BI 171 - Third Exam - Answer Key - 2010

Each question's number is linked to the relevant part of the online book, if possible (some questions relate to multiple sections).

Multiple Choice.

Place the letter of the choice that best answers the question on the line to the left.
Two Points Each. NOTE: "e" answers are never the correct answer.

___C___ 1.  Which will have a lot of RNA in it?

                    a. Chromosome             b. Nuclear envelope             c. Nucleolus            d. Intermediate filament             e. The RNA supermarket

                        ...its main function is to store and process RNA.

___D___ 2.  The rate "drop off" from optimum temperature and pH may both involve

                    a. Changes in flux             b. Changes in particle speed            c. Changes in substrates             d. Breaking of hydrogen bonds
                                                                                e. How close to the weekend it is

                        ...both rising temperatures and extra ions can disrupt H bonds and make it hard for the enzyme molecules to
                                stay in a working shape.


___B___ 3.  Recycling of materials generally happens in

                    a. Golgi bodies             b. Peroxisomes             c. Ribosomes            d. MTOCs             e. Itty-bitty special bins

                        ...match the organelle with the function.

___A___ 4.  Microfilaments provide motion to

                    a. Muscle cells             b. Cilia             c. Flagella            d. Mitotic chromosomes             e. Avatar effects

                        ...match the structural element with a function.


___D___ 5.  An enzyme always works by affecting

                    a. Substrate shape             b. Electron distribution            c. Speed of breakdown             d. Activation energy
                                                                            e. How angry the tiny bits are

                        ...that's how it gets reactions to go more easily.


___B___ 6.  Which division stages are the most different compared to mitosis?

                    a. Prophase and anaphase of Meiosis II                                        b. Prophase and anaphase of Meiosis I
                    c. Anaphase and telophase of Meiosis I                                        d. Anaphase and telophase of Meiosis I
                                        e. Differ-phase and not-so-much-the-same-phase of Meiosis Whatever

                        ...during prophase, homologous pairs are put together in the middle, and in anaphase, chromatids do not
                                separate, and double-stranded chromosomes move toward the poles.

___C___ 7.  Minerals are commonly working in

                    a. Enzymes and coenzymes             b. Osmosis and enzymes            c. Cofactors and prosthetic groups             d. Cofactors and coenzymes
                                                            e. Small third-world countries, where they are being exploited

                        ...cofactors work separately, prosthetic groups are actually parts of the molecules, but both are usually minerals.


___A___ 8.  In response to insulin, sugar moves from the blood into liver cells; soon, the concentration in the liver cells exceeds that of the blood,
                        and it keeps moving in. This involves

                    a. Active transport             b. Facilitated diffusion             c. Osmotic pressure            d. Passive transport             e. The liver...and the blood...

                        ...figure the relative concentrations - movement from high to low (downhill) is diffusion, happens by itself, passively;
                                if movement is low to high (uphill), it's got to be pushed, active.


___C___ 9.  A high chromosome number is associated with what type of mutation?

                    a. Deletion point mutation             b. Extra set of chromosomes            c. Extra or missing chromosome             d. Crossing over mutation
                                                                                e. Chromosomes mutate by getting high???

                        ...more pieces, more chance for a piece to not go where it's supposed to be during cell division.  Extra in one daughter cell,
                                missing in the other.


___D___ 10.  The inside layer of a cell membrane stays in place because it is

                    a. Covalently bonded             b. Hydrogen bonded             c. Hydrophilic             d. Hydrophobic             e. Under contract

              's sandwiched between the hydrophilic layers facing in and out, stable because there's water there.


___C___ 11.  Chromatin (but not chromosomes) is visible to a light microscope during

                    a. Prophase and interphase                     b. Metaphase and anaphase                    c. Prophase and telophase
                    d. Anaphase and telophase                                        e. Is it nice to spy on chromatin?

                        ...that's when it's either condensing on its way to visible chromosomes, or unwinding back to invisible but usable chromatin.


___B___ 12.  Radiation damage often kills cells

                    a. Just before they divide                 b. After they divide                 c. Just after exposure                 d. Weeks after exposure
                                                                                e. After they become dog-sized and eat people

               breaks chromosomes, and if they aren't repaired properly, leaves pieces that can't be distributed correctly during
                                divisions - that's why radiation illnesses are tied to fast-dividing tissues and it's used to kill fast-dividing cancers.

