6.In an experiment,cells are subjected to radiant energy in the form of x-rays This results in cell injury caused by hydrolysis of water and free radical generation.Which of the following cellular enzymes normally protects cells from free radical injury? A.Endonuclease B.Glutathione peroxidase C.Lactate dehydrogenase D.Phosholipase E.Protease Ans:B Glutathione peroxidase is one of three key enzymes that neutralize free radicals (the others are superoxide dismuase and caalase).Endonuclease cleaves phosphodiester bonds chain of tides. Lactate dehydrogend 2 the re nate to e and the fatty acids. e bonds in the process ofproteolysis robzes lipids 7.A30 year old man fract tures his left femur in a biking a cide d his leg is pl ced in a plaster cast. fter the leg has been immobilized for several week the diameter the left cal This change is most likely to result from which of the following alterations in the calf muscles A.Aplasia B.Atrophy C.Dystrophy D.Hypoplasia E.Metaplasia Ans:B Atrophy refers to the reduction in n umber or size ofcells.In this case,disuse of the limb results d neuronal stimulation to the skeletal n Aplasia is the failr of his leg. which leads to atre etof元 m D the dege of tissue Hypop acement ofone cell type with another in response to stress or irritation 8. A experiment ana yme activity associated wit A.Endothelial cells B.Erythrocytes C.Germ cells D.Neurons E.Neutrophils 5 - 5 - 6. In an experiment, cells are subjected to radiant energy in the form of x-rays. This results in cell injury caused by hydrolysis of water and free radical generation. Which of the following cellular enzymes normally protects cells from free radical injury? A. Endonuclease B. Glutathione peroxidase C. Lactate dehydrogenase D. Phosholipase E. Protease Ans: B Glutathione peroxidase is one of three key enzymes that neutralize free radicals (the others are superoxide dismutase and catalase). Endonuclease cleaves phosphodiester bonds of a chain of nucleotides. Lactate dehydrogenase catalyzes the reduction of pyruvate to lactate and the oxidation of lactate to pyruvate in the liver (Cori cycle). Phospholipase hydrolyzes lipids into fatty acids. Protease hydrolyzes peptide bonds in the process of proteolysis. 7. A 30 year-old man fractures his left femur in a biking accident, and his leg is placed in a plaster cast. After the leg has been immobilized for several weeks, the diameter of the left calf has decreased. This change is most likely to result from which of the following alterations in the calf muscles? A. Aplasia B. Atrophy C. Dystrophy D. Hypoplasia E. Metaplasia Ans: B Atrophy refers to the reduction in number or size of cells. In this case, disuse of the limb results in decreased neuronal stimulation to the skeletal muscles of his leg, which leads to atrophy. Aplasia is the failure of a structure to form. Dystrophy is the degeneration of tissue due to a pathologic process. Hypoplasia refers to incomplete development of a tissue or organ. Metaplasia is replacement of one cell type with another in response to stress or irritation. 8. An experiment analyzes cells for enzyme activity associated with sustained cellular proliferation. Which of the following cell types is most likely to have the highest telomerase activity? A. Endothelial cells B. Erythrocytes C. Germ cells D. Neurons E. Neutrophils