A nurse is reviewing the laboratory results of a client who has phenylketonuria (PKU). The nurse expects to find an elevated level of what substance in the client's blood?

Choice A reason: Phenylketonuria (PKU) is a genetic disorder where phenylalanine, an amino acid, cannot be converted into tyrosine, another amino acid, due to a deficiency of an enzyme called phenylalanine hydroxylase. This leads to a buildup of phenylalanine and its metabolites in the blood and tissues, causing brain damage and mental retardation.

Choice B reason: Tyrosine is another amino acid that is normally produced from phenylalanine by the enzyme phenylalanine hydroxylase. However, in PKU, this enzyme is deficient, so tyrosine levels are low in the blood and tissues.

Choice C reason: Glucose is a simple sugar that is the main source of energy for the cells. It is not directly related to PKU, although some people with PKU may have low blood glucose levels due to dietary restrictions.

Choice D reason: Glycogen is a complex carbohydrate that is stored in the liver and muscles as a reserve source of energy. It is not directly related to PKU, although some people with PKU may have glycogen storage disease, which is a separate genetic disorder where glycogen cannot be broken down into glucose due to a deficiency of an enzyme called glucose-6-phosphatase.

Choice A reason: "An unregulated and passive process of cell death that causes inflammation and tissue damage." This is a description of necrosis, not apoptosis. Necrosis is an abnormal and harmful process that occurs when the cells are exposed to severe or persistent stressors that overwhelm their adaptive capacity. It involves the loss of cell membrane integrity, the release of cellular contents into the extracellular space, and the initiation of an inflammatory response that can damage the surrounding tissues.

Choice B reason: Apoptosis is also known as programmed cell death or cell suicide. It is a normal and beneficial process that maintains the balance between cell proliferation and cell death. It involves a series of biochemical events that lead to the activation of enzymes called caspases, which degrade the cell's DNA, proteins, and organelles. The cell then shrinks and forms membrane-bound fragments called apoptotic bodies, which are phagocytosed by macrophages or neighboring cells without causing inflammation or tissue damage.

Choice C reason: "A reversible process of cell injury that occurs when the stressor is mild or removed." This is a description of reversible cell injury, not apoptosis. Reversible cell injury is a process that occurs when the cells are exposed to mild or transient stressors that do not exceed their adaptive capacity. It involves changes in cell metabolism, function, and structure that can be restored if the stressor is removed or the cells are able to adapt.

Choice D reason: "An irreversible process of cell injury that occurs when the stressor is severe or persistent." This is a description of irreversible cell injury, not apoptosis. Irreversible cell injury is a process that occurs when the cells are exposed to severe or persistent stressors that exceed their adaptive capacity. It involves changes in cell metabolism, function, and structure that cannot be restored and lead to cell death by necrosis or apoptosis.