Lecture 2 Flashcards
What properties do you need to associate with each amino acid?
- Polarity
- Charge (neg., pos., neutral)
What is electronegativity?
The ability for an atom to attract electrons towards itself.
How many amino acids have very non-polar side chains?
6
How many amino acids have moderately non-polar side chains?
5
How many amino acids have polar but uncharged side chains?
4
How many amino acids have positively charged (very polar) side chains?
3
How many amino acids have negatively charged (very polar) side chains?
2
What do amino acids with very non-polar side chains have?
They are dominated by hydrocarbons and consist only of C-C bonds and C-H bonds
What is a hydrocarbon?
Non-polar and hydrophobic.
What is Polarity a result of?
Atoms having different electronegativity or tendency to hold bonding electrons
What is the order of electronegativity of the atoms we will be dealing with?
O > N > S > C = H
What happens with elements that have similar electronegativity?
They share bonding electrons equally and are always non-polar (Example C - H bond)
What happens with elements that have different electronegativity?
The more EN atoms such as O or N get greater than 50% share and this leads to unbalanced charged and polar bonds
(Example C = O bond)
Why is Glycine considered moderately non-polar?
It has a single H atom as a side chain which is not enough to be VERY non polar
What is hydrophobicity related to?
The number of CH, CH2, or CH3 groups present.
Why is cysteine moderately non-polar?
Contains the ‘slightly’ polar SH group
Why is proline moderately non-polar?
It is a unique amino acid as the side chain links to an alpha-N as well as an alpha-C
The polar N moderates the non-polar hydrocarbon.
Why is Tyrosine and Tryptophan moderately non-polar?
Has a single polar group that partly offsets the very non-polar benzene ring
What are the amino acids with polar uncharged side chains?
Ser, Thr, Asn, Gln
What do serine and threonine have?
Sidde groups that include the polar hydroxyl group - OH (simple alcohol)
What do Asn and Gln contain?
The polar amide group
Why do Asn, Ser, Thr, and Gln have polar uncharged side chains?
They do not gain or lose H+ in aqueous solution at pH 7, so they are uncharged.
What do the polar uncharged side chains act as?
Good hydrogen bond donors or acceptors
