Lecture 3

Question 1

What makes up a polyribosome?

Answer 1

Ribosomes attach to single mRNA molecules

Question 2

What is the function of polyribosomes?

Answer 2

coupling transcription and translation

Question 3

Is E. coli gram positive or negative?

Answer 3

negative

Question 4

Which (+/-) has a thick cell wall made of peptidoglycan? what does this prevent?

Answer 4

Gram-positive, limits the passage of hydrophobic compounds

Question 5

What is another name for peptidoglycan?

Answer 5

murein

Question 6

Which (+/-) has teichoic and lipoteichoic acids?

Answer 6

Gram-positive

Question 7

Which (+/-) has an outer membrane made of lipopolysaccharide (LPS)?

Answer 7

Gram-negative

Question 8

Gram’s method used what as the primary stain?

Answer 8

Crystal Violet

Question 9

Gram used what as a mordant?

Answer 9

iodine

Question 10

Gram used what as a decolorizer?

Answer 10

ethanol

Question 11

What is the Gram Stain Procedure?

Answer 11

1) stain with crystal violet (purple); wash
2) mordant (bind) the dye with potassium iodide; wash
3) flush with alcohol; wash. Gram-negative bacteria are decolorized; Gram-positive bacteria remain purple
4) counterstain with safranin (red); wash. Gram-negative bacteria become red; Gram-positive bacteria remain purple.

Question 12

What does the amphipathic nature of phospholipids allow?

Answer 12

self assembly

Question 13

What helps protect against osmotic stress?

Answer 13

cell wall

Question 14

What 4 functions do proteins in the cell membrane do?

Answer 14

1) respiration and photosynthesis
2) nutrient uptake
3) appendages
4) signaling

Question 15

What are the glycan chains made up?

Answer 15

alternating N-Acetylglucosamine (NAG) and N-Acetylmuramic acid (NAM)

Question 16

What is peptidoglycan made of?

Answer 16

NAG (GlcNAc) and NAM (MurNAc)

Question 17

What type of bonds are NAG and NAM connected by?

Answer 17

beta (1,4) glycosidic bonds

Question 18

Which is the peptide chain attached to?

Answer 18

NAM

Question 19

What is DAP?

Answer 19

diaminopimelic acid, a derivative of lysine

Question 20

What are the crosslinks between peptidoglycan in Gram-?

Answer 20

DAP and D-Ala

Question 21

What are the crosslinks between peptidoglycan in Gram+?

Answer 21

L-Lys and D-Ala

Question 22

Where is DAP only found in?

Answer 22

Gram-

Question 23

Where is Lysine only found in?

Answer 23

Gram+

Question 24

What are teichoic acids made of?

Answer 24

chains of glycerol phosphate or ribitol phosphate linked by phosphodiester bonds

Question 25

Where do teichoic acids connect?

Answer 25

peptidoglycan or cell membrane

Question 26

Function of teichoic acids?

Answer 26

give rigidity to cell wall, and promote adherence of bacteria to specific surfaces

Question 27

How are wall teichoic acids linked to PG?

Answer 27

covalently, vis phosphodiester bond to C6-hydroxyl of NAM

Question 28

Where are lipid teichoic acids anchored?

Answer 28

cell membrane via glycolipid and a glycerol phosphate

Question 29

LPS has what type of leaflets?

Answer 29

inner and outer

Question 30

What are the 3 parts that make up the LPS?

Answer 30

1) lipid A --- amphipathic 2) core polysaccharide 3) o-antigen

Question 31

What is Lipid A made of?

Answer 31

short chain of fatty acids attached to a disaccharide

Question 32

What is another name for Lipid A? why?

Answer 32

endotoxin, b/c can indue toxic shock

Question 33

What is the core polysaccharide made of?

Answer 33

2 sugars: keto-deoxyocatanoic acid and heptose

Question 34

What is the O-antigen made of?

Answer 34

long carbohydrate chain (40 sugars_

Question 35

What is the role of the O-antigen?

Answer 35

creates a polar barrier which is important for bile salt and antibiotic resistance

Question 36

What are 2 key points about the O-antigen?

Answer 36

1) variable and specific to organism 2) high immunogenic

Question 37

How does the LPS affect nutrient uptake and growth?

Answer 37

slows both of them down

Question 38

How does Gram- bacteria counteract the effect of the LPS?

Answer 38

they have many channel proteins = porins

Question 39

How big does a molecule have to be to need a special transporter?

Answer 39

larger than a trisaccharide

Question 40

What type of bacteria (+ or -) can vancomycin be used against? why?

Answer 40

only Gram- b/c it can't pass through the outer membrane porins

Question 41

What type of bacteria (+ or -) can polymyxins be used against? why?

Answer 41

only Gram- b/c they specifically bind to LPS

Question 42

Where is the periplasm found?

Answer 42

Gram-, between the inner and outer membrane

Question 43

What happens in the periplasm? (3)

Answer 43

1) allows passage of enzymes across inner membrane 2) trap nutrients in cell 3) inactivates antibiotics

Question 44

What has an acid-fast cell envelope?

Answer 44

mycobacterium tuberculosis and its relatives

Question 45

What does the acid-fast cell envelope do?

Answer 45

it is so thick (lots of waxes called mycolic acids) that it makes the bacteria resistant to harsh chemicals (disinfectants and strong acids)

Question 46

What does the acid-fast cell envelope prevent?

Answer 46

severely reduces nutrient uptake and growth rate

Question 47

What are the steps to acid-fast stain? (3)

Answer 47

1) stain with hot fuchsin (red); wash 2) decolorize with acid alcohol; wash. only acid-fast bacteria remain red. 3) counterstain with methylene blue; wash. All other material becomes blue.

Question 48

How can hot fuchsin stain be taken up?

Answer 48

brieft heating

Question 49

How is the dye removed?

Answer 49

dilute HCl acid treatment

Question 50

Why is the dye not removed from mycobacteria?

Answer 50

b/c waxy cell wall makes it resistant to acid