Ch. 4. STUDY. Flashcards. ... layers of pleated sheets provide toughness ... protein kinase to amino acids in protein causing a conformational change-change in ... B. Secondary Structure. Secondary structure refers to highly regular local structures within a polypeptide (e.g., a helix) and either within or between polypeptides (b-pleated sheets). Linus Pauling and coworkers suggested these two types of secondary structure in 1951. A little Linus Pauling history is would be relevant here! Conformational Isomers. Let us understand the fundamentals of conformation with the example of ethane. If we observe the ball and stick model of ethane and rotate one carbon atom keeping another carbon atom stationary about C-C axis. MULTIPLE CHOICE QUESTIONS Part 5: Stereochemistry Answers on page 24 -26 Topic: Identifications and Comparisons 1. Which of the following is the enantiomer of the following substance? H Br CH 3 H H H Br C3 H 3 r I II III A) I B) II C) III D) It does not have a non -superposable enantiom er. E) Both II and III 2. Answers to Practice Exam 1 Question 1 (20 points). The following questions refer to the compound propyne, shown below. H3C C CH propyne sp3 sp sp a) On the structure above, identify the hybridization state of all carbon atoms. These isomers are termed as Conformational isomers. In case of single bond rotation, Rotational Energy acts as a barrier Conformational Isomerism to occur, the energy barrier must be a small one. There are numerous types of conformational isomers, such as Ethane and Butane.