The functional groups on most amino acids are

Multiple choice question.

1) The functional groups on most amino acids are:

A. Alpha amino and alpha carboxyl groups

B. Alpha amino and alpha carbonyl groups

C. Aldehyde and beta carboxyl groups

D. Alkene and ketone groups

E. Alpha alkane and beta alkyne groups

2) The overall charge of a protein is confered by:

A. The amino group at the N-terminus

B. The carboxyl group at the C-terminus

C. The side chains of the amino acids in the polypeptide

D. Only the positive charge of amino groups in the side chains

E. Only the negative charge of carboxyl groups in the side chains

3) When the pH of the environment is below the pI, the protein:

A. Precipitates out of solution

B. Becomes positively charged

C. Becomes negatively charged

D. Becomes neutral

E. Is broken down into its individual amino acids

4) When the pH of the environment is equal to the pI, the protein:

A. Precipitates out of solution

B. Becomes positively charged

C. Becomes negatively charged

D. Becomes neutral

E. Is broken down into its individual amino acids

5) When the pH of the environment is above the pI, the protein:

A. Precipitates out of solution

B. Becomes positively charged

C. Becomes negatively charged

D. Becomes neutral

E. Is broken down into its individual amino acids

6) Cytochrome C has a pI of 10.6. Select all of the following statements that are predicted to be true for cytochrome C. (Hint: there are 5 correct responses.)

  • Positively-charged in 0.01 M phosphate buffer solution of pH 6.3
  • Negatively-charged in 0.01 M phosphate buffer solution of pH 6.3
  • Neutral overall charge in 0.01 M phosphate buffer solution of pH 6.3
  • Positively-charged in 0.01 M phosphate buffer solution of pH 7.5
  • Negatively-charged in 0.01 M phosphate buffer solution of pH 7.5
  • Neutral overall charge in 0.01 M phosphate buffer solution of pH 7.5
  • Negatively-charged in 0.01 M phosphate buffer solution of pH 9.5
  • Positively-charged in 0.01 M phosphate buffer solution of pH 9.5
  • Neutral overall charge in 0.01 M phosphate buffer solution of pH 9.5
  • Negatively-charged in 0.1 M phosphate buffer solution of pH 9.5
  • Positively-charged in 0.1 M phosphate buffer solution of pH 9.5
  • Neutral overall charge in 0.1 M phosphate buffer solution of pH 9.5
  • Negatively-charged in 0.1 M phosphate buffer solution of pH 10.7
  • Positively-charged in 0.1 M phosphate buffer solution of pH 10.7
  • Neutral overall charge in 0.1 M phosphate buffer solution of pH 10.7

7) Haemoglobin has a pI of 6.8. Select all of the following statements that are predicted to be true for haemoglobin. (Hint: there are 5 correct responses.)

  • Positively-charged in 0.01 M phosphate buffer solution of pH 6.3
  • Negatively-charged in 0.01 M phosphate buffer solution of pH 6.3
  • Neutral overall charge in 0.01 M phosphate buffer solution of pH 6.3
  • Positively-charged in 0.01 M phosphate buffer solution of pH 7.5
  • Negatively-charged in 0.01 M phosphate buffer solution of pH 7.5
  • Neutral overall charge in 0.01 M phosphate buffer solution of pH 7.5
  • Negatively-charged in 0.01 M phosphate buffer solution of pH 9.5
  • Positively-charged in 0.01 M phosphate buffer solution of pH 9.5
  • Neutral overall charge in 0.01 M phosphate buffer solution of pH 9.5
  • Negatively-charged in 0.1 M phosphate buffer solution of pH 9.5
  • Positively-charged in 0.1 M phosphate buffer solution of pH 9.5
  • Neutral overall charge in 0.1 M phosphate buffer solution of pH 9.5
  • Negatively-charged in 0.1 M phosphate buffer solution of pH 10.7
  • Positively-charged in 0.1 M phosphate buffer solution of pH 10.7
  • Neutral overall charge in 0.1 M phosphate buffer solution of pH 10.7

8) An appropriate matrix for ion-exchange chromatography would be:

A. Carboxymethyl (CM) cellulose

B. Sephadex

C. Agarose

D. Agar

9) Haemoglobin has a pI of 6.8. Why would haemoglobin not move through the column in 0.01M phosphate buffer solution of pH 6.3? Select all responses that are true. (Hint: there are 2 correct responses.)

  • The protein is negatively-charged
  • The protein is positively-charged
  • The protein has no overall charge
  • The positively-charged protein is bound to the negatively-charged beads in the column
  • The negatively-charged protein is bound to the positively-charged beads in the column
  • The protein cannot bind to the column beads
  • Positively-charged ions in the buffer solution out-compete the protein for binding to the beads
  • Negatively-charged ions in the buffer solution out-compete the protein for binding to the beads

10) Haemoglobin has a pI of 6.8. Why would haemoglobin move through the column in 0.01M phosphate buffer solution of pH 9.5? (Hint: there are 2 correct responses.)

  • The protein is negatively-charged
  • The protein is positively-charged
  • The protein has no overall charge
  • The positively-charged protein is bound to the negatively-charged beads in the column
  • The negatively-charged protein is bound to the positively-charged beads in the column
  • The protein cannot bind to the column beads

11) Cytochrome C has a pI of 10.6. Why would Cytochrome C not move through the column in 0.01M phosphate buffer solution of pH 9.5? Select all responses that are true:  (Hint: there are 3 correct responses.)

  • The protein is negatively-charged
  • The protein is positively-charged
  • The protein has no overall charge
  • The positively-charged protein is bound to the negatively-charged beads in the column
  • The negatively-charged protein is bound to the positively-charged beads in the column
  • The protein cannot bind to the column beads
  • The ionic strength of the buffer solution is relatively low
  • The ionic strength of the buffer solution is relatively high
  • Positively-charged ions in the buffer solution out-compete the protein for binding to the beads
  • Negatively-charged ions in the buffer solution out-compete the protein for binding to the beads
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