Fundamentals of Anatomy and Physiology

Cell Structure

Another molecule will now go into the cytoplasm and
collect the amino acids. This molecule is transfer RNA
(tRNA). It is coded for a particular amino acid by means of
three nitrogen bases at one end of the mole-cule known as
the anticodon (Figure 3-10). These three bases will fit or
match with three bases on the mRNA molecule called the
codon. In this way, a series of tRNA molecules bring amino
acids to certain sites on the mRNA molecule. This process
is called translation- (read-ing the code and bringing the
appropriate amino acids in sequence along the mRNA).
Now the ribosomes, with the assistance of enzymes, put the
amino acids together by linking them up and forming a
-polypeptide chain (Figure- 3-11). The numerous
ribosomes found in the

49

cell indicate the importance and significance of protein

synthesis to the survival and function of the cell.

Centrioles

Two centrioles (SEN-tree-olz) are found only in cer-tain

animal cells at right angles to each other near the nuclear

membrane. The pair together is referred to as a

centrosome- (SEN-troh-sohm). They are composed of

nine sets of triplet fibers (Figure 3-12). The inner fiber of

each triplet is connected to the outer fiber of the adja-cent

triplet by a subfiber.

During cell division, the centrioles move to each side

of the dividing cell and position themselves at a location

Nucleus

DNA strand^
Nucleolus

Transcription

Cytoplasm^
mRNA strand

mRNA strand

Ribosome

tRNA tRNA^

(^) tRNA (^)
Amino acid (^) Translation
pool (^)
(^) ®
Learning
Cengage ©
Figure 3- 11 An overview of the process of protein synthesis.