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Microbiology > Cell Structure and Function (Pt. 2) > Flashcards

Cell Structure and Function (Pt. 2) Flashcards

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Biology 101 flashcards
1
Q

What makes up the cell envelope?

A

The cell wall + the plasma membrane

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2
Q

What is the difference between a gram-positive and a gram-negative bacteria?

A

They have different cell walls!

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3
Q

What is the cell wall?

A

Every layer of the cell outside the plasma membrane (not including filamentous appendages)

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4
Q

What is the purpose of the cell wall?

A

Shape & rigidity

-> helps to withstand cell pressure to prevent lysis

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5
Q

What is gram positive?

A

ONE membrane

One periplasm layer with thick peptidoglycan layer

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6
Q

What is gram negative?

A

TWO membranes

Two periplasm layers with a thin peptidoglycan layer in between

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7
Q

What is periplasim?

A

the gel-like substance that contains a lot of proteins in the cell walls of bacteria

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8
Q

What is peptidoglycan?

A

A carbohydrate in the bacterial cell wall that is used for structural support.

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9
Q

How is peptidoglycan synthesized?

A

The necessary enzymes are made inside of the cell and then sit within the plasma membrane. These complex structures then build the peptidoglycan on the outside of the membrane.

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10
Q

Why is peptidoglycan synthesis a good target for antibiotics?

A

Because if you’re going to target a cell for antibiotics, you don’t want to accidently destroy your own cells. The structures that make peptidoglycan are not present in the other domains (Archaea or Eukarya) and so we can target only bacteria in this way.

As well, these enzymes are essential to bacteria, without them, they cannot properly form their cell walls. This kills the bacteria.

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11
Q

Why are lysozymes important?

Where are these present on the human body?

A

Because it can destroy peptidoglycan, killing a cell.

This is important because gram positive cells cannot be killed just by heating them.

This is present in human secretions such as saliva and tears and acts as a defense mechanism. (This is part of the reason we blink)

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12
Q

What is the difference between the peptidoglycan of gram-positive cells vs gram-negative cells?

A

Gram-positive cells have multiple layers of peptidoglycan with teichoic acids inlaid.

Gram-negative cells have only a single layer of peptidoglycan.

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13
Q

What type of acids act as reinforcement for the peptidoglycan layers?

Are these found in gram-positive or gram-negative cells?

A

Teichoic Acids

Gram-positive cells

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14
Q

What are lipopolysaccharides?

Where are they anchored to and by what structure?

A

Structurally unique phospholipids found in the outer layer of the outer membrane of gram-negative cells walls.

Anchored to the peptidoglycan by lipoproteins.

Can act as an endotoxin.

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15
Q

What are endotoxins?

A

A part of the bacteria (lipopolysaccharides) that become loose in the body in great number and become toxic to the host causing a reaction by the immune system.

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16
Q

What are the three types of optional layers to the optional layers to a bacterial cell wall?

Which are considered a part of the cell envelope if present?

A

Capsule
- part of envelope

Slime layer
- part of envelope

Filamentous appendages (pili, flagella)
- NOT part of envelope
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17
Q

Can a bacteria have a capsule AND a slime layer at the same time?

A

NO!

Only one or the other or neither.

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18
Q

What is a capsule?

A

A slippery outer layer that surrounds the cell envelope of some bacteria.

This is a very dense and organized matrix that excludes small molecules.

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19
Q

What is a slime layer?

A

An unorganized and easily deformed matrix surrounding the cell envelope of some bacteria.

This is loosely attached to the cell wall.

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20
Q

What is the difference between a capsule and a slime layer?

A

A capsule is organized, densely packed, and firmly attached to the cell wall.

A slime layer is unorganized, loosely packed, and loosely attached to the cell wall.

21
Q

How do capsules and slime layers attach to each other / surfaces?

A

they stick to things via biofilms.

22
Q

What are two benefits to capsules or slimes layers.

A
  1. They prevent dehydration
  2. That can increase the virulence factor of those pathogenic species. Those species that do use these can use then to hide from host bodies as only the sugars on the outside will be seen.
23
Q

What are the three types of filamentous appendages?

A
  • fimbriae
  • pili
  • flagella
24
Q

What are the three parts of a flagellum?

A
  • Basal body
  • Hook
  • Filament (outside the bacteria)
25
Q

What is polar flagellation (aka monotrichous)?

A

One flagellum on one certain pole of the cell

NOTE:
Not really possible on a coccus because it’s a sphere without a pole

26
Q

What is lophotrichous flagellation?

A

Multiple flagella on one pole

27
Q

What is amphitrichous flagellation?

A

Flagella on both ends

28
Q

What is peritrichous flagellation?

A

Flagella are more or less evenly distributed over the body.

29
Q

What are the four types of cell locamotion?

A
  • Swimming (swarming)
  • Twitching
  • Gliding
  • Sliding
30
Q

How do monotrichous swim?

What does it do when it wants to turn?

A

Can only go forward

If it wants to turn all it can do is stop and hope that something in the environment turns it.

In SOME clockwise v counterclockwise can be the difference between forward and back.

31
Q

How do lophotrichous and peritrichous swim?

A

All flagella move into a bundle then rotate in the same direction & that pushes the bacteria forward
- This is called a run

When they want to stop they rotate flagella in opposite direction and spread them out

  • they tumble over into a different direction
  • then they can start a new run

NOTE: they still aren’t really deciding which way they end up

32
Q

What is is called when a bacteria moves toward or away from something?

A

Taxes

33
Q

What is the attractant or repellant for CHEMOTAXIS?

A

Chemicals

34
Q

What is the attractant or repellant for PHOTOTAXES?

A

Light

35
Q

What is the attractant or repellant for AREOTAXIS?

A

Air / Oxygen

36
Q

What is the attractant or repellant for OSMOTAXES?

A

Osmolarity

37
Q

What is the attractant or repellant for HYDROTAXES?

A

Water

38
Q

How do bacteria move via twitching?

A

This is an active process in which a type IV pili extends and retracts.

Slower than swimming.

39
Q

How do bacteria move via gliding?

A

The cells move using pili as little “feet” to give them little pushes in a direction over surfaces.

40
Q

How do bacteria move via sliding?

A

The cells secrete a polysaccharide slime so that when they grow, they don’t pile up, they smoosh and slide away from one another.

41
Q

What is the cytoskeleton?

A

A network of protein filaments that helps to maintain the cell shape and provide the framework for important cell functions.

42
Q

What is the cytoplasm?

A

This is everything inside of the cell.

43
Q

What is the nucleoid?

A

This is where the usually circular, supercoiled, DNA molecule is located.

44
Q

What is a plasmid?

A

This is an extrachromosomal piece of DNA that contains extra genetic elements.

These genes are usually non-essential to life but can give advantages in certain circumstances.

45
Q

What is an endospore?

A

A durable, inert, heat-resistant spore that can remain viable for thousands of years.

REMEMBER AS:
dormant, tough, non-reproductive, forms of certain bacteria

46
Q

What are two specialized structures within bacteria?

A
  • Gas vesicles (in aquatic bacteria)

- Photosynthetic membranes (progenitor of chloroplasts)

47
Q

What type of endospore forms at the tip of the bacillus? (like a matchstick)

A

terminal endospores

48
Q

What type of endospore forms off to one side of the bacillus? (but not at the very end)

A

subterminal endospores

49
Q

What type of endospore forms in the middle of the bacillus?

A

central endospores

Microbiology (6 decks)

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