26. Which of the following is a second messenger?

A. lnositol 1,4,5-triphosphate
B. Diacyl glycerol
C. Phospholipase C
D. Both (a) and (b)

27. Which of the following statement is incorrect?

A. The principal lipophilic hormones that binds to receptors located in the plasma membranes are prostaglandins
B. Prostaglandins are synthesized from arachidonic acid
C. Prostaglandins act as paracrine signaling molecules
D. None of the above

28. Two key organizing principles for large multicellular organisms are

A. prokaryotic cell structure and cell specialization
B. cell specialization and communication between cells
C. communication between cells and simple nerve reflexes
D. simple nerve reflexes and cell specialization

29. Which of the following is a hormone whose action requires a cell surface receptor?

A. Nitric oxide
B. Progesterone
C. Adrenaline
D. Growth factors

30. The hormone or ligand can be considered as

A. first messenger
B. second messenger
C. both (a) and (b)
D. none of these