1.6 - Proteins

Question 1

Are proteins usually small or large molecules?

Answer 1

Large

Question 2

What is the polymer of amino acids?

Answer 2

Polypeptides

Question 3

Polypeptides can be combined to form what?

Answer 3

Proteins

Question 4

How many amino acids naturally occur in proteins?

Answer 4

20

Question 5

Every amino acids has a central what?

Answer 5

Carbon atom

Question 6

What are the four different chemicals groups that the central carbon atoms of amino acids joins too?

Answer 6

• amino group
• carboxyl group
• hydrogen atom
• R (side) group

Question 7

What is an amino group?

Answer 7

(-NH2) - a basic group from which the amino part of the amino part of the name amino acids is derived

Question 8

What is a carboxyl group?

Answer 8

(-COOH) - an acidic group which gives the amino acid the acid part of the name

Question 9

What is the R (side) group?

Answer 9

A variety of differnt chemicals groups. Each amino acid has a different R group. There 20 naturaly occurring amino acids differ only in there R groups.

Question 10

Through a series of condensation reactions, many amino acid monomers can be joined together in a process called?

Answer 10

Polymerisation

Question 11

What is the primary structure of a protein?

Answer 11

The sequence of amino acids in a polypeptide chain

Question 12

The primary structure of a protein determines what?

Answer 12

Its ultimate shape and hence its function

Question 13

What is the secondary structure of proteins?

Answer 13

Alpha helix or beta pleated sheet, held by hydrogen bonds

Question 14

What is it called when two amino acids join together?

Answer 14

Dipeptide

Question 15

What is the type of reaction when making a dipeptide?

Answer 15

Condensation reaction

Question 16

What bond forms between amino acids?

Answer 16

Peptide bond

Question 17

Where does the peptide bond from between amino acids?

Answer 17

Between the carbon atoms on one amino acids and the nitrogen atom of the other

Question 18

Is a protein shape important to its function?

Answer 18

Yes it is very important and specific to its function

Question 19

What is the tertiary structure of a protein?

Answer 19

Folding of a polypeptide chin due to interactions between side chains of amino acids that lie in different regions of the primary structure

Question 20

Give me 3 types of bonds found in the tertiary structure of proteins

Answer 20

1. Disulphide bridges
2. Ionic bonds
3. Hydrogen bonds

Question 21

Give me a characteristic of disulphide bridges

Answer 21

They are very strong and therefore not easily broken

Question 22

Where are the ionic bonds formed in the tertiary structure of proteins?

Answer 22

Formed between any carboxyl groups that are not involved in forming peptide bonds

Question 23

Give me a characteristic of ionic bonds

Answer 23

They are weaker than disulphide bonds and are easily broken by changes in pH

Question 24

Why is ti important that each protein is distinctive?

Answer 24

It allows it to recognised by other molecules - it can then interact with them in a very specific way

Question 25

What determines the quaternary structure of a protein?

Answer 25

The combination of a number of different polypeptide chains and associates non protein (prosthetic) groups into a large complex molecule

Question 26

What is the test for proteins?

Answer 26

Buiret test

Question 27

Give me an example of a quaternary structure of protein?

Answer 27

Haemoglobin

Question 28

What is the method of the buiret test?

Answer 28

1. Place a sample of the solution to be tested in a test tube and add an equal volume of sodium hydroxide solution at room temperature 2. Add a few drops of very dilute copper (II) sulphate and mis gently

Question 29

What would the result be of the buiret test?

Answer 29

A purple coloration indicates presence of a peptide bond and hence a protein. If no protein is present the solution remains blue.