Question

(1). Discuss how proteins can fold rapidly and reliably to their native conformation and how misfolded proteins can lead to diseases.

(2). What are the differences of saturated, polyunsaturated and monounsaturated fats? How do they affect human health.

(3). What are the differences of cellulose, starch and glycogen? Which one is the most abundant organic compound on earth?

(4). What are the differences between DNA and RNA? What is the chemical mechanism of complementary base pairing?

Answer 1

1).

According to the two-state protein model, the protein can exist either in folded or unfolded state, which follows the principle of all-or-none process. The cooperativity of protein folding determines the protein be folded or unfolded. If the protein folding is very cooperative, any deviation from one interaction disrupts or destabilizes all other interactions.

The alpha-helical proteins fold at a faster rate than the beta sheets. The helices follow the downhill folding, where the folding process does not require any energy inputs. Means, folding occurs by free energy in alpha helices, whereas, beta sheets more energy to separate the folded and unfolded states.

In case of alpha helices, the fixation of residues in their native conformation triggers the formation of hydrogen bonds. Means, the elongation process is thermodynamically favorable.

In contrast, in case of beta sheets, to stabilize one hydrogen bond, two peptide bonds are to be formed. Means, the folding process is (uphill) not thermodynamically favorable, side chain interactions stabilize the beta sheets.

The three-dimensional (3-D) structure of the protein determines its function. If the protein folding alters, its 3-D structure alters, which alters its functioning. So, the protein misfolding results in non-functional or dysfunctional proteins, which lead to diseases.