6.1- bacteria and disease

Question 1

pathogenic bacteria

Answer 1

-only some bacteria are pathogenic
-this means they are capable of causing disease in other organisms
-other examples of pathogens are fungi and protists

Question 2

2 ways bacteria can cause disease

Answer 2

1.tissue invasion-growing and dividing in tissues, they can disrupt their normal functions
2.toxin production- bacteria release chemical toxins which can cause cell damage

Question 3

endotoxins

Answer 3

-toxins that are restricted to bacterias cell wall
-they are not freely released in to extracellular spaces or tissue
-they therefore cause damage around the site of infection
-they are the lipid part of lipopolysaccharides that form peptidoglycan
e.g. salmonella

Question 4

exotoxins

Answer 4

-typically soluble proteins that are released and free to move around the body
-they are very diverse
e.g. staphylococcus

Question 5

what can exotoxins do

Answer 5

-act as enzymes to break down cells
-act as enzyme inhibitors to prevent normal enzyme function
-bind to proteins to prevent normal protein function

Question 6

which people are particulary vulnerable to TB infections

Answer 6

-those with HIV
-young or old
-pregnant
-compromised immune system

Question 7

bacteria as prokaryotes

Answer 7

-no membrane bound organelles
-70s ribosomes

Question 8

gram positive bacteria only

Answer 8

-thick peptidoglycan cell wall layer

Question 9

gram negative bacteria only

Answer 9

-thin peptidoglycan cell wall
-2 lipid membranes
-lipoproteins linking peptidoglucan cell wall to outer plasma membrane
-lipopolysaccharides on outer plasma membrane

Question 10

gram positive and gram negative bacteria

Answer 10

-plasma cytoplasmic membrane
-periplasmic space
-peptidoglycan cell wall layer
-proteins in plasma membrane

Question 11

structures in bacteria

Answer 11

-capsule
-cell wall
-nucleoid
-70S ribosomes
-plasmids

Question 12

culturing microorganisms

Answer 12

-means to grow them in large numbers
-need a growth medium such as liquid nutrient broth or nutrient agar (solid)

Question 13

what do growth mediums need to contain

Answer 13

-right level of nutrients and oxygen for microorganisms to grow

Question 14

selective medium

Answer 14

-a growth medium for microorganisms, commonly used in petri dishes

Question 15

inoculation

Answer 15

-process by which microorganisms are transferred into a culture medium under sterile conditions

Question 16

sterile

Answer 16

-term used to describe something that is free from living microorganisms and their spores

Question 17

why is the bunsen on a constant blue flame

Answer 17

-creates an upward draft keeping aerosols from landing in petri dish

Question 18

what is a nutrient medium?

Answer 18

-substance used for the culture of microorganisms, which can be liquid form (BROTH)
or solid form (agar)

Question 19

what is nutrient broth?

Answer 19

-liquid nutrient for culturing microorganisms, commonly used in flask, test tube or bottles

Question 20

what is nutrient agar?

Answer 20

-jelly extracted from seaweed and used as a solid nutrient for culturing microorganisms in petri dish

Question 21

what is a selective medium?

Answer 21

-growth medium for microorganisms containing a very specific mixture of nutrients, so only a particular type of microorganism will grow on it

Question 22

methods of measuring growth of a bacterial culture

Answer 22

1.viable cell count= measure of the number of cells alive in a given volume of a culture
2. dilution plating= method used to obtain a culture plate with a countable number of bacterial colonies- dilute original culture using water in stages until colonies can be counted
3. turbidimetry (optical method)= measuring conc of a substance by measuring the amount of light passing through it, as a solution becomes more turbid (cloudy) it absorbs more light so less passes through, calibration curve produced

Question 23

phases of a bacterial growth curve

Answer 23

lag- when bacteria adapting to new environment and not yet reproducing at max rate
log- when rate of bacterial reproduction is close to max, repeatedly doubling
stationary- total growth is 0, number of cells forming by binary fission is equal to number dying
death- reproduction has almost ceased and death rate still inc

Question 24

what is generation time?

Answer 24

• time span between bacterial divisions

Question 25

calculating exponential growth rates

Answer 25

k=log10Nt-log10N0 / log102*t

Question 26

invasion of host tissue

Answer 26

-third way bacteria act as pathogens
-the response of the host organism to cell damage causes the symptoms of disease
e.g. TB

Question 27

types of antibiotics

Answer 27

1. bacteriostatic- used completely to inhibit the growth of the microorganism e.g. tetracycline
2. bactericidal- destroys almost all present pathogens, used in severe and dangerous infections, also used when patient has suppressed immune system e.g. penicillin