Peptides(AA, Peptides, proteins)

Question 1

What determines the primary structure of a protein?

Answer 1

The protein sequence.

Question 2

How flexible is the peptide backbone in polypeptide chains?

Answer 2

It has limited flexibility.

Question 3

How are amino acids joined?

Answer 3

Peptide bonds

Question 4

What are the 4 levels of protein structure?

Answer 4

Primary
Secondary
Tertiary
Quaternary

ALSO… PTM proteolytic trimming groups.

Question 5

Overview of levels of protein structure…?

Answer 5

Primary- sequence of amino acids

Secondary- local regions of regular structure

Tertiary- overall 3-D folding pattern of chains

Quaternary- co-assembly of chains (not all proteins)

PTM proteolytic trimming - sidechain modification

Question 6

How many AA does the average protein contain?

Answer 6

50 amino acids.

Question 7

What does a single change at a position in a AA sequence do?

Answer 7

Completely change the properties of a protein.

Question 8

Do the 3 letter code an a full amino acid name? And then the one letter code?

Answer 8

serylglycyltyrosylalanylleucine=Ser-Gly-Tyr-Ala-Leu
=SGYAL

Question 9

Give some varieties of functions for peptides…?

Answer 9

Insulin (think sugar metabolism)

Oxytocin (think childbirth)

Bacitracin (gram+ bacteria)

Question 10

What do you call a cluster of conserved residues(AA regions)?

Answer 10

Motif- they carry out a particular function or form a particular structure that is important for the conserved protein.

Question 11

How does the overall composition of protein primary sequence give clues to the protein structure and function?(basically protein shape at primary sequence)

Answer 11

Histone proteins- large amounts of basic, + charged AA. R and K up to 20%

Regions of transmembrane proteins that pass through cell membranes- 20 consecutive hydrophobic AA.

Question 12

Where are the amino and carboxyl terminus positioned on protein primary sequence?

Answer 12

Amino terminus on the left
Carboxyl terminus on the right

Question 13

The peptide bond is a _________ hybrid of two _________ structures.

Answer 13

resonance
canonical

Question 14

What does the resonance cause the peptide bonds to do?

Answer 14

to be less reactive compared with esters, for example
to be quite rigid and nearly planar
to exhibit a large dipole moment in the favored trans configuration

Question 15

What is resonance in bonding?

Answer 15

Resonance is a way of describing delocalized electrons within certain molecules or polyatomic ions where the bonding cannot be expressed by a single Lewis formula.

Question 16

What are the two common regular arrangements at a polypeptide backbone?

Answer 16

Alpha helix- Stabilised by hydrogen bonds between nearby residues.

Beta sheet- stabilised by hydrogen bonds between adjacent segments that may not be nearby.

Question 17

What do you call the irregular arrangement of the polypeptide chain?

Answer 17

Random coil or unstructured.

Question 18

How many amide residues are there in the alpha helix per turn?

Answer 18

3.6 residues per turn(approx 7 for 7 turns).

Question 19

is the protein alpha helix the same or different in right vs left hand side as the DNA double helix?

Answer 19

Not the same, inverted.

Question 20

Give an example of a protein with a large alpha helical structure?

Answer 20

Globin(component of haemoglobin and myoglobin)f