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CELS191 > Lecture 27 > Flashcards

Lecture 27 Flashcards

1
Q

Prokaryotic cell structure

A
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2
Q

Chromosomes

A

Single circular chromosome
1 - 2 micrometer long

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3
Q

Three types of prokaryotic cells

A

Cocci
Rods
Spirals

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4
Q

Circular Chromosome nuclear membrane?

A

No nuclear membrane

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5
Q
A
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6
Q

Region of the chromosome within the cell

A

Defined region known as nucleoid

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7
Q

What can be found in the cytosol of the bacteria?

A

Other small self-replicating DNA moleculecules (seperate to the main chromosome)
- these are known as plasmids

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8
Q

Average bacteria genome compared to human

A

Bacteria: 5000 genes / 5 million base pairs

Human: 20-25000 genes / 3 billion base pairs

Greater then 90% of the genome is giving rise to functional proteins

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9
Q

Major structural component of the cell wall of bacteria

A

Peptidoglycan

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10
Q

Cell wall, peptidoglycan function:

A
  • rigid macromolecular layer that provided strength to cell
  • protect cells from osmotic lysis and confers cell shape
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11
Q

Structure that betalactin targets and how they target them

A

Peptidoglycan

They target the enzymes that are involved in assembling peptidoglycan

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12
Q

Prokaryotes that lack cell walls

A

Mycoplasmas - group of pathogenic bacteria

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13
Q

Physical structure of the cell wall - mesh like structure

A
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14
Q

Structure of petioglycan

A
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15
Q
A
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16
Q

Petdiglycan stucture and how its made kinda

A
  • consists of a network of fibres
  • chain of sugars called NAM and NAG all linked together and repeating
  • on NAM molecules there is a sort stretch of amino acids - a tetrapeptide - 4 amino acids are assembled onto NAM
  • all chains stack together to create macromolecular molecule
  • glycan chains are being wrapped around the cell
  • cell is synthesising them inside cytoplasm and exports them to outside of cell and get assembled into larger network
  • nag nams held together by strong bonds
  • glycan chains are linked by tetrapeptides (a cross bridge)

Therefore strong

17
Q

What enzyme catalyses the cross linking of the peptidoglycan chains to form rigid cell walls ?

A

Trandpeptidate (penacilin targets this enzyme)

18
Q

Gram stain

A

A gram stain of mixed:
- staphylococcus aureus, gram-positive cocci (purple)
- Escherichia, gram negative bacilli (red)

Most common bacteria in reference bacteria

19
Q

Gram stain proceedure

A
  1. Application of crystal violet (purple die)
  2. Application of iodine (mordant - fixes cell into cell wall)
  3. Alcohols wash (decolourization)
  4. Application of safranin (counterstain
20
Q

Structure of gram- positive bacterial cell wall

A
  • peptidoglycan traps crystal violet, which masks the red safranin dye - when washed away - too thick to leave.
  • they will stain a darker colour and have a thicker cell wall of peptidoglycan (20-80nm)
21
Q

What is the reason for the difference in the Gram stain reaction?

A

Structural differences between cell walls of gram-positive and gram-negative bacteria

22
Q

Structure of gram negative bacterial cell wall

A
  • crystal violets is easily rinsed away, revealing the red safranin dye
  • there is a thinner layer (5-10mm) of peptidoglycan between plasma and outer membranes
23
Q

Function of bacterial flagella

A

Some bacteria are capable of movement in liquid medium

24
Q

How are bacterial flagella capable of movement in a liquid medium

A
  • motile bacteria produce flagella
  • long flexible appendage resembling “tails”
  • proteinaceous 10-20nm in diameter, 5-10 per cell
  • number of flagella and location on cell surface varies
  • act like a propellant; cell rotates them to move through a liquid medium
25
Q

Tactic responses: chemotaxis

A

Bacteria move along a concentration gradient towards a chemical attractant (positive) or away form a chemical repellent

From lecture voice
- too small to sense glucose difference at each end of cell
- thus it senses the tempal gradient (swims along, senses conc outside the cell, swims off again, senses concentration again, senses whether that concentration was either higher or lower)

26
Q

Fimbiae - bacterial adherence factors

A

Function: structures with adhesive properties that cause bacteria to stick/adhere to surfaces

  • not all bacteria possess fimbriae: it is an inherited trait
  • can be mistaken for flagella but are not involved in motitily
  • much shorter and more numerous then flagella “hair-like”
  • 100-1000 per cell and 2-8 nm in diameter
  • 1 micrometer in length
  • receptors that recognise the cells they’re colonises - they are specific
27
Q

Pili (sex conjugation pili or F pili)

A
  • attachment to other bacteria
  • transfer genetic material from one cell to another
  • the genetic transfer is called conjugation
  • conjugation is a form of horizontal gene transfer
28
Q

Glycocalyx

A

A gelatinous polysaccharide and / or polypeptide outer covering

Forms a sticky mesh work of fibres

29
Q

Another structure bacteria can use to attach to surfaces

A

Glycocalyx - capsules and slime layers

30
Q

Two arrangements of Glycocalyx - capsules and slime layers

A

Organised into a friended structure attached firmly to a cell wall: CAPSULE

Disorganised without cell shape, attached loosely to cell wall = slime layer

31
Q

Functions of capsules

A
  • Virulence factors - protecting bacteria from phagocytosis and engulfment by immune cellls
  • bacterial that make capsules are difficult to eradicate
  • prevent cell from drying out (desiccation)
32
Q

When are Bacterial Endo spores formed

A
  • during unfavourable growth conditions and germinate under favourable conditions
33
Q

What do bacterial Endo spores do

A
  • protect cells from stress
34
Q

Only two gram-positive bacteria that contain bacterial Endo spores

A
  • genus bacillus (anthrax caused by the bacterium bacillus anthracis)
  • clostridium (e.g clostridium difficle)
35
Q

Stresses that trigger endospore formation

A
  • nutrient starvation
  • high cell density
  • mother cell produces endospore via asymmetric cell division and dies
36
Q

Endospore definition

A
  • highly defines differentiated cells resistant to heat, harsh chemicals, antibiotics, disinfectants and radiation.
  • dormant stage of bacterial life cycle
  • can stay dormant for a very long time - all machinery for life is preserved on the inside of the endospore so when conditions become right they can germinate and goes back to normal life cycle
  • survival strategy

CELS191 (37 decks)

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