Bacterial Cell Structures

Question 1

How many ribomsomes are there in Prokaryotic cells vs Eukaryotic cells

Answer 1

Pro - 70S Ribosomes
Euk - 80S Ribosomes

Question 2

Diff bacterial cell morphology and examples

Answer 2

1. Cocci - e.g streptpcoccus pneumoniae
2. Bacilli - e.g bacillus subtilis
3. Spirilla - e.g vibrio cholerae
   Other - filamentous, