Proteins

Question 1

What four groups are attached to the central carbon of an amino acid?

Answer 1

NH2, COOH, H and variable component R

Question 2

What are the four classes of amino acids?

Answer 2

acidic, basic, polar and non-polar

Question 3

Which part of the amino acid decides which class the amino acid belongs to?

Answer 3

The R group

Question 4

Which class of R group gives a hydrophobic reaction with water?

Answer 4

Non-polar

Question 5

Give examples of Proteins which are, acidic, basic, polar and non-polar, and the functional group which causes this.

Answer 5

Acidic: aspartic acid COOH
Basic: Lysine, NH2
Polar: Serine OH
Non-polar: Alanine CH3

Question 6

When are amino acids linked together?

Answer 6

During translation of mRNA at the ribosome

Question 7

What type of reaction is the formation of a peptide bond?

Answer 7

Condensation reaction caused by an enzyme.

Question 8

What is the the primary structure of a protein?

Answer 8

The sequence of amino acids that make up a polypeptide chain.

Question 9

What are the two ends of a polypeptide chain known as?

Answer 9

N terminus and a C terminus

Question 10

What is the secondary structure of a protein stabilised by?

Answer 10

Hydrogen bonds between the atoms of different peptide bonds in the chain.

Question 11

Which part of the polypeptide with a slight negative and positive charge?

Answer 11

Positive: The hydrogen of the NH2 group.
Negative: Oxygen of the COOH

Question 12

What are the two type of secondary structure

Answer 12

Alpha Helix and Beta Sheet

Question 13

Describe the structure of an alpha helix

Answer 13

A spiral with the R groups sticking outwards

Question 14

What is the structure of a Beta sheet

Answer 14

Parts of polypeptide chain running alongside each other forming a corrugated sheet, with the R groups sitting above and below.

Question 15

What does an anti-parallel and parallel chain consist of?

Answer 15

anti-parallel: Chains in opposite directions with respect to NC polarity
parallel: Chains in the same direction with respect to NC polarity.

Question 16

What is the tertiary shape of a protein?

Answer 16

The 3-dimensional shape of a protein

Question 17

What is the tertiary shape of a protein stabilised by?

Answer 17

Interactions between R groups of amino acids

Question 18

Why are the R groups close together in the tertiary structure?

Answer 18

Because of the folding in the secondary structure

Question 19

Name five types of interactions between R groups

Answer 19

Hydrophobic interactions
Van der Waals interactions
Hydrogen bonding
Ionic bonds
Disulphide bridges

Question 20

Describe hydrophobic interactions

Answer 20

Non polar R groups are usually found on the inside of the protein. Other R groups are usually found on the outside.

Question 21

Describe van der waals interactions

Answer 21

Very weak attractions between the electron clouds of atoms

Question 22

Describe hydrogen bonding

Answer 22

The weak negative charge of oxygen on C=O is attracted to the weak positive charge of the hydrogen on an OH or NH2 group.

Question 23

Describe ionic bonds

Answer 23

The COOH and NH2 groups ionise to become COOH- and NH3+. These groups are strongly charged and can attract one another

Question 24

Describe disulphide bridges

Answer 24

Covalent bonds form due to reactions between the sulphur-containing R groups of cysteines.

Question 25

What is the name given to the non-protein groups that are incorporated into the polypeptide chain in the tertiary structure

Answer 25

Prosthetic groups

Question 26

What does the quaternary structure of a protein consist of?

Answer 26

Different polypeptide sub-units linked by R group interactions