Prokaryotic Cells

Question 1

How many bacterial cells are estimated to be on earth?

Answer 1

5x10^30

Question 2

What is the size of bacterial cells?

Answer 2

Approximately 10^-18m^3

Question 3

How much of the biomass of earth do bacteria make up?

Answer 3

Half

Question 4

How many bacterial species are there?

Answer 4

10^19 across two kingdoms (bacteria and archaea)

Question 5

How many species of mammals are there?

Answer 5

4300

Question 6

What does the structure of bacteria include?

Answer 6

Fimbriae, nucleoid (where DNA sits but is not bound by a membrane), ribosomes, plasma membrane, cell wall, capsule and flagella

Question 7

What is cell wall peptidoglycan in bacteria?

Answer 7

A rigid macromolecular layer that provides strength to the cell

Question 8

What is the function of peptidoglycan in cell walls?

Answer 8

Protects the cell from osmotic lysis (bursting) and confers cell shape

Question 9

What is the structure of peptidoglycan?

Answer 9

Carbohydrate backbone made of alternating NAG and NAM linked together. Cross linking of carbohydrate backbone with a peptide cross bridge of amino acids

Question 10

What is transpeptidase?

Answer 10

The enzyme that cross links the peptidoglycan chains to form rigid cell walls

Question 11

What is the result of a gram stain?

Answer 11

A mixture of gram positive cocci appearing in purple and gram negative bacilli appearing in red

Question 12

What is the first step of a gram stain?

Answer 12

Application of crystal violet (purple dye) to a mixed culture of bacteria

Question 13

What happens after application of crystal violet?

Answer 13

Application of iodine which is a mordant that fixes the dye

Question 14

What happens after application of iodine?

Answer 14

Alcohol wash which causes decolorisation of the gram negative cells while gram positive remains violet

Question 15

What happens after the alcohol wash?

Answer 15

Application of safranin which is a counterstain that will only show up on gram negative cells as the violet in gram positive cells masks any effect

Question 16

What is the structure of a gram positive cell wall?

Answer 16

Thick peptidoglycan layer (20-80nm)

Question 17

What does the gram positive cell wall do in a gram stain?

Answer 17

Traps the crystal violet which masks the red sarafanin dye

Question 18

What is the structure of a gram negative cell wall?

Answer 18

Thin layer of peptidoglycan (5-10nm) with inner and outer membranes

Question 19

What does the gram negative cell wall do in a gram stain?

Answer 19

Crystal violet is easily rinsed away revealing the red safranin dye

Question 20

What are some bacteria capable of?

Answer 20

Movement in a liquid medium

Question 21

How can bacteria move?

Answer 21

Motile bacteria produce flagella

Question 22

What are flagella?

Answer 22

Long flexible appendages reassembling tails

Question 23

What are flagella made of?

Answer 23

Proteins (they are proteinaceous)

Question 24

What is the diameter of flagella?

Answer 24

10-20nm

Question 25

How many flagella are on a bacteria?

Answer 25

5-10 on average

Question 26

What to do with flagella varies?

Answer 26

The number of flagellant location on the cell surface

Question 27

What does a flagella act like?

Answer 27

A propeller. The cell rotates them to move through a liquid medium

Question 28

What is the 3 major sections of a flagella?

Answer 28

Long filament (F), Hook (H) and Basal Body (B)

Question 29

What does the long filament do?

Answer 29

Extends into surrounding medium. Composed of subunits (protein=flagellin)

Question 30

What is the hook?

Answer 30

A curved section connecting the filament to the cell surface

Question 31

What does the basal body do?

Answer 31

Anchors the flagellum into the cell membrane of the bacterium by special disc shaped structures called rings or plates

Question 32

What happens in chemotaxis?

Answer 32

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

Question 33

What does being able to move allow bacteria to do?

Answer 33

Sense and respond to their environment

Question 34

How does chemotaxis occur?

Answer 34

Bacteria sense the change in chemical concentration outside the cell over time "TEMPORAL GRADIENT" and thus respond to the change in concentration as the cell moves

Question 35

Why can't bacteria use a spatial gradient for chemotaxis?

Answer 35

Because they are too small

Question 36

What are the bacterial adherence factors?

Answer 36

Fimbria and glycocalyx

Question 37

What are Fimbria?

Answer 37

Structures with adhesive properties that cause bacteria to stick/adhere to surfaces

Question 38

What type of trait is fimbria?

Answer 38

It is an inherited trait so not all bacteria have them

Question 39

What can fimbria be mistaken for?

Answer 39

Flagella, but they are not involved in motility

Question 40

How many fimbria on a bacteria cell?

Answer 40

100-1000

Question 41

What is the diameter of fimbria?

Answer 41

2-8nm

Question 42

What is the length of fimbria?

Answer 42

1 micrometre

Question 43

What is they types of glycocalyx?

Answer 43

Capsules and slime layers

Question 44

What is the glycocalyx?

Answer 44

A gelatinous polysaccharide and/or polypeptide outer covering. Forms a sticky meshwork of fibres/

Question 45

What is a capsule?

Answer 45

Glycocalyx organised into a defined structure attached firmly to the cell wall

Question 46

What is a slime layer?

Answer 46

Glycocalyx disorganised without cell shape, attached loosely to the cell wall

Question 47

What is the function of capsules?

Answer 47

They are virulence factors, help with adherence to cell surfaces and structures and also prevent the cell drying out (desiccation)

Question 48

What is meant by virulence factors?

Answer 48

Protecting bacteria from phagocytosis and engulfment by immune cells

Question 49

When are bacterial endospores formed?

Answer 49

During unfavourable growth conditions

Question 50

When are bacterial endospores germinated?

Answer 50

Under favourable conditions

Question 51

What do bacterial endospores do?

Answer 51

Protects the cell from stress

Question 52

What cells are bacterial endospores present in?

Answer 52

Only present in some gram-positive bacteria (genus = bacillus and clostridium)

Question 53

What stressors trigger endospore formation?

Answer 53

Nutrient starvation and high cell density (competition)

Question 54

What are endospores?

Answer 54

Highly differentiated cells resistant to heat, harsh chemicals, antibiotics, disinfectants and radiation

Question 55

What stage of the bacterial life cycle are endospores found?

Answer 55

The dormant stage and they may stay dormant for a very long time