I. Oxytocin causes contraction of the smooth muscle of the uterus.

II. The suckling of an infant at the breast stimulates the touch receptors, the nuclei are stimulated, oxytocin is released.

III. The sensitivity of the uterine musculature to oxytocin is enhanced by estrogen.

IV. Progesterone directly stimulates myometrial contraction while simultaneously reducing oxytocin clearance.

#Question id: 7028

#Unit 5. Developmental Biology

Between the blastoderm and the yolk of avian eggs is a space called the subgerminal cavity, which is created when:

#Question id: 11588

#Unit 7. System Physiology – Animal

Correct and appropriate signal transduction processes are generally under strong selective pressure and are determined by the properties of the molecules involved, the concentrations of signal and receptor molecules, and the binding affinities between signal and receptor. Therefore, a hormone action is very specific in a species at any one point in time. However, there are examples of very diverse functions of a specific hormone between groups of organisms. For example, thyroxin, which is produced in all vertebrates and many invertebrates, can trigger growth, differentiation, metamorphosis, maturation, reproduction, behavior, temperature tolerance, osmoregulation, or seasonal adaptation depending on the organism in which it is produced. What is the most logical explanation for such different responses triggered by thyroxin in organisms?

#Question id: 4372

#Unit 3. Fundamental Processes

Which statement is not true about the binding of TBP (TATA binding protein)?

#Question id: 11839

#Unit 6. System Physiology – Plant

Ethylene receptor are localized  in___

#Question id: 1255

#Unit 4. Cell Communication and Cell Signaling

Following statements are regarding to the mechanism of action of cholera toxin.

A. cholera toxin is a homodimeric protein, target G proteins, interfering with normal signaling in host cells.

B. cholera toxin associates with a small G protein, known as ARF6.

C. association with ARF6 activates cholera toxin, which catalyzes the transfer of ADP-ribose from NAD+ to the critical Arg residue in the P loop of the alpha subunit of Gs.

D. ADP-ribosylation blocks the GEF activity of Gs and thereby renders Gs permanently inactive.

E. This results in continuous activation of the adenylyl cyclase of intestinal epithelial cells, chronically high cAMP, and active PKA dephosphorylates the CFTR Cl- channel and a sodium-proton exchanger in the intestinal epithelial cells.

Which of the following combination is correct?