Proteins

Question 1

What do only some proteins contains (two things)

Answer 1

Sulfur and phosphorus

Question 2

What are proteins (simple)

Answer 2

Polymers made of monomers called amino acids.

Question 3

What are the chains of amino acids called?

Answer 3

Polypeptides

Question 4

How many different amino acids are used to make up proteins and therefore how many different proteins are there?

Answer 4

About 20 amino acids are used to make up proteins.

There are thousands of different proteins.

Question 5

What is the shape of proteins determined by?

Answer 5

The specific sequence of amino acids in the chain.

Question 6

All amino acids have the same basic structure.

What is attached to a central carbon atom? (4 things)

Also draw a generalised structure of an amino acid if possible.

Answer 6

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

Question 7

Is the amino group basic or acidic?

Answer 7

Basic

Question 8

What happens at pH7 of an amino group?

Answer 8

The cell gains an H and becomes positively charged.

The carboxyl group is acidic and at pH7, it loses an H, becoming negatively charged.

So at pH7, an amino acid has both positive and a negative charge. Such an ion is a ‘zwitterion’

Question 9

Describe the formation of a peptide bond

Draw out an example if possible.

Answer 9

Proteins are linear sequences of amino acids.

The amino group of one amino acid reacts with the carboxyl group of another with the elimination of water.

The bond that is formed from this condensation reaction is a peptide bond.

The resulting compound is a dipeptide.

Question 10

How do proteins differ from carbohydrates and lipids?

Answer 10

As well as containing hydrogen, carbon and oxygen, they also always contain nitrogen.