unit 2C

Acellular

Not made of cells

Genetic material in a virus

The nucleic acid found at the core of the virus, which carries the instructions for making new virus particles

Capsid

The outer protein coat that surrounds and protects the genetic material

Attachment protein

The surface proteins on the outside of the virus that allow it to attach o a host cell

HIV

Human immunodeficiency virus, a spherical virus made of a core, a capsid and an envelope with attachment proteins

Genetic material (RNA)

The molecule carrying HIV’s genes, in HIV this is RNA not DNA

Reverse transcriptase

An enzyme found in the core that the virus needs for replication

Envelope

The outmost layer, made from membrane taken from a previous host cells cell surface membrane

Uncoats

The process where the capsid breaks open and releases the viral RNA into the cytoplasm

Complementary strand

A new strand of DNA whose bases pair with the bases on the RNA template

Bud

The way a newly assembled virus pushes out through the host cell membrane to leave the cell

AIDS

Acquired immune deficiency syndrome, when helper T-cell numbers reach a critically low level

Reverse-transcriptase inhibitors

Drugs that block reverse transcriptase, stopping HIV from replicating without interfering with the host cell’s own processes

1998 MMR study

A study published that suggested there may be a link between the MMR vaccine and autism

Sample size

The number of participants in a study

Bias

The tendency for a study to be inclined towards or against a certain group, skewing the results

Yokohama study

A much larger, more controlled study carried out in Japan that disproved the theory that the MMR vaccine causes autism

Monoclonal

Many copies from one original clone

Monoclonal antibodies

Antibodies produced from a single group of genetically identical plasma cells, so they are all identical in structure and bind to the same target

Plasma cells

The B-cell derived cells that produce and release antibodies

Antigen

A molecule, often on a cell surface, that a specific antibody binds to

Binding site

The region of an antibody that attaches to an antigen

Tertiary structure

The specific three-dimensional folded shape of the binding site, which determines what it can bind

Complementary shape

An antigen shape that fits precisely into a particular binding site

Surface antigens

Molecules found on the surface of cells, different cells carry different antigens

Tumour markers

Specific antigens found on cancer cells but not on normal body cells

Therapeutic drug

A drug used to treat a disease

Anti-cancer drug

A therapeutic drug that kills or slows the growth of cancer cells

Application area of a pregnancy test

The region where the urine sample is applied. It contains antibodies specific to hCG, each bound to a coloured bead

Antibody-antigen compels (pregnancy test)

The structure formed when an antibody binds to its specific antigen. Here, hCG acts as the antigen and binds to the anti-hCG antibody

Test strip of a pregnancy test

The section further up the stick where a coloured line either appears or does not, giving the result

Immobilised antibody

An antibody fixed firmly in place on the test strip so it cannot move as the liquid flows past

ELISA

Enzyme-linked immunosorbent assay, that tests for a particular molecule in a sample

Attenuated

A weakened version of a pathogen

Vaccine

A form of antibodies usually injected that triggers an immune response and the production of memory cells

Herd immunity

The indirect protection of the unvaccinated from the majority of the population being vaccinated

Antigenic variation

When a pathogen changes the antigens on its surface. These different antigens are produced because of changes in the pathogens genes

Natural active immunity

Happens when you catch a disease. These different antigens pathogen gets into the body, and makes antibodies against it, becoming immune from the infection itself

Artificial active immunity

Happens when a person receives a vaccination containing a harmless dose of an antigen. This sis enough to stimulate their immune system, which responds by making its own antibodies

Passive immunity

When a person is given antibodies that were made by a different organism, rather than themselves

Natural passive immunity

Passive immunity that happens without any medical intervention. A baby receives antibodies from its mother, that protect the baby while its immune system is still developing

Artificial passive immunity

Passive immunity that happens when antibodies are deliberately injected into someone, that were collected from someone else

Antigen

A molecule, usually a protein, found on the surface of a cell that the immune system can identify and respond to

Foreign antigen

An antigen that is not part of your own body, so it is recognised as coming from outside and can trigger an immune response

Phagocyte

A white blood cell such as a macrophage that engulfs and destroys pathogens by phagocytosis

Phagocytosis

The process by which a phagocyte engulfs the pathogen, encloses it and breaks it down

Antigen-presenting cell

A cell that displays a pathogen’s antigens on it’s own surface so that the other immune cells can be activates

Humoral response

The part of the immune response involving B-cells, their selection by a complementary antigen (clonal selection) and the production of monoclonal antibodies by plasma cells

Antibody

A protein made of chains of amino acids that binds to a specific antigen

Variable region

The tips of the antibody, where the antigen binding sites are found. These regions have a unique tertiary structure, so their shape is complementary to one specific antigen and nothing else

Constant region

The rest of the antibody, which is the same in every antibody regardless of which antigen it targets