Chapter 3
Subcellular organelle function and pathophysiology.1
Cytoplasm: excess bilirubin (a normal pigment of bile) in the cytoplasm can lead to a yellowing
color of the skin. In severe cases, patients appear jaundiced. This condition sometimes indicates a
problem with liver function.
Endoplasmic reticulum: the smooth endoplasmic reticulum of the liver is the major storage site
for glycogen and the metabolism of lipid-soluble drugs.
Golgi apparatus: many cells synthesize proteins that are inactive and larger than the functional
subunit, such as the proinsulin molecule in the islet cells of the pancreas. This larger molecule is
processed in the Golgi and cut into smaller, active insulin molecules. The smaller molecules then
travel from the Golgi and transported outside the cell through secretary vesicles.
Lysosomes: are the digestive system of the cell which break down foreign substances using
lysosomal enzymes, such as acid hydrolases. The pH of the interior of lysosomes is about 5 so
they are much more acidic than other compartments of the cell.
There are lysosomal storage diseases that occur if a lysosomal enzyme is absent or inactive. TaySachs disease- the enzyme, hexosaminidase A (hex A) is not functioning so that affected children
cannot breakdown gangliosides (fatty substances) in the cells of the nervous system
Infants are typically normal, but as gangliosides build up the nervous system there are motor
development problems, mental deterioration and sometimes blindness and death by the 3rd to 5th
year of life.
Peroxisomes: smaller than lysosomes, contain an enzyme, catalase which degrades hydrogen
peroxide. Peroxisomes also contain enzymes to degrade long fatty acid chains. Build up of fatty
acids in the brain can lead to dementia (loss of cognitive function).
1
Mattson Porth, C. (2002) Pathophysiology. Concepts of altered health states. (6th ed.)
Lippincott, Williams & Wilkins. New York, NY.