Question

Which of the following statements is NOT consistent with the four principles of evolution?

a. Genetic mutations are random and are not "designed" to guide evolution in a given direction.

b. The development of new structures or features of an organism can occur spontaneously and do not have to arise from existing features - this helps account for the diversity among all organisms on earth.

c. Evolution occurs continuously and is still happening.

d. A genetic variation that allows an organism to survive or thrive in new conditions is more likely to be passed on to future generations.

e. Highly similar organisms with little variation in their makeup can be more susceptible to disease and less likely to survive such a challenge.

Which of the following statements is true about calculating the isoelectric point of amino acids and peptides?

	a.	Ionizable R groups can be ignored when calculating the isoelectric point.
	b.	The formula for calculating the isoelectric point (pI) of an α-amino acid is: pI = 1/2(pKi + pKj)
	c.	The isoelectric point is always calculated using pK1 (for the carboxylic acid group) and pK2(for the amino group) of an amino acid.
	d.	The pK values of ionizable groups do not change after a peptide bond is formed; it is possible to easily predict the isoelectric point for a polypeptide.
	e.	The isoelectric point of an amino acid is when the carboxylic acid group is protonated and the amino group is deprotonated, leading to an overall charge of 0 for the amino acid.

Answer 1

1)

The four principles involved in evolution are: variation, inheritance, selection and time.

Here, option b is not consistent with the principle of variation. According to this principle, species undergo modification over time and such modification sometimes results in the formation of new separate species. This accounts for the diversity among all organisms.

Evolution is still happening actively resulting in genetic mutations which are random in nature. Principle of natural selection allows an organism to pass on the the best fitting traits for survival.

2)

Isoelectric point is the pH at which the amino acid is neutral and exists as a zwitter ion dominantly.

Ionizable are groups cannot be ignored when calculating the isoelectric point.

The formula for calculating the isoelectric point of an Alpha amino acid is equal to pI = 1/2( pK1 + pK2). Option b is correct.

The isoelectric point for neutral side chains is calculated using pK1 and pK2 whereas for acidic side chains pI = 1/2(pK1 +o pK3) where pK3 is for the ionizable acidic side chain.

The pk values of ionizable groups to change after a peptide bond is formed and cannot be predicted easily.

the isoelectric point of an amino acid is calculated differently for a neutral side chain, acidic side chain and basic side chain.