Please I REALY need help on this, I have looked in my book for hours and I am so
ID: 132510 • Letter: P
Question
Please I REALY need help on this, I have looked in my book for hours and I am so lost on answering this question. Please help!
Note: We are looking for detailed answers. Very little credit will be earned for partial or incomplete answers.
Amino acids can have very specific properties. Some specific properties of interest are size (small/medium/large), If its is bulky/rigid/flexible, if it is hydrophilic or hydrophobic and if is positively or negatively charged.
1A. For the properies of size, bulk/rigidity/flexibility, hydrophilic or hydrophobic and positive or negatively charged, provide detailed descriptions of what we woud look for in the "R" group of the amino acid to decide what traits give it these properties. (10 points)
1B. For each of the twenty amino acids, name if it is big/medium/small, bulky/rigid/flexible, hydrophilic or hydrophobic and positive or negatively charged.
If any of the twenty amino acids you describe do not follow the trend that you provided in part A, provide a detailed explanation for why. (30 points)
Explanation / Answer
Answer 1A
Very Small are those with smallest R groups just one atom or one functional moiety
Small are those which have two carbon atoms (or carbon and sulfur) in side chain
Medium are those with three carbon atoms in side chain
Large are those containing long chain side groups (more than four carbons)
Very Large are with aromatic side chains
Amino acid would be considered negatively charged if it has more carboxylic groups than amino groups i.e. it has overall -ve charge at pH 7.
Amino acid would be considered positively charged if it has more amino groups than carboxylic groups i.e. it has overall +ve charge at pH 7.
Amino acid would be considered uncharged if it has equal number of carboxylic groups and amino groups i.e. it has overall zero charge at pH 7.
Amino acid is considered hydrophilic if it has groups which can form hydrogen bonds with water like those having carboxylic (COOH), amino (-NH2) in its side chain.
Amino acid is considered slightly hydrophilic if it has groups like hydroxyl (OH), sulphahydral (SH) in its side chain
Amino acid is considered hydrophobic if it lacks the groups like carboxylic (COOH), amino (-NH2), hydroxyl (OH), sulphahydral (SH) in its side chain.
??Amino acid is considered Rigid if it has side chain heterocyclic groups or rigid bonds like double bonds in side chain
Amino acid is bulky if it has benzene ring in side chain.
Amino acid is considered Flexible if side chains are of carbon chain and no ring or cyclic structure.
Answer 1B
The amino acids with the above properties are tabulated as follows:
S.No.
Name of amino acid
Hydrophilicity
Charge at pH 7
Size
Flexibility/Rigidity/Bulkiness
1
Glycine
Slightly hydrophilic
Uncharged
Very Small
Flexible
2
Alanine
Hydrophobic
Uncharged
Very Small
Flexible
3
Leucine
Hydrophobic
Uncharged
Large
Flexible
4
Isoleucine
Hydrophobic
Uncharged
Large
Flexible
5
Phenylalanine
Hydrophobic
Uncharged
Very Large
Bulky
6
Cysteine
Hydrophobic
Uncharged
Small
Flexible
7
Methionine
Hydrophobic
Uncharged
Large
Flexible
8
Tyrosine
Slightly hydrophilic
Uncharged
Very Large
Bulky
9
Tryptophan
Hydrophobic
Uncharged
Very Large
Bulky
10
Arginine
Hydrophilic
Positive
Large
Rigid
11
Lysine
Hydrophilic
Positive
Large
Flexible
12
Glutamic acid
Hydrophilic
Negative
Medium
Flexible
13
Aspartic Acid
Hydrophilic
Negative
Small
Flexible
14
Glutamine
Hydrophilic
Uncharged
Medium
Flexible
15
Asparagine
Hydrophilic
Uncharged
Small
Flexible
16
Histidine
Hydrophilic
Positive
Medium
Rigid
17
Proline
Hydrophobic
Uncharged
Small
Rigid
18
Valine
Hydrophobic
Uncharged
Medium
Flexible
19
Serine
Slightly hydrophilic
Uncharged
Very Small
Flexible
20
Threonine
Slightly hydrophilic
Uncharged
Small
Flexible
S.No.
Name of amino acid
Hydrophilicity
Charge at pH 7
Size
Flexibility/Rigidity/Bulkiness
1
Glycine
Slightly hydrophilic
Uncharged
Very Small
Flexible
2
Alanine
Hydrophobic
Uncharged
Very Small
Flexible
3
Leucine
Hydrophobic
Uncharged
Large
Flexible
4
Isoleucine
Hydrophobic
Uncharged
Large
Flexible
5
Phenylalanine
Hydrophobic
Uncharged
Very Large
Bulky
6
Cysteine
Hydrophobic
Uncharged
Small
Flexible
7
Methionine
Hydrophobic
Uncharged
Large
Flexible
8
Tyrosine
Slightly hydrophilic
Uncharged
Very Large
Bulky
9
Tryptophan
Hydrophobic
Uncharged
Very Large
Bulky
10
Arginine
Hydrophilic
Positive
Large
Rigid
11
Lysine
Hydrophilic
Positive
Large
Flexible
12
Glutamic acid
Hydrophilic
Negative
Medium
Flexible
13
Aspartic Acid
Hydrophilic
Negative
Small
Flexible
14
Glutamine
Hydrophilic
Uncharged
Medium
Flexible
15
Asparagine
Hydrophilic
Uncharged
Small
Flexible
16
Histidine
Hydrophilic
Positive
Medium
Rigid
17
Proline
Hydrophobic
Uncharged
Small
Rigid
18
Valine
Hydrophobic
Uncharged
Medium
Flexible
19
Serine
Slightly hydrophilic
Uncharged
Very Small
Flexible
20
Threonine
Slightly hydrophilic
Uncharged
Small
Flexible