The Nature of Infection

Question 1

What 2 main domains can life be split into?

Answer 1

Eubacteria (bacteria) and archaea (eukaryotes are found here)

Question 2

What are the 4 major groups of human pathogens?

Answer 2

Protozoa, fungi, bacteria and viruses

Question 3

What are protozoa?

Answer 3

Single celled animals (eukaryotes)

Question 4

What are fungi?

Answer 4

High plant like organism (eukaryotes)

Question 5

What are bacteria?

Answer 5

Generally small, single celled prokaryotes

Question 6

What are viruses?

Answer 6

Very small obligate parasites (non-living)

Question 7

What are some features of eukaryotes?

Answer 7

5-50mms, compartments, frequently multi-cellular, linear chromosomes (with histones), introns/exons, 80S ribosomes, no/flexible cell wall and a cell cycle (mitosis/meiosis)

Question 8

What are some features of prokaryotes?

Answer 8

0.5-10mms, simple, often single celled, single circular chromosome, gene structure (introns are rare), 70S ribosomes, co-transcription/translation, rigid cell walls and a rapid cell cycle

Question 9

What is a nucleoid?

Answer 9

A prokaryotic structure containing DNA and proteins with no nuclear membrane, single circular chromosome, and primitive DNA segregation machinery

Question 10

How is energy generated across the bacterial cytoplasmic membrane?

Answer 10

Electrons are released from high energy compounds in the cytoplasm to the membrane and pass through a series of electron acceptors. As a consequence protons passed outside the membrane produce a +ve charge and a proton gradient across the membrane

Question 11

What is in the gram +ve cell wall?

Answer 11

Peptidoglycan - rigid layer, barrier, repeated polysaccharide structure, gram +ve (thick multi-layer peptidoglycan) - target of penicillin. Much better at surviving the environment

Question 12

What is in the gram -ve cell wall?

Answer 12

Peptidoglycan - rigid layer, barrier, repeated polysaccharide structure, gram -ve (outer membrane, periplasm and thiner layer of peptidoglycan) - target of penicillin. It is much harder to penetrate a gram -ve with drugs to kill it

Question 13

What is a lipopolysaccharide made of?

Answer 13

Glycolipid (lipid A, core polysaccharide and O-chain/antigen). Gram -ve (outer membrane is asymmetric and surface of nearly all LPS)

Question 14

What is the role of lipopolysaccharide?

Answer 14

Structural role and antigen and bacterial toxin

Question 15

What is the role of pili, flagella and fimbriae?

Answer 15

Used for adherence, sex, motility, invasion and pathology

Question 16

What is flagellin?

Answer 16

A protein unit making up a multi stranded filament with core

Question 17

What is gram +ve fimbriae?

Answer 17

Non-flagella protein appendages

Question 18

What is gram -ve plus?

Answer 18

Pilin repeated protein unit with no motor

Question 19

What are the key differences in prokaryotic protein synthesis?

Answer 19

Co-transcription/translation, in the cytoplasmic membrane and there is no polyadenylation of transcript (adding a poly(A) tail to the mRNA)

Question 20

What is the use of the prokaryotic plasma membrane?

Answer 20

Sonication and ethanol

Question 21

What is the use of the prokaryotic cell wall?

Answer 21

Penicillin and glycopeptides

Question 22

What is the use of the prokaryotic outer membrane and LPS?

Answer 22

Antibiotic uptake and inflammation

Question 23

What is the use of the prokaryotic chromosome

Answer 23

Gyrases antibiotic target

Question 24

What is the role of the prokaryotic ribosomes?

Answer 24

Protein synthesis inhibitors

Question 25

What is prokaryotes food source?

Answer 25

``` C source organic eg protein and sugars C source inorganic eg fix CO2 O&H N source eg amino acids, ammonia, inorganic salts (P, S, K, Mg, Ca, Fe) Trace elements - Zn, Cu, Mn, Ni, Mo Vitamins ```

Question 26

What are the 3 types of prokaryotes classified by temperature?

Answer 26

Psycrophiles (low temp), thermophiles (high temp) and mesophiles (body temp)

Question 27

What is the optimal pH for prokaryotic growth?

Answer 27

Human commensals - 6.8-7.2

Question 28

What is the optimal osmotic protection for prokaryotic growth?

Answer 28

Human commensals - 0.85% NaCl

Question 29

What are the different types of prokaryotes as affected by oxygen?

Answer 29

Aerobes, micro-aerophiles, facultative anaerobes, obligate anaerobes and capnophilics (thrive in high conc CO2)

Question 30

What does the bacterial growth curve indicate?

Answer 30

How infection is spread

Question 31

What are the 4 targets for antimicrobials?

Answer 31

Cell membrane, cell wall, ribosomes and DNA

Question 32

What are the 4 phases of bacterial growth?

Answer 32

Lag phase, exponential phase, stationary phase and decline phase (LESD)