Protiens

Question 0

What elements are amino acids built out of?

Answer 0

Carbon, Hydrogen, Oxygen, Nitrogen and sometimes Sulphur.

Question 1

What is the name given to the sub-units that proteins are constructed out of?

Answer 1

Amino acids

Question 2

What does the structure of an amino acid consist of?

Answer 2

An amino group (NH2), Carboxyl acid (COOH) and a variable “R” group (facing upwards) bonded to a central carbon with a hydrogen bonded to it.

Question 4

What are these variations due to?

Answer 4

Changes in the composition of the R(radical) side group

Question 5

What are the three simplest amino acids?

Answer 5

1. ) Glycine where R=H
2. ) Alanine where R=(C-H3)
3. ) Valine where R=(C3-H7)

Question 6

What happens when an amino acid dissolves in water and what is the importance of this property?

Answer 6

It becomes a dipole (amide=-ve and Carboxyl=+ve)

Because of this proteins and amino acids act as pH buffers in the cytoplasm of cells which keeps enzymes stable by maintaining a pH close to 7.0

Question 7

How are dipeptides formed?

Answer 7

Through a condensation reaction between the Carboxyl group of one amino acid and the amide group of another to create a peptide bond in which Nitrogen and Carbon are bonded together. These dipeptides then undergo further condensation reactions to create linear polypeptide chain which is the basis of all protiens.

Question 8

What is the primary structure of a polypeptide?

Answer 8

This refers to the the formation of a linear chain of amino acids.

Question 9

How does primary structure vary?

Answer 9

In the length of the chain and the sequence of amino acids.

Question 10

Why is there an almost infinite variety of protiens?

Answer 10

Because the are normally 2-300 amino acids in the polypeptide chain and so the number of possible polypeptide sequences approaches infinity.

Question 11

What is secondary structure?

Answer 11

This involves the folding of a single polypeptide chain due to the formation of hydrogen bonds.

Question 12

What is the name for proteins that remain at the secondary level and what are their identifying feaures?

Answer 12

These are called secondary proteins and are identified by two features;

1-involve hydrogen bonding only
2-No “R” group bonding occurs.

Question 13

What are the two most common types of secondary protein?

Answer 13

The alpha helix and Beta pleated sheet.

Question 14

Describe the structure of an alpha helix.

Answer 14

This type of protein is held in in a anticlockwise helix by hydrogen bonds which form between the amide and carboxylic groups of the amino acids in the polypeptide chain.

Question 15

How many types of amino acid are there?

Answer 15

22

Question 16

Describe the structure of a beta-pleated sheet.

Answer 16

In this type of protein at least three polypeptide chains are held together by hydrogen bonds, creating a pleated structure which although strong is more elastic than alpha helices.

Question 17

Give an example of an alpha helix.

Answer 17

Keratin which forms hair, nails, skin, fur, claws and feathers.

Question 18

Explain the term tertiary structure.

Answer 18

This refers to the complex folding of a secondary protein to create a tertiary protein with a unique 3D shape.

Question 19

What is ultimately responsible for the 3D structure of the tertiary protein?

Answer 19

The sequence of amino acids in the primary chain which in turn controls the “R” group sequence and therefore the bonds that occur and the folds that created and the final 3D shape of the molecule.

Question 20

What determines the function of a tertiary protein?

Answer 20

As most tertiary proteins are enzymes their 3D shape dictates what substrates they interact with and therefore their function.

Question 21

What are the three primary types of bonding in a tertiary protein? Strongest to weakest.

Answer 21

Disulphide bridges
Ionic bonds
Hydrogen bonds

Question 22

What other types of forces are present?

Answer 22

Van der Walls forces
Covalent bonds
And many other repulsion forces.

Question 23

What is the advantage of a tertiary protein being so compact?

Answer 23

They are able to move easily and as such can take part in chemical reactions.

Question 24

What are the two biggest groups of tertiary proteins

Answer 24

Enzymes and hormones.

Question 25

Outline Quaternary structure.

Answer 25

Tis refers to the bonding of two or more tertiary proteins together to form macro-molecules such as heamaglobin.

Question 26

Describe the structure of heamaglobin.

Answer 26

It has a mass of 68000 and consists of four tertiary molecules two alpha and two beta subunits. In the centre of each those subunits there is a a prosthetic iron group called the heam group

Question 27

Describe the structure of the heam group.

Answer 27

This consists of one iron molecule which is held in place by four nitrogen atoms.

Question 28

What are the four main protein functions.

Answer 28

1-Regulation of metabolic processes.
2-Communication
3-Structural functions
4-pH buffers.

Question 29

How do proteins help regulate metabolic processes?

Answer 29

Enzymes in the body are used to speed up chemical processes.

Question 30

How are proteins involved in communication?

Answer 30

Many hormones are proteins. These molecules act as chemical messenger molecules allowing parts of the body to communicate with each other e.g insulin (two alpha helices).

Question 31

What are the structural functions of proteins?

Answer 31

Secondary fibrous proteins are used to build structures in the body such as tendons and ligaments.

Question 32

How do enzymes act as pH buffers?

Answer 32

As amino acids and proteins are dipoles they help to maintain pH close to 7.0 by removing both excess +ve and -ve charge. This allows intracellular enzymes to work at their optimum pH.

Question 34

Give an example of a beta pleated sheet.

Answer 34

Fibroin which is found in a spiders web.