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TLS Online TPP Program

#Question id: 1370

H. V. Wilson worked with sponges to gain some insight into exactly what was responsible for holding adjacent cells together. He exposed two species of differently pigmented sponges to a chemical that disrupted intercellular junctions, and the cells of the sponges dissociated. Wilson then mixed the cells of the two species and removed the chemical that caused the cells to dissociate. Wilson found that the sponges reassembled into two separate species. The cells from one species did not interact or form associations with the cells of the other species.

How do you explain the results of Wilson's experiments?

#Unit 4. Cell Communication and Cell Signaling

  1. The two species of sponge had different enzymes that functioned in the reassembly process.

  2. The molecules responsible for cell-cell adhesion (cell junctions) were irreversibly destroyed during the experiment.

  3. The molecules responsible for cell-cell adhesion (cell junctions) differed between the two species of sponge.

  4. One cell functioned as an organizer for each organism, thereby attracting only cells of the same species.

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TLS Online TPP Program

#Question id: 5672

#Unit 5. Developmental Biology

Following statements are regarding to recognition of sperm by mammalian zona pellucida.

A. Sperm that have undergone the acrosome reaction bind directly to zona protein ZP2 and begin making a channel toward the oocyte.

B. Sperm with an intact acrosome bind to ZP2; they undergo the acrosome reaction on the zona pellucida and then transfer their binding to ZP3.

C. When a sperm reaches the oocyte and fuses with it, the cortical granules release proteins that digest portions of ZP2 and ZP3, making them nonfunctional and prevent polyspermy.

D. When a sperm reaches the oocyte and fuses with it, the cortical granules release proteins that digest ZP3 only, not ZP2 because ZP2 involve in the process of slow block to polyspermy.

Which of the above statements are correct?
TLS Online TPP Program

#Question id: 10224

#Unit 6. System Physiology – Plant

Exposure to high levels of excess light that damage the photosynthetic system and decrease both quantum efficiency and maximum photosynthetic rate results
TLS Online TPP Program

#Question id: 1943

#Unit 4. Cell Communication and Cell Signaling

What is HLA-DR2 a risk factor for?
TLS Online TPP Program

#Question id: 26982

#Unit 10. Ecological Principles

Which of the following statements about the evolution of life histories is correct?

a.Unstable environments with unlimited resources favor r-selected populations.

b.K-selected populations are most often found in environments where density-independent factors are important regulators of population size.

c.Most populations have both r- and K-selected characteristics that vary under different environmental conditions.

d.The reproductive efforts of r-selected populations are directed at producing just a few offspring with good competitive abilities.
TLS Online TPP Program

#Question id: 14686

#Unit 4. Cell Communication and Cell Signaling

This member of the AKAP family, designated mAKAP, anchors both PDE and the regulatory subunit  of PKA to the nuclear membrane, maintaining them in a negative feedback loop that provides close local control of the ATP level and PKA activity.
B- The basal level of PDE activity in the presence of hormone (resting state) keeps cAMP levels below those necessary for PKA activation. 
C- Activation of β-adrenergic receptors causes an increase in cAMP to a level in excess of that which can be degraded by PDE. 
D- The resulting binding of cAMP to the R subunits of PKA releases the active catalytic (C) subunits into the cytosol. Some C subunits enter the nucleus, where they phosphorylate and thus activate certain transcription factors . Other C subunits phosphorylate PDE, stimulating its catalytic activity.
E-  Active PDE hydrolyzes cAMP, thereby driving cAMP levels back to basal levels and causing re-formation of the inactive PKA C-R complex. Subsequent de-phosphorylation of PDE returns the complex to the resting state.