BMS2052 FINAL EXAM A FULL-SCALE EXAM QUESTION AND ANSWER
GUIDE CONTAINING VERIFIED CONTENT DESIGNED TO MAXIMIZE TEST
PERFORMANCE AND UNDERSTANDING OF KEY CONCEPTS
Classes of microorganisms/infectious agents relevant to human/animal health
and disease - ANSWER - bacteria
- yeasts and fungi
- viruses
- parasites
- archaea
- prions
important difference between bacteria (prokaryotes) and eukaryotes -
ANSWER 1. some bacteria do not have their NA enclosed in a membrane
(planctomycetes)
2. some bacteria do not have membrane-bound organelles (eg. an
anammoxosome for ammonia oxidation) and extensive intra-cytoplasmic
membrane structures
3. some bacteria do have cytoskeletal elements (eg. actin) and a rudimentary
cytoskeleton
Similarity of archaea to bacteria - ANSWER - anucleate cells (no nucleus)
- cell envelope
- generally possess single circular chromosome
- vary in shape and size
Similarity of archaea to eukarya - ANSWER - DNA replication, transcription
and translation seems more like Eukarya
-archaea DNA has histones (DNA binding proteins considered to be a defining
characteristic of Eukarya)
- many enzymes involved in DNA replication (DNA polymerase, primes, etc.)
are similar to those found
The role of archaea in human disease - ANSWER - unlike bacteria, the
diversity of the archaea in the human body is substantially lower, including
representatives of only one phylum (euryachaeota)
,- unlike bacteria, there are virtually on known bona fide pathogens of humans
Methanobrevibacter smithii - ANSWER Common in human gut and vagina
Methanosphaera stadtmanae - ANSWER Common in human gut
Methanosphaera oralis - ANSWER Common in the human mouth;
Structure of a 'typical' bacterium - ANSWER - flagellum
- 70S ribosomes
- plasmid
- cytoplasm
- plasma membrane
- pili
- cytoplasmic inclusion
- infolding of plasma membrane
- capsule
- cell wall
- DNA coiled into nucleoid
- basal body
Cocci - ANSWER Spherical bacteria
Bacilli - ANSWER Rod-shaped bacteria
Spirochaete - ANSWER Spiral bacteria
Comma's - ANSWER Curved bacteria
Bacterial cell walls - ANSWER - rigid structure outside of the plasma
membrane: creates the characteristic shape
- peptidoglycan = polymer of peptides: unique to bacteria, complex
carbohydrate, forms a strong mesh surrounding the cell
Typical gram positive cell wall (negatively charged) - ANSWER - 20-80nm
thick, homogenous peptidoglycan layer
- contains large amounts of secondary cell polymers including teichoic acid and
lipoteichoic acids
,Teichoic acid and lipoteichoic acid - ANSWER Function in cell wall
maintenance and enlargement during cell division; move cations across the cell
envelope; stimulate a specific immune response.
Teichoic acid is a polymer of ribitol of glycerol joined by phosphate groups.
Lipoteichoic acids are covalently connected to the peptidoglycan or plasma
membrane.
Gram negative cell wall (positive charge) - ANSWER - single think (1-3nm)
sheet of peptidoglycan
- acts as a rigid protective structure
- its thinness makes the structure more flexible, but sensitive to lysis
- well developed periplasmic space surrounding the peptidoglycan
Peptidoglycan layer - ANSWER Glycan: it is made up of two alternating
sugars
- N-acetyl glucosamine (NAG)
- N-acetylmuramic acid (NAM)
- both are very similar to glucose
- NAG and NAM are covalently linked in long chains, one alternating with the
other
Peptide: made up of four amino acids (tetrapeptides), contains both D- and L-
amino acids
Functions of the cell wall - ANSWER - maintains shape of the bacterium
- provides strong structural support (preventing bursting or collapsing due to
osmotic pressure)
- attachment
- can contribute to pathogenicity
- can protect the cell from toxic substances
- site of action of some antibiotics
- cel wall of most bacteria gain their relatively rigid quality from peptidoglycan
Gram negative periplasmic space - ANSWER Surrounds the peptidoglycan and
is an important reaction site for a large and varied pool of substances that enter
the cell.
, Gram negative outer membrane - ANSWER Contains:
- protein (eg. porin proteins)
- lipoprotein (eg. Braun's lipoprotein)
- phospholipid (part of the membrane bilayer)
- lipopolysaccharide (LPSs) n the upper most layer
Lipid forms about 15% of the outer membrane
Lipopolysaccharide (LPS) - ANSWER The polysaccharide chains extending
off the surface functions as antigens and receptors. Two major parts of LPS are
Lipid A and O-specific polysaccharide side chain (O antigen).
