93' SBIOA Exam

PART A:  MULTIPLE CHOICE.  THERE IS AN ANSWER PAGE FOR THESE QUESTIONS.  USE IT.

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1 .    Atoms of a single element which have a different number of neutrons in the nucleus are called

       a .    *correct*isotopes.

       b .    ions.

       c .    electronegative atoms.

       d .    electropositive atoms.

       e .    isomers.

2 .     Buffers in living organisms

       a .     maintain cytoplasm in a fluid condition.

       b .     *correct*maintain pH in the cells within a narrow range, allowing enzymes to function efficiently.

       c .      allow the pH of cells to change without affecting the action of the enzymes.

       d .     neutralize the effect of enzymes.

       e .      prevent charged particles from entering the cells.

3 .     In biological systems, oxidation involves

       a .    gain of electrons.

       b .    *correct* loss of hydrogen atoms.

       c .     free oxygen.

       d .    gain of hydrogen atoms.

       e .    loss of oxygen atoms.

4 .     Which of the following is NOT a polymer?

       a .    protein

       b .    *correct* fat

       c .     RNA

       d .    starch

       e .    cellulose

5 .     The four chemical elements that make up all amino acid molecules are: carbon, hydrogen,

       a .    oxygen and phosphorus.

       b .    oxygen and sulphur.

       c .     nitrogen and phosphorus.

       d .    *correct* oxygen and nitrogen.

       e .    nitogen and sulphur.

6 .     An example of a monosaccharide is

       a .     sucrose.

       b .    cellulose.

       c .    glycogen.

       d .   *correct*glucose.

       e .    maltose.

7 .     The great diversity of structure in proteins is mainly due to

       a .     *correct*different numbers, kinds, and sequences of amino acids.

       b .    different kinds of bonds between successive amino acids.

       c .     the action of the ribosomes.

       d .    the precise location of specific amino acids, common to all proteins. 

       e .    the disulphide and hydrogen bonds which determine molecular shape.

8 .     Which of the following is NOT true about enzymes?

       a .    They function best at specific temperatures but break down at high temperatures.

       b .     Some enzymes require activators.

       c .     They are essential to the metabolism of cells for the conversion of energy.

       d .    They function best at a particular pH.

       e .    *correct*They undergo a major chemical change after reacting with their specific substrate.

9 .     Which of the following statements about enzymes is most correct?

       a .    All catalysts are enzymes.

       b .    Catalysts prevent chemical reactions.

       c .    Denaturation of proteins always involves enzymes.

       d .    *correct*All enzymes are catalysts.

       e .    A denatured enzyme is more specific in its action.

10 .   Some water, a small amount of soil, a few green aquatic plants and a fish were placed in a large bottle. The bottle was sealed to prevent the exchange of gases and other materials between its contents and the outside.  The bottle was placed in a window to receive light during the daytime.  Is carbon dioxide produced by the plants?

       a .    *correct*Yes, it is produced all the time as a result of cellular respiration.

       b .    Yes, but it is produced only at night when the plants can no longer carry on photosynthesis.

       c .     No, it is a waste product of animals only.

       d .    No, plants take in only the waste products exhaled by animals.

       e .    No, plants only produce oxygen.

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