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CELS > L27 - Prokaryotes > Flashcards

L27 - Prokaryotes Flashcards

1
Q

Estmate of bacteria on earth

A

5 x 10ˆ30

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2
Q

Why are microbes everywhere

A

Because they have been around for 3.8 billion years

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3
Q

Two kingdoms of bacteria

A

Archaea (ancient bacteria) and Eubacteria

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4
Q

DNA present in Bacteria

A

Single circular chromosome in the nucleoid

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5
Q

Parameters of the bacteria

A

rod shaped, 1-2µm long and 1/2 µm in diameter

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6
Q

What helps with bacteria motility

A

Flagella

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7
Q

Glycocalyx

A

Extracellular cell protection

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8
Q

Do prokaryotes have nuclear envelope or organelles

A

no

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9
Q

What component present in the cell wall allows antibiotics to be effective against bacteria

A

Peptidoglycan

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10
Q

What are Plasmids?

A

Small circular, self-replicating DNA molecules found in the cytosol, can be v small/big

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11
Q

Prokaryotes that lack cell walls

A

Mycoplasms

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12
Q

What does peptidoglycan do?

A

*Its a rigid macromolecular shape that gives strength to the cell
*Protects the cells from osmotic lysis and confers cell shape

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13
Q

What does penicillin do to the peptidoglycan

A

*Targets the enzymes that makes this
*Makes the cell shape from rod to round

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14
Q

What is peptidoglycan made of?

A

A mesh like structure:
*Make of short stretches of amino acids that stack to make a macromolecule
*Repeating units of NAM-NAG Glycan

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15
Q

Where is NAM-NAG synthesised

A

Made in the cell and transported through constitutive exocytosis

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16
Q

What is on the NAM side

A

The tetrapeptide bond

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17
Q

How is the structure of the cell wall formed

A

The NAM-NAG are strong and resists tension one way
*The tetrapeptide on the NAM is linked to another tetrapeptide to another NAM through crossbridge of amino acids

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18
Q

What enzyme catalyses the cross-linking of the NAM units

A

Transpeptidase - flemings penicillin targets

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19
Q

Colour for gram positive w example

A

Purple - staph. Aureus

20
Q

Colour for gram negative w example

A

Red - E. coli

21
Q

How to carry out a gram stain

A

*Crystal violet to stain culture purple
*Add iodine (mordant) - fixes the stain to the cell wall
*Alcohol - washed crystal violet, not from all cells only gram neg ones
*Stain with red safranin

22
Q

Why do different cells stain differently

A

Due to differences in the chemical and structural composition of the peptidoglycan wall

23
Q

Why do some cells stain purple

A

Due to a thick peptidoglycan cell wall (20-80nm):
*Traps crystal violet
*OH cannot wash away the crystal violet cause wall so thick
*Safarin stains but cant see because of violet stain

24
Q

Why do gram negative stain red

A

Have two layers and pepti inbetween the layers i.e the plasma and outer membrane
*Thinner (5-10nm) hence the OH washes away the crystal violet

25
Q

How fast do bacteria move in liquid media

A

100m in 5s

26
Q

How do the bacteria move in liquid media?

A

Flagella that acts as a propellor

27
Q

What are the flagella made of?

A

They are made of proteins, 10-20nm in diameter and 5/10 per cell

They all move to the back and propel the bacteria in one direction

28
Q

Tactic response of the bacteria

A

Chemotaxis - has +ve and -ve chemotaxis
*Bacteria moves along conc. gradient towards a chem attractant or away from it

29
Q

How do bacteria detect sugar if they are too small?

A

Move around to sense the temporal gradient, sense and remembers the higher conc through chemoreceptors and send info to the flagellar motor

30
Q

What are Fimbriae?

A

Protein structures with adhesions aka adhesion pili/adhesins
*Causes bacteria to stick to surfaces
*Have receptors to recognise the structures that they are colonising

31
Q

Are fimbriae involved in motility

A

No

32
Q

Do all bacteria have Fimbriae

A

No, it is an inherited trait

Exp in lab showed that overtime, trait is lost if no surface to attatch to

33
Q

Parameters of Fimbraie

A

Much shorter and more numerous than flagalla
*Hair like
*100-1000/cell
*2-8nm in diameter
1µm in length

34
Q

What is Pili (sing.pillus) aka?

A

Sex pilli/ F pilli

35
Q

What do Pili do?

A

Attaches to another cell and transfers DNA through Conjugation, a form of horizontal gene transfer

36
Q

What is a Glycocalyx?

A

*Gelatinous polysaccharide (like snot hehe) and/or polypeptide outer covering
*Forms a sticky meshwork

37
Q

Where is Glycocalyx made?

A

Synthesised in the outside of the cell

38
Q

2 forms of Glycocalyx

A

*Capsule
*Slime layer

39
Q

Capsule

A

*Organised into a define structure that is stuck to the cell wall
*Made from sugar + peptide so prevents from dessication
*Strep dangerous as our immune cells cant do phagocytosis

40
Q

Slime layer

A

*Disorganised and surrounds the cell, loosely attached without shape

41
Q

What are bacterial endospores?

A

Form during unfavourable conditions and germinate under favourable ones

42
Q

Where are bacterial endospores present?

A

In gram pos bacteria i.e Bascillus anthracis and Clostridium difficile

43
Q

Usual state of the bacteria

A

Vegetative state - binary fission

44
Q

State of bacteria under nutrient starvation and high cell density

A

Asymm division, endospore with nutrients and chromosomes at one end, mother dies
*Process takes 8 hours

45
Q

What are dangerous part of endospores

A

*Resistant to heat, harsh chemicals, antibiotics, disinfectants and radiation
*Has all the machinery for life
*Can stay dormant for millions of years

CELS (26 decks)

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