Microbiology

Question 1

what are the 4 major groups of human pathogens and what cell type are they?

Answer 1

protozoa - eukaryotes
fungi - eukaryotes
bacteria - prokaryotes
viruses - obligate parasites

Question 2

what is the size difference between prokaryotes and eukaryotes?

Answer 2

eukaryotes are 5-10 times bigger than prokaryotes

Question 3

how does DNA in prokaryotes compare to that of eukaryotes?

Answer 3

single circular chromosome rather that linear chromosomes and histones

Question 4

prokaryotes contain cell walls T/F

Answer 4

True aka peptidoglycan

Question 5

what are the structural components of a prokaryotic cell?

Answer 5

• plasma membrane
• cell wall (peptidoglycan)
• Nucleoid (DNA and associated proteins)
• ribosomes
• cytoplasm
• capsule, flagella, pilli

Question 6

what is the role of the cytoplasmic membrane in prokaryotic cells?

Answer 6

• a lipid bilayer that retains cytoplasm.
• contains proteins (rafts or transmembrane)
• selective
• reaction surface also used for transport of molecules
• energy generation

Question 7

how is the shape of the plasma membrane in prokaryotic cells determined?

Answer 7

by the type of phospholipids present.

e.g. rods are bent more due to more highly phosphorylated glycoproteins.

Question 8

how does the nucleoid differ from a nucleus?

Answer 8

no defined location
no histones
no membrane

Question 9

where does prokaryotic protein synthesis occur in the cell?

Answer 9

near the membrane

Question 10

what is signifiant to clinicians about prokaryotic protein synthesis?

Answer 10

it is the target of several classes of antibiotic

specifically the tRNA step in the ribosome which is susceptible to interference from drugs

Question 11

what is the peptidoglycan cell wall made of?

Answer 11

alternating long chain sugars

NAM–NAG

with peptide bridges of 5 amino acids in between

Question 12

what is the role of the peptidoglycan cell wall?

Answer 12

provide a ‘cage’ around the cell, preventing it from bursting

Question 13

GRAM POSITIVE

Answer 13

• Thick Multilayered peptidoglycan Layer
• Contains secondary polymer
• strong
• Resistant to osmotic stress

(tends to be slightly more charged)

Question 14

GRAM NEGATIVE

Answer 14

• Thin peptidoglycan layer
• Outer membrane between extracellular space and peptidoglycan
• Periplasmic space
• Lipopolysaccharides (LPS) (Endotoxin)
• sensitive to osmotic stress

Question 15

What does penicillin target in both gram neg and gram pos bacterias and why?

Answer 15

The peptidoglycan as human cells do not contain peptidoglycan so it leaves human cells untouched whilst killing bacterial cells

Question 16

why can drugs like vancomycin target gram positive bacteria but not gram negative?

Answer 16

due to the lack of outer membrane and LPS, large vancomycin molecules can travel down through the peptidoglycan layer and reach the reaction site of the cytoplasmic membrane on gram positive bacteria

Question 17

what is meant by an endotoxin?

Answer 17

Endotoxins are lipopolysaccharides found in the cell wall of Gram-negative bacteria, which can induce inflammation and fever as an immune response

Question 18

are flagella and fimbrae present in Gm -ve or Gm +ve bacteria

Answer 18

both

Question 19

what is the role of fimbrae and flagella?

Answer 19

adherence, (bacterial) sex, motility

Question 20

what are fimbrae/pilus and flagella?

Answer 20

hair like projections made of protein

Question 21

what is bacterial sex?

Answer 21

the transfer of DNA between bacteria aka conjugation

Question 22

what are the 4 requirements for prokaryotic growth?

Answer 22

• food
• temp
• hydrogen ion conc
• osmotic protection

Question 23

what ‘food’ is required for prokaryotic growth?

Answer 23

*carbon
*oxygen
*hydrogen
*nitrogen source
*inorganic salts (P, S, K, Mg, Ca, Fe)
*trace elements
*vitamins

Question 24

what is the name given to prokaryotes that grow at body temp?

Answer 24

mesophiles

Question 25

what are the 4 pashes of the bacterial growth phase?

Answer 25

lag phase
exponential phase
stationary phase
decline phase