Proteins Biochemistry Quiz: Amino Acids and Folding

Secondary structures in proteins are comprised of alpha-helices or parallel or antiparallel beta-pleated sheets. The primary structure of a protein refers to the sequence of amino acids in the polypeptide chain, while the secondary structure refers to the local folding patterns that arise due to hydrogen bonding between nearby amino acids. These folding patterns can include alpha-helices, which are coiled structures, or beta-pleated sheets, which are formed by extended strands of amino acids. Therefore, the correct answer is secondary structures.

Disulfide covalent linkages can occur between adjacent alpha-helices in keratin, the major protein of hair, and in nails. These linkages are formed between the sulfur atoms of two cysteine residues, creating a strong bond that contributes to the structural stability of these proteins. Therefore, the correct answer is "all of the above."

Collagen is an incomplete dietary protein found in connective tissues. It is considered incomplete because it lacks one or more essential amino acids required by the body. Collagen is a structural protein that provides strength and support to connective tissues such as tendons, ligaments, and skin. It is also found in bones, cartilage, and blood vessels. Keratin is another protein found in hair, nails, and skin, while RNase A is an enzyme. Therefore, the correct answer is collagen, as it is the only option that fits the given description.

Oligopeptides are short polypeptides consisting of a small number of amino acids. They are smaller than polypeptides but larger than peptides. Oligopeptides play important roles in various biological processes, such as hormone regulation and cell signaling. They are formed through the process of peptide bond formation between amino acids. Therefore, oligopeptides are the correct term for short polypeptides.

Beta-turns are secondary structural motifs in proteins where the polypeptide chain reverses direction. They are commonly found at two specific amino acids: glycine and proline. Glycine is the smallest amino acid and lacks a side chain, allowing for flexibility in the polypeptide chain. Proline, on the other hand, has a rigid structure due to the cyclic nature of its side chain, which promotes the formation of turns. Therefore, beta-turns can occur at glycine and proline residues in proteins.

Molecular chaperones assist large proteins in folding. They are a class of proteins that help other proteins achieve their correct three-dimensional structure. By interacting with unfolded or misfolded proteins, molecular chaperones prevent aggregation and promote proper folding, ensuring that proteins function correctly. This assistance is crucial for the proper functioning of many cellular processes. Both prions (prp) and amyloid fibers are not involved in assisting protein folding, making the correct answer "molecular chaperones."

Scurvy is caused by a deficiency of vitamin C, which is essential for the production of collagen. Collagen is a protein that helps in the formation of connective tissues, such as skin, blood vessels, and bones. Without enough vitamin C, the body is unable to produce healthy collagen, leading to the symptoms of scurvy. The other options mentioned, not being exposed to enough sunlight and misfolding proteins, are not directly related to the cause of scurvy.

Type 2 diabetes, Alzheimer's disease, Huntington's disease, and Parkinson's disease are all caused by amyliodoses. Amyliodoses refers to the accumulation of abnormal proteins, specifically amyloid proteins, in various tissues and organs of the body. In these diseases, amyloid proteins build up and form plaques or tangles, leading to dysfunction and damage in the affected tissues. This common factor of amyliodoses helps to explain the similarities in the pathogenesis and clinical features observed in these different diseases.

Crutzfeld Jacob Disease (CJD) is the correct answer because it is a disease that results from the misfolding of prion (prp). CJD is a rare and fatal degenerative brain disorder that affects memory, thinking, and movement. The misfolded prions accumulate in the brain, causing damage and leading to the characteristic symptoms of the disease. Cystic Fibrosis and Alzheimer's Disease are unrelated to the misfolding of prions and have different causes and symptoms. Therefore, the correct answer is CJD.

All of the mentioned options, Mad Cow Disease, Kuru, and Scrapie, are forms of spongiform encephalopathies. Spongiform encephalopathies are a group of rare neurodegenerative diseases characterized by the accumulation of abnormal prion proteins in the brain, leading to the formation of sponge-like holes in the tissue. Mad Cow Disease affects cows, Kuru is found in humans, and Scrapie affects sheep and goats. Therefore, all of these options are correct forms of spongiform encephalopathies.