Topic 1 - Year 1 - Biological Molecules - Proteins

Question 1

Proteins are polymers , what is the monomer of a protein?

Answer 1

The monomer of a protein is an amino acid.

Question 2

What is a dipeptide?

Answer 2

A dipeptide is what is made when two amino acids join together

Question 3

What is a polypeptide?

Answer 3

A polypeptide is what is created when many amino acids join together.

Question 4

What are proteins made up of?

Answer 4

Proteins are made up of one or more chains of polypeptides .

Question 5

How are amino acids linked together?

Answer 5

Amino acids are linked together in condensation reactions, the bonds that are made between the amino acids are known as peptide bonds.

Question 6

What type of bond forms between two amino acids when a condensation reaction takes place?

Answer 6

A peptide bond.

Question 7

What molecule is released in the formation of a peptide bond?

Answer 7

A molecule of water is released as peptide bonds form in condensation reactions.

Question 8

What reaction takes place to break peptide bonds?

Answer 8

Hydrolysis happens to break down peptide bonds , hydrolysis uses a molecule of water to break the bond.

Question 9

Describe the structure of an amino acid.

Answer 9

Amino acids have the same general structure , a carboxyl group (COOH) , an amine group / amino group (NH^2) and an R group which can also be referred to as a variable side group.

                         R
                          |
       H2N ------  C  --------- COOH
                          |
                         H
Could also be displayed as:

 H          R           O
  \          |          //
   N ---- C ----- C
  /          |          \
H         H            OH

Question 10

How many amino acids are there ?

Answer 10

20

Question 11

Which two groups on the amino acid join by peptide bond in the condensation reaction ?

Answer 11

The carboxyl group of one amino acid bonds one of its OH molecules to one of the 2 hydrogen atoms in the amine group of the second amino acid.

H R O H R O
\ | // \ | //
N —- C —– C N —- C —– C
/ | . / | \
H H OH + H H OH

=

H R O H. R. O
\ | // . |. //
N —- C —– C ——— N —– C —– C. + H20
/ | |. \
H H H. OH

Question 12

What is Primary structure?

Answer 12

Primary structure is the sequence of amino acids that make up a polypeptide chain.

Question 13

What is Secondary structure?

Answer 13

The secondary structure of a protein is the way in which it is twisted or folded. the poly peptide chain doesn’t remain flat or straight . Hydrogen bonds form between amino acids in the polly peptide chains, these hydrogen bonds make the polypeptide chain twist or fold into an alpha helix or a beta pleated sheet.

Question 14

What type of bonds cause the polypeptide chain to twist into an alpha helix or cause it to fold into a beta pleated sheet ?

Answer 14

Hydrogen bonds.

Question 15

What is tertiary structure?

Answer 15

Tertiary structure is a progression from secondary structure the structure occurs as alpha helix or beta pelted sheets are folded and twisted further in consequence of the formation of new bonds. Further hydrogen bonding occurs in this type of structure , ionic bonds also form between negative and positive charges o different parts of the polypeptide chain. In the tertiary structure there also can be disulphide bridges , disulphide bridges form when two amino acids with the R group that makes them cysteine come close together. The sulphur atom in one cysteine bonds to the sulphur atom in another. For many proteins made of a single polypeptide chain the tertiary structure forms the proteins final 3 dimensional structure.

Question 16

What is a disulphide bridge?

Answer 16

A disulphide bridge is a type of bond that forms in a polypeptide chain it occurs if two amino acids of the cysteine variation come close to one another , the sulphur atom in one cysteine bonds to the sulphur atom in another cysteine.

Question 17

What is quaternary structure?

Answer 17

Quaternary structure is when multiple polypeptide chains assemble together to make a single protein.

Question 18

What determines a proteins shape?

Answer 18

Ultimately it is the sequence of amino acids hence the primary structure that determines a proteins 3 dimensional shape.

Question 19

What determines a proteins function?

Answer 19

The shape of a protein determines its function.

Question 20

What test is use to find out if a sample contains proteins?

Answer 20

The Biuret Test

Question 21

How do you conduct the Biuret test

Answer 21

You first place your sample in solution and then add buret reagent , if a protein is present then the solution will go purple, if there is no protein present then the solution will stay blue. It Is a good idea to use a control in this test as purple and blue are similar colours so it maybe hard to identify if there has been a colour change.

Question 22

Why would you set up a control when you perform the Biuret test for proteins?

Answer 22

You would set up a control in the buret test as a positive result is purple where as a negative result is blue , blue and purple are quite similar colours hence it is best to have a control to make it easier to identify any colour change.

Question 23

Types of protein

Answer 23

• Enzymes
• Antibodies
• Transport proteins
• structural proteins
• chemical messengers

Question 24

What 4 elements are found in every amino acid?

Answer 24

Hydrogen
Nitrogen
Oxygen
Carbon

Question 25

Which type of bonding is present in the primary structure?

Answer 25

Peptide

Disulphide (if there are multiple cysteine amino acids)

Question 26

Which type of bonding is present in the secondary structure?

Answer 26

Peptide
Hydrogen
Disulphide (if there are multiple cysteine amino acids)

Question 27

Which type of bonding is present in the tertiary structure?

Answer 27

Peptide
Hydrogen
Ionic
Disulphide (if there are multiple cysteine amino acids)

Question 28

Which type of bonding is present in the quaternary structure?

Answer 28

Peptide
Hydrogen
Ionic
Disulphide (if there are multiple cysteine amino acids)