Immune system

Question 1

Active immunity

Answer 1

Your body protects itself against microorganisms by producing antibodies

Question 2

Passive immunity

Answer 2

The body doesn’t produce the antibodies itself but is given. For example through vaccine or the placenta from a mother to a baby.

Question 3

Pathogen

Answer 3

A microorganism that causes disease

Question 4

Bacteria

Answer 4

A small microorganism that is a prokaryotic cell. Singled celled organism.

Question 5

Eliza method

Answer 5

Place the antigens into the well and they should bind to the plastic coating. Then add the primary antibody. Then wash away any unbound antibodies. Then add the secondary antibody which should have a colorimetric tag.. Then wash away any unbound antibodies. Then add the substrates. If the test is positive a colour change should take place. The stronger the colour change the higher the concentration of antibodies which can be identified with a spectrometer.

Question 6

Elisa definition

Answer 6

Stands for Enzyme linked immunosorbent assay. Uses enzymes and colour change to identify a substance, metabolite (disease) or surface marker. It uses antibodies to identity and quantitate protein.

Question 7

Radioimmunoassay RIA method

Answer 7

A quantity of antigen is made radioactive by labelling it with gamma radioactive isotopes of iodine attached to tyrosine (amino acid). The radiolabelled antigen is then mixed with a known quantity of antibody complementary for that antigen. The two chemically bind together. A sample containing a unknown quantity of that antigen is added. This causes the unlabelled antigen from the serum to compete with the radiolabelled antigen for the antibody binding site. As the concentration of unlabelled antigens increase more complexes form, displacing the radiolabelled variable. The bound antigens are then separated from the unbound antigens and the radioactivity of the free antigen remaining in the supernatant is measured.

Question 8

Radioimmunoassay RIA definition

Answer 8

Uses antibodies to detect and quantitate the amount of antigen present in a sample. The test is highly sensitive detecting low quantities. the radioactive antigens (known as tracers) compete with non-radioactive antigens for a fixed number of antibodies or receptor binding sites so this test is highly specific.

Question 9

Worms

Answer 9

Flat, ribbon like organisms that can live inside the gut if a newly hatched worm or egg is ingested.

Question 10

Prions

Answer 10

Misfolded proteins which cause a change in shape. One miss fold can lead to other proteins changing shape too. This can transmit between people (communicable) The change to the primary structure of proteins can cause cells not to function.

Question 11

Protozoa

Answer 11

Similar to bacteria but much bigger and have a nucleus. A similar cell organism. They are motile and feed on organic matter.

Question 12

Virus

Answer 12

Smallest of organisms containing just a strand of RNA or DNA and a protein coat. It is a parasite so only causes harm and reproduce once inside a host cell.

Question 13

Antigens

Answer 13

Cause disease and is identified as foreign causing an immune response. Made up of protein and glycoprotein that are present on the cell surface.

Question 14

Cell mediated response

Answer 14

Made up of T lymphocytes. T helper cells identify a foreign pathogen stimulating phagocytes, B-lymphocytes and cytotoxic T cells. Cytotoxic T cells (effector cells) produce toxins which lysis the pathogen. Effected cells display fragments of the antigens on the cell surface to signal that they need to be lysis.

Question 15

Humoral response

Answer 15

B Lymphocytes are activated by T helper cells when a foreign pathogens are identified. This takes place in the bone marrow. Plasma cells identify the correct antibody for the antigen to form the specific complex at the binding site and replicate flooding the bloodstream with the antibody. The antibodies then clump to the antigen. This deactivates the antigen and signals with cytokines to phagocytes (increasing phagocytosis rate) and cytotoxic t cells that it needs to be lysis. Some plasma cells remain in the blood even after the pathogen has gone. These become memory cells so that is the pathogen is encountered again the correct antibody can be replicated much quicker preventing you from getting ill.

Question 16

Antibody

Answer 16

Made up of a quaternary protein structure and contains disulphide bonds. It is highly specific to the antigen. Clumps to antigens to stop the antigens binding to a host cell and deactivates the antigen. A few remain in the blood as memory cells after.

Question 17

Spleen

Answer 17

Filters the blood. Contains an emergency set of blood and leukocytes. Removes old and damaged erythrocytes.

Question 18

Blood clot

Answer 18

Blood pores out to flush out pathogens. Phagocytes and leukocytes leave the capillary because it becomes more leaky and permeable. The leaking tissue fluid supplies the area with more nutrients but the swelling causes pain my pressure on the nerve pressure. Thrombocytes accumulate in the area and produce a fibrin (protein) net. Erythrocytes then get trapped in the net leading to a scab forming while a new layer of skin is made.

Question 19

Phagocytosis

Answer 19

A pathogen is identified by chemoattractant which attracts a phagocyte to the pathogen. The phagocyte moves along the concentration gradient and then binds to the antigens presented on the cell surface. Then it engulfs the pathogen forming a phagosome. Lysozymes then fuse to the phagosome and help to lysis the pathogen into useful molecules including amino acids and fats which are then absorbed by phagocyte.

Question 20

Gram staining theory

Answer 20

Gram stain penetrates the bacteria cells wall affecting the peptidoglycan so has the most effect on gram positive turning it purple.

Question 21

Counter stain

Answer 21

Had no effect on gram positive because it stains anything that hasn’t been stained. It stains gram negative pink.

Question 22

Decolourisation

Answer 22

Removes stain that hasn’t been able to penetrate the peptidoglycan so is not bound. This causes gram negative to have any stain removed because it hasn’t bound or penetrated the membrane.

Question 23

Gram positive bacteria

Answer 23

Has a single membrane and thick layer of peptidoglycan. Turns purple by gram staining.

Question 24

Gram negative

Answer 24

Has a double membrane enclosing the thin layer of peptidoglycan. Turns pink by gram staining.

Question 25

Gram staining method

Answer 25

First fix the bacteria to the slide by heating the slide. This fixation process is so that dye doesn’t wash away any bacteria. Add crystal violet leading to it turning purple. This tries to bind and penetrate the peptidoglycan. Add iodine solution that acts as a mordant leading to Crystal violet trying to bind with peptidoglycan more. Decolourise the bacteria with ethanol. This washes away any unbound crystal violet. Add counter stain (safranin) which stains anything that hasn’t been stained already turning it pink.