Asked in PMC Practice Test 27 (2021) 2021Moderate

Left handed helix in protein secondary structure is called as_?

Correct answer: B. Beta helix

  • A. Alpha helix
  • B. Beta helix
  • C. Spiral
  • D. Concentrate

Explanation

Option B is correct since B-pleated sheets found in globular protein X-ray structures are twisted. This twist is left-handed.Option A is incorrect since proteins typically consist of right-handed alpha helices, whereas left-handed alpha helices are rare in natureOption C is incorrect since spirals are not a common structure seen in secondary structures. The structures are mostly alpha-helix and beta-pleated sheets.Option D is incorrect since it states concentrated structures which are not seen in secondary structures.

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About Classification of Proteins

Proteins are classified by composition as simple, conjugated and derived proteins, and by shape as fibrous or globular proteins. The topic relates these classes to examples such as albumin, keratin, collagen, haemoglobin and casein, while distinguishing structural proteins from proteins with transport, catalytic or regulatory roles.

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