Calculate the net charge of lysine at pH 1. Question options: a)0 b)-1 c)-2 d)+1

Question

Calculate the net charge of lysine at pH 1.

Question options:

a)0

b)-1

c)-2

d)+1

e)+2

2. Which of the following pairings regarding protein structure is/are incorrect?

Question options:

primary structure: alpha helix

quaternary structure: hydrophobic interactions between different regions of the same polypeptide strand

tertiary structure: interactions between R groups on different polypeptide chains

secondary structure: hydrogen bonding between R groups on the same polypeptide strand

All of the above are incorrect.

3. Given the following pairs of amino acids, which pair contains the correct type of interaction through which the two amino acids most likely interact?

Question options:

valine and leucine: charge-charge (salt bridge)

threonine and cysteine: disulfide bond

aspartic acid and glutamic acid: hydrophobic interaction

threonine and serine: hydrogen bonding

None of the above is correct.

4. Which statement is correct regarding the comparison of the following three tripeptides:

1) lys-lys-lys

2) asp-asp-asp

3) lys-asp-val

Question options:

Under physiological conditions, peptide #1 elutes last using cation exchange chromatography.

Under physiological conditions, peptide #2 elutes first using anion exchange chromatography.

Under physiological conditions, peptide #3 elutes last using anion exchange chromatography.

Under physiological conditions, peptide #3 elutes first using either cation or anion exchange chromatography.

5. When varying the substrate concentration at a fixed concentration of enzyme it is observed that at low concentrations of substrate the reaction is ________ (with respect to substrate),while at high concentrations of substrate the reaction is ________ (with respect to substrate).

Question options:

initial; maximal

maximal; initial

second order; first order

first order; zero order

primary structure: alpha helix

quaternary structure: hydrophobic interactions between different regions of the same polypeptide strand

tertiary structure: interactions between R groups on different polypeptide chains

secondary structure: hydrogen bonding between R groups on the same polypeptide strand

All of the above are incorrect.

Explanation / Answer

Lysine contains carboxylate group, side chain and a terminal amino group.

At pH 1, charge of carboxylate is 0; charge of side chain is +1 and charge of terminal amino group is +1.

Therefore, net charge = 0+1+1= +2

2. a, b and c are incorrect.

Alpha helix is termed as secondary structure of protein formed by repeated helix of a polypeptide which is stable by hydrogen bonding between carbonyl and amino group of amino acids.

Quaternary structure contains hydrophobic interactions between different polypeptide strands (more than one polypeptide).

Tertiary structure contains interaction between R groups on same polypeptide chain.

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