Amino Acids/Proteins

Question 1

what (ultimately) happens to the COOH in a Hell-Volhard-Zelinsky rxn?

Answer 1

One of the alpha carbon’s get’s replaced with NH2

so the structure goes from COOH to amino acid

Question 2

what are the 3 reactants in the Hell-Volhard-Zelinsky amino acid synthesis?

Answer 2

1. Br2, PB3
2. H2O
3. xs NH3

Question 3

Why does Hell-Volhard-Zelinsky amino acid synthesis make racemic products?

Answer 3

Because the alpha carbon where the NH2 ends up becomes a chiral center

Question 4

what is the general pka for NH3+ in an amino acid?

Answer 4

9-10

Question 5

what happens to NH3+ if you raise its sln pH above 9-10?

Answer 5

the pH becomes high enough to make the NH3+ switch to basic NH2

Question 6

what is the general pka for COOH in an amino acid?

Answer 6

2

Question 7

what happens to COOH if you raise its sln pH above 2?

Answer 7

the pH becomes high enough to make the COOH switch to basic COO-

Question 8

what does an amino acid’s pI represent?

Answer 8

The pH at which there is no net charge and the molecule is LEAST soluble.

Question 9

Why can’t you protonate lone pairs that are participating in resonance when you adjust an amino acid in response to changes in pH?

Answer 9

the resonance lone pairs are not localized/not available. Lone pairs have to be localized to get protonated.

Question 10

Which amino acid synthesis has COOH as its starting material?

Answer 10

Hell-Volhard Zelinsky

Question 11

Which amino acid synthesis has aldehyde as its starting material?

Answer 11

Strecker

Question 12

WTF is an amino acid residue?

Answer 12

what you get/have left when two or more amino acids combine to form a peptide and the elements of water are removed,

what remains of each original amino acid

Question 13

what does the primary representation of protein structures look like?

Answer 13

a string of pearls with the animo acid’s 3 letter abbreviations written on them

read anal beads

Question 14

what does the SECONDARY representation of protein structures look like?

Answer 14

a chain shown with 3D ball and stick model

usually only shows you sections of the chain and gives you a sense of the protein’s amino acid’s geometries

but says nothing of the overall protein’s shape

Question 15

which representation of protein structures shows you alpha helix shapes and beta pleated shapes: primary, secondary, tertiary, or quaternary?

Answer 15

secondary

Question 16

do beta pleated sheet shaped proteins look like curly fries or accordions?

Answer 16

accordions

Question 17

do alpha helix shaped proteins look like curly fries or accordions?

Answer 17

curly fries

Question 18

what does the TERTIARY representation of protein structures look like?

Answer 18

chewed up bubble gum;

refers to the 3D shape of the protein AS A WHOLE /shows how it folds over onto itself to increase stability of its weak bonds

Question 19

what does the QUATERNARY representation of protein structures look like?

Answer 19

a colorful, curly hair ball?

most complicated representation; shows one big protein made out of a bunch of other proteins

Question 20

what is an alpha halo acid?

Answer 20

…

Question 21

Is the line structure for amino acids written in R configuration or S?

Answer 21

S; amine group will be on a wedge.

Question 22

why is the tertiary/chewing gum structure of protein the most important one?

Answer 22

It shows you the 3d fold/shape of the entire protein.

Question 23

what are the 4 types of interactions that hold tertiary structures of proteins together?

Answer 23

1. disulfide bridges
2. salt bridges
3. hydrogen bonds
4. hydrophobic interactions

Question 24

what’s the difference between the sources of shapes for secondary and tertiary protein structures?

Answer 24

secondary shape is entirely based on hydrogen bonds.

tertiary shape is somewhat based on hydrogen bonds but mostly based on interactions between side chains/R groups

Question 25

what is the difference between the charges involved in a salt bridge and the charges involved in a hydrogen bond?

Answer 25

salt bridges involve full blown charges

hydrogen bonds involve PARTIAL charges

Question 26

when can an amino acid’s nitrogen get protonated/become acidic?

Answer 26

when it’s lone pair is localized (meaning it’s not participating in resonance or aromaticity)