Page 21 - 84 human physiolofy part-1

Cell Physiology

Inside each cell nucleus are chromosomes. Chromosomes are
made up of chromatin, which is made up of protein and
deoxyribonucleic acid strands. Deoxyribonucleic acid is DNA, the
genetic material that is in the shape of a twisted ladder, also called
the double helix. Humans have 23 pairs of chromosomes. Down
Syndrome and Cri du Chat Syndrome result from having an
abnormal number of chromosomes.

• Centrioles

Centrioles are rod like structures composed of 9 bundles which
contain three microtubules each. Two perpendicularly placed
centrioles surrounded by proteins make up the centrosome.
Centrioles are very important in cellular division, where they arrange
the mitotic spindles that pull the chromosome apart.

Centrioles and basal bodies act as microtubule organizing
centers. A pair of centrioles (enclosed in a centrosome) located A rough sketch of a chromosome.
(GFDL - Magnus Manske)
outside the nuclear envelope gives rise to the microtubules that make
up the spindle apparatus used during cell division. Basal bodies are at the base of each flagellum and
cilium and appear to organize their development.

• Ribosomes

Ribosomes play an active role in the
complex process of protein synthesis, where
they serve as the structures that facilitate the
joining of amino acids. Each ribosome is
composed of a large and small subunit
which are made up of ribosomal proteins
and ribosomal RNAs. They can either be
found in groups called polyribosomes within
the cytoplasm or found alone. Occasionally
they are attached to the endoplasmic Ribosome structure (GFDL - Dominus, MaxPower)
reticulum.

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