Session 4.1e - Pre-Reading [What is a Protein]

Question 1

What are the roles of proteins in biology?

Answer 1

Proteins play countless roles throughout the biological world - from catalysing chemical reactions to building the structures of all living things e.g. collagen, insulin and antibodies are all proteins.

Question 2

What are the building blocks of proteins?

Answer 2

Despite this wide range of functions, all proteins are made out of the same 20 building blocks, called amino acids.

Question 3

All proteins are made out of the same 20 building blocks, despite proteins having a wide range of functions. How does this occur?

Answer 3

The way these 20 amino acids are arranged dictates the folding of the protein into its unique final shape and its function.

Question 4

What atoms are amino acids made up of?

Answer 4

Carbon
Oxygen
Nitrogen
Hydrogen
Sulfur

Question 5

What is every amino acid contain?

Answer 5

• Amino group
• Carboxyl group
• Side chain

attached to a central carbon atom.

Question 6

Which part of the amino acid is unique?

Answer 6

The side chain

Question 7

What does the side chain of amino acids do?

Answer 7

Because it is the only part of the amino acid that is unique, it determines each amino acid’s chemical properties.

Question 8

What are the properties of hydrophobic amino acids?

Answer 8

Hydrophobic amino acids, such as leucine and isoleucine, have carbon-rich side chains, which don’t interact well with water.

Question 9

What are the properties of hydrophilic amino acids?

Answer 9

Hydrophilic amino acids, such as serine, or threonine, interact well with water.

Question 10

What do charged amino acids interact with?

Answer 10

Charged amino acids, like glutamic acid (acidic) or arginine (basic) interact with oppositely charged amino acids or with water.

Question 11

What is the primary structure of a protein?

Answer 11

The primary structure of the protein is the linear sequence of amino acids as encoded by DNA.

Question 12

How are amino acids joined in the primary structure of a protein?

Answer 12

The amino acids are joined by peptide bonds, which link an amino group and a carboxyl group.

Question 13

What is released each time a peptide bond is formed?

Answer 13

A water molecule is released each time a bond is formed.

Question 14

What gives proteins their distinct shapes and chemical characteristics?

Answer 14

Specific amino acid sequences give proteins their distinct shapes and chemical characteristics

Question 15

What do primary structures of a protein then go on to form?

Answer 15

These protein chains often folds into two types of secondary structures stabilised by hydrogen bonds.

Question 16

What are the properties of the alpha helix secondary structure?

Answer 16

A protein chain can fold into a rigid alpha helix, forming regular patterns of hydrogen bonds between the backbone atoms of nearby amino acids.

Question 17

What are the properties of the beta sheet secondary structure?

Answer 17

Backbone atoms of the chain can interact side-by-side to form beta sheets.

Question 18

Describe a common tertiary structure of a protein.

Answer 18

Many proteins fold into a compact globular shape, with hydrophobic side chains sheltered inside away from the surrounding water

Question 19

Give an example of a protein that relies of the globular tertiary structure.

Answer 19

The functions of many proteins rely on this folded structure: for instance, haemoglobin forms a pocket to hold haem.

Question 20

What is haem?

Answer 20

A small molecule with an iron atom in the centre that binds oxygen.

Question 21

What is the quaternary structure of a protein?

Answer 21

Two or more polypeptide chains can come together to form one functional molecule with several subunits.

Question 22

Give an example of a protein whose function relies on the subunit component of the quaternary structure.

Answer 22

The four subunits of haemoglobin cooperate so that the complex can pick up more oxygen in the lungs and release it in the body.

Question 23

Why is molecular shape important to function?

Answer 23

Many proteins rely on the ability to recognise the shape of specific molecules in order to function correctly.

Question 24

Give an example of how molecular shape is used in defence?

Answer 24

The flexible arms of antibodies protect the body from disease by recognising and binding to foreign molecules and thus preventing the viral RNA or DNA to enter the cell.

Question 25

Give an example of how molecular shape is used in structure?

Answer 25

Collagen forms a strong triple helix that is used through the body for structural support.

Question 26

Give an example of how molecular shape is used in transport?

Answer 26

The calcium pump moves ions (calcium ions) across cell membranes allowing the synchronised contraction of muscle cells.

Question 27

Give an example of how molecular shape is used in communication?

Answer 27

The hormone insulin is a small, stable protein that can easily maintain its shape while travelling through the blood to regulate blood sugar levels.

Question 28

Give an example of how molecular shape is used in enzymes?

Answer 28

Alpha amylase is an enzyme with a catalytic site that begins the breakdown of carbohydrates in our saliva.

Question 29

Give an example of how molecular shape is used in storage?

Answer 29

Ferritin forms a hollow shell that stores iron from our food.

Question 30

What are the standard amino acids?

Answer 30

Glycine (G), Alanine (A), Serine (S), Threonine (T), Cysteine (C), Valine (V), Leucine (L), Isoleucine (I), Methionine (M), Proline (P), Phenylalanine (F), Tyrosine (Y), Tryptophan (W), Aspartic acid (D), Glutamic acid (E), Asparagine (N), Glutamine (Q), Histidine (H), Lysine (K), Arginine (R).

Question 31

How is the primary structure of a protein formed?

Answer 31

The amino group and carboxyl group of adjacent amino acids are joined by a polypeptide bond, releasing water. This forms the protein backbone.

Question 32

What are the two types of secondary structures?

Answer 32

Alpha helix

Beta sheet

Question 33

How are secondary structures stabilised?

Answer 33

By hydrogen bonds

Question 34

Which secondary structure involves regular hydrogen bonds between the backbone atoms of nearby amino acids?

Answer 34

Alpha helix

Question 35

Which secondary structure involves regular hydrogen bonds between the backbone atoms of amino acids side-by-side?

Answer 35

Beta sheets

Question 36

The compact globular shape of a protein is an example of which structure in proteins?

Answer 36

Tertiary structure

Question 37

Where do hydrophobic side chains of amino acids lie?

Answer 37

Sheltered inside, away from surrounding water

Question 38

Where does haemoglobin interact with oxygen?

Answer 38

It picks up oxygen in the lungs via capillaries and releases it into the body.

Question 39

Where are haemoglobin molecules found?

Answer 39

In red blood cells

Question 40

How many haemoglobin molecules in each red blood cell?

Answer 40

There are about 280 million haemoglobin molecules in each red blood cell

Question 41

What are the functions of proteins?

Answer 41

Defence
Structure
Transport
Communication
Enzymes
Storage

Question 42

What does insulin bind to?

Answer 42

Insulin receptors