Globular proteins

Question 1

What are the 2 types of proteins?

Answer 1

Globular and Fibrous

Question 2

Properties of Globular proteins

Answer 2

• Spherical in shape with Hydrophobic R groups on the inside of the Protein and Hydrophilic R groups on the outside
• Hydrophilic groups on the outside means protein is soluble in water as hydrophilic R groups can interact with water
• Have VERY SPECIFIC shapes so they carry out VERY SPECIFIC functions

Question 3

Protein examples:
- Transport protein
- Hormone
- Enzyme

Answer 3

• Haemoglobin
• Insulin
• Pepsin

Question 4

Globular protein definition

Answer 4

Globular Proteins are proteins that are usually spherical in shape and are soluble in water, and usually have metabolic roles.

Question 5

Where is haemoglobin found? What is its main function?

Answer 5

in Red blood cells in the blood
Transport of oxygen from lungs to the body tissues

Question 6

How many polpeptide chains make up haemoglobin and what structure does it have?

Answer 6

4 POLYPEPTIDE CHAINS
Quaternary structure

Question 7

What are the names of chains it is made of

Answer 7

2 alpha globin chains and
2 beta globin

Question 8

Haemoglobin is a _______ protein as it has a _________ group called a ________ group attached to each polypeptide chain/

Answer 8

Conjugated
Prosthetic
Haem

Question 9

What is a prosthetic group

Answer 9

a non protein component which is bonded to polypeptides and is necessary for proteins to carry out their functions

Question 10

What does each Haem group have and what does that allow it to do

Answer 10

Each Haem group has 1 Fe 2+ ion and that allows each Haem group to hold an oxygen molecule, and overall a single Haemoglobin protein molecule carries 4 oxygen atoms.

Question 11

What secretes insulin

Answer 11

the pancreas

Question 12

What is the role of insulin

Answer 12

maintain blood glucose concentration

Question 13

Insulin is composed of ________ polypeptide chains, one which is an ________- and the other is a ______________ sheet.

Answer 13

2
alpha helix
beta pleated

Question 14

How are the 2 polypeptide chains joined in insulin

Answer 14

by disulfide links

Question 15

The specific ________ of insulin allows it to bond to certain receptors on cell membranes to be able to lower blood glucose concentration

Answer 15

shape

Question 16

Insulin is soluble in water, why?

Answer 16

Has outer hydrophilic R groups which make it soluble in water

Question 17

What is the benefit of insulin being soluble

Answer 17

dissolves in blood and easily transported throughout the body

Question 18

What does pepsin do? Is it a globular protein?

Answer 18

it catalyses breakdown of proteins and yes it is a globlular enzyme

Question 19

where is pepsin found and what is the nature of its location?

Answer 19

Stomache where there is a very acidic environment with a pH of 2

Question 20

Why do enzymes denature at low pH and how?

Answer 20

They have amino acids with Basic R groups which accept hydrogen ions, become positively charged, disrupt the bonding between the polypeptide chains in the tertiary structure and the enzyme shape changes and it denatures and can no more carry out its function.

Question 21

Pepsin is not affected by low ph and why is that?

Answer 21

• Amino acids in pepsin have very few basic R groups and therefore the tertiary structure is not affected by low pH
• Structure is kept stable by disulphide links and hydrogen bonds in the tertiary structure of pepsin