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The correct answer is (b) conformation

To explain: Protein KINASES are enzymes that add PHOSPHATE groups while protein phosphatases REMOVE phosphate groups. These enzymes ALTER the conformation of signaling PROTEINS.

The correct ANSWER is (d) S-nitrosylation

Explanation: The posttranslational modification wherein NITRIC oxide (NO) is covalently ADDED to the thiol group of a PROTEIN cysteine RESIDUE (S-NO) is called S-nitrosylation.This modification alters the activity and interactions of the protein.

The correct answer is (a) True

For explanation I WOULD say: Cyclic AMP acts as an initiator of cascade that leads to mobilization of glucose. However it can also act to inhibit a variety of cells by blocking signals TRANSMITTED through MAP kinase cascade.

Right option is (a) True

Best explanation: Diabetes Mellitus is a common HUMAN DISORDER that is CAUSED by defects in insulin signaling. The TYPE I diabetes accounts for 5-10% cases and the type II accounts for remaining 90-95%.

The correct OPTION is (b) 2

The best EXPLANATION: There are 2 types of PROTEIN tyrosine kinases – receptor protein-tyrosine kinases and non-receptor or cytoplasmic protein-tyrosine kinases. The mechanism of ACTIVATION for both is different.

Correct CHOICE is (d) G-PROTEINS

Explanation: Arrestins are small group of proteins that bind to the G-protein coupled receptors. To bind to these receptors, the arrestins compete with heterotrimeric G-proteins. In the process of desensitization, ARRESTIN binding PREVENTS further ACTIVATION of the G-proteins.

Correct answer is (a) True

To explain I would say: The TNFR1 is a trimeric RECEPTOR that contains a domain of 70 AMINO ACIDS to which the tumor NECROSIS factor binds and brings about a change in the shape of the receptor. After there is a conformational change, proteins are recruited.

The correct answer is (a) True

Easy explanation: The nitric oxide PRODUCED in the endothelial cells diffuses through the plasma MEMBRANE and into the ADJOINING smooth muscle cells. There it binds to and stimulates the guanylyl cyclase.

The correct ANSWER is (a) modifying G-protein

The best EXPLANATION: The cholera toxin exerts its effect by inhibiting the GTPase ACTIVITY of G-proteins in the CELLS of intestinal epithelium and modifying their G-alpha subunits. This causes the epithelial cells to secrete large volumes of FLUID into the intestinal lumen.

Right OPTION is (a) phosphatidylserine

The best explanation: The APOPTOTIC bodies can be recognized by the presence of phosphatidylserine on their surface. Phosphatidylserine is a compound usually PRESENT on the inner surface of the plasma MEMBRANE.

Correct CHOICE is (b) nitric oxide

The BEST I can explain: In 1986, it was discovered LOUIS Ignarro at UCLA and SALVADOR Moncada at the Wellcome Research LABS in England that the diffusible compound produced by the binding of acetylcholine to endothelial cells is nitric oxide.

Right choice is (a) LIGHT

The best I can explain: Rhodopsin is a very STABLE G-protein coupled receptor. This receptor is always bound to a retinal GROUP (the ligand). Rhodopsin is ALSO a biological pigment in the RETINA and is very sensitive to light.

Right CHOICE is (a) Bcl-2

Explanation: BCl-2 FAMILY consists of regulator proteins. These proteins are present inside the cell i.e intrinsic in NATURE. They CARRY out APOPTOSIS in damaged or old cells.

Correct answer is (b) False

Explanation: A SOMATIC MUTATION is present in one cell type of an individual, such as a thyroid cell in case of an adenoma, while an inherited mutation is present in all the cells of an individual. Somatic mutations are the primary CAUSE of HUMAN cancer.

Right answer is (c) Rhodopsin

The best I can explain: Retinitis pigmentosa (RP) is an inherited disorder CHARACTERIZED by progressive degeneration of the retina and EVENTUAL blindness. The DISEASE is caused due to mutation in a gene that encodes the visual PIGMENT of rods – rhodopsin.

Right ANSWER is (a) AMINO terminus

To EXPLAIN: The G-protein coupled receptors have their amino-terminus outside the CELL and carboxyl-terminus inside the cell. The 7 TRANSMEMBRANE helices (alpha-helices) traverse the plasma membrane.

Right choice is (a) TRANSCRIPTION FACTOR

Explanation: CREB is a transcription factor that also acts as an important signaling effector. It is a SUBSTRATE for a wide range of kinases INCLUDING cyclic AMP-dependent kinase, protein kinase A.

The correct choice is (c) non-stimulated cells

For explanation: CALMODULIN contains 4 binding SITES for calcium. It does not have sufficient affinity for Ca^2+ IONS in non-stimulated cells. When the calcium ions concentration increases in response to a stimulus, the ions bind to calmodulin, changing its CONFORMATION.

Correct OPTION is (B) 2

Explanation: Two types of calcium channels are present on the membrane of endoplasmic reticulum – IP3 receptors and RYANODINE receptors. The latter are present primary in excitable CELLS like cardiac cells.

Correct OPTION is (a) autocrine

Explanation: In autocrine signaling, the cells that EXPRESS MESSENGER molecules also synthesize surface receptors. Surface receptors can respond to the messengers synthesized by the cell itself.

Right OPTION is (c) 3

To explain: There are three types of CELL signaling pathways – autocrine, paracrine and endocrine. Cells COMMUNICATE with each other through EXTRACELLULAR messenger molecules. Based on the distances these messenger molecules TRAVEL, the signaling pathways differ.