Protein structure and bonding

Question 1

What is the primary structure of a protein?

Answer 1

The sequence of amino acids found in the molecule.

Question 2

What is the quaternary structure?

Answer 2

Protein structure where a protein consists of more than one polypeptide chain.

Question 3

What is the secondary structure?

Answer 3

The coiling or folding of an amino acid chain, which arises often as a result of the formation of hydrogen bonds between different parts of the chain.

Question 4

What are the main forms of the secondary structure?

Answer 4

The helix and the beta pleated sheet.

Question 5

What is the tertiary structure?

Answer 5

The overall 3D shape of a protein molecule.

Question 6

Why does the tertiary structure of a protein arise?

Answer 6

Due to interactions including hydrogen bonds, disulphide bridges, ionic bonds and hydrophobic interactions.

Question 7

If one amino acid is changed in a sequence what is likely to happen?

Answer 7

The function of the protein changes.

Question 8

The function of a protein is determined by what?

Answer 8

Its structure.

Question 9

True or false. The primary structure has no affect on what will happen at the other stages.

Answer 9

False. The primary structure directly affects what shape the protein will take at the tertiary and secondary structure.

Question 10

In an alpha helix and beta pleated sheet what molecules are the hydrogen bonds between?

Answer 10

The NH group and the CO group.

Question 11

What makes the secondary structures stable at optimum temperature/pH?

Answer 11

The large amount of hydrogen bonds. Although they are generally weak interactions because of their number they cause the structures to be strong.

Question 12

What are the variations of the secondary structure stage?

Answer 12

Some chains have both at either end and some amino acids chains don’t take a particular shape at all.

Question 13

What is the tertiary structure?

Answer 13

When helix and pleats fold themselves.

Question 14

In the tertiary structure what are the bonds between?

Answer 14

The amino acids.

Question 15

If a protein adopts a supercoiled shape what is this called?

Answer 15

A fibrous protein.

Question 16

If a protein adopts a spherical shape what is this called?

Answer 16

A globular protein.

Question 17

What happens in the quaternary structure?

Answer 17

Multiple polypeptide chains are arranged to make a complete protein molecule.

Question 18

Where do hydrogen bonds form?

Answer 18

Between hydrogen atoms with a slightly positive charge and other atoms with a slightly negative charge.

Question 19

Bonds between polar areas of R-groups are key to holding which structures together?

Answer 19

Tertiary and quaternary.

Question 20

Where do ionic bonds form?

Answer 20

Between the carboxyl and amino groups that are part of the R-groups.

Question 21

What do the carboxyl and amino groups ionise into when an ionic bond is formed?

Answer 21

NH3+ and COO-

Question 22

Why are ionic bonds very strong?

Answer 22

The positive and negative groups are strongly attracted to each other.

Question 23

Where are disulphide links?

Answer 23

The R-group of the amino acid cysteine contains sulphur. Disulphide bridges form between two R-groups.

Question 24

What are disulphide bridges a form of?

Answer 24

Strong covalent bonds.

Question 25

What parts of a protein are hydrophobic?

Answer 25

Parts of the R-groups associate together in the centre of polypeptides to avoid water.

Question 26

What parts of polypeptides are hydrophilic?

Answer 26

Hydrophilic parts are found at the edge of the polypeptide to be close to the water.

Question 27

What do the hydrophobic and hydrophilic interactions cause polypeptides to do?

Answer 27

Fold into the tertiary and quaternary structures