Amino Acids And Proteins

Question 0

In cell membranes, what is the fluid mosaic model?

Answer 0

Lipid bilayer with proteins embedded in it.

Question 1

What is an amphiphatic molecule?

Answer 1

A molecule with both polar and non-polar regions.

Question 2

What type of protein isomers are found in humans?

Answer 2

L isomers

Question 3

If the pH of a solution is < than the pK value of an amino acid, then it will be protonated or de-protonated?

Answer 3

Protonated

Question 4

If the pH of a solution is > than the pK value of an amino acid, then it will be protonated or de-protonated?

Answer 4

De-protonated

Question 5

What is the pI (isoelectric point) of an amino acid?

Answer 5

The pH at which the amino acid has no overall net charge.

Question 6

What is the secondary structure of an amino acid?

Answer 6

The local spatial arrangement of the polypeptide backbone.

Question 7

How many amino acids are there per turn in the alpha helix?

Answer 7

3.6

Question 8

Is a peptide alpha helix left or right handed?

Answer 8

Right handed

Question 9

What is a pK value?

Answer 9

How much an acid dissociates

Question 10

The lower the pK value, the more acidic/basic a substance is

Answer 10

Acidic

Question 11

Give details about the structure of collagen.

Answer 11

Triple helical arrangement of collagen chains.
Contains Gly - X - Y repeating sequence.
Hydrogen bonds stabilise interactions between the chains.

Question 12

What is the domain of a protein?

Answer 12

Part of a polypeptide chain that folds into a distinct shape and often has a specific functional role.

Question 13

Give four forces involved in maintaining the quaternary structure of a protein.

Answer 13

Covalent, ionic, hydrogen, Van der Waals, hydrophobic

Question 14

How does pH denature a protein?

Answer 14

Alters ionisation states of amino acids.

Question 15

How does temperature denature a protein?

Answer 15

Increased vibrational energy of bonds.

Question 16

What do chaperones do?

Answer 16

Assist proteins in folding.

Question 17

What is the strength of an acid?

Answer 17

The extent to which it dissociates in solution.

Question 18

What does Ka mean and how is it worked out?

Answer 18

The acid dissociation constant

[H+][A-]/[HA]

Question 19

Will a strong acid have a large or a small Ka value?

Answer 19

Large

Question 20

What is a buffer?

Answer 20

A solution that resists changes in pH on the addition of a small amount of acid or alkali.

Question 21

What is a biological buffer made up of?

Answer 21

An acid and it’s conjugate base

Question 22

Give some features of the peptide bond (3)

Answer 22

• Planar because the C-N bond has partial double bond characteristics
• Cannot be twisted
• Peptides always form trans (chair) isomers (opposite sides of the C-C bond)

Question 23

What does the sequence of amino acids in a protein determine?

Answer 23

• The way in which the polypeptide folds

- The physical characteristics of the protein

Question 24

What charge to acidic proteins mostly carry?

Answer 24

Negatively charged amino acids

Question 25

What is a conjugated protein?

Answer 25

A protein with a covalently linked chemical component eg lipoproteins (lipids) and glycoproteins (carbohydrates)

Question 26

What is the quaternary structure of a protein?

Answer 26

The 3-D arrangement of protein sub-units

Question 27

What is an amyloid fibre?

Answer 27

A mis-folded, insoluble form of a normally soluble protein

Question 28

Give features of a beta pleated sheet (3)

Answer 28

• Extended conformation
• Parallel or anti-parallel
• Multiple inter-strand H bonds