6.2.4 - Antigen & Antibodies

Question 1

What Are Antigens?
(2 Points)

Answer 1

~ Are molecules such as proteins or glycoproteins, located on the surface of cells.

~ They recognise other antigens on cell surfaces as being self or non-self, triggering the relevant immune response.

Question 2

What Are The 2 Forms Antigens Can Be?

Answer 2

~ Self antigens.

~ Non-self antigens.

Question 3

What Are Self Antigens?
(2 Points)

Answer 3

~ Are antigens produced by the organisms own body cells.

~ They do not stimulate an immune response.

Question 4

What Are Non-Self Antigens?
(2 Points)

Answer 4

~ Are antigens which are not produced by the organisms own body cells.

~ They do stimulate an immune response.

Question 5

What Are Plasma Cells?

Answer 5

Clones of B cells.

Question 6

What Is The Role Of Plasma Cells?

Answer 6

They secrete loads of antibodies, specific to the antigen forming loads of antigen-antibody complexes.

Question 7

What Is Another Name For Antibodies?

Answer 7

Immunoglobulins.

Question 8

What Is The Structure Of An Antibody?
(6 Points)

Answer 8

~ Y-shaped.

~ Have 4 polypeptide chains -> 2 heavy chains attached by disulfide bridges (Bonds) to 2 light chains.

~ Each polypeptide chain has a constant region and a variable region.

~ Variable regions form antigen binding sites, shape of the variable region is complementary to a particular antigen, variable regions vary between antibodies.

~ Hinge region, allows flexibility when the antibody bins to the antigen.

~ Constant region, allow binding of receptors on the immune system cells (Phagocytes), it is the same for all antibodies.

Question 9

How Can Antibodies Disable Pathogens?
(3 Points)

Answer 9

~ Agglutinating pathogens.

~ Neutralising toxins.

~ Preventing the pathogen from binding to human cells.

Question 10

Describe How Antibodies Disable Pathogens By ‘Agglutination’
(3 Points)

Answer 10

~ Cause pathogens to clump together.

~ Reducing the chance that pathogens will spread through the body.

~ Makes it possible for phagocytes to engulf a number of pathogens at one time.

Question 11

Describe How Antibodies Disable Pathogens By ‘Neutralising Toxins’
(2 Points)

Answer 11

~ Bind to the toxin produced by pathogens, neutralising it.

~ Preventing toxins from affecting humans cell.

Question 12

Describe How Antibodies Disable Pathogens By ‘Preventing The Pathogen Binding To Human Cells’
(2 Points)

Answer 12

~ When antibodies bind to the antigens on pathogens, they block the cell surface receptors needed to bind to host cells.

~ Pathogen can no longer attach to or infect the host cells.

Question 13

What Are The 2 Forms Of Antibodies?

Answer 13

~ Membrane-bound.

~ Secreted.

Question 14

Describe Membrane-Bound Antibodies
(2 Points)

Answer 14

~ Attached to the cell membrane surface of a B cell.

~ Have an extra section of polypeptide chain within their heavy chains, forming attachments to the B cell.

Question 15

Describe Secreted Antibodies
(2 Points)

Answer 15

~ Free from any attachment.

~ Meaning they do not have the extra section of polypeptide chain within their heavy chains.

Question 16

How Can This Extra Section Of Polypeptide Chain Within The Heavy Chains Be Removed For The Secreted Antibodies?
(3 Points)

Answer 16

~ The gene which codes for the antibody heavy chains undergo ‘alternative spicing’, which removes the extra section.

~ Spicing removes the non-coding sections of mRNA called introns.

~ Alternative splicing removes coding sections called exons, these code for the extra section of the heavy chains, so they are removed.