L27 - Prokaryotes

Question 1

Estmate of bacteria on earth

Answer 1

5 x 10ˆ30

Question 2

Why are microbes everywhere

Answer 2

Because they have been around for 3.8 billion years

Question 3

Two kingdoms of bacteria

Answer 3

Archaea (ancient bacteria) and Eubacteria

Question 4

DNA present in Bacteria

Answer 4

Single circular chromosome in the nucleoid

Question 5

Parameters of the bacteria

Answer 5

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

Question 6

What helps with bacteria motility

Answer 6

Flagella

Question 7

Glycocalyx

Answer 7

Extracellular cell protection

Question 8

Do prokaryotes have nuclear envelope or organelles

Answer 8

no

Question 9

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

Answer 9

Peptidoglycan

Question 10

What are Plasmids?

Answer 10

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

Question 11

Prokaryotes that lack cell walls

Answer 11

Mycoplasms

Question 12

What does peptidoglycan do?

Answer 12

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

Question 13

What does penicillin do to the peptidoglycan

Answer 13

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

Question 14

What is peptidoglycan made of?

Answer 14

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

Question 15

Where is NAM-NAG synthesised

Answer 15

Made in the cell and transported through constitutive exocytosis

Question 16

What is on the NAM side

Answer 16

The tetrapeptide bond

Question 17

How is the structure of the cell wall formed

Answer 17

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

Question 18

What enzyme catalyses the cross-linking of the NAM units

Answer 18

Transpeptidase - flemings penicillin targets

Question 19

Colour for gram positive w example

Answer 19

Purple - staph. Aureus

Question 20

Colour for gram negative w example

Answer 20

Red - E. coli

Question 21

How to carry out a gram stain

Answer 21

*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

Question 22

Why do different cells stain differently

Answer 22

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

Question 23

Why do some cells stain purple

Answer 23

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

Question 24

Why do gram negative stain red

Answer 24

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

Question 25

How fast do bacteria move in liquid media

Answer 25

100m in 5s

Question 26

How do the bacteria move in liquid media?

Answer 26

Flagella that acts as a propellor

Question 27

What are the flagella made of?

Answer 27

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

Question 28

Tactic response of the bacteria

Answer 28

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

Question 29

How do bacteria detect sugar if they are too small?

Answer 29

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

Question 30

What are Fimbriae?

Answer 30

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

Question 31

Are fimbriae involved in motility

Answer 31

No

Question 32

Do all bacteria have Fimbriae

Answer 32

No, it is an inherited trait Exp in lab showed that overtime, trait is lost if no surface to attatch to

Question 33

Parameters of Fimbraie

Answer 33

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

Question 34

What is Pili (sing.pillus) aka?

Answer 34

Sex pilli/ F pilli

Question 35

What do Pili do?

Answer 35

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

Question 36

What is a Glycocalyx?

Answer 36

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

Question 37

Where is Glycocalyx made?

Answer 37

Synthesised in the outside of the cell

Question 38

2 forms of Glycocalyx

Answer 38

*Capsule *Slime layer

Question 39

Capsule

Answer 39

*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

Question 40

Slime layer

Answer 40

*Disorganised and surrounds the cell, loosely attached without shape

Question 41

What are bacterial endospores?

Answer 41

Form during unfavourable conditions and germinate under favourable ones

Question 42

Where are bacterial endospores present?

Answer 42

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

Question 43

Usual state of the bacteria

Answer 43

Vegetative state - binary fission

Question 44

State of bacteria under nutrient starvation and high cell density

Answer 44

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

Question 45

What are dangerous part of endospores

Answer 45

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