___D___ 13.  Okazaki fragments are a feature of

                    a. Translation                 b. Transcription                 c. Breakdown                d. Replication                 e. Sushi slices

                        ...copying happens on just a small opened area of DNA - because of polarity, it can happen continuously on one side,
                                but must be done bit-by-bit (fragments) on the other.


___C___ 14.  A regulatory site would be a

                    a. Cofactor                 b. Coenzyme                 c. Domain                d. Prosthetic group                 e. Little government office

                        ...a functional region on an protein molecule (here, used to turn it on and off).


___A___ 15.  Two research areas very interested in telomeres:

                    a. Aging and cancer             b. Alzheimer's and diabetes            c. Birth defects and heart disease             d. Mutations and evolution
                                                                    e. Erectile dysfunction and megaburping

                        ...non-repair of telomeres may be a big factor in aging, and continuous repair may allow cancers to grow indefinitely.


___D___ 16.  The purpose of a typical polar body is to

                    a. Increase sperm count             b. Store nutrients            c. Produce spindle             d. Remove unneeded chromosomes
                                                                                e. Look like it's wearing a tuxedo

                        ...during egg cell production, where only one food-filled egg cell will be produced, but meiosis divisions have to be done.


___B___ 17.  In dynamic equilibrium,

                    a. Reactant amounts equal product amounts                                b. Reaction rates are equal forward and backward
                    c. Flux rates are equal across and back                                       d. Particle amounts are equal on both sides of a barrier
                                                            e. It sounds like it was named by an ad executive

                        ...both equilibria are about rates, but dynamic is about reactions.


___A___ 18.  In group translocation, which two functions occur together?

                    a. Transport through membrane and chemical change                    b. Osmosis and diffusion            c. Synthesis and breakdown
                    d. Messenger RNA production and DNA replication                                e. You stick them on a bus and drive them somewhere

                        ...carriers are also enzymes.


Short Answer.

Pick NINE questions to answer in the spaces provided.
NOTE: if you answer MORE than nine, only the first nine will be corrected.
Four Points each. Partial credit is possible.

1.  What are the two functional ends of transfer RNA?
Attaches to codon of mRNA Carries in amino acid to attach to growing chain
2.  What are two totally different ways to move materials around in the cytoplasm?
On microfilaments

On microtubules

In endoplasmic reticulum
3.  What is a turnover number?

 many substrate molecules an enzyme molecule can process per second.

4.  What are two different functions of spindle fibers?
Attach to and move chromosomes Attach to membrane for anchoring
5.  What are two different organelles found inside both prokaryote and eukaryote cells?
Chromosomes Ribosomes
6.  For apoptosis -
What      Cell dies on purpose /
is                programmed cell death /
it?                   cell suicide
What organelle        Lysosomes (release digestive enzymes)
is commonly
7.  What are two different ways that fresh-water organisms prevent damage from osmosis?
Pump water back out (contractile vacuoles, kidneys...)

Waterproof surfaces

Cell containers that won't break from pressure
8.  Why exactly would a cell be in trouble if its chaperonins weren't working?

          ...since chaperonins make sure new proteins take on their proper functional shapes, new proteins wouldn't work and do what the cell needs to be done.

9. What is likely to be a major function in a cell with lots of -
                    (Process materials for release)
MICROVILLI              Absorption or secretion
                            (Increase surface area for movement in or out)

10.  Name two different enzymes that are active in DNA replication.
Topoisomerase (unravels DNA from histones)

Helicase (gets strands apart)
Primase (gets RNA primers attached)

DNA polymerase (makes new strand on old strand)
11.  What can be typically expected from a chemical reaction if you run it at a temperature that is 10o C warmer?

          ...that's the Q10, and usually the rate doubles.

