Question

5 (4 pts). Briefly differentiate between PRIMARY and QUATERNARY structure in proteins, 6. (5 pts) Define the Damköhler number. Briefly explain why this number is important. (variables are OK-if you use any define them! the definition should be expressed as a phrase)

Answer 1

ANSWER(1)

Primary Structure

(a).The primary structure of a protein refers to the sequence of amino acids in the polypeptide chain.

(b).When two amino acids are in such a position that the carboxyl groups of each amino acid are adjacent to each other, they can be combined by undergoing a dehydration reaction which results in the formation of a peptide bond.

(c).There are 20 different amino acid and they are connected by a peptide bond between the carboxyl group and the amino group in a linear chain called a polypeptide.

(d).The amino acids in the primary structure can help maintain the tertiary structure depending on whether they are hydrophobic or hydrophilic.

Quaternary Structure

(a). Quaternary structures are reserved for proteins composed of two or more polypeptide chains.

(b).Proteins that have quaternary structures contain more than one polypeptide and each adopt a tertiary structure and then assemble with each other via intermolecular interactions.

(c).The quaternary structure of a protein is the overall structure that is the result of the addition of these polypeptide subunits . The individual polypeptides are called protein subunits, which means different polypeptides folded separately.

(d).Hemoglobin is an example of a quaternary structure that is composed of two alpha subunits and two beta subunits.

ANSWER(2)

The Damköhler numbers (Da) are dimensionless numbers used in chemical engineering to relate the chemical reaction timescale (reaction rate) to the transport phenomena rate occurring in a system. It is named after German chemist Gerhard Damkohler.

A Damköhler number (Da) is a useful ratio for determining whether diffusion rates or reaction rates are more ‘important’ for defining a steady-state chemical distribution over the length and time scales of interest. Hence the definition:

Da=Reaction rate/Diffusion rate = Diffusion time/Reaction time

Da is associated with characteristic diffusion and reaction times therefore scaling is necessary.

For Da >>1 the reaction rate is much greater than the diffusion rate distribution is said to be diffusion limited (diffusion is slowest so diffusion characteristics dominate and the reaction is assumed to be instantaneously in equilibrium).

For Da <<1 diffusion occurs much faster than the reaction, thus diffusion reaches an ‘equilibrium’ well before the reaction is at equilibrium.