Page 14 - Pharmacy College Admission Test Review Book

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11.(b) The nucleus is an essential organelle for
survival of a cell. If a nucleus is removed from
any cell it dies within a short period. Moreover
an enucleated cell neither divides regularly nor
differentiates since there is DNA in the nucleus
which is responsible for all the life processes of
an organism. Every Eukaryotic cell, during the
interphase stage (when the cell is not dividing it
is said to be in the interphase stage), possesses
a distinct nucleus.
12. (d) Nuclear membrane (Nucleolemma) is a
membrane surrounding the nucleus. It
separates the nucleus from the cytoplasm. The
presence of nuclear membrane is of great
significance for the mutual exchange taking
place between the nucleus and the cytoplasm.
The pores in the nuclear membrane are
believed to be the paths for the exchange of
giant molecules between the cytoplasm and
nucleus.
13.(b) Generally, a plant cell wall is formed of
polysaccharides like cellulose and pectin. The
principal function of the cell wall is to protect
the plant cell from an attack of microorganisms,
gravity and increased osmotic pressure
developed in the cell.
14.(c) A small saclike structure filled with liquid
and appearing like small dots in the cytoplasm
is known as the vacuole. It consists of different
types of soluble and insoluble substances and
water.
15.(a) Cell division is a very complex process.
There are two main types of cell division:
1. Mitosis
2. Meiosis
Mitosis: In this type of cell division,
chromosomes are equally distributed in each
daughter cell.
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Krisman
As a result, the numbers of chromosomes in
the mother cells and daughter cells are the
same (e.g. somatic cells division).
Meiosis: In this type of cell division,
chromosomes are divided in half of the original
numbers of chromosomes found in mother
cells (e.g. reproductive or sex cells division).
16. (b) The cell cycle is normally divided into
two phases:
1. Interphase
2. Mitosis
Interphase: It is a period between two active
divisions, during which the cell prepares itself
for an active division. An active division is
divided into three sub-phases, known as G , S
1
and G . The G phase follows mitosis and is the
2 1
period in which the cell synthesizes its
structural proteins and enzymes to perform its
functions. For example, a pancreas cell in the
1
G phase will be producing and secreting
insulin, or a salivary gland cell will be secreting
salivary enzymes to assist digestion.
During the S phase, each chromosome is
copied, and therefore by the end of the S
phase, the cell has two DNA. In human cells,
there are forty-six chromosomes per cell in the