12.  Near genes are short sequences that get involved in transcription. What are two?


Initiation Factors

Boundary Elements / Insulators


13.  In the dialysis tubing lab experiment, maybe the sugar flux was too slow to show up in the time allotted. What are two different reasons why the iodine flux might have been faster?   Think of things that affect flux rates.
The particles of iodine might have been much smaller The concentration of iodine (and therefore the relative concentration across the membrane) might have been much higher.
14.  What are the two main molecular components of chromatin?
DNA Protein (histones)
15.  Which two point mutations involve a frame shift?  This is a change that changes all of the "downstream" codons because they start in a different spot.
(shifts the codon starts back a space)
(pushes the codon starts down a space)
16.  Using this DNA code and the chart attached to the back of the exam, give the coded amino acid sequence.

             Starting   ______________________________________________________________________
  T A C G C T A G T G C T T A T G T G C A T T G C A T C
      Codons        AUG    CGA  UCA    CGA   AUA   CAC  GUA   ACG   UAG

   Amino acids -  Methionine-Arginine-Serine-Arginine-Isoleucine-Histidine-Valine-Threonine (Stop)


Long Answer.

Select and answer completely any four of the following questions.
Note: if you answer more than four, only the first four will be corrected.
Seven Points Each. Partial credit is possible.

1.  For dynamic equilibrium - What does          Reaction rates forward and back
it mean?               are equal. 
One way to
delay reaching        Keep adding substrates.     
it -
way to                Remove products.
delay it -
2.  For the two cell organelles that are thought to have started as endosymbionts:
Organelle: Function: Feature that indicates that it once was a prokaryote
(Give 2 different features)
Mitochondrion Aerobic respiration Very similar structure to existing prokaryotes.

Very similar chemistry to existing prokaryotes.

Chloroplast Photosynthesis Have small prokaryote chromosomes in them.
3. Fill in the arrow-headed labels on this drawing of eukaryote cell structures.

This was a drawing with different organelles and such pointed at.   Use links in the book to get familiar with how organelles look.


3. Describe the functions of three different types of membrane proteins.

Allow particles small enough and properly charged in and out
(Pores / channels)

Open on command to allow particles through
Grab and move particles through membrane
React to external stimuli
Move materials against concentration gradient
Produce chemical changes
4.  Give three sets of differences between -
Smaller Larger
Always many on a cell Rarely more than 12 on a cell
Coordinated Often not well-coordinated
Tend to stroke Tend to spin
Do not have add-on structures May have add-on structures
5.  Give three sets of differences between the chromosomes of -
Only one per cell Usually in matched pairs
Loop-shaped Two ends
Often produce plasmids Do not produce plasmids
Genes for pathway enzymes are usually together, in pathway sequence Pathway enzyme genes often randomly distributed
6.  Briefly describe three different ways that enzymes can be inhibited. Inhibitor molecule attaches in active site

Inhibitor molecule attaches, not in active site but blocking access to it

Inhibitor molecule attaches to enzyme, changes shape, including active site shape
7.  In the graph below of Michaelis-Menten Kinetics, explain why the curve is doing what it's doing at each marked point, in terms of the enzyme molecules at work.

                                                                                                                               Along the top flat part Enzymes are all busy all the time
                                                                                                                                                           so adding substrate can't speed the reaction.


                                                                                     Where the rising curve begins to flatten out Enzymes are getting too busy, hard to get
Rate                                                                                                                                           them to work faster with more substrate.

V                                      As the curve rises steeply   Many enzymes available - more substrate gets quickly processed, increasing rate.
                                          Substrate Concentration (as Enzymes remain constant) ---->



Answer as many or as few as you wish. You can't lose points on the rest of the exam by getting these wrong. Partial credit is possible.

Explain the evolutionary significance of position effect. Three Points.

What was recently discovered about related genes in eukaryote nuclei? Three Points.

Why are chromosomes in drawings almost always shown in double-stranded form? Three Points.

What cell structure apparently has no name? Three Points.

Some people feel that the appearance of exons and introns in organisms in the distance past led to complex life. Why would they be important? Three Points.

What evidence supports the idea that a fusion event happened during human evolution? Three Points.

What organisms seem to be "okay" with polyploidy mutations? Three Points.

What seems to be the limiting factor in many ocean algae populations? Three Points

What other processes follow a Michaelis- Menten pattern? Two Points Each, up to 3.

What happens during crossing over that helps solve a huge question about evolution? Three Points.




BI 171



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