Ibo 2010

ENVELOPE COVER SHEET

Student Code: __________________

The 21st INTERNATIONAL BIOLOGY OLYMPIAD
Changwon, KOREA

11th – 18th July, 2010

THEORETICAL TEST: PART A
Time available: 120 minutes
GENERAL INSTRUCTIONS

1. Open the envelope after the start bell rings.
2. A set of questions and an answer sheet are in the envelope.
3. Write your 4-digit student code in every student codebox.
4. Mark only one correct answer with “” on the Answer Sheet clearly, as shown below.
A

B

C

D

E


5. Use pencils and erasers. You may use a scale and a calculator provided.
6. Some of the questions may be crossed-out. DO NOT answer these questions.
7. Stop answering and put down your pencil IMMEDIATELY after the end bell rings.
8. At the end of the test session you shouldleave all papers at your table. It is not allowed to take
anything out.

IBO2010 KOREA
THEORETICAL TEST Part A

Country: _______________

Student Code:

1

___________

IBO2010 KOREA
THEORETICAL TEST Part A

The 21st INTERNATIONAL BIOLOGY OLYMPIAD
11th – 18th July, 2010

Changwon, KOREA

THEORETICAL TEST: PART A
Time available: 120 minutes
GENERAL INSTRUCTIONS
1. Writeyour 4-digit student code in every student code box.
2. Mark the correct answer with “” in the Answer Sheet clearly, as shown below.
A

B

C

D

E



3. Use pencils and erasers. You can use a ruler and a calculator provided.
4. Some of the questions may be crossed-out. Do not answer these questions.
5. The maximal point of Part A is 51 (1 point for each question).
6. Stop answeringand put down your pencil immediately after the end bell rings.
7. At the end of the test session you should leave all papers at your table. It is not allowed to take
anything out.

CELL BIOLOGY

2

IBO2010 KOREA
THEORETICAL TEST Part A

A1.

Select the chemical property that is shared by all types of lipids forming the plasma membrane.
A. Polar head
B. Sugar component
C. Glycerolbackbone
D. Phosphate group
E.

Hydrophobic region

-

3

IBO2010 KOREA
THEORETICAL TEST Part A

A2.

The following photograph shows filamentous growth of a kind of cyanobacteria, Nostoc sp. The
bacteria form heterocysts (thick-walled cells), when nitrogen sources such as ammonia or nitrates are
deficient in the environment.

Which of the following statements describing theseheterocysts is/are true?

I.

Nitrogen is fixed in the heterocyst.

II.

Photosystem I does not function in the heterocyst.

III.

Photosystem II does not function in the heterocyst.

A. Only I
B.

Only II

C.

Only I and II

D. Only I and III
E. Only II and III

4

IBO2010 KOREA
THEORETICAL TEST Part A

A3.

A generegulatory protein X controls cellproliferation. Protein X is found in the cytosol and has
no typical nuclear localization signal (NLS). When cells are treated with a specific growth hormone,
protein X re-localizes from the cytoplasm into the nucleus where it activ ates the transcription factors
involved in cell proliferation.
Recently, a protein (Y) that interacts with protein X has been identified in unstimulated cells. To
investigatethe function of protein Y, a mutant lacking the gene encoding protein Y was generated.
Fractionation of cells from the wild type and mutant produced membrane (M), cytoplasmic (C), and
nuclear (N) fractions for each cell type. Proteins extracted from each fraction were separated by
SDS-PAGE and analyzed by Western blotting for the presence of proteins X and Y.

On the basis of the results shownabove, which of the following statements is the most plausible
characterization of protein Y?
A. In the absence of growth hormone, protein Y associates with protein X, and the X/Y
complex is subjected to a degradation pathway.
B.

In the presence of growth hormone, protein Y interacts with protein X, and the complex
remains in the cytoplasm.

C.

Protein X interacts with protein Y in...