Exam 1 Lecture 3

Question 1

Archaeal traits are _____ bacteria and eukaryotes

- distinct from or same as?

Answer 1

Distinct from

Question 2

Gram-positive has how much % Peptidoglycan?

Answer 2

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

Question 3

Gram negative has how much % peptidoglycan?

Answer 3

5-10% (1-2 layers thick)

Question 4

Do archaea have peptidoglycan?

Answer 4

No!! They have pseudomurein/pseudopeptidoglycan

Question 5

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

Answer 5

Teichoic acids

Question 6

Where are lipoproteins found?

Answer 6

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

Question 7

What can you find in Gram-negative outer membrane?

Answer 7

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

Question 8

Where is S-layer found?

Answer 8

Gram positive bacteria between peptidoglycan and glycosyl chains

Question 9

Do Gram positive bacteria have LPS?

Answer 9

No - only gram negative

Question 10

Peptidoglycan subunits

Answer 10

NAG and NAM

Question 11

Peptidoglycan linkage

Answer 11

Beta 1,4

Question 12

Where is the peptide sidechain found in Peptidoglycan?

Answer 12

On NAM coming off of the lactic acid

Question 13

Where does cross linking occur?

Answer 13

On the sidechain.

mDAP in gram negative, L-lysine in G+

Question 14

lysozyme

Answer 14

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

Question 15

Pentapeptide is mostly made of _____

Answer 15

D-amino acids

Question 16

True or false: ribosomes synthesize pentapeptides

Answer 16

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

Question 17

Significance of mDAP

Answer 17

site of crosslinking

links mDAP to D-Ala

Question 18

Vancomycin

Answer 18

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

Question 19

Penicillin

Answer 19

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

Question 20

Why is crosslinking important?

Answer 20

Provides structure, mesh bag

Question 21

Steps of PG biosynthesis

Answer 21

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

Question 22

Describe making subunit (step 1) in PG biosynthesis

Answer 22

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

Question 23

Describe bactoprenol

Answer 23

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

Question 24

Describe step 2 of PG biosynthesis

Answer 24

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.

Question 25

Gram positive - where does crosslinking occur

Answer 25

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

Question 26

Gram negative - where does cross linking occur

Answer 26

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

Question 27

Components of archaeal cell wall

Answer 27

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

Question 28

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

Answer 28

False - only some use it

Question 29

Inhibitors of PG biosynthesis

Answer 29

- beta-lactam antibiotics - bacitracin - vancomycin

Question 30

How do beta-lactam antibiotics work

Answer 30

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

Question 31

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

Answer 31

Yes bc more PG

Question 32

How do bacteria become resistant to beta-lactams?

Answer 32

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-)

Question 33

Teichoic acids

Answer 33

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

Question 34

How are teichoic acids linked

Answer 34

Phosphodiester bonds | - also covalently linked to membrane lipids

Question 35

Teichoic acids characterized by:

Answer 35

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

Question 36

Do all bacteria have S layer?

Answer 36

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

Question 37

Outer membrane properties of cell envelope:

Answer 37

- 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