Proteins

Question 1

Describe basic structure of an amino acid

Answer 1

carboxyl group

side chain

amino group

Question 2

What are the different R group properites of amino acids?

Answer 2

Polar or non-polar

hydrophilic/hydrophobic

acidic or basic

Question 3

What is the significance of the R group characteristics?

Answer 3

They determine how the Amino acid will behave in the polypeptide

Question 4

Which Amino acid has the smallest R group?

Answer 4

Glycine - has a single hydrogen as the R group

Question 5

What are the essential hydrophobic amino acids?

Answer 5

Valine

Leucine

Isoleucine

Phenylalanine

and Tryptophan

Question 6

Which amino acid interacts with carbohydrates and allows for glycosylation of proteins?

Answer 6

Asparagine (has a partial positive charge)

Question 7

Which amino acid allows for phosphorylation of the protein along with threonine?

Answer 7

Serine

they both have a hydroxyl group with a partial negative charge

Question 8

Which charged amino acid (hydrophilic) is also an essential amino acid?

Answer 8

Threonine and lysine

Question 9

Which amino acid is only considered essential in children?

Answer 9

Arginine

Question 10

What charge do aspartic acid and glutamic acid carry?

Answer 10

They carry a negative charge at normal body pH

Question 11

Which amino acid contains an aromatic ring with a hydroxyl group - giving it a partial or full negative charge?

Answer 11

Tyrosine

Question 12

Which amino acid forms sulfur hydrogen bonds in a protein structure?

Answer 12

Cysteine

Question 13

Which amino acid is found in the bends of a protein chain?

Answer 13

proline - it’s the kinky amino acid

Question 14

what type of bond is a peptide bond?

Answer 14

It’s an amide bond- where the carboxyl group of one amino acid interacts with the amino group of the second amino aicd

Question 15

what sort of reaction produces a peptide bond?

Answer 15

a condensation reaction - results in a loss of H2O

Question 16

What controls the folding of a polypeptide?

Answer 16

amino acid sequence controls the folding - due to R group interactions/attractions

Question 17

Describe the alpha helix formation

Answer 17

spiral structure - where the side chains extend outwards into a helical array - stabilized by hydrogen bonds formed between every fourth amino acid -

Question 18

how many amino acid residues per 360 degree turn of the helix?

Answer 18

3.6

Question 19

Describe the beta pleated sheet formation

Answer 19

stretched otu sheet structure

hydrogenb bonds between the NH and CO in side polypeptide chains

adjacent chains can run in the same direction (parallel) or in opposite directions (antiparallel)

Question 20

What type of structure makes up collagen? How about Silk?

Answer 20

collagen is made up of alpha helices

silk is made up of beta sheets

Question 21

What drives the formation of a tertiary protein structure?

Answer 21

it is driven by the strong tendency of hydrophobic residues to congregate away from the water

it is stabilized by disuphide bonds, hydrophobic interactions, hydrogen bonding and ionic interactions

Question 22

What are fibrous proteins rich in?

Answer 22

They are usually long, rigid structures, with three polypeptide alpha chains wound around one another in a rope like helix - they are generaly rich in proline and glycine as a result

Question 23

Why is vitamin C deficiency detrimental to the collagen structure?

Answer 23

Without Vitamin C, the lycine and proline are not hydroxylated properly and you get leaky collagen layers due to the weak interactions between chains - this explains the common symptom of scurvey = bleeding gums

Question 24

What holds together the quaternary structure of proteins?

Answer 24

non-covalent ineractions and interchain disulphide bonds

Question 25

What is the native conformation of a protein?

Answer 25

it is the fully functional folded protein structure - that determines the biological function of the protein

Question 26

What is post-translational modification of the protein ?

Answer 26

It is chemical modification of a protein after translation - where a functional group is attached to an amino acid and it results in change in protein function

Question 27

What are the common post translational modifications of proteins?

Answer 27

phosphorylation- of a serine, threonine, or tyrosine residue

glycosylation - of an asparagine, serine, or threonine

acylation = add fatty acid

ubiquitination = add ubiquitin = death signal

nitrosylation = add nitric oxide