Function and importance of LPS - ANSWER - contributes to the structural
integrity of the outer membrane and forms a permeability barrier for certain
chemcials
- increases the negative charge of the cell membrane and helps stabilise overall
membrane structure (core polysaccharide)
- essential for bacterial survival (possible therapeutic target)
- collectively highly immunogenic, but molecular mimicry and rapid antigen
variation provided by the glycan O
- Lipid A portion if a major, potent endotoxin
Bacteria with atypical cell walsl - ANSWER 1. Bacteria that completely lack
peptidoglycan
2. Bacteria that lack a cell wall altogether
3. Bacteria with a unique 'atypical' outer membrane
Bacteria that completely lack peptidoglycan - ANSWER Two phyla:
chlamydiae and planctomycetes
- contain a typical outer membrane and stain gram negative
- despite a lack of PG they maintain a characteristic shape (rigidity provided by
cell membrane) but are relatively fragile
- intracellular 'parasites'
- major cause of STIs globally
- also cause trachoma (C. trachomatis in the eyes) and psittacosis (C. psittaci in
the lungs)
GUIDE CONTAINING VERIFIED CONTENT DESIGNED TO MAXIMIZE TEST
PERFORMANCE AND UNDERSTANDING OF KEY CONCEPTS
Classes of microorganisms/infectious agents relevant to human/animal health
and disease - ANSWER - bacteria
- yeasts and fungi
- viruses
- parasites
- archaea
- prions
important difference between bacteria (prokaryotes) and eukaryotes -
ANSWER 1. some bacteria do not have their NA enclosed in a membrane
(planctomycetes)
2. some bacteria do not have membrane-bound organelles (eg. an
anammoxosome for ammonia oxidation) and extensive intra-cytoplasmic
membrane structures
3. some bacteria do have cytoskeletal elements (eg. actin) and a rudimentary
cytoskeleton
Similarity of archaea to bacteria - ANSWER - anucleate cells (no nucleus)
- cell envelope
- generally possess single circular chromosome
- vary in shape and size
Similarity of archaea to eukarya - ANSWER - DNA replication, transcription
and translation seems more like Eukarya
-archaea DNA has histones (DNA binding proteins considered to be a defining
characteristic of Eukarya)
- many enzymes involved in DNA replication (DNA polymerase, primes, etc.)
are similar to those found
The role of archaea in human disease - ANSWER - unlike bacteria, the
diversity of the archaea in the human body is substantially lower, including
representatives of only one phylum (euryachaeota)
,- unlike bacteria, there are virtually on known bona fide pathogens of humans
Methanobrevibacter smithii - ANSWER Common in human gut and vagina
Methanosphaera stadtmanae - ANSWER Common in human gut
Methanosphaera oralis - ANSWER Common in the human mouth;
Structure of a 'typical' bacterium - ANSWER - flagellum
- 70S ribosomes
- plasmid
- cytoplasm
- plasma membrane
- pili
- cytoplasmic inclusion
- infolding of plasma membrane
- capsule
- cell wall
- DNA coiled into nucleoid
- basal body
Cocci - ANSWER Spherical bacteria
Bacilli - ANSWER Rod-shaped bacteria
Spirochaete - ANSWER Spiral bacteria
Comma's - ANSWER Curved bacteria
Bacterial cell walls - ANSWER - rigid structure outside of the plasma
membrane: creates the characteristic shape
- peptidoglycan = polymer of peptides: unique to bacteria, complex
carbohydrate, forms a strong mesh surrounding the cell
Typical gram positive cell wall (negatively charged) - ANSWER - 20-80nm
thick, homogenous peptidoglycan layer
- contains large amounts of secondary cell polymers including teichoic acid and
lipoteichoic acids
,Teichoic acid and lipoteichoic acid - ANSWER Function in cell wall
maintenance and enlargement during cell division; move cations across the cell
envelope; stimulate a specific immune response.
Teichoic acid is a polymer of ribitol of glycerol joined by phosphate groups.
Lipoteichoic acids are covalently connected to the peptidoglycan or plasma
membrane.
Gram negative cell wall (positive charge) - ANSWER - single think (1-3nm)
sheet of peptidoglycan
- acts as a rigid protective structure
- its thinness makes the structure more flexible, but sensitive to lysis
- well developed periplasmic space surrounding the peptidoglycan
Peptidoglycan layer - ANSWER Glycan: it is made up of two alternating
sugars
- N-acetyl glucosamine (NAG)
- N-acetylmuramic acid (NAM)
- both are very similar to glucose
- NAG and NAM are covalently linked in long chains, one alternating with the
other
Peptide: made up of four amino acids (tetrapeptides), contains both D- and L-
amino acids
Functions of the cell wall - ANSWER - maintains shape of the bacterium
- provides strong structural support (preventing bursting or collapsing due to
osmotic pressure)
- attachment
- can contribute to pathogenicity
- can protect the cell from toxic substances
- site of action of some antibiotics
- cel wall of most bacteria gain their relatively rigid quality from peptidoglycan
Gram negative periplasmic space - ANSWER Surrounds the peptidoglycan and
is an important reaction site for a large and varied pool of substances that enter
the cell.
, Gram negative outer membrane - ANSWER Contains:
- protein (eg. porin proteins)
- lipoprotein (eg. Braun's lipoprotein)
- phospholipid (part of the membrane bilayer)
- lipopolysaccharide (LPSs) n the upper most layer
Lipid forms about 15% of the outer membrane
Lipopolysaccharide (LPS) - ANSWER The polysaccharide chains extending
off the surface functions as antigens and receptors. Two major parts of LPS are
Lipid A and O-specific polysaccharide side chain (O antigen).
Function and importance of LPS - ANSWER - contributes to the structural
integrity of the outer membrane and forms a permeability barrier for certain
chemcials
- increases the negative charge of the cell membrane and helps stabilise overall
membrane structure (core polysaccharide)
- essential for bacterial survival (possible therapeutic target)
- collectively highly immunogenic, but molecular mimicry and rapid antigen
variation provided by the glycan O
- Lipid A portion if a major, potent endotoxin
Bacteria with atypical cell walsl - ANSWER 1. Bacteria that completely lack
peptidoglycan
2. Bacteria that lack a cell wall altogether
3. Bacteria with a unique 'atypical' outer membrane
Bacteria that completely lack peptidoglycan - ANSWER Two phyla:
chlamydiae and planctomycetes
- contain a typical outer membrane and stain gram negative
- despite a lack of PG they maintain a characteristic shape (rigidity provided by
cell membrane) but are relatively fragile
- intracellular 'parasites'
- major cause of STIs globally
- also cause trachoma (C. trachomatis in the eyes) and psittacosis (C. psittaci in
the lungs)
