One Form of Anemia Results When Individuals Have a Deficiency

question 24

Multiple Choice

One form of anemia results when individuals have a deficiency in the enzyme phosphatidylinositol glycan A (PIGA) . This enzyme is required for the membrane attachment of proteins anchored by glycolipids to the plasma membrane, using what is called a 'GPI-linkage.' Included in the group of GPI-linked cell surface proteins is DAF/CD55. These individuals become anemic because:

• A) DAF/CD55 prevents the lysis of red blood cells by infecting pathogens.
• B) DAF/CD55 normally prevents the spleen from clearing healthy red blood cells from the circulation.
• C) In the absence of PIGA, the red blood cell membrane is bare of proteins allowing increased access of complement activating proteins to attach to the cell membrane.
• D) DAF/CD55 is a complement inhibitory protein that inactivates any C3 convertase that may form on host cell surfaces.
• E) In the absence of PIGA, red blood cells are unable to synthesize high levels of hemoglobin.

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An amount that is subtracted from someone's gross income, reducing the taxable income and thus the amount of tax owed.

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