Question

Which of the four elements of secondary structures are NOT dependant on intra-chain hydrogen bonding?

1. Alpha Helices

2. Beta Loops

3. Beta Sheets

4. Beta Turns

2. What would be the expected orientation of this protein's alpha helix?

1. Hydrophilic amino acids are complementary to hydrophobic amino acids, so the hydrophilic side of the alpha helix should be facing toward the hydrophobic core of the protein

2. This protein will have mostly hydrophobic amino acids in its core, so the helix will be arranged to have the hydrophobic side facing toward the core of the protein

3. This protein will have a hydrophobic surface, so hydrophobic amino acids will be arranged facing the outside of the helix

4. This protein will have a hydrophobic core and a hydrophilic surface, so hydrophilic and hydrophobic amino acids will be equally distributed in the helix

3. If a protein is heated enough to disrupt weak interactions, will this have a greater impact on the primary or secondary structure? Explain your reasoning.

4.Where in a cell might a protein, with its amphipathic alpha helices oriented so that amino acids such as leucine and phenylalanine are pointing toward the OUTSIDE of the protein, be found? Explain your reasoning

Answer 1

Which of the four elements of secondary structures are NOT dependant on intra-chain hydrogen bonding?

The correct answer is

Beta loops

Beta Loops, unlike alpha helices or beta sheets, are an irregular secondary structure in proteins, and they are not dependant on intra chain hydrogen bonding.

2. What would be the expected orientation of this protein's alpha helix?

The correct answer is

This protein will have mostly hydrophobic amino acids in its core, so the helix will be arranged to have the hydrophobic side facing toward the core of the protein.

3. If a protein is heated enough to disrupt weak interactions, will this have a greater impact on the primary or secondary structure.

The correct answer is

Secondary structure, heating of proteins involves the disruption and possible destruction of both the secondary and tertiary structures. Since heating reactions are not strong enough to break the peptide bonds, the primary structure (sequence of amino acids) remains the same after a heating process.

4.Where in a cell might a protein, with its amphipathic alpha helices oriented so that amino acids such as leucine and phenylalanine are pointing toward the OUTSIDE of the protein, be found? Explain your reasoning

These amlhipathic alpha helices proteins are usually found in the cell membrane as membrane proteins, as their amphipathic nature enables them to insert themselves into the hydrophobic, nonpolar region of a biological membrane and at the same time expose their hydrophilic portion to the polar aqueous medium.