A 35-year-old woman presents with symptoms of joint hypermobility, skin fragility, and poor wound healing. Genetic testing reveals a mutation in the COL1A1 gene, leading to a defective structural protein. Further studies indicate that the mutation replaces glycine with proline, disrupting the formation of the normal secondary structure of the protein. Which of the following best describes how proline disrupts the α-helix in proteins like collagen?
A 52-year-old male presents with progressive difficulty walking and muscle stiffness. He was previously diagnosed with a neurodegenerative disorder characterized by protein misfolding and aggregation in the brain. A brain biopsy reveals abnormal β-sheet-rich protein deposits, leading the physician to suspect amyloid plaques as a key pathological feature. Which of the following secondary protein structures is primarily involved in protein misfolding diseases such as Alzheimer’s and prion diseases?
Which of the following best explains why mass spectrometry is a valuable tool in biochemical and clinical applications?
Which of the following chromatography techniques is most appropriate for isolating a specific protein based on its binding affinity to a particular ligand?
Selenocysteine is often referred to as the “21st amino acid” due to its unique incorporation into proteins during translation. Which of the following best describes the mechanism by which selenocysteine is incorporated into growing polypeptides?
Which of the following statements correctly explains why selenocysteine is referred to as the “21st amino acid”?
Which of the following correctly matches a nonprotein toxic L-α-amino acid with its medical relevance?
A 5-year-old child is brought to the clinic with growth retardation, muscle wasting, and edema. The mother reports that the child has been on a predominantly corn-based diet for several months. Physical examination reveals hypoalbuminemia and pitting edema in the lower extremities. Which essential amino acid is most likely deficient in this child’s diet?
