Lactase is an enzyme composed of a single polypeptide that hydrolyzes the disaccharide lactose to produce monosaccharides. the optimal ph for lactase activity is 6. transfer of lactase to ph 5 results in a substantial decrease in enzyme activity, likely due to the disruption of ?
(a) only the primary structure of the enzyme. the primary and secondary structure of the enzyme.
(b) the secondary and tertiary structure of the enzyme
(c) the secondary, tertiary, and quaternary structure of the enzyme.
(d) none of the above

(b) The secondary and tertiary structure of the enzyme

Explanation:

The amino acid sequence of a polypeptide chain makes the primary structure of the protein while the arrangement of particular amino acid residues of a chain makes its secondary structure. Folding of protein in three-dimensional space makes its tertiary structure. Enzymes are proteins and can work in properly folded form only. Any factor that disrupts the protein folding or affects its secondary and tertiary structure makes it non-functional. The process is called denaturation.

Enzymes can work under optimum cellular conditions such as temperature, pH, etc. Any deviations from these conditions lead to loss of function of enzymes due to denaturation. When the lactase enzyme is exposed to the pH conditions below its optimum pH range, the net charge of its polypeptide chain is altered leading to electrostatic repulsion and may also break some hydrogen bonds.

Secondary and tertiary structures of enzymes are stabilized by these weak interactions. Lactase at pH 5 will be non-functional due to the loss of its secondary and tertiary structures.

i think the answer is b.

hope it

from almost the creation of the first true maps of the earth, people started seeing how continents would be able to fit together.   in particular, people noticed that south america fits almost exactly into africa.

you should be aware that while world maps were around early in the 1600’s and better defined by the end of the 1700’s, those maps were not ‘public’ but were treated as state secrets.   and so it was not till much later that the broader ‘science’ community had access to good quality and accurate world maps.

get the whole story here…

it is now known that most of the major continental masses can be fit together in a jigsaw process.   in fact we now know that the continents were indeed once all joined together as one land mass – the supercontinent of pangaea.

if you look at most world maps you will ponder how this is evidence, as the continents really don’t appear to ‘fit’ together very well.   what you need to understand is that the vast majority of maps are drawn using a map projection that has the north and south poles (which are points) are a line the width of the map at the top and bottom.   this means that the map distorts the true shape of the earth’s land and oceans as you love closer to the poles.     some other map projections distort less, but have the map shape looking like segments of an orange.   see here for a range of map projections.   check out the way greenland changes size in each!

what is more remarkable, is the next piece of evidence when added to the shape of continents.

location of mountains and fossils

what is remarkable, when you reassemble all the continents together, the ancient mountain ranges (many now eroded to their cores) and the location of rock types and fossils all match up.