Figure 1-4. A "typical" animal cell (as seen in an electron microscope).
1-13. MAJOR COMPONENTS OF A "TYPICAL" ANIMAL CELL
a. Nucleus. The nucleus plays a central role in the cell. Information is stored in
the nucleus and distributed to guide the life processes of the cell. This information is in
a chemical form called nucleic acids. Two types of structures found in the nucleus are
chromosomes and nucleoli. Chromosomes can be seen clearly only during cell
divisions. Chromosomes are composed of both nucleic acid and protein.
Chromosomes contain genes. Genes are the basic units of heredity which are passed
from parents to their children. Genes guide the activities of each individual cell.
b. Cell Membrane. The cell membrane surrounds and separates the cell from
its environment. The cell membrane allows certain materials to pass through it as they
enter or leave the cell.
c. Cytoplasm. The semifluid found inside the cell, but outside the nucleus, is
called the cytoplasm.