest of the protein into its
tertiary structure or conformation and is usually associated with a specific function of the
protein
6. Most reactions in cells require enzymes because
a. the free energy of the products is higher than the reactants.
b. the free energy of the products is less than the reactants.
c. their spontaneous (uncatalyzed) rates of reactions occur too slowly for cells to survive.
d. they are more complex than other reactions in nature, such as the combustion of gasoline.
e. they could never possibly occur without the action of a catalyst.
7. Some enzymes lower the activation energy for a reaction
a. by bringing substrates close together in the active site.
b. by bringing reactants close together between two different protein domains in the enzyme.
c. by using the hydrolysis of ATP to provide the energy for a reaction to occur.
d. by coupling the hydrolysis of ATP to a reaction requiring energy.
e. by readily releasing the products of a reaction.
8. In order for a specific ligand to bind to a protein found in the cytosol,
a. the protein must have a specific binding site in its tertiary structure in which the ligand
fits.
b. the protein must have a specific binding site in its secondary structure in which the ligand fits.
c. the protein must have a specific binding site in its primary structure in which the ligand fits.
d. the ligand must be hydrophobic to interact with the core, or central part, of the protein.
9. The α helix and β sheet are found in many different proteins because
they are formed by
a. hydrogen bonding between the amino acid side chains most commonly found in proteins.
b. noncovalent interactions between amino acid side chains and the polypeptide backbone.
c. ionic interactions between charged amino acid side chains.
d. hydrogen bonding between atoms of the polypeptide backbone.
e. hydrophobic interactions between the many nonpolar amino acids.
You have purchased a filtration unit off the internet. It is supposed to purify water of any
contaminating biological agent. When you read the fine print included with the product, you
discover that the pore size is 10 µm.
10. What does µ (micro) mean? _________________
a. 10-3 b. 10-6 c. 10-9 c. 10-10
11. With this pore size, your water is likely to be contaminated with
a. single-celled eukaryotes only
b. viruses only
c. both prokaryotic and eukaryotic cells
d. viruses and prokaryotic cells
2
e. None of the above – the product performs as advertised.
QUESTIONS 12 -16. MORE MULTIPLE CHOICE BUT THERE MAY BE MORE THAN
ONE CORRECT ANSWER. INDICATE ALL CORRECT ANSWERS
12. Prokaryotic cells differ from eukaryotic cells in that they
a. use RNA as their genetic material.
b. use DNA as their genetic material.
c. do not have a membrane-bound nucleus.
d. have a plasma membrane that is permable to some solutes but not to others
e. have cytoplasm
13. Which of the following statements is(are) FALSE?
a. Peptide bonds are the covalent bonds that link together two amino acids in proteins.
b. The polypeptide backbone is free to rotate about each peptide bond.
c. Nonpolar amino acids tend to be found in the interior of cytosolic proteins.
d. The sequence of the atoms in the polypeptide backbone varies between different
proteins.
14. Given what you know about the differences between procaryotic cells and eucaryotic cells,
study of the model organism E. coli might provide a general (universally applicable)
understanding of which of the following processes:
answers given the full two points: b only, c only or b and c
a. formation of the endoplasmic reticulum
b. DNA replication
c. how cells decode their genetic instructions to make proteins
d. how mitochondria get distributed to cells during cell division
15. Which of the following statements about hydrogen bonds are TRUE?
a. They are weak covalent bonds that are easily disrupted by heat.
b. They are weak bonds formed between hydrocarbons in water.
c. They are weak bonds formed between nonpolar groups.
d. They are weak bonds involved in maintaining the conformation of
macromolecules.
16.
Which of the following statement(s) about amino acids is(are) TRUE?
a. Twenty-two amino acids are commonly found in proteins.
b. Most of the amino acids used in protein biosynthesis have charged side chains.
c. Amino acids are often linked together to form branched polymers.
d. All amino acids contain an NH2 and a COOH group.
3
CHOOSE TRUE OR FALSE. ANSWER FALSE IF ANY PART OF THE STATEMENT
IS INCORRECT. 2 PT EACH.
