3.7 - Types of proteins (new)

Question 1

What is a globular protein?

Answer 1

Spherical Water-soluble proteins

Question 2

Give 3 characteristics of globular proteins

Answer 2

• compact
• water soluble
• roughly spherical

Question 3

Why are globular proteins water soluble?

Answer 3

TERTIARY structures are folded so that the hydrophobic R-groups are kept away from the aqueous environment -hydrophilic R-groups are on the outside

Question 4

What is an example of a globular protein and its function?

Answer 4

Insulin is a globular protein that regulates blood glucose levels. It is soluble in the bloodstream and has a precise shape to bind to specific receptors on cell membranes.

Question 4

Why is the solubility of globular proteins important?

Answer 4

The solubility allows globular proteins to perform vital functions in the body, such as chemical reactions, immunity, and muscle contraction.

Question 5

What is insulin made up of?

Answer 5

Insulin is made up of two polypeptide chains held together by disulphide bonds.

Question 6

What are globular proteins used for?

Answer 6

Catalysing reactions, Regulating processes, and immune response.

Question 7

Give examples of the processes globular proteins regulate

Answer 7

• Muscle contraction
• Immunity
• Chemical processes

Question 8

What metabolic roles do globular proteins have in the body?

Answer 8

• Enzymes - These speed up chemical reactions in the body.
• Hormones - These are chemical messengers that travel in the bloodstream.
• Antibodies - These bind to and prevent the spread of pathogens.

Question 9

Are conjugated proteins a type of globular protein?

Answer 9

Yes.

Question 10

What is amylase? What is its role? What is it made up of?

Answer 10

• Amylase is a globular protein known as an enzyme. It is responsible for the breakdown of starch into maltose.
• This enzyme is made up of a single polypeptide chain folded using both alpha-helixes and beta-pleated sheets.

Question 11

What are conjugated proteins?

Answer 11

Conjugated proteins are globular proteins that contain a non-protein component called a prosthetic group. Proteins without prosthetic groups are called simple proteins.

Question 12

What do conjugated proteins contain?

Answer 12

A non-protein prosthetic group

Question 13

What is a prosthetic group and give an example?

Answer 13

A prosthetic group is a non-protein component that binds to a protein, such as a metal ion or molecule derived from vitamins.

An example is the haem group, which contains an iron ion (Fe²⁺).

Question 14

Give an example of 2 conjugated proteins

Answer 14

• Haemoglobin
• Catalase

Question 14

What is the function of haemoglobin?

Answer 14

Carries oxygen in the blood in erythrocytes

Question 15

What polypeptide subunits is haemoglobin made up of?

Answer 15

2 alpha-helices 2 beta-pleated sheets

Question 15

How many subunits make up haemoglobin?

Answer 15

4

Question 16

What does each haem group contain?

Answer 16

Iron 2+ ion

Question 16

What does each subunit of haemoglobin contain?

Answer 16

A haem group

Question 17

How do haem groups allow erythrocytes to carry out their function?

Answer 17

Iron ions in haem groups can reversibly combine with an oxygen molecule

Question 18

How many oxygen atoms can one haemoglobin molecule carry?

Answer 18

8- remember ATOMS not MOLECULES

Question 19

How does haemoglobin transport oxygen?

Answer 19

• Haemoglobin is a quaternary protein with four polypeptide subunits (two alpha and two beta) and prosthetic haem groups.
• Each haem group can bind reversibly with an oxygen molecule, allowing haemoglobin to pick up oxygen in the lungs and release it in tissues.

Question 19

What type of protein is catalase?

Answer 19

Conjugated

Question 19

What type of prosthetic group does catalase contain?

Answer 19

Haem

Question 20

What is catalase and how does it function? What does it produce?

Answer 20

Catalase is a quaternary protein containing haem groups, which allows it to catalyse the breakdown of hydrogen peroxide, a harmful by-product of metabolism, into water and oxygen.

Question 21

How many haem groups does catalase contain?

Answer 21

4

Question 22

What is a fibrous protein?

Answer 22

Long, insoluble, structural proteins

Question 23

What are the characteristics of fibrous proteins?

Answer 23

Fibrous proteins are long, insoluble molecules with a high proportion of hydrophobic R groups. They typically have a repetitive primary structure, which leads to organised, strong, and often unstructured forms.

Question 24

Give 3 examples of fibrous proteins.

Answer 24

* Collagen * Elastin * Keratin

Question 25

Where is Keratin found?

Answer 25

In hair, skin, and nails

Question 26

Which amino acid does keratin contain in a high proportion?

Answer 26

Cysteine

Question 27

What does Cysteine contain in its R-group?

Answer 27

Sulfur

Question 28

What type of bonding occurs a lot in keratin?

Answer 28

Disulphide bonds

Question 29

How does a high proportion of disulphide affect the properties of keratin?

Answer 29

It makes it inflexible and strong

Question 29

Where is elastin found?

Answer 29

In the walls of blood vessels and alveoli of lungs

Question 30

Why is it beneficial for tissues to contain elastin?

Answer 30

It confers strength and elasticity

Question 30

What does elastin allow tissues to do?

Answer 30

Expand and return to size

Question 31

What makes up elastin?

Answer 31

Aggregates of tropoelastin

Question 32

Where is collagen found?

Answer 32

In the skin, tendons, ligaments, and nervous system

Question 33

What is the structure of collagen?

Answer 33

Collagen is made up of three polypeptide chains wound around each other in a rope-like structure. This provides strength and flexibility to the molecule.

Question 34

Why does collagen contain glycine for every 3rd amino acid?

Answer 34

Glycine is the smallest amino acid and so they can pack together more tightly

Question 35

What property does collagen have?

Answer 35

Flexibility

Question 36

Define polypeptide.

Answer 36

Chains of 3 or more amino acids

Question 37

Define protein.

Answer 37

One or more polypeptides arranged as a complex macromolecule