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Microbiology and immunology > Bacterial cell wall > Flashcards

Bacterial cell wall Flashcards

1
Q

List the types of microorganisms

A

Virus

Archaea

Bacteria

Fungi

Algae

Protists

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2
Q

What is the cell structure of a virus?

A

No cell - Non living

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3
Q

What is the cell structure of Archaea?

A

Prokaryotic

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4
Q

What is the cell structure of Bacteria?

A

prokaryotic

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5
Q

What is the cell structure of Fungi?

A

Eukaryotic

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6
Q

What is the cell structure of Algae?

A

Eukaryotic

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7
Q

What is the cell structure of Protists?

A

Eukaryotic

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8
Q

What are the common Eukaryota and Prokaryotic features?

A

Cytoplasmic membrane- Boundary between the living cell and the environment.

Cytoplasm- Fluid substance where biological reactions take place

DNA- Hereditary/ genetic material

Ribosomes- Translations or genetic information into proteins.

ATP - Universal energy currency

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9
Q

Do prokaryotes have a cell membrane?

A

Yes

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10
Q

Do Eukaryotes have a cell membrane?

A

Yes

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11
Q

Do Prokaryotes have a cell wall?

A

Yes

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12
Q

Do Eukaryotes have a cell wall?

A

Some

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13
Q

Do Prokaryotes have a nucleus?

A

No

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14
Q

Do Eukaryotes have a Nucleus?

A

Yes

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15
Q

Do prokaryotes have Organelles?

A

Yes but some think they don’t

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16
Q

Do Eukaryotes have a Organelles?

A

Yes

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17
Q

What is the Ribosome size for Prokaryotes?

A

70s

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18
Q

What is the Ribosome size for Eukaryotes?

A

80s except for mitochondria

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19
Q

What was the original description of the bacterial cell structure?

A

Bags of enzymes

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20
Q

Bacteria - How was the Distinct anatomical structures revealed?

A

The electron microscope in the 1950’s

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21
Q

What was the distinct anatomical structures discovered in bacteria cells?

A

Distinct cell wall

No nucleus

Appendages- movement and interactions

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22
Q

List and explain the 3 architectural regions in the bacterial cell?

A

1) Appendages: Attachments to the cell surface flagella and Pili or Fimbriae
2) Cytoplasmic region: Nucleoid (DNA), Ribosomes and inclusions
3) Cell envelope: Capsule, cell wall and plasma membrane

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23
Q

What is the function of the capsules and slime layers?

A

Resistance to stress and adherance

24
Q

What is the function of flagella?

25
Q

What is the function of Endospores? (only some species).

A

Survival in harsh conditions

26
Q

What is the function of Pili/Fimbrae?

A

Various roles in interaction with other bacteria and environment

27
Q

What is the function of Plasmids?

A

Extra-chromosomal genetic information

28
Q

What is the function of the cell membrane?

A

Selective permeability

29
Q

What is the function of the cell wall?

A

Support and protection

30
Q

What is the function of Ribosomes?

A

Protein synthesis

31
Q

What is the function of the inclusion bodies?

A

Storage of carbohydrates/Proteins and other substances

32
Q

What is the function of the Nucleoid?

A

Genetic material

33
Q

What is the function of the Bacterial cell wall in detail?

A

Protect the cell from mechanical disruption and from being burst by osmotic pressure

Gives the cell is shape and rigidity

Essential for viability

34
Q

What are the features of the bacterial cell wall?

A

Composed of unique components found nowhere else in nature.

One of the most important sites antibiotic attack

Provide ligands for adherence to host cell receptors and receptor sites for drugs or viruses.

Cause symptoms of disease in animals

Provide immunological distinction and immunological variation among strains of bacteria

35
Q

What are the two main kinds of bacterial cell wall structure?

A

Gram negative and gram positive

36
Q

How are the two main kinds of bacterial cell wall determined?

A

Using a very simple method known as the gram stain which was discovered in 1884 by Christian Gram.

37
Q

How does gram staining work?

A

Uses two dyes Crystal violet (purple) and Safranin (red), iodine and ethanol

–Cells dyed purplefirst

–Due to structural differences extraction of iodine/crystal violet complexes from bacterial cells with ethanol is variable

–Gram positive cells hold onto purple

–This is readily extracted from Gram negative cells, which are counter stained red with safranin

–Counter stained Gram positive cells remain purple

38
Q

Why can’t certain bacterial be assigned a Gram response?

A

Mycobacteria fail to stain because of their unique cell wall structure

  • Presence of mycolic acids (waxy).
  • M. tuberculosis (TB)
  • M.Laprae (Leprosy)
  • Known as acid fast
39
Q

How is Peptidoglycan involved in gram response?