17. One "lesson" from the study of prions is that although the amino acid of a polypeptide will
determine its shape, a given primary structure can result in more than one stable secondary and
tertiary structure. This statement is TRUE
18. Even though it doesn’t have cytoplasm, the mimivirus is thought to be more like a living
organism than a typical virus because its genome is similar in size to a prokaryotic cell.
This statement is TRUE
PART II: WRITE YOUR ANSWERS TO THESE QUESTIONS DIRECTLY
ON THE EXAM
1. (3 pts.)
a
b
DNA
 mRNA  protein
 c
DNA
Next to each letter indicate the name (proper term for the process shown above.
a
transcription
b
translation
c
(copying a DNA sequence into RNA)
(converting the information in RNA into protein)
replication (copying an entire genome)
2. (3 pts.) Which of the two bases on the right will form the most hydrogen bonds with the
base on the left? Circle: TOP or BOTTOM. Then defend your answer by showing H-bonds
and indicating the critical difference between the top and bottom structure. The base pairing
surfaces are facing each other. Don’t worry about distance between atoms.
The top purine forms two H-bonds and the bottom 3 H bonds with the pyrimidine
3. ( 8 pts.)
4
5
3
1
2
4
(3 pts.) Write out the complete formal name for this macromolecule:
(Do not use its acronym and be sure to include the relevant number….)
2’ deoxyribonucleic acid
Pick from the list of term below an fill in the blank ( 5 pts total)
The structure indicated by arrow # 1 is deoxyribose
The structure indicated by arrow # 2 is a purine
The functional group indicated by arrow # 3 is an amino or amine
The general category of bond indicated by arrow # 4 covalent bond
The general category of bond indicated by arrow # 5 non-covalent bond
purine
pyrimidine methyl hydroxyl
carbonyl phospholipid
carboxyl
ribose deoxyribose
phosphate amino acid ligand
fatty acid steroid
cholesterol
phosphate
amino
methyl hydrophobic bond
non-covalent bond
covalent bond
5
4. (15 pts.)
Non-mutated
version of the gene
codes for a leucine
Mutated version of
the gene codes for
an aspartic acid
aspartic acid
3 a. On one of the structures above, circle a carboxyl group and label it with a C
3 b. Circle the R-group on aspartic acid and label R
3 c. A researcher discovers that mutation (change) in the DNA sequence of a gene causes
replacement of an isoleucine by an asparatic acid in the polypeptide coded for by the gene.
The researcher isolates the mutant protein, examines its structure and says: "Oh my gosh, this
cytosolic protein has been turned inside out."
Using protein folding/structure terminology, briefly explain what she meant by this comment.
Be sure to briefly discuss the bonding forces. 3 sentences (maximum)
OR
Draw a vcry clearly labelled diagram (schematic) to show what has happened. Label your
diagram and include a one sentence caption
6
5. (15 pts) One of the themes that we will continue to explore this quarter is how
specific cellular processes are controlled by modulating the activity level of specific
proteins. In lecture we talked about a couple of mechanisms (see below) by which the function
of a plasma membrane ion channel could be regulated such that it is either open or shut.
Draw a detailed, schematic diagram which illustrates one of these strategies.
• Use simple symbols to illustrate the structure of the channel protein, the lipid bilayer
(show generic components in a very schematic form) and the regulatory molecule.
Indicate the extracellular and cytoplasmic face of the membrane.
• Be sure to provide a detailed key to your symbols (example:  = regulatory molecule)
• You do not need to draw out any specific chemical structures (atoms, bonds etc.)
• PROVIDE a two sentence caption for your diagram to help the viewer understand the
regulatory process. Use proper terminology
Circle the mechanism that you choose to illustrate (and fill in the long blank if you choose
#3):
Mechanism 1: involved allosteric regulation of a channel protein that exhibited quaternary
structure
Mechanism 2: involved regulation of the cystic fibrosis channel – which doesn’t show
quaternary structure but does a number of specific functional domains
Mechanism 3: a hypothetical regulatory mechanism that you will propose that respects the
properties of membranes and proteins and has some basis in biological reality:
_____________________________________________________________________________
____________________________________________________________________
7