Proteins

Question 1

What are proteins made up of?

Answer 1

One or more polypeptides (one polypeptide is more than two amino acid joined together)

Question 2

Describe the general structure of amino acids.

Answer 2

variable group
amino group
carboxyl group
hydrogen

Question 3

how are polypeptides formed?

Answer 3

By condensation reactions.

A molecule of water is released and peptide bonds are formed.

Question 4

What are the four structural levels of protein?

Answer 4

Primary structure
Secondary structure
Tertiary structure
Quarternary structure

Question 5

Describe the primary structure in protein?

Answer 5

the sequence of amino acids in a polypeptide chain

Question 6

Describe the secondary structure in protein?

Answer 6

Hydrogen bonds form between amino acids in the chain. This makes it automatically coil into an alpha helix or fold into a beta pleated sheet.

Question 7

Describe the tertiary structure in protein?

Answer 7

The coiled or folded chain of amino acids is often couled and folded further. More bonds form, including hydrogen bonds, ionic bonds, disulfide bridges.
Final 3D structure for proteins made from a single polypeptide chain

Question 8

Describe the quarternary structure in protein?

Answer 8

The way in which the numerous polypeptide chains arr assembled together. Proteins final 3D structure.

Question 9

How do proteins function as enzymes?

Answer 9

Usually roughly spherical in shape due to tight folding of polypeptide chains.
Soluble and often have roles in metabolism.

Question 10

How do proteins function as antibodies?

Answer 10

Made up of two short polypeptide chains and two long pp chains bonded together.
Antibodies have variable regions, the amino acid sequences in these regions vary greatly.

Question 11

How do proteins function as transport proteins?

Answer 11

Channel proteins present in cell membrane.

Contain hydrophobic and hydrophilic amino acids.

Question 12

How do proteins function as structural proteins?

Answer 12

Physically strong
Long pp chains lying parallel to each other with cross links between them.
Eg Keratin and collagen

Question 13

How to test for proteins?

Answer 13

Biuret test.

• add few drops of sodium hydroxide solution to make sample alkaline
• add copper (ll) sulfate solution
• positive: solution turns purple
• negative: solution stays blue