A

The difference in Gram response is in part due to different thickness of a polymer called Peptidoglycan

Consists of a linear glycan chain of alternating sugar derivatives linked by B1:4 Glycosidic bonds:

  • N-acetyglyucosamine (NAG)
  • N-acetylmuramic acid (NAM)

Present in both Gram negative and gram prositive types

Gives strength to cell wall

40
Q

How is the Peptidogylcan layer in Gram positive structures?

A

The Peptidoglycan is much more thicker

41
Q

How is the Peptidoglycan layer in Gram Negative structures?

A

The Peptidoglycan is much more thin

42
Q

Explain How Peptidoglycan makes a cell wall?

A

NAG and NAM

Cross-links between other tetrapeptides connect the sheets to form a 3-D, rigid matrix.

Forms a scaffold -like giant molecule, the peptidoglycan sac

Shape of cell is determined by length of peptidoglycan chains and manner and extent of cross linking.

43
Q

Explain Teichoic acid in the gram positive cell wall?

A

In Gram-positive cell walls only

Acidic polysaccharides- Polymers

  • Glycerol phosphate
  • Ribitol phosphate
  • Length of the chain and the nature and location of the side-chain constituents vary species to species
  • Up to 50% of the wall may be teichoic acid
  • Some covalently linked to NAM residues of peptidoglycan- Teichoic acid
  • Linked to lipids in the plasma membrane- Lipoteichoic acid
44
Q

Explain the Teichoic acid functions

A

Anchorage of the cell wall to the plasma membrane- Lipoteichoic acids.

Provides chemical groups that give an over all negative charge

Major antigenic determinant of the cell surface

45
Q

Explain Peptidoglycan in the Gram negative cell wall?

A

Some peptidoglycan forms a single layered sheet around the cell.

  • The rest, with minimal cross-linking
  • Forms, a gel-like substance- the periplasmic gel that fills the periplasmic space.

External to the periplasm is a complex outer membrane

Reduced Peptidoglycan sac still gives the cell its shape and integrity

46
Q

Explain The periplasm in the Gram negative cell wall?

A

Contains proteins with a variety of roles

Nutrients acquisition

  • Hydrolytic enzymes
  • Binding proteins for solute transport

Detoxifying enzymes
-Antibiotics (beta lactamase)

Enzymes for peptidoglycan synthesis

Proteins involved in chemotaxis

47
Q

Explain the outer membrane in the Gram negative cell wall?

A

Consists of two components

  • Normal phospholipids
  • Lipopolysaccharide (LPS)

LPS is extermely toxic to humans and other animals and is referred to as an endotoxin

  • Minute amounts of LPS can produce fever and shock
  • Promotes cytokine release (IL’s)
  • Gram-negative shock or endotoxic shock
48
Q

Explain the outer membrane permeability in the Gram negative cell wall?

A

–LPS in the outer membrane results in a barrier

  • Blocks the passage of most organic molecules into the cell
  • Including nutrients

–Special proteins form pores through the outer membrane called porins

  • This allows the bacteria count the issue of the barrier
  • Porinsallow hydrophilic molecules of low MW to diffuse into the periplasm
49
Q

Briefly explain Binary fission

A

Separation of a single cell into two identical daughter cells, each containing one copy of the parental DNA.

50
Q

Explain Peptidoglycan synthesis in cell division

A

New cell wall synthesis must take place during cell division so the cell can increase its size

–Links in the peptidoglycan must be broken

–New peptidoglycan monomers must be inserted

–Peptide cross links must be resealed.

–Happens in 3 stages

51
Q

Explain Peptidoglycan synthesis in cell division - What do Autolysins do?

A

break the glycosidicbonds between the peptidoglycan monomers and break peptide cross-bridges

52
Q

Explain Peptidoglycan synthesis in cell division - What does Transglycosidase do?

A

enzymes insert and link new peptidoglycan monomers into the breaks in the peptidoglycan

53
Q

Explain Peptidoglycan synthesis in cell division - What does Transpeptidase do?

A

enzymes reform the peptide cross-links between the rows and layers of peptidoglycan.

54
Q

Antibiotic action against cell synthesis- How is transpeptidation important?

A

–This is the reaction that antibiotics such as penicillin inhibits

–Penicillium (Fungus/Mould –Eukaryotic cell)

55
Q

What does the presence of penicillin cause?

A

–Newly synthesised peptidoglycan cannot be cross linked

–New cell wall cannot be made

–Resulting in cell lysis

56
Q

What is MRSA?

A

–Stands for Methicillin Staphylococcus aureus

–S. aureus is a gram +vebacterium

57
Q

Explain Methicillin

A

–Penicillin class beta lactam antibiotic

–Like penicillin it kills gram +vebacteria by binding to the ‘PBP’ blocking peptidoglycan synthesis

–Resistance to penicillin occurs when bacteria produce beta lactamases

–However > Methicillin is resistant to beta lactamase

–Resistance to methicillin occurs through a mutation to the PBP

Microbiology and immunology (17 decks)

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