Amino Acids

Question 1

How many amino acids do proteins typically contain

Answer 1

50-2000 AA residues

Question 2

In neutral solution which end of the AA is positively charged

Answer 2

Amino group

Question 3

In neutral solution which end of the AA is negatively charged

Answer 3

Carboxyl group

Question 4

What is a zwitterion and why are AA zwitterions

Answer 4

Ends are oppositely charged in solution

Question 5

What is the N-terminal of the polypeptide

Answer 5

The amino group first AA in chain

Question 6

What is the C-terminal of the polypeptide

Answer 6

Carboxyl group of last AA in chain

Question 7

How many proteinaceous AAs are there

Answer 7

20

Question 8

What is the common core of AA

Answer 8

Central C joined to H-atom

Question 9

What is a chiral molecule

Answer 9

all four sites are occupied by different groups, so two versions of the molecule can exist as the same atoms connected in the same sequence but with different positions

Question 10

Why are chiral molecules enantiomers

Answer 10

Mirror image versions of each other than cannot be superimposed on eachother

Question 11

How are chiral molecules distinguished

Answer 11

Named D and L isomers of molecule

Question 12

What determines the character/behaviour of an amino acid

Answer 12

The R group/side chain

Question 13

How do side chains determine AA behaviour (6 ways)

Answer 13

Vary in size, shape, charge, hydrogen bonding capacity, hydrophobicity and chemical reactivity

Question 14

What are the 5 main groups of amino acids

Answer 14

Hydrophobic (with nonpolar aliphatic), hydrophobic (with aromatic), polar (with neutral R groups and uneven charge distribution), positively charged (with +charged R groups at pH 7), negatively charged (with -charged R groups at physiological pH)

Question 15

What does aliphatic mean

Answer 15

No aromatic rings present

Question 16

Which version of AA are found in proteins (D or L)

Answer 16

L isomer

Question 17

Named the 7 hydrophobic with non polar aliphatic AAs

Answer 17

Glycine, alanine, proline, valine, leucine, isoleucine, methionine

Question 18

Which AA is a chiral (no D or L form) and why

Answer 18

Glycine- has hydrogen as R group (simplest AA)

Question 19

What are the features of hydrophobic with nonpolar aliphatic R group AAS

Answer 19

Mainly hydrocarbon side chains, hydrophobic

Question 20

Name the 2 hydrophobic with nonpolar aromatic side chains AAs

Answer 20

Phenylalanine and tryptophan

Question 21

What are the properties of hydrophobic with non polar aromatic R group AAs

Answer 21

Large, hydrophobic

Question 22

How does the large size of hydrophobic with non polar aromatic R group AA impact protein structure

Answer 22

Take up more space in the polypeptide so food is less tight

Question 23

What does aromatic means

Answer 23

Aromatic benzene-type rings present

Question 24

Why are covalent bonds polar

Answer 24

Electrons unequally shared

Question 25

Name the polar, with neutral R groups but uneven charge distribution AAs

Answer 25

Serine, threonine, cysteine, tyrosine, asparagine, glutamine

Question 26

What are the properties of polar, with neutral R groups but uneven charge distribution AAs

Answer 26

Side chains with polarity due to uneven share of electrons, more hydrophilic R groups than nonpolar, form H bonds with water

Question 27

What does the -SH group in cysteine mean for a polypeptide

Answer 27

Pairs of SH groups close together may form a disulphide bond linking parts of the polypeptide together

Question 28

Name the positively charged R group AAs

Answer 28

Lysine, Arginine, Histidine

Question 29

What are the characteristics of positively charged R group AAs

Answer 29

Side chains with positive charge at pH 7, hydrophilic R groups due to ionic charge

Question 30

What feature of Histidine makes it a useful component of active sites

Answer 30

Able to bind to or release H+ near physiological pH so can serve as a proton donor/ acceptor

Question 31

Name the negatively charged R group AAs

Answer 31

Aspartate, Glutamate

Question 32

Name the features of negatively charged R group AAs

Answer 32

Posses a Carboxyl group in the side chain, negatively charged at physiological pH, ionic charge makes R group hydrophilic, side chains can be important proton acceptors in proteins