1. "A" represent the nucleolus of the nucleus. It is not bound by a membrane and consist of condensed RNA, protein and DNA. The function of the nucleolus is that is synthesizes organelles called ribosome. The structure and function of ribosomes will be investigated later in this lesson. The nucleus may contain anywhere from one to many nucleoli. "D" represents chromatin. Chromatin consists of DNA and protein in the form of uncoiled, uncondensed molecules which are bound by a double membrane. In a dividing cell the DNA of the nucleus will coil tightly and condensed into chromosomes. "C" represents nuclear pores of the nuclear membrane. They prevent DNA and protein from leaving the nucleus but allow large molecules pass from the nucleus into the cytoplasm..
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2. The correct answer is "d". The pores of the nuclear membrane are
not water tight.
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3. The correct answer is "b". The nucleoli is not membrane bound. It
is highly condensed material consisting of RNA, protein and DNA.
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4. The correct answer is "C". Chromatin is the dark colored mass of
DNA and protein of the nucleus. This difference will be further explained
later is this lesson.
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5. The nuclear pores will allow fairly large macromolecules such as
RNA to move into the cytoplasm while preventing larger DNA from leaving
the nucleus.
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6. The correct answer is "e". Ribosomes are synthesized of RNA
and protein by the nucleoli of the nucleus. The ribosomes are assembled
in the cytoplasm where they carry out the process of protein synthesis.
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8. The correct answer is is "B". All cell types must contain
ribosomes to synthesize their protein..
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9. The correct answer is "C". Ribosomes are both free floating in the
cytoplasm and attached to to membranes (Endoplasmic Reticulum). This difference
will be further explained later is this lesson.
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10. The organelle which consist of 9 + 2 microtubular arrangement
are the cilia and flagella. These organelles are located extending from
the cell membrane and function in movement of the organism or to
create currents along the outside of the living cells.
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11. The correct answer is centrioles. These consist of nine sets
of microtubules arranged in a circle with no microtubules in the inside.
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12. The correct answer is basal bodies. These 9 + 1 set of microtubules
are formed by the centrioles and move just under the cell membrane where
they initiate the synthesis of cilia or flagella.
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13. The correct answer is centrioles. Centrioles exist in pair near
the nucleus of animal cells. They are not present in plant cells. Prior
to cell division they replicate forming a total of two pair. Each
of these pair will than migrate in opposite directions and station themselves
at opposites sides of the nucleus during cell division. This will be discussed
in miniunit Gamma.
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14. The correct answer is basal bodies. These structures are formed
by the centrioles and move to the underside of the cell membranes. Usually
flagella are present as single tails of a cell or present in small numbers;
whereas, cilia are present in large numbers. Cilia are much shorter than
the flagella. Cilia move in an "oar like" fashion and flagella move in
a "whip like" fashion.
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15 The correct answer is flagella. The tail of human sperm is a single
flagellum. Some of the single cell algae contain two flagella to help propel
them along.
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16. The correct answer is cilia. Paramecium (single cell protozoan)
contain hundreds of these structures to aid them in moving through water.
The upper lining of your trachea contains millions of these structures
which beat to force dust particle from your trachea into your
throat.
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17. The correct answer is centrioles.
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18. The correct answer is "a". Mitochondria will be examined in the
next lesson. It consists of a double membrane. ribosomes, nucleoli,
centrioles, cilia and flagella are lacking a membrane.
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Last modified October 22, 1997.