Amino acids(AA, peptides, proteins)

Question 1

Define proteinogenic?

Answer 1

‘Protein creating’

Question 2

How many natural proteinogenic amino acids are there?

Answer 2

20

Question 3

What form of chirality are amino acids incorporated into (translated) proteins?

Answer 3

L-amino acids ONLY

Question 4

How many amino acids are hydrophillic?

Answer 4

10

Question 5

How many amino acids are hydrophobic?

Answer 5

10

Question 6

What characteristics do the hydrophilic amino acids have?

Answer 6

2, have negative charge
3, have a positive charge
5, are polar uncharged

Question 7

What characteristics do the hydrophobic amino acids have?

Answer 7

3, are aromatic
7, are non-polar aliphatic

Question 8

How do the aromatic R-groups absorb light?

Answer 8

These aromatic rings absorb light at particular wavelengths (in the ultra violet spectrum) allowing them to be used to monitor proteins (e.g. their concentration).

Question 9

How do amino acids join together?

Answer 9

Condensation reaction.
Removes water leaving aa residues. It requires energy and is performed by ribosomes.

Question 10

What is the bond formed between amino acids?

Answer 10

Peptide bond.

Question 11

If two monomers are joined then what bond is formed?

Answer 11

dipeptide.

Question 12

What does a polypeptide chain begin and end with?

Answer 12

Begins with a free amino acid terminus and ends with a carboxyl group.

Question 13

Why are some amino acids modified?

Answer 13

To add extra functional groups for added function.

Question 14

What decides the structure and properties of a protein(polypeptide)?

Answer 14

sidechain (R groups)

Question 15

How many ionizable protons does an amino acid have?

Answer 15

At least two each with its own pKa.

Question 16

At what pH is a carboxylic acid protonated?

Answer 16

Carboxylic acid has an acidic pKa value and will be protonated at an acidic (low) pH.

Question 17

At what pH is an amino group protonated?

Answer 17

The amino group has a basic pKa and will be protonated until basic pH (high).

Question 18

At low pH, the amino acid exists in a _________ charge form(______)

Answer 18

positively
cation

Question 19

At high pH, the amino acid exists in a ___________charged form (______).

Answer 19

negatively
anion

Question 20

What is a zwitterion?

Answer 20

A molecule with an equal number of positive and negative charges, resulting in a net charge of zero.

Question 21

What is the equation for the isoelectric point(equivalence point, pl)?

Answer 21

pI=pK1+pK2/2

Question 22

At what pH do Amino Acids(AA) carry zero charge?

Answer 22

the pl.

-AA is least soluble in water
-AA does not migrate in electric field.