Question

(a) Identify all the amino acids from the structures below and use these structures to describe the meaning of the following in terms of protein structure; i. an intramolecular disulphide bond, "hydrophobic interaction”, iii. pH dependent electrostatic forces. а) соон yoon с) соон H.N—C—H H.N— C—H HNg–H | d) соон H,N—C—H CH2 SH CH, CH (b) Describe the process of protein denaturation and explain why high temperatures promote denaturation. Include a description of the role of protein denaturation in the preparation of tofu from soy protein. (c) Getting the perfect foam requires a balance between protein-protein and protein-water interaction. Discuss this statement in terms of the whipping and over whipping of egg whites. (d) Discuss how the amino acid composition influences the structure of gelatine proteins and the nature of the junction zones in gelatine gels. (e) Describe how the “Protein Digestibility Corrected Amino Acid Score” is determined and state the typical "limiting amino acid” in cereal protein and the typical "limiting amino acid” in legume protein.

Answer 1

d) Gelatin contains several amino acids. Amino acids are compounds that combine to make proteins, and are essential for the proper functioning of various organs, as well as for providing energy.

While the human body makes some amino acids, most people need to get additional amino acids through their diet.

The amino acids found in gelatin are also usually found in the bones and organs of certain animals. Since most people do not eat those parts of the animal, adding gelatin to a varied and nutritious diet may be beneficial.

Specific amino acids found in gelatin may vary, depending on the method of preparation and the animal tissues used.

Typically, the most abundant amino acids in gelatin include glycine, proline, and valine. Gelatin also contains the amino acids lysine, alanine, and arginine.

Valine is an essential amino acid that cannot be produced by the human body, which means it must come from the diet.

Gelatin is a mixture of peptides and proteins produced by partial hydrolysis of collagen extracted from the skin, bones, and connective tissues of animals such as domesticated cattle, chicken, pigs, and fish. Some clinical studies report that the oral ingestion of hydrolyzed collagen decreases joint pain, those with the most severe symptoms showing the most benefit. Beneficial action is likely due to hydrolyzed collagen accumulation in the cartilage^[4] and stimulated production of collagen by the chondrocytes, the cells of cartilage.Several studies have shown that a daily intake of hydrolyzed collagen increases bone mass density in rats. It seems that hydrolyzed collagen peptides stimulated differentiation and osteoblasts activity – the cells that build bone – over that of osteoclasts (cells that destroy bone).

However, other clinical trials have yielded mixed results. In 2011, the European Food Safety Authority Panel on Dietetic Products, Nutrition and Allergies concluded that "a cause and effect relationship has not been established between the consumption of collagen hydrolysate and maintenance of joints".Four other studies reported benefit with no side effects; however, the studies were not extensive, and all recommended further controlled study. One study found that oral collagen only improved symptoms in a minority of patients and reported nausea as a side effect. Another study reported no improvement in disease activity in patients with rheumatoid arthritis. Another study found that collagen treatment may actually cause an exacerbation of rheumatoid arthritis symptoms.

e) Protein digestibility-corrected amino acid score (PDCAAS) is a method of evaluating the quality of a protein based on both the amino acid requirements of humans and their ability to digest it. Protein quality, as determined by the PDCAAS method, is a measure of a protein’s ability to provide adequate levels of essential amino acids for human needs. PDCAAS is calculated using an amino acid profile and true digestibility of a food protein.

Lysine is the limiting amino acid of all cereals

Methionine, Cystine and Tryptophan is the limiting amino acid of all legumes