B3

Question 1

name 4 non specific defence systems that work to prevent pathogens from entering the body

Answer 1

• skin (a physical barrier which produces antimicrobial secretions to kill pathogens and has good microorganisms such as skin flora to compete with the bad ones for space and nutrients)
• the nose (has little hairs and mucus to trap the pathogens and prevent particles from entering your lungs
• trachea and bronchi (secrete mucus and has cilia to waft mucus upwards so that it can be swallowed or coughed out)
• stomach (high pH of the HCL in the stomach kills any pathogens that enters it)

Question 2

three different ways white blood cells can act

Answer 2

• phagocytosis (track, bind and engulfing pathogens which destroys them, so that they can no longer make you feel ill)
• produce antibodies (small proteins produced by lymphocytes. each pathogen has an antigen on its surface which a specific complementary antibody can bind to. the antibodies clump together, making it easier for the white blood cells to find them)
• produce antitoxins (they neutralise and counter the toxins released by the pathogen by binding to them)

Question 3

describe how the human body prevents pathogens from entering and defends itself against pathogens inside the body

Answer 3

human body has two types of defences: primary and secondary)

primary defences - skin, tears and mucus and hairs in the nose.
secondary - acid in stomach, white blood cells - antibodies, phagocytosis, antitoxins and memory cells

Question 4

what is a physical defence for plants

Answer 4

one which prevents and invasion of microorganisms. e.g. tough waxy cuticle or cellulose cell walls or a layer of dead cells around stems which stop pathogens from entering as when the dead cells fall off, so do the pathogens

Question 5

what is a chemical defence for plants

Answer 5

one which deters predators or kill bacteria. e.g. poisons deter herbivores, and antibacterial compounds (mint/witch hazel)

Question 6

what is a mechanical defence for plants

Answer 6

thorns hairs, leaves that droop/curl when touched, mimicry to trick animals

Question 7

describe how mAbs (Monoclonal antibodies) and a fluorescent dye could be used to see pathogens on a slide

Answer 7

• bind dye to mAbs
• fluorescent mAbs on the slide
• mAbs will bind to pathogens and show up under the microscope

Question 8

explain how increased phagocytosis of a pathogen can help a patient

Answer 8

more pathogens will be engulfed by the white blood cells and therefore less damage will be done to the cells

Question 9

describe how clinical trials should be carried out

Answer 9

• first trial - healthy volunteers. check the toxicity and efficacy of the drug. must be given in small doses.
• second trials, correct dosage should be figured out
• then the drug must be tested on all ages to see if the pathogens work efficiently
• placebos and double blind trials must also be carried out.

Question 10

plants infected with aphids may show symptoms of magnesium deficiency.

magnesium deficiency symptoms include: yellow leaves, stunted growth

explain how a deficiency of magnesium could cause these symptoms

Answer 10

yellow leaves due to lack of chlorophyll. therefore less light is absorbed by chlorophyll thus a lower rate of photosynthesis occurs. therefore the plant converts less sugar into protein which is used for growth. so the growth is stunted.

Question 11

how are monoclonal antibodies made

Answer 11

you inject a protein into a mouse. you then combine lymphocytes with tumour/cancer cells to make hybridoma cells. then, you find a hybridoma cell that makes a monoclonal antibody specific to the (). the scientist then clones the hybridoma to produce many cells that produce the same antibody.