"N-Tosylamido-L-phenylethyl, also called tosyl phenylalanyl chloromethyl ketone (TPCK), irreversibly inhibits chymotrypsin, and is used to label the active site histidine residue. The COCH2Cl group is the reactive group that binds to the His residue." 1. Why does chymotrypsin bind TPCK?

a. TPCK is a polar molecule and easily forms several noncovalent interactions with the active site of chyrnotrypsin, reversibly outcompeting the usual substrate.
b. The chlorine of TPCK is a strong nucleophile, and attacks the His 157 residue.
c. The serine residue at position 195 in & pymotrypsin is a strong nucleophile.
d. The phenyl group of TPCK is structurally similar to regular chymotrypsin substrates.

2. Trypsin, another serine protease, does not bind TPCK. How could TPCK be modified to enable its recognition by trypsin?

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.