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MICROM 410 > Exam 1 Lecture 3 > Flashcards

Exam 1 Lecture 3 Flashcards

1
Q

Archaeal traits are _____ bacteria and eukaryotes

- distinct from or same as?

A

Distinct from

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2
Q

Gram-positive has how much % Peptidoglycan?

A

40-90% of the wall (40 layers thick)

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3
Q

Gram negative has how much % peptidoglycan?

A

5-10% (1-2 layers thick)

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4
Q

Do archaea have peptidoglycan?

A

No!! They have pseudomurein/pseudopeptidoglycan

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5
Q

How is peptidoglycan linked in (not the individual disaccharide, but PG in general)?

A

Teichoic acids

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6
Q

Where are lipoproteins found?

A

Gram-negative bacteria. Used to connect PG to outer membrane.

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7
Q

What can you find in Gram-negative outer membrane?

A

Proteins (like porins), lipids (including LPS),

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8
Q

Where is S-layer found?

A

Gram positive bacteria between peptidoglycan and glycosyl chains

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9
Q

Do Gram positive bacteria have LPS?

A

No - only gram negative

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10
Q

Peptidoglycan subunits

A

NAG and NAM

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11
Q

Peptidoglycan linkage

A

Beta 1,4

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12
Q

Where is the peptide sidechain found in Peptidoglycan?

A

On NAM coming off of the lactic acid

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13
Q

Where does cross linking occur?

A

On the sidechain.

mDAP in gram negative, L-lysine in G+

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14
Q

lysozyme

A

can cleave beta 1,4 linkage of PG –> can degrade bacterial cell wall

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15
Q

Pentapeptide is mostly made of _____

A

D-amino acids

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16
Q

True or false: ribosomes synthesize pentapeptides

A

False due to them mainly being D amino acids. Other enzymes make pentapeptide specific to PG biosynthesis

17
Q

Significance of mDAP

A

site of crosslinking

links mDAP to D-Ala

18
Q

Vancomycin

A

Binds D-ala-D-ala and blocks cross bridge formation

19
Q

Penicillin

A

Blocks Peptide cross-bridge formation by binding to 4th d-ala releasing 5th D-ala

20
Q

Why is crosslinking important?

A

Provides structure, mesh bag

21
Q

Steps of PG biosynthesis

A
  1. make subunit
  2. get it across the membrane
  3. insert it into existing PG
22
Q

Describe making subunit (step 1) in PG biosynthesis

A

Amino acids add sequentially to NAM, then D-ala-D-ala is attached. NAM plus pentapeptide is then added to bactoprenol

23
Q

Describe bactoprenol

A

Lipid that is part of cell membrane. Gets attached to NAM peptide. bactoprenol activated with another phosphate

24
Q

Describe step 2 of PG biosynthesis

A

NAG links to NAM via UDP-NAG, UDP leaves. Then bactoprenol flips and moves the PG to the outside of cell. Transglycosylase attaches new disaccharide to existing chain.

25
Q

Gram positive - where does crosslinking occur

A

On L-Lys. Attached d-ala of other PG disaccharide via pentaglycine

26
Q

Gram negative - where does cross linking occur

A

On mDAP of one disacc. and bonds directly to D-ala of other

27
Q

Components of archaeal cell wall

A
  • NAT instead of NAM
  • Beta 1-3 linkage
  • no lactic acid between NAT and peptide
  • no D amino acids
28
Q

True or false: all archaea use pseudomurein/pseudoPG in cell wall

A

False - only some use it

29
Q

Inhibitors of PG biosynthesis

A
  • beta-lactam antibiotics
  • bacitracin
  • vancomycin
30
Q

How do beta-lactam antibiotics work

A

beta lactam ring = cysteine/valine condense to form this ring (done by fungal enzymes)

  • resembles d-ala-d-ala, thus uses molecular mimicry to enable binding to transpeptidase and transglycosylase (PBP’s)
  • different R groups = dif antibiotic w dif properties
31
Q

Are gram positive more susceptible to beta-lactam antibiotics than g negative?

A

Yes bc more PG

32
Q

How do bacteria become resistant to beta-lactams?

A
  1. secrete beta-lactamase enzymes that cleave critical ring structure
  2. mutate PBP to no longer bind penicillin
  3. limit access of antibiotic to target site (OM of gram-)
33
Q

Teichoic acids

A
  1. provide structural integrity, can be linked to terminal d-ala of NAM
  2. can act as receptor for bacteriophage
34
Q

How are teichoic acids linked

A

Phosphodiester bonds

- also covalently linked to membrane lipids

35
Q

Teichoic acids characterized by:

A

-overall negative charge –> helps to retain gram stain, helps to accumulate divalent cations that are important for growth

36
Q

Do all bacteria have S layer?

A

No - some gram positive have S layer, some don’t

37
Q

Outer membrane properties of cell envelope:

A
  • Porins (beta barrels, non specific channels)
  • Lipoproteins (connects outer membrane to cell wall, N-term Cys with 3 fatty acid side chains in membrane, C-term Lys binds mDap of PG)
  • LPS

MICROM 410 (19 decks)

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