Globular Proteins

Question 1

What does the overall 3D structure of the protein determine?

Answer 1

Which type of protein is formed

Question 2

What are the 2 types of proteins that can be formed?

Answer 2

Fibrous

Globular

Question 3

What are the important properties of globular proteins?

3

Answer 3

Roughly spherical in shape

Soluble in water

Very specific shapes

Question 4

What do the roughly spherical shape of the globular have on the inside and outside?

Answer 4

Hydrophobic R groups on the inside

Hydrophilic R groups on the outside

Question 5

What do the very specific shapes allow?

Answer 5

It allows them to carry out very specific functions

Question 6

What are 3 roles of globular proteins?

Answer 6

Transport proteins

Hormones

Enzymes

Question 7

What is an example of a transport protein?

Answer 7

Haemoglobin

Question 8

What is an example of a hormone?

Answer 8

Insulin

Question 9

What is an example of an enzyme?

Answer 9

Pepsin

Question 10

What is the definition of a globular protein?

Answer 10

A protein with a spherical shape that is soluble in water. Globular proteins typically have metabolic roles

Question 11

Haemoglobin

Where is haemoglobin found?

Answer 11

In red blood cells

Question 12

Haemoglobin

What does haemoglobin have an important role in?

Answer 12

The transportation of oxygen from the lungs to the body tissues

Question 13

Haemoglobin

What is haemoglobin made up of?

What does this mean?

Answer 13

4 polypeptide chains meaning that the protein has a quaternary structure

Question 14

Haemoglobin

What other protein is haemoglobin also?

Why?

Answer 14

A conjugated protein

As it has a prosthetic group attached to each polypeptide chain

Question 15

Haemoglobin

What is the definition of a prosthetic group?

Answer 15

A non-protein component that is necessary for the protein to carry out its function

Question 16

Haemoglobin

What are the 4 prosthetic groups in haemoglobin called?

What do they contain?

Answer 16

Haem groups

They contain an iron ion (Fe2-)

Question 17

Haemoglobin

How many oxygen molecules bind to each haem group?

What does this allow?

Answer 17

One oxygen molecule

Allowing each haemoglobin to transport 4 oxygen molecules

Question 18

Insulin

What is insulin secreted by?

Answer 18

The pancreas

Question 19

Insulin

What is the important role of insulin?

Answer 19

Maintaining blood glucose concentration

Question 20

Insulin

What is insulin composed of?

(2)

Answer 20

2 polypeptide chains

An a-helix

A ß-pleated sheet

Question 21

Insulin

How are the 2 polypeptide chains joined together?

Answer 21

By disulphide links

Question 22

Insulin

What does the shape of insulin allow?

Answer 22

It to specifically bind to receptors on cell membranes to help lower blood glucose concentrations

Question 23

Insulin

What makes insulin soluble in water?

Answer 23

It has hydrophilic R groups on the outside

Question 24

Insulin

What does insulin being soluble allow?

Answer 24

It allows insulin to dissolve in the blood and be easily transported around the body

Question 25

Pepsin What does pepsin do?

Answer 25

Catalysts the digestion of proteins

Question 26

Pepsin Where is pepsin found?

Answer 26

In the stomach

Question 27

Pepsin What kind of environment is the stomach?

Answer 27

An acidic environment One with a low pH

Question 28

Pepsin What kind of pH do many enzymes become denatured at? (high/low)

Answer 28

At a low pH

Question 29

Pepsin Why do many enzymes become denatured at a low pH?

Answer 29

Because they contain amino acids with basic R groups

Question 30

Pepsin Why do enzymes that contain amino acids with basic R groups denature?

Answer 30

Basic R groups accept hydrogen ions (H+) and become positively charged The positively charged R groups can affect the ionic bonds + hydrogen bonds in the protein - this denatures the enzyme and therefore alters its function

Question 31

Pepsin What prevents the tertiary structure of the pepsin being affected by low pH?

Answer 31

The primary structure of pepsin has very few basic R groups

Question 32

Pepsin How is the tertiary structure of pepsin kept stable? (2)

Answer 32

By hydrogen bonds and disulphide links