Which of the following statements regarding hydrogen bonding in secondary structures is true? Group of answer choices Both α-helices and β-sheets only use intrachain hydrogen bonds. Both α-helices and β-sheets only use interchain hydrogen bonds. α-helices only use intrachain hydrogen bonds and β-sheets can use either intrachain or interchain hydrogen bonds. α-helices can use either intrachain or interchain hydrogen bonds and β-sheets only use interchain hydrogen bonds.

The correct answer is "α-helices only use intrachain hydrogen bonds and β-sheets can use either intrachain or interchain hydrogen bonds".

Explanation:

Hydrogen bonding are essential forces for the formation of the secondary structures of proteins. The alpha helix is a coiled secondary structure that is stabilized only by intrachain hydrogen bonds, which are formed between the NH and CO groups of the main chain. On the other hand,  β-sheets can use either intrachain or interchain hydrogen bonds for its stabilization. Adjacent chains in β-sheets can run either in the same or opposite directions, which are stabilized by interchain hydrogen bonds.

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acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.