lab4 - 4 Cellular Form and Function Objectives In this...

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23 4 Cellular Form and Function Objectives In this chapter we will study diseases that result from malfunctions of human organelles; the structures of various pathogens; and some diseases caused by viruses, bacteria, protozoans, fungi, and parasites. Organelles and Disease Each organelle plays a specific role in the overall function of a cell. Thus, a change in the number or functional capacity of organelles can produce cellular dysfunctions, or diseases. In this section, we consider two examples: mitochondrial cytopathies and lysosomal storage diseases. Mitochondrial Cytopathies The term cytopathy refers to any disorder of a cell or its components; thus, a mitochondrial cytopathy is any disease or cellular dysfunction caused by defective mitochondria. Mitochondrial DNA (mtDNA) contains genes for 13 proteins and some RNA molecules (other than the mRNA that codes for those proteins). Mutations in mtDNA can occur in the human egg before conception and thus be passed on to a child. Sperm mitochondria do not survive in the fertilized egg. The cells most severely affected are those with the highest energy (ATP) demands—neurons, some receptor cells in the eye, and muscle cells—although mitochondrial diseases are not limited to those cells. Some diseases caused by mtDNA mutations are briefly described here: Leber hereditary optic neuropathy is characterized by loss of vision, with dark areas in the center of the visual field and abnormal color vision. The mean age of onset is 23 years, and for unknown reasons, about three times as many men as women exhibit the disease. MERRF syndrome ( myoclonic epilepsy and ragged red fibers ) is a syndrome in which the patient exhibits hearing loss, seizures, myoclonus (sudden, shocklike muscle contractions), loss of motor control, intellectual deterioration, and ragged red (slow-twitch) muscle fibers. Pearson marrow-pancreas syndrome i s a disease of infants characterized by anemia and defective pancreatic function. Kearns-Sayre syndrome includes paralysis of the muscles of eye movement, infiltration of the retina with pigment cells, and sometimes heart block and incoordination resulting from damage to the part of the brain called the cerebellum. It typically begins before age 20 and has a poor prognosis, with most patients dying in their 20s or 30s. Lysosomal Storage Diseases Lysosomes are membrane-enclosed packets of enzymes in the cytoplasm. More than 30 diseases have been linked to deficiencies in these stored enzymes— deficiencies that lead to the inability to metabolize certain macromolecules and to the accumulation of those macromolecules in the cell. Thus, these disorders are called
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This note was uploaded on 11/16/2011 for the course SCIENCE Anatomy an taught by Professor Tory during the Spring '11 term at Kennesaw.

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lab4 - 4 Cellular Form and Function Objectives In this...

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