Diprotic Acids, Amino Acids, and Protein Isoelectric Focusing

What are the three main components of amino acids?

An acidic carboxylic acid, a basic amino group, and a variable substituent 'R'.

What is a zwitterion?

A zwitterion is a nonionized form of an amino acid that has both positive and negative sites.

What happens to amino acids at low pH?

Both the ammonium group and the carbonyl group are protonated.

What happens to amino acids at high pH?

Neither the ammonium group nor the carbonyl group is protonated.

How are zwitterions stabilized in solution?

By interactions between the ammonium and carbonyl groups.

What does the acid dissociation constant (Ka) indicate?

It determines the strength of a weak acid.

What is the effect of increasing atmospheric CO2 on ocean pH?

It increases CO2 concentration in the ocean, consuming dissolved carbonate and lowering pH.

What principle explains the dissolution of solid calcium carbonate in low carbonate concentration?

Le Chatelier's principle.

What is the acidic form of a diprotic acid represented as?

H2L+ can dissociate twice.

What is the basic form of a diprotic acid represented as?

L- can undergo two hydrolysis reactions.

What is an amphiprotic molecule?

A molecule that can act as both an acid and a base.

What is the pH of the intermediate form of a diprotic acid related to?

It is close to midway between pK1 and pK2.

How is the pH of a diprotic buffer calculated?

Using the formulas pH=pk1+log(HA^-/H2A) and pH=pk2+log(A^2-/HA^-).

What is the isoionic pH?

The pH produced by the pure, neutral polyprotic acid in water.

What is the isoelectric pH?

The pH at which the average charge of a polyprotic acid is 0.

What are some biological functions of proteins?

Catalysis of reactions, immune response, transport of molecules, control of genetic expression, and structural support.

What determines the 3D structure and function of a protein?

The sequence of amino acids.

What is isoelectric focusing?

A technique for protein separation using an electric field in a medium with a pH gradient.

What happens to proteins during isoelectric focusing?

Proteins migrate until they reach the pH equal to their isoelectric pH, where they have no net charge.