infectious diseases

Question 1

viuses

Answer 1

• smaller than bacteria- protein coat ( no cell wall/ membrane)
• no nucleus
• only divide using host cell
• always damage cells

Question 2

pasteur’s experiment to disprove spontaneous generation

Answer 2

all contain nutrient broth

1) cotton wool plug- slightly dark as it is unsterilised
2) nothing- cloudy because microbes will enter from he air
3) tin foil and cotton wool- stay clear; no microbes
4) straight glass tube and cotton wool- cloudy; some microbes may have entered
5) s shaped tube + cotton wool- microbes can’t move through the bends

Question 3

culturing bacteria

Answer 3

1) take a sterilised Petri dish and pour sterilised nutrient agar into the dish
2) replace the lid as quickly possible and allow it to cool
3) once solidified, take a sterile inoculation loop and take a small sample of your chosen microbes
4) wipe the loop across the surface of tthe agar in a zig zag fashion, this spreads out bacteria s they can grow into isolated colonies
5) seal the Petri dish with sellotape and incubate at 25 degrees celcius for 1 week.

Question 4

bacteria

Answer 4

• small
• cell wall
• cytoplasm
• no nucleus
• divided by binary fission
• sometimes damage cells

Question 5

phagocytosis

Answer 5

• some white blood cells ingest pathogens, destroying them

Question 6

antibodies

Answer 6

• some white blood cells produce antibodies- these target specific bacteria or viruses
• unique antibody for each type of pathogen
• once your body has produced antibodies against a particular pathogen once they can be made very quickly if the pathogen enters the body again which makes you immune to tthat disease

Question 7

anti toxins

Answer 7

• some white blood cells produce anti toxins released by pathogens

Question 8

immunisiation/ vaccination

Answer 8

• small dose of dead or inactive pathogen into the body-white blood cells produce antibodies
• these destroy the antigens without any risk of you getting the disease
• some wbcs remain as memory cells
• the patient is now immune to that disease
• when you meet the antigens again the memory cells produce the correct antibodies and destroy the pathogen before it has the chance to reproduce
• some pathogens mutate so their antigens change. as a result the memory cells do not respond
• a new set of wbcs with new antibodies will have to be produced. this takes time so you will suffer from the disease

Question 9

antibiotic resistance

Answer 9

• some bacteria mutate to produce new DNA
• some survive treatment with the antibiotic
• the surviving reproduce asexually
• the gene for resistance is past on to offspring