Cell Envolope

Question 1

What are aquaporins?

Answer 1

Protein channels for water

Question 2

How do small nonpolar solutes pass through membrane?

Answer 2

simple diffusion

Question 3

How do polar solutes and ions pass through membrane?

Answer 3

gated channels (facilitated diffusion)

Question 4

How do large molecules pass through membrane?

Answer 4

large complex transporters

Question 5

The inside of channels are lined with ______ groups

Answer 5

polar

Question 6

Water flow results in ______ across the membrane

Answer 6

osmosis

Question 7

What happens when you place a cell in a hypotonic environment?

Answer 7

Water moves into the cell (lysis)

Question 8

What happens when you place a cell in a hypertonic environment?

Answer 8

Water moves out of the cell (plasmolysis)

Question 9

How does cell prevent water from leaving?

Answer 9

Cell imports osmoprotectants,

Question 10

What are a motive gradients a result of?

Answer 10

both a charge and concentration difference

Question 11

What is proton motive force?

Answer 11

electrochemical gradient from protons being transported to the extracellular during electron transport system

Question 12

What is another source of PMF?

Answer 12

bacteriorhodopsin (uses light energy)

Question 13

What is H+ used for as it reenters the cell

Answer 13

a. to power flagella motor
b. to transport
c. to make ATP (ATP synthase)

Question 14

Symport vs antiport

Answer 14

Symport: molecules head in the same direction
Antiport: one brought in while other brought out

Question 15

Describe the cell wall of gram positive bacteria

Answer 15

thick peptidoglycan

Question 16

Describe the cell wall of gram negative bacteria

Answer 16

thin peptidoglycan and a secondary membrane (outer membrane) called lipopolysaccharide (LPS)

Question 17

Describe mycobacteria cell wall

Answer 17

thin peptidoglycan but thick layer of waxy mycolic acid

Question 18

What bacteria don’t have cell walls?

Answer 18

Mycoplasma and spiroplasma

Question 19

Describe archaea cells walls

Answer 19

they have cell walls. Some are made of protein, others pseudoPG, and others from chondroitin

Question 20

What are the base units of peptidoglycan?

Answer 20

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

Question 21

Where are NAG and NAM synthesized?

Answer 21

cytoplasm

Question 22

What are PBPs?

Answer 22

penicillin binding proteins, they synthesize peptidoglycan using NAG and NAM

Question 23

What are the two classes of PBP?

Answer 23

Class A: does transglycocylation (links NAG and NAM horizontally)
Class B: does transpeptidase (crosslinks peptide chains on NAM together from different layers)

Question 24

What bridge is unique to gram-positive?

Answer 24

pentaglycine bridge (joins peptide chains on NAM units)

Question 25

What is the periplasm?

Answer 25

space between cytoplasm (inner) membrane and outer membrane

Question 26

What two common antibiotics are used and what do they do?

Answer 26

Penecillin (prevents pentaglycine bridge) Vancomycin (prevents transglycosylation)

Question 27

What are the issue with antiobiotics?

Answer 27

only works when bacteria are actively growing and dividing

Question 28

What else can be used to weaken bacteria cell walls?

Answer 28

lysozyme (hydrolyzes beta-1,4 bond)

Question 29

What can be found in the cell wall of gram-positive bacteria?

Answer 29

teichoic acid (only in cell wall) lipoteichoic acid (links cytoplasmic membrane and cell wall)

Question 30

What can be found in the outer membrane of gram-negative bacteria?

Answer 30

porins (channels) lipoprotein (has LPS)

Question 31

Why do we care about LPS?

Answer 31

LPS is also known as endotoxin. When bacteria lyse, LPS is released, it is a potent stimulator of inflammation. So when giving antibiotics, you don't want to give it all at once.

Question 32

Describe the LPS structure

Answer 32

O antigen Core polysaccharide Disaccharide diphosphate 4 fatty acids

Question 33

What does LPS do for transport?

Answer 33

It can surround materials, bud off, and transport to another bacteria

Question 34

What does mycobacterium resemble more - gram (+) or (-)

Answer 34

gram negative because peptidoglycan is loosely organized

Question 35

What is mycolic acid?

Answer 35

Long chain hydrocarbons that look like a wax (nonpolar) that are found in mycobacterium.

Question 36

Pros and Cons of mycobacterium

Answer 36

Can prevent phagocytosis by white blood cells Really slow to grow

Question 37

Why do mycoplasma have no cell wall?

Answer 37

they are very small. also makes it unaffected by antibiotics