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BIOL 221 > Cell Envolope > Flashcards

Cell Envolope Flashcards

1
Q

What are aquaporins?

A

Protein channels for water

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2
Q

How do small nonpolar solutes pass through membrane?

A

simple diffusion

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3
Q

How do polar solutes and ions pass through membrane?

A

gated channels (facilitated diffusion)

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4
Q

How do large molecules pass through membrane?

A

large complex transporters

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5
Q

The inside of channels are lined with ______ groups

A

polar

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6
Q

Water flow results in ______ across the membrane

A

osmosis

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7
Q

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

A

Water moves into the cell (lysis)

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8
Q

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

A

Water moves out of the cell (plasmolysis)

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9
Q

How does cell prevent water from leaving?

A

Cell imports osmoprotectants,

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10
Q

What are a motive gradients a result of?

A

both a charge and concentration difference

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11
Q

What is proton motive force?

A

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

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12
Q

What is another source of PMF?

A

bacteriorhodopsin (uses light energy)

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13
Q

What is H+ used for as it reenters the cell

A

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

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14
Q

Symport vs antiport

A

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

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15
Q

Describe the cell wall of gram positive bacteria

A

thick peptidoglycan

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16
Q

Describe the cell wall of gram negative bacteria

A

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

17
Q

Describe mycobacteria cell wall

A

thin peptidoglycan but thick layer of waxy mycolic acid

18
Q

What bacteria don’t have cell walls?

A

Mycoplasma and spiroplasma

19
Q

Describe archaea cells walls

A

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

20
Q

What are the base units of peptidoglycan?

A

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

21
Q

Where are NAG and NAM synthesized?

A

cytoplasm

22
Q

What are PBPs?

A

penicillin binding proteins, they synthesize peptidoglycan using NAG and NAM

23
Q

What are the two classes of PBP?

A

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

24
Q

What bridge is unique to gram-positive?

A

pentaglycine bridge (joins peptide chains on NAM units)

25
Q

What is the periplasm?

A

space between cytoplasm (inner) membrane and outer membrane

26
Q

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

A

Penecillin (prevents pentaglycine bridge)
Vancomycin (prevents transglycosylation)

27
Q

What are the issue with antiobiotics?

A

only works when bacteria are actively growing and dividing

28
Q

What else can be used to weaken bacteria cell walls?

A

lysozyme (hydrolyzes beta-1,4 bond)

29
Q

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

A

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

30
Q

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

A

porins (channels)
lipoprotein (has LPS)

31
Q

Why do we care about LPS?

A

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.

32
Q

Describe the LPS structure

A

O antigen
Core polysaccharide
Disaccharide diphosphate
4 fatty acids

33
Q

What does LPS do for transport?

A

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

34
Q

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

A

gram negative because peptidoglycan is loosely organized

35
Q

What is mycolic acid?

A

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

36
Q

Pros and Cons of mycobacterium

A

Can prevent phagocytosis by white blood cells
Really slow to grow

37
Q

Why do mycoplasma have no cell wall?

A

they are very small. also makes it unaffected by antibiotics

BIOL 221 (32 decks)

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