Biology topic 6

Question 1

Aseptic technique

Answer 1

Steralise work surface
Flame mouth of culture + innoculating loop
Dip and streak, flame and repeat

Question 2

Growth curve of microorganism

Answer 2

1. Lag- Adapting to environment
2. Log- Grow at max rate, as long as nutrients sufficient
3. Stationary- Build up of wast products + lack of nutrients
   Death rate = reproduction rate
4. Death- Death > new cell population

Question 3

Methods of measuring bacterial growth

Answer 3

Cell count- haemocytometer
Turbidimetry
Dilution plating

Question 4

Exotoxin

Answer 4

Soluble proteins are produced and released by bacteria as they metabolise and reproduce.
Spread around body in blood and bodily fluid

Question 5

Endotoxin

Answer 5

Lipopolysaccharides in outer lipid membrane of gram -ve bacteria (e.g salmonella)
Endotoxins may be released from bacteria if broken down, effects specific site of infection

Question 6

Bactericidal antibiotics

Answer 6

Kill bacteria by destroying cell wall, causing them to burst
E.g penicillin

Question 7

Bacteriostatic antibiotics

Answer 7

Inhibit growth + reproduction of bacteria by stopping protein synthesis + reproduction of nucleic acids - bacteria cannot grow or divide.

Question 8

Resistant bacteria

Answer 8

Result of natural selection
Resistant bacteria possess selective advantage, allows them to survive and reproduce
Allele for antibiotic resistance is passed onto offspring, creating resistant strain.

Question 9

Physical barriers to infection

Answer 9

Skin- made of keratin
Stomach acid- kills bacteria
Gut and skin flora

Question 10

Non-specific responses of body to infection

Answer 10

Inflammation- histamines released by WBC causing vasodilation- increased blood flow. WBC + plasma leak out into the infected area
Fever- Hypothalamus increases body temp, decreases pathogen reproduction
Lysozome action- Enzyme that kills bacteria by damaging cell wall.
Phagocytosis- WBC engulf pathogens + destroy them

Question 11

Specific immune response

Answer 11

Antigen specific + pathogen specific
Relies on lymphocytes produced in bone marrow
B cells- mature in bone marrow- involved in HIR
T cells- move from bone marrow to thymus gland- mature, involved in CMIR

Question 12

Cell mediated immune response

Answer 12

1. Pathogen invades host cell
2. Host cell displays antigens on its major histocompatibility complexes. Becomes antigen-presenting cell
3. T killer cells w complimentary receptors bind to APC
4. Cytokines secreted by T helper cells stimulate T killer cells to divide by mitosis.
5. T killer cells divide to form active T killer cells + T killer memory cells
6. Active T killer cells bind to APC’s + secrete chemicals which cause pores to form in cell membrane
7. Infected cell dies