BCCB2000 Lecture 4 Questions

Question 1

The name of the amino acid lysine can be abbreviated either as a three letter code or a one letter code. The three letter code for lysine is [a] and the one letter code [b]

Answer 1

Specified Answer for: a Lys Specified Answer for: b K

Question 2

The three letter code for the following peptide sequence: GGYWALIEN is [b]

Answer 2

Gly-Gly-Tyr-Trp-Ala-Leu-Ile-Glu-Asn

Question 3

The name of the amino acid methionine can be abbreviated either as a three letter code or a one letter code. The three letter code for methionine is [a] and the one letter code [b]

Answer 3

Specified Answer for: a Met Specified Answer for: b M

Question 4

The name of the amino acid serine can be abbreviated either as a three letter code or a one letter code. The three letter code for serine is [a] and the one letter code [b]

Answer 4

Specified Answer for: a Ser Specified Answer for: b S

Question 5

Select the correct statements from the following: A. All amino acids within a protein have at least one charged amino group and one charged carboxyl group B. The amine group and the carboxyl group are both attached to the same carbon in an amino acid C. Amino acids not considered part of the 20 common amino acids are never found in proteins D. Proteins are made from a set of amino acids generally labelled as the 20 ‘common’ amino acids E. Amino acids in proteins can only be distinguished by their side chains otherwise known as R groups

Answer 5

B. The amine group and the carboxyl group are both attached to the same carbon in an amino acid D. Proteins are made from a set of amino acids generally labelled as the 20 ‘common’ amino acids E. Amino acids in proteins can only be distinguished by their side chains otherwise known as R groups

Question 6

The name of the amino acid valine can be abbreviated either as a three letter code or a one letter code. The three letter code for valine is [a] and the one letter code [b]

Answer 6

Specified Answer for: a Val Specified Answer for: b V

Question 7

The R group of an amino acid determines if it is: A. hyrophilic or hydrophobic. B. polar or nonpolar. C. charged or uncharged. D. an acid or a base. E. All of the above

Answer 7

E. All of the above

Question 8

The pH inside the cell cytoplasm is usually about pH 7. At pH 7 which statement is true about the charges (ionization state) of the α-Carboxyl and α-Amino groups of an amino acid? A. The α-Carboxyl group is -1 and the α-Amino group is +1. B. The α-Carboxyl group is +1 and the α-Amino group is -1. C. The α-Carboxyl group is -1 and the α-Amino group is uncharged. D. Both groups are uncharged (not ionized) at pH 7.

Answer 8

A. The α-Carboxyl group is -1 and the α-Amino group is +1.

Question 9

For the amino acid lysine, the Henderson-Hasselbalch equation can be applied to ________ ionization group(s).

Answer 9

3

Question 10

The name of the amino acid phenylalanine can be abbreviated either as a three letter code or a one letter code. The three letter code for phenylalanine is [a] and the one letter code [b]

Answer 10

Specified Answer for: a Phe Specified Answer for: b F

Question 11

The name of the amino acid glutamate (glutamic acid) can be abbreviated either as a three letter code or a one letter code. The three letter code for glutamate is [a] and the one letter code [b]

Answer 11

Specified Answer for: a Glu Specified Answer for: b E

Question 12

Which of the following molecules is amphoteric? A. hydrochloric acid B. acetic acid C. ammonia D. sodium acetate E. glycine

Answer 12

E. glycine

Question 13

The amino acids in polypeptide chains which contain sulfur (S) are: A. cysteine, cystine, and methionine B. cystine C. methionine only D. cysteine only E. cysteine and methionine

Answer 13

E. cysteine and methionine

Question 14

Proline is distinct among the 20 commonly found amino acids because: A. it is a ring compound. B. it is hydrophilic and ionic. C. the nitrogen of the amino group is in a ring. D. the carbon of the carboxyl group is in a ring. E. it has little effect on protein structure.

Answer 14

C. the nitrogen of the amino group is in a ring.

Question 15

The name of the amino acid tyrosine can be abbreviated either as a three letter code or a one letter code. The three letter code for tyrosine is [a] and the one letter code [b]

Answer 15

Specified Answer for: a Tyr Specified Answer for: b Y

Question 16

Which amino acid is ideal for the transfer of protons within the catalytic site of enzymes due to the presence of significant amounts of both the protonated and deprotonated forms of its side chain at biological pH? A. Lysine B. Asparagine C. Tyrosine D. Cysteine E. Histidine

Answer 16

E. Histidine

Question 17

The name of the amino acid leucine can be abbreviated either as a three letter code or a one letter code. The three letter code for leucine is [a] and the one letter code [b]

Answer 17

Specified Answer for: a Leu Specified Answer for: b L

Question 18

Which amino acid does not exist as the D or L optical isomer? A. Histidine B. Glycine C. Proline D. Isoleucine E. No amino acid - they all exist as the L-form

Answer 18

B. Glycine

Question 19

Identify the amino acids from the following descriptions. Type the one-letter or three-letter code for the amino acid opposite the description: Positively charged amino acid with a long aliphatic side chain [a] Aromatic amino acid with a hydroxyl functional group [b] The side chain of this amino acid is bent back upon itself [c] This amino acid has a sulphur atom that can form covalent bonds [d]

Answer 19

Specified Answer for: a Arg/R Specified Answer for: b Tyr/Y Specified Answer for: c Pro/P Specified Answer for: d Cys/C

Question 20

An amino acid named for a plant from which it was first isolated is: A. proline B. methionine C. threonine D. asparagine

Answer 20

D. asparagine

Question 21

The carbon responsible for the chirality of most amino acids is known as the [a] carbon. The first carbon in the side chain of most amino acids is known as the [b] carbon.

