Proteins

Question 1

Structure

Answer 1

Structure
Proteins are polymers that are made out of amino acids(monomers). Proteins are polypeptides (a long
chain of amino acids).
* Dipeptide – a chain of two amino acids.
* Tripeptide – a chain of three amino acids.
* Peptide – a chain of four to nine amino acids.
* Polypeptides – a chain of ten amino acids and above.

Question 2

Amino acids connections

Answer 2

In a polypeptide chain, amino acids are connected via peptide bonds – a result of a condensation reaction. In this reaction, the carboxyl carbon loses the 𝑂𝐻 and is connected to the 𝑁 of an adjacent amino acid. The 𝑁 loses its 𝐻 and 𝐻2𝑂 molecule leaves the structure.

***The chain of amino acids can interact with itself (intramolecular interaction), causing the protein to twist
and fold, giving it a specific structure which is extremely important.

Question 3

Level of Protein Structure:

Answer 3

1. Primary Structure – a sequence of amino acids in the chain (made by peptide bond – polar and
   non-polar bonds between the molecules).
2. Secondary Structure – beginning of a 3𝐷 formation structure: 𝛼-helixes or 𝛽-sheets (made by
   hydrogen bonds between the molecule itself).
3. Tertiary Structure – a complete 3𝐷 structure by farter folding of the 𝛼-helixes and 𝛽-sheets – was
   found by Van der Waals: hydrophobic, ionic and disulphide bridges (made by all types of bonds
   between molecules).
4. Quaternary Structure – when several polypeptide chains connect with one another (made by all
   types of bonds between molecules).

Question 4

Example of Proteins in different level structures:

Answer 4

**Hemoglobin consists of 4 polypeptide chains and therefore has a Quaternary Structure. Its 
function is to transfer and carry oxygen in the blood. 

**Myoglobin has only one chain and
therefore has only the Tertiary Structure. Its function is to bind oxygen in the muscles.

Question 5

Protein function:

Answer 5

**Enzyme type–> Breaks or builds other molecules
(Amylase – breaks down starch)

**Protection type–> Fights pathogens and toxins
(Antibodies)

**Hormone type–> Regulate processes in the body
(Insulin – decrease the amount of glucose in the body)

**Transport type–> Transfer materials in the body (Haemoglobin – transfers air through the blood)

**Structure type–> Provides shape and strength
(Keratin – shape of hair)

**Contractile type–> Allows the movement of the body
(Myosin)

Question 6

Types of amino acids:

Answer 6

there are 20 amino acids in nature which can be divided into different classes:

1. Essential (have to be obtained through diet) –methionine, tryptophan, phenylalanine.
2. Non-essential – alanine, glutamic acid, aspartic acid.
3. Polar.
4. Non-polar.
5. Positive/negative.
6. Aromatic.

**Amino acids are either aliphatic or aromatic.

Question 7

Phenylketonuria (𝑃𝐾𝑈)

Answer 7

A case when the body lucks phenylketonuria hydroxylase, therefore cannot beak down phenylalanine. It is very dangerous for the nervous system. They have lots of phenylalanine in the blood that goes out in the urine. It causes the urine to look black due to phenylalanine reaction with oxygen.