all12- Flashcards
What are the three ways a pathogen can damage hosts cells?
1) rupturing them to release nutrients inside them
2) breaking down nutrients inside the cell for their own use. This starves and eventually kills the cell.
3) replicating inside the cells and bursting them when they’re released
What are the two ways pathogens cause disease?
1) production of toxins
2) cell damage
What are the lifestyle factors that can affect your chances of getting cancer?
1) smoking
2) excessive exposure to sunlight
3) excessive alcohol intake
What are the three surfaces of contact- where pathogens enter our body? and how do they get in?
1) gas-exchange system = if you breathe in air that contains pathogens, most of them will be trapped in mucus lining the lung epithelium. Some pathogens are able to reach the alveoli where they can invade cells and cause damage.
2) Skin = if you damage your skin, pathogens on the surface can enter your bloodstream. blood clots prevent pathogens from entering.
3) Digestive system = if you eat or drink food that contains pathogens. Some will survive from the acidic conditions of the stomach, and invade cells of the gut wall and cause disease.
Explain the process of phagocytosis.
1) A phagocyte recognises the antigens on a pathogene
2) The cytoplasm of the phagocyte moves round the pathogen, engulfing it.
3) The pathogen is now contained in a vacuole or a vesicle in the cytoplasm of the phagocyte.
4) A lysosome fuses with the phagocytic vacuole and the lytic enzymes break down with the pathogen
5) The phagocyte presents the pathogens antigens, it sticks the antigens on its surface to activate other immune system cells.
What is the cellular and humoral response?
Cellular = The T-cells and other immune system cells that they interact with e.g phagocytes , form the cellular response
Humoral - B cells and the production of antibodies form the humoral response.
Explain what is meant by a primary response.
The primary response is slow because there aren’t many B-cells that can make the antibody needed to bind to it.
The infected person will show symptoms of the disease while the body produces enough of the right antibody to overcome the infection.
T-cells and B-cells produce memory cells. Memory T-cells remember the specific antigen and will recognise it second time round. Memory B-cells record the specific antibodies needed to bind the antigen.
The body is now immune.
Explain what is meant by the secondary response.
If the same pathogen enters the body again, the immune system will produce a quicker, stronger immune response.
Memory B-cells divide into plasma cells that produce the right antibody to the antigen. Memory T-cells divide into the correct type of T cells to kill the cell carrying the antigen.
The secondary response often gets rid of the pathogen before you begin to show any symptoms.
Explain how monoclonal antibodies target cancer
1) Cancer cells have antigens called tumour markers that are not found on body cells.
2) Monoclonal antibodies can be made that will bind to the tumour markers.
3) You can also attach anti-cancer drugs to the antibodies
4) Antibodies come into contact with the cancer cells and bind to the tumour markers
5) This means the drug will acuumulate in the body where there are cancer cells.
6) side effects of an antibody based drug are lower than other drugs because they accumulate near specific cells
how do monoclonal cells work in pregnancy tests?
1) The application area contains antibodies for hCG bound to a coloured bead
2) when urine is applied to the application area any hCG will bind to the antibody on the beads, forming an antigen-antibody complex.
3) the urine moves up the stick to the test strip, carrying any beads with it
4) the test strip contains antibodies to hCG that are stuck in place.
5) if there is hCG present the test strip turns blue because the immobilised antibody binds to any hCG. if no hCG is present, the beads will pass through the test area without binding to anything so it won’t go blue.
How do vaccines protect individuals and populations against disease?
Vaccines contain antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease. This means you become immune without getting the symptoms.
Vaccines protect individuals because they reduce the occurance of the disease. Those not vaccinated are less likely to catch the diease because there are fewer people to catch it from - this is called herd immunity.
Explain the primary, secondary, tertiary and quaternary structure of a protein.
Primary structure = A sequence of amino acids in the polypeptide chain
Secondary structure = Hydrogen bonds form between the amino acids. This makes it coil or fold.
Tertiary structure = The coiled or folded chain is coiled or folded furthur. More bonds form between different parts of the polypeptide chain. For proteins made from a single polypeptide chain, It forms their final 3D structure
Quaternary structure = the way the polypeptide chains are assembled together. Several different polypeptide chains held together by bonds. For proteins made from more than one polypeptide chain this is their final 3D structure
Describe the test for proteins.
1) add sodium hydroxide solution
2) add a few drops of copper (II) sulfate solution
3) if theres protein = it will go purple
if theres no protein = it will stay blue
Describe three functions of proteins.
three from:
Enzymes = break down large food molecules or help to synthesise large molecules
Antibodies = involved in the immune response, they have variable regions.
Transport proteins = transport ions and molecules across membranes
Structural proteins = physically strong. They consist of long polypeptide chains lying parallel to each other with cross links between them.
Describe the cause and symptoms of lactose intolerance
When you don’t have enough of the enzyme lactase, you can’t break down lactose in milk properly.
undigested lactose is fermented by bacteria and can cause a whole host of intestinal complaints such as stomach cramps, excessive flatulence and diarrhoea
Describe the test for reducing sugars
Add benedicts and heat
if the sample contains reducing sugars = will turn red
Describe the test for non-reducing sugars
1) boil with hydrocholric acid and neutralise with sodium hydrogencarbonate.
2) carry out the benedicts test as if you would for the reducing sugars test.
Describe the test for starch
1) Add iodine dissolved in potassium iodide solution
2) if there is starch = will turn a blue-black colour
Explain the effect of temperature on enzymes.
1) The rise in temperature makes the enzymes molecules vibrate more
2) If the temperature goes above a certain level, this vibration breaks some of the bonds that hold the enzyme in shape
3) The active site changes shape and the enzyme and subtrate no longer fit together
4) At this point, the enzyme in denatured
Explain the effect of PH on enzymes
1) All enzymes have an optimum PH value
2) Above and below the optimum PH, the H + and OH - ions can mess up the ionic and hydrogen bonds that hold the enzymes tertiary structure in place.
3) The active site changes shape, so the enzyme is denatured
