Biomolecules- Proteins

Question 1

What elements do proteins contain?

Answer 1

They contain carbon, hydrogen, oxygen, nitrogen with some containing sulphur and phosphorus.

Question 2

What are proteins?

Answer 2

They are polymers made from monomers called amino acids.

Question 3

What are the chains of amino acids called?

Answer 3

Polypeptides

Question 4

How many amino acids are there?

Answer 4

There are 20 naturally occurring amino acids. There are 8 which are known as ‘essential’ these can’t be synthesised by the body so have to be obtained by the diet whereas the others which are known as ‘non-essential’ can be synthesised by the body.

Question 5

What is a protein shape determined by?

Answer 5

This specific sequence of amino acids in the chain.

Question 6

What is a basic structure of amino acids. Attached to a central atom are:

Answer 6

An amino group - NH2 at one end of the molecule is called the N terminal.
A carboxyl group -COOH at the other end called the C terminal.
A hydrogen atom
The R group which is different for each amino acid

Question 7

Is an amino acid polar at PH7?

Answer 7

A pH seven the cell gains a hydrogen becoming positively charged the carboxyl group is acidic soil pH and ion is lost becoming negatively charged so an amino acid is polar at pH7

Question 8

How is a peptide bond formed?

Answer 8

Hate when the amino group of one amino acid reacts with a carboxyl group of another one which eliminates water the peptide bond is formed in a condensation reaction which results in a dipeptide.

Question 9

What is the primary structure of a protein?

Answer 9

It is the order of amino acid in a polypeptide chain. They can be joined in any order, number or combination with the primary structure being determined by the base sequence on one strand of DNA.

Question 10

What is the secondary structure of a protein?

Answer 10

This is the shape of the polypeptide chain which formed as a result of hydrogen bonding between the O and H and the peptide bonds along the chain this causes a change of twist into a 3-D shape as well as the folding of the polypeptide chain.

Question 11

What are the two examples of a secondary structure.

Answer 11

Alpha helix and beta pleated sheet.

Question 12

What is the tertiary structure of a protein?

Answer 12

It is the continuous folding of the protein giving it some more complex and compact 3-D structure.

Question 13

What are the bonds that can be found within the tertiary structure?

Answer 13

Hydrogen bonds, ionic bond, disulphide bonds, hydrophobic interactions and hydrophilic interactions.

Question 14

What is the Quaternary structure of a protein?

Answer 14

They can be made up of a combination of polypeptide chains. They can combine with a different polypeptide chain, they can also be associated with non-protein groups ‘prosthetic groups’ which form large complex molecules e.g. haemoglobin

Question 15

What is the structure of fibrous proteins?

Answer 15

They have long, thin molecules with the polypeptides in parallel chains or sheets with several crosslinks forming fibres. They are long and tough.

Question 16

What function do fibrous proteins have?

Answer 16

As they are insoluble in water they have a structural function like bone. They are also found in keratin.

Question 17

What is an example of a fibrous protein?

Answer 17

Collagen provides strength and toughness needed in tendons. A single fibre is sometimes called tropocollagen which consists of three identical polypeptide chains twisted tightly around each other these three chains are linked by hydrogen bonds making the molecule very stable.

Question 18

What is the structure of globular proteins?

Answer 18

They are compact and folded into spherical molecules making them soluble in water.

Question 19

What different functions do you globular proteins have?

Answer 19

Enzymes, antibodies, plasma proteins and hormones

Question 20

What is an example of a globular protein?

Answer 20

Haemoglobin consists of four folded polypeptide chains at the centre of each is an iron containing group called haem.

Question 21

What causes denaturation of proteins?

Answer 21

It is caused by shifts in pH, temperature or if exposed to detergents or salts.

Question 22

What does heating are protein do to its structure?

Answer 22

It causes the protein to the denature as an increase in temperature increases the kinetic energy in the molecules. The atoms start to vibrate and some bonds holding the tertiary structure will start to break as the bonds are weak (hydrogen). This can lead to the whole structure unravelling causing the protein to permanently denature.