Chapter 3- Proteins

Question 1

What type of molecule is protein?

Answer 1

A polymer

Question 2

What are the monomers for proteins?

Answer 2

Amino acids

Question 3

What are Polypeptides?

Answer 3

When more than two amino acids are bonded together.

Question 4

What is the general structure of an amino acid?

Answer 4

A carboxylic group (COOH) and an amino group (NH2) attached to a carbon. They all vary by a R group.

Question 5

What is the smallest amino acid?

Answer 5

Glycine is the smallest as the R group is just a hydrogen.

Question 6

What are the chemical elements in amino acids?

Answer 6

Carbon
Hydrogen
Oxygen
Nitrogen
Some also contain sulfur

Question 7

What bonds exist between amino acids ?

Answer 7

Peptide bonds

Question 8

How do amino acids react to form a dipeptide?

Answer 8

A OH from the carboxylic group on one amino acid reacts with a H from the amine group on the neighbouring amino acid. This forms a peptide bond and a molecule of water.

Question 9

What type of reaction occurs when you break a peptide bond?

Answer 9

Hydrolysis

Question 10

What is the primary structure of proteins?

Answer 10

This is the sequence of amino acids in the polypeptide chain. One change in the sequence can change the structure of the entire protein.

Question 11

What is the secondary structure of proteins?

Answer 11

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

Question 12

What is the tertiary structure?

Answer 12

The coiled or folded secondary structure is often coiled ans folded further. More bonds form between different parts of the polypeptide chain. For proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure.

Question 13

What is quartenary structure of proteins?

Answer 13

Some proteins are made form multiple polypeptide chains held together by bonds. The quarternary structure is how these polypeptide chains are assembled together, for example haemoglobin.

Question 14

What bonds exist in the primary structure?

Answer 14

Peptide bonds

Question 15

What bonds exist in the secondary structure?

Answer 15

Hydrogen bonds

Question 16

What bonds exist in the tertiary structure?

Answer 16

1) ionic - attractions between negatively and positively charged R groups

2) disulphide - two molecules of amino acid cyctseine come close together. The Sulfur atoms in the amino acid bond together.

3) Hydrophobic/hydrophilic interactions - when hydrophobic R groups are close together they tend to clump together. This means hydrophilic R groups are more likely to be pushed outside.

4) hydrogen bonds- weak bonds between positively charged hydrogen atoms in one amino acid, and negatively charged atoms on another amino acid.

Question 17

What bonds exist in the Quarternary structure?

Answer 17

This is determined by the tertiary structure and can be affected by all bonds

Question 18

What are globular proteins ?

Answer 18

In a globular protein, the hydrophilic R groups on the amino acids tend to be pushed to the outside of the molecule. This is cause by hydrophilic, hydrophobic interactions in the tertiary structure.

Question 19

What are the properties of globular proteins?

Answer 19

They are roughly spherical
They are compact
They are solube so easily transported in fluids

Question 20

What are some examples of globular proteins?

Answer 20

Haemoglobin
Insulin
Amylase

Question 21

What is Haemoglobin?

Answer 21

Haemoglobin is a globular Protein that carries oxygen around the body in red blood cells. It’s known as a conjugated protein because it has a non protein group attached, called a prosthetic group. Each of the four polypeptide groups have a haem group attached. Haem contains iron which oxygen binds to.

Question 22

What is insulin?

Answer 22

It is a hormone secreted by the pancreas. It helps to regulate the blood glucose level. It’s solubility is important. It means it can be transported in the blood to the tissues where it acts. An insulin molecule consisting of two polypeptide chains, which are held together by disulphide bonds.

Question 23

What is amylase?

Answer 23

It is an enzyme that catalysed the breakdown of starch in the digestive system. It is made up of a single chain of amino acids. It’s secondary structure contains both alpha helix and beta pleated sheets. Most enzymes are globular proteins.

Question 24

What are fibrous proteins?

Answer 24

They are insoluble and strong. They’re structural proteins and fairly unreactive and usually composed of long strands.

Question 25

What are three fibrous proteins?

Answer 25

Keratin
Collagen
Elastin

Question 26

What is collagen?

Answer 26

It is found in animal connective tissues, such as bone, skin and muscle. It is very strong. Minerals bind to the protein to increase its rigidity. Eg in bone

Question 27

What is keratin?

Answer 27

It is found in many of the external structures of animals such as hair skin and nails. It can be either flexible as in skin or hard and tough as in nails.

Question 28

What is elastin?

Answer 28

It is found in elastic connective tissue such as skin, large blood vessels and some ligaments. It is elastic, so it allows tissues to return to their original shape after they have been stretched eg when blood vessels dilate and contract.