Answer 21

Specified Answer for: a alpha Specified Answer for: b beta

Question 22

The one letter code for this peptide sequence: Glu-Tyr-Cys-Gly-Ala-Ser-Trp-Val-Ile-Ala-Ser-Asn-Gln is [a]

Answer 22

EYCGASWVIASNQ

Question 23

For amino acids with neutral R groups, at any pH below the pI of the amino acid, the population of amino acids in solution will: A. have no charged groups. B. have no net charge. C. have a net positive charge. D. have positive and negative charges in equal concentration. E. have a net negative charge.

Answer 23

C. have a net positive charge.

Question 24

Glycine is not a stereoisomer because: A. it has no chiral carbon. B. it does not form enantiomers. C. it does not exist in two non-superimposable mirror-image forms. D. A, B, & C above E. A and B only

Answer 24

D. A, B, & C above

Question 25

The chirality of an amino acid results from the fact that its alpha carbon: A. is a carboxylic acid. B. is bonded to four different chemical groups. C. is symmetric. D. is in the L absolute configuration in naturally occurringproteins. E. has no net charge.

Answer 25

B. is bonded to four different chemical groups.

Question 26

The side chains of nonpolar amino acids are best categorized as: A. aromatic. B. positively charged. C. negatively charged. D. uncharged. E. hydrophilic.

Answer 26

D. uncharged.

Question 27

The name of the amino acid arginine can be abbreviated either as a three letter code or a one letter code. The three letter code for arginine is [a] and the one letter code [b]

Answer 27

Specified Answer for: a Arg Specified Answer for: b R

Question 28

Calculate, using the Henderson-Hasselbalch equation the predominant structure of alanine at pH 8.4. Note that the pKa's of the amine and carboxyl groups in alanine are 9.6 and 2.3 respectively. A. Alanine contains predominantly NH2 - and COO- functional groups B. Alanine contains predominantly NH3+ and COOH functional groups C. Alanine contains predominantly NH2 and COO- functional groups D. Alanine contains predominantly NH3+ and COO- functional groups E. Alanine contains predominantly NH2 and COOH functional groups

Answer 28

D. Alanine contains predominantly NH3+ and COO- functional groups Using the Henderson-Hasselbalch equation: For the amine group pH = pka + log [base]/[acid] 8.4 = 9.6 + log[base]/[acid] 8.4-9.6 = -1.2 = log[base]/[acid] 10-1.2= [base]/[acid] That is for every 1 of acid there is 10-1.2 of base, so there is more of the acid form of the amine group ie. NH3+ For the carboxly group pH = pka + log [base]/[acid] 8.4 = 2.3 + log[base]/[acid] 8.4-2.3 = 6.1 = log[base]/[acid] 106.1= [base]/[acid] That is for every 1 of acid there is 106.1 of base, so there is more of the base form of the carboxyl group ie. COO-

Question 29

Amino acids with non-ionizable side chains are zwitterions when they are ________. A. in any solution B. at physiological pH, pH = 7.4 C. in acidic solutions only D. in alkaline solutions only E. All of the above

Answer 29

B. at physiological pH, pH = 7.4

Question 30

Select the correct statements from the following A. The amine group and the carboxyl group are both attached to the same carbon in an amino acid B. Amino acids in proteins can only be distinguished by their side chains otherwise known as R groups C. All amino acids within a protein have at least one charged amino group and one charged carboxyl group D. Proteins are made from a set of amino acids generally labelled as the 20 'common' amino acids E. Amino acids not considered part of the 20 common amino acids are never found in proteins

Answer 30

A. The amine group and the carboxyl group are both attached to the same carbon in an amino acid B. Amino acids in proteins can only be distinguished by their side chains otherwise known as R groups D. Proteins are made from a set of amino acids generally labelled as the 20 'common' amino acids

Question 31

Although the hydroxyl groups in serine and threonine are uncharged, they can react within active sites of some enzymes ________.

Answer 31

because the hydroxyl group is polar

Question 32

All amino acids except [a] have an chiral carbon. All amino acids except [b] have a beta carbon.

Answer 32

Specified Answer for: a glycine Specified Answer for: b glycine

Question 33

The name of the amino acid alanine can be abbreviated either as a three letter code or a one letter code. The three letter code for alanine is [a] and the one letter code [b]

Answer 33

Specified Answer for: a Ala Specified Answer for: b A

Question 34

The pKa's of the side chain group and the α-carboxyl group of glutamate are 4.1 and 2.1,respectively. Which statement accounts for this difference? A. The side chain has more possible resonance structures. B. The α-carboxyl group has less steric hindrance and is therefore ionized more easily. C. The side chain is a different functional group than the α-carboxyl group. D. The α-carboxyl group is closer to the α-amino group and the side chain is further away

Answer 34

D. The α-carboxyl group is closer to the α-amino group and the side chain is further away

Question 35

The D and L configurations of an amino acid indicate the way that the plane of polarizable light is rotated by the amino acid. True or False?

Answer 35

False

Question 36

The amino acid that can help stabilise and maintain protein three dimensional structure by forming covalent bonds is [a]

Answer 36

Cysteine

Question 37

A protein needs to use all of the 20 common amino acids in its sequence. True or False?

Answer 37

False

Question 38

Tyrosine and tryptophan are less hydrophobic than phenylalanine because A. phenylalanine has an indole group. B. phenylalanine has no polar group in the side chain. C. phenylalanine is a phenol. D. tyrosine and tryptophan have smaller R groups. E. All of the above

Answer 38

B. phenylalanine has no polar group in the side chain.

Question 39

The name of the amino acid isoleucine can be abbreviated either as a three letter code or a one letter code. The three letter code for isoleucine is [a] and the one letter code [b]

Answer 39

Specified Answer for: a Ile Specified Answer for: b I