The energy of incident solar radiation reaching the surface of the earth declines toward the poles from its maximum in equatorial regions. One cause of this phenomenon is greater absorption of solar energy by the earth's atmosphere at high latitudes. Why is this?

#Question id: 909

#Unit 1. Molecules and their Interaction Relevant to Biology

Most proteins denature at both high and low pH. At high pH, the ionization of internal tyrosines is thought to be the main destabilizing influence, whereas at low pH, the protonation of buried histidines. A titration curve for the unfolding of the enzyme ribonuclease is shown in Figure. Given the relation between the titration curves for protein unfolding and histidine protonation, which of the following conclusion can be drawn correctly?

A. The sharp transition in graph indicates a highly cooperative process; when the protein starts to unfold, it completes the process rapidly

B. The sharp transition in graph indicates a highly noncooperative process

C. Several buried histidines can ionize when the chain starts to unfold, so that when one goes, they all go together due to cooperative behaviour of protein folding

D. Buried histidine (pK of 4 in this example) becomes accessible to solvent, its pK will shift toward its normal value of 6, significantly steepening its titration curve.

#Question id: 19462

#Unit 13. Methods in Biology

#Question id: 18874

#Unit 9. Diversity of Life Forms

#Question id: 169

#Unit 1. Molecules and their Interaction Relevant to Biology

 An octapeptide composed of four repeating glycylalanyl units has:

#Question id: 11332

#Unit 10. Ecological Principles

The most plausible hypothesis to explain why species richness is higher in tropical than in temperate regions is that

 A) tropical communities are older.

 B) tropical regions generally have more available water and higher levels of solar radiation.

 C) higher temperatures cause more rapid speciation.

 D) diversity increases as evapotranspiration decreases.