27.\"The\"crystal\"structure\"of\"your\"protein\"reveals\"a\"central\"!sheet.\"W

Question

27."The"crystal"structure"of"your"protein"reveals"a"central"!sheet."Which"of"the"

following"statements"about"!sheets"is"TRUE?"

a.""Amino"acid"side"chains"in"!sheets"all"extend"out"on"one"side"of"the"!sheet."

b.""!sheets"have"a"straight"edge on"appearance."

c.""!sheets"are"composed"of" strands"running"in"only"an"antiparallel"direction."

d."Two"adjacent" strands"in"a"!sheet"will"fulfill"all"of"the"possible"hydrogen"bonds"

between"their"peptide"back"bone"atoms."

e.""None"of"the"above"statements"are"true."

Explanation / Answer

Ans a. False

Because amino acids side chains are directed to both inside and outside of the sheet.

b. False.

Beta sheets have pleated appearance and they are rarely perfectly extended rather they exhibit a twist.

c. False.

Beta sheets are composed of beta strands running in both type of directions antiparallel or parallel.

d. True

Two adjacent beta strands in a beta sheet form hydrogen bonds between N-H group in the backbone of one strand with the C=O group in the backbone of adjacent neighbour strands.

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