Location: USABO Open Exam 2012 2012 USABO Open Exam Page 1 1. Rank the following biological molecules in order of how readily they diffuse across the plasma membrane from the most diffusible to the least diffusible. I. CO2 II. ClIII. Sucrose IV. Glycerol A. I, III,

Joined Jan 16, 2013 at 12:58AM EST



Karma Received
+244 +280 (88%) -36 (12%)
Karma Given
+355 +390 (91%) -35 (9%)


USABO Open Exam
February 5 to 15, 2013
1. Which statement is true about enzymes? Enzymes
A. Are made up of a base containing nitrogen, phosphate, and ribose.
B. Have activity that is independent of temperature and pH.
C. Lose some or all of their normal activity when their 3-D structure is disrupted.
D. Provide the activation energy needed to activate a reaction.
E. Work once only and then are destroyed.
2. You have a multicellular organism that reproduces asexually by fission. When you excise
a ~10,000 cell portion of its body, both the original organism and the excised portion
grow into fully formed, healthy organisms. You take one of the offspring and repeat the
procedure for one hundred and twenty-three generations. Each time, the resulting
organisms are healthy. What must be true of the nuclei of this species?
A. The cells contain plasmids.
B. The cells have multiple forms of DNA polymerase.
C. The cells have the majority of their genome stored in circular DNA.
D. The cells contain active telomerase.
E. The cells contain active fissonase.
3. Which of the following correctly describes how the lifespan of a protein is regulated?
A. The part of the sequence coded for by the UTR tags it for destruction.
B. Giant protein complexes called ubiquitins destroy proteins after they have remained in the
cell for a certain time.
C. Proteins are methylated over time; heavily methylated proteins are destroyed by
D. Proteins are tagged with ubiquitins, which are recognized by proteasomes; the proteasomes
destroy the proteins.
E. Proteins tagged with methyl groups are destroyed by ubiquitins.2013 USABO Open Exam Page 2
4. Of the following amino acids, which is least likely to form strong interactions with other
amino acids that contribute to the tertiary structure of a given protein?
A. Histidine
B. Glutamate
C. Cysteine
D. Glycine
E. Serine
5. Thymine dimers arise when two adjacent thymine bases become covalently linked. This
interferes with normal DNA geometry and will cause replication errors. Which of the
following agents is the primary cause of the thymine dimers?
A. Chemical mutagens
B. Beta emissions from radioactive decay
C. Gamma rays
D. X-rays
E. UV rays
6. Which of the following oligonucleotides would have the highest melting point when
paired with the proper complementary strand?
7. Which of the following is a way in which the cell increases gene expression in the
A. Acetylation of histone tails
B. DNA methylation
C. Locating a gene within heterochromatin
D. Dephosphorylating DNA
E. Alternative splicing
8. Below are the structures of five amino acids. Select the amino acid that would contribute
most significantly to stability of the tertiary structure of a protein.
\A. B. C. D. E.2013 USABO Open Exam Page 3
9. Which of the following statements about cellular ultrastructure is FALSE?
A. Nonmotile eukaryotic cilia are composed of 9 doublets of microtubules in a ring, with no
microtubules in the center (‘9+0’).
B. Bacterial flagella are composed of 9 doublets of microtubules in a ring, with two
microtubules in the center (‘9+2’).
C. Motile eukaryotic cilia are composed of 9 doublets of microtubules in a ring, with two
microtubules in the center (‘9+2’).
D. Centrioles are composed of nine triplets of microtubules arranged in a ring.
E. The basal bodies of eukaryotic flagella are composed of nine triplets of microtubules
arranged in a ring.
10. In a secret cabinet of a lab, you find two Petri dishes in storage and a mysterious lab
notebook. In an effort to identify the bacteria, you run some tests (taking all necessary
safety precautions) and look through the lab notebook. You find that the two Petri
dishes contain the same type of nutrient medium and both bacteria seem to be
Escherichia sp., but that the bacteria in plate 1 are producing large amounts of a variety
of neurotoxins. The bacteria in plate 2 are not producing any major exported product.
You also find this chart in the lab notebook:
Given that Strain 2 is normal E.coli (the control) and Strain 1 is a genetically engineered
strain of E.coli, which line is most likely to represent strain 1, and why?
A. Line B, since strain 1 should exhibit lower than normal growth efficiency.
B. Line B, since strain 1 should exhibit higher than normal growth efficiency.
C. Line A, since strain 1 should exhibit lower than normal growth efficiency.
D. Line A, since strain 1 should exhibit higher than normal growth efficiency.
E. The E. coli line should represent both, since Strain 1 should have the same growth efficiency
as a normal E. coli strain.2013 USABO Open Exam Page 4
11. Which of the following chemicals or groups of chemicals is not a major determinant of
flower color?
A. Flavonols
B. Carotenoids
C. Cyanidin
D. Phytoalexins
E. Betacyanins
12. Which of the following is not a characteristic of cycads?
A. Secondary growth from a vascular cambium
B. Fruit
C. True leaves
D. Insect pollination
E. Presence of neurotoxins and carcinogens in plant tissues
13. Which of the following does not take part in the light reactions of photosynthesis?
A. Photosystem I
B. Photosystem II
C. Rubisco
D. ATP synthase
E. Cytochrome complex
14. Lettuce seeds receive flashes of far red and red light in this order: far red, red, far red,
red, red, red, red, far red. The seeds will
A. Germinate since far red light induces germination.
B. Germinate since the first flash of light determines germination.
C. Germinate since there are more flashes of red light.
D. Not germinate since the flashes of light have destroyed the seeds.
E. Not germinate since only the last flash of light determines germination.
15. Which of the following statements about alternation of generations in land plants is
A. The gametophyte produces haploid cells by meiosis.
B. In nonvascular plants (Bryophyta), the gametophyte stage is dominant.
C. The sporophyte produces diploid spores that later undergo meiosis.
D. The gametophyte stage is diploid.
E. (A) and (D) are BOTH true. 2013 USABO Open Exam Page 5


Recent Activity

Commented on HorribleGhost's wall


Feb 17, 2015 at 05:58PM EST

Commented on History Fandom

Seeing this featured feels like reading one of my math tests from like 7th grade. Boy was I a dumbass and boy am I unable to do anything about it

Feb 16, 2015 at 06:25PM EST

Commented on HorribleGhost's wall


Feb 14, 2015 at 04:55PM EST

Commented on HorribleGhost's wall

I have 4 new wall posts today do I need to add an annoying autoplay along with my anime spoilers

Feb 07, 2015 at 11:43PM EST

Commented on HorribleGhost's wall

OH. That’s what you meant.

I was telling people to delete a meme that mocked men’s body image issues and body positivity. An already little-known issue didn’t need to be hijacked with TF2 pics or whatever people felt like inserting into the post.

Jan 13, 2015 at 11:20PM EST

Commented on HorribleGhost's wall

Thank you. Xkit is taking care of the notification spam for me, so I should be OK.

I’m very glad that there aren’t more KYM users who also use Tumblr.

Jan 10, 2015 at 01:22AM EST

Commented on HorribleGhost's wall

OH. OK, I see what you mean.

I was scrolling through “top posts” for the bath bomb tag so yeah that’s how I found him

Jan 08, 2015 at 07:05PM EST

Commented on HorribleGhost's wall

Think about what the original joke was.
It was implying that the whole “post pics of my bath bomb results” thing is ridiculous and kind of gross. (idk some people used ramen)
Bath bombs are mostly used by young white girls, so of course they’re gonna work up a storm about it. I didn’t really participate in any of it until I saw antifems using it as an “argument” and went aw hell nah

Did your friend call me a sad little person and predict that I would drop out of my science major to become a “professional victim”? (??? I’m not in college?) That’s the only person I remember carrying a full conversation with over bath bombs. There were a couple of other people that I just one-off talked to but I don’t remember how many. Mostly just reminding them that thehorribleghost.tumblr.com is a solo blog and I am one person. Not sure where they were getting multiple folks from.

Jan 08, 2015 at 01:57AM EST

Commented on HorribleGhost's wall

Mostly disappointed with the people who like the meme only because it’s offensive or using it like “FEMINISTS?SS? CONCERN WITH NOT MURDER ISLAM AND THIRD WORLD COUNTRIES!!! THAT MALE BODY POSITIVYIT POST MEME

(For the record that meme was shit and I messaged a ton of people about it asking them to delete it. A few actually did it but eeeeh I’m still not comfortable with people wielding men’s body image like a trump card whenever something gets called out)

The only good ones are the one with an actual bomb (the joke is a pun and not "ha ha girls who upload bath bomb pics) and the vine where someone throws soap with Jesus on it into the tub and then suddenly there’s a guy dressed like Jesus floating in the water (the joke is that Jesus is here wtf)

Jan 06, 2015 at 08:10PM EST

Commented on But even Neo-Nazis are OK with calling themselves Nazis...

(oh god this is so fucking old but idgaf i’m not even active anymore)

baguettethefuckout made this post for whatever reason.

a “SJW” screencapped it and it began to circulate.

baguettethefuckout began to argue with a whole bunch of people, indicating that they intend to defend their views on Nazis. Most troll blogs just let their detractors scream into the abyss.

One of those arguments wound up on my dash along with a screencap. I uploaded that image here.

Dec 23, 2014 at 12:53AM EST

Commented on #Metalgate

tbh metal is probably the least conservative thing ever

Dec 17, 2014 at 07:08PM EST

Commented on HorribleGhost's wall

OKAPI fainted!

Partially from eating a bug, partially from Perish Song!

HORRIBLEGHOST leaves with the cash!

Dec 03, 2014 at 01:57AM EST

Commented on HorribleGhost's wall


it’s super gross!

Nov 29, 2014 at 04:37PM EST

Commented on HorribleGhost's wall

sorry I can’t hear you over the sound of this sick Pokemon battle

Nov 28, 2014 at 02:49PM EST

Greetings! You must login or signup first!