Enzyme glutamine synthase is not found in a. astrocytes b. oligodendrocytes c. none of the above is true d. all are true

Glutamine synthase is an enzyme that plays a crucial role in the synthesis of glutamine in cells. Glutamine is an essential amino acid, which is used by various cells in the body. It is important to know which cell types contain this enzyme.

a. Astrocytes: Astrocytes are a type of glial cell in the central nervous system. They have various functions, including the control of the synapse, metabolic support for neurons, uptake and recycling of neurotransmitters, and many others. Importantly, astrocytes express the enzyme glutamine synthase and play a role in the glutamate-glutamine cycle. b. Oligodendrocytes: Oligodendrocytes are another type of glial cell found in the central nervous system. They are responsible for producing the myelin sheath, which insulates the axons of neurons and facilitates the conduction of electrical signals. Oligodendrocytes do not have a significant expression of glutamine synthase. c. None of the above is true: If neither of the above options is correct, this option would be the answer. d. All are true: If both astrocytes and oligodendrocytes do not have glutamine synthase, this option would be the answer.

As mentioned earlier, astrocytes express the enzyme glutamine synthase, while oligodendrocytes do not. This means that option (a) is incorrect and option (b) is correct. Since option (b) is true, neither option (c) nor option (d) can be correct. So, the correct answer is: b. Oligodendrocytes