#Question id: 12567

#Unit 10. Ecological Principles

#Question id: 1257

#Unit 4. Cell Communication and Cell Signaling

Following statements are regarding to protein kinase A which phosphorylates multiple intracellular target proteins expressed in different cell types.

A. Inactive PKA is a tetramer consisting of two regulatory (R) subunits and two catalytic (C) subunits.

B. Each R subunit contains a pseudo-substrate domain whose sequence resembles that of a peptide substrate and binds to the active site in the catalytic domain but is not phosphorylated; thus the pseudo-substrate domain inhibits the activity of the catalytic subunits.

C. active PKA is turned off by binding of cAMP Each R subunit has two distinct cAMP-binding sites, called CNB-A and CNB-B.

D. Binding of cAMP by an R subunit of PKA occurs in a cooperative fashion; that is, binding of the first cAMP molecule to CNB-B increases the Kd for binding of the second cAMP to CNB-A. Thus small changes in the level of cytosolic cAMP can cause proportionately large changes in the number of dissociated C subunits and, hence, in cellular kinase activity.

Which of the following statements are incorrect?

#Question id: 14505

#Unit 13. Methods in Biology

#Question id: 2952

#Unit 2. Cellular Organization

Throughout interphase,.. .........  are synthesized at a relatively constant rate, whereas  ............ are synthesized only during the S phase.

#Question id: 2168

#Unit 2. Cellular Organization

Classes of membrane transport proteins include all of the following EXCEPT: