Lecture 10 Flashcards
What is a proteins function determined by?
Its structure
What are the four parts to an amino acid?
- Amine group
- Carboxyl group
- Alpha carbon
- Variable R-group
What varies between one amino acid an another?
The R-group
What is a Zwitterion?
A molecule that is overall neutral in terms of its net charge even though it has formal charges present because every molecules charge balances out
When is pKa smaller?
When an acid becomes stronger
What are the concentrations of acids and bases when pH = pKa?
[base] = [acid]. The concentration of the base equals the acid
What happens to the concentrations of the acid and base in the following situation?: pH < pKa
[acid] > [base]
What happens to the concentrations of the acid and base in the following situation?: pH > pKa
[acid] < [base]
What happens to the concentration of protons if pH is elevated?
The concentrated of protons goes down
What is the pKa of a carboxyl group for a typical amino acid?
pKa is around 2
What is the pKa of NH3?
Around 9.5
What happens to the carboxyl and amine group in a pH of 1?
The carboxyl becomes protonated and adds an it and is neutral and the NH3 keeps its H+ and become +1 making the overall molecule +1
What happen to carboxyl and amine at pH 11?
The carboxyl remains deprotonated (no H) and has a -1 charge and the amine group loses it H and is neutral making the overall molecule -1
What form of the carboxyl group and amine predominate at pH 7?
The carboxyl usually has the negative charge and the amine group usually has all 3 H’s and has a positive charge making the overall molecule neutral
What formal charge does an amino acid have at pH 7?
It has no formal charge
What is a chiral molecule?
An asymmetric molecule that cannot be superimposed on its mirror image
How are pH and protons related?
pH relates to the concentration of protons. The higher the pH the lower the concentration of protons
What condition must the R have in order to ensure amino acids are chiral?
The R group must not be the same as any of the other three groups
Which form of stereoisomers is incorporated into proteins?
The L-form
How many amino acids are commonly incorporated into proteins?
20
What are amino acids classified by?
Their side chains (R groups)
What are the 20 amino acids grouped on the basis of?
- Nonpolar (hydrophobic)
- Polar (uncharged)
- Charged (very polar)
What are the overall characteristics of an Hydrophobic Amino acids?
- The side chain is largely hydrophobic
* The side chain usually contain carbon and hydrogen (except tryptophan and methionine)
What is the relative size of alanine?
It is a relatively small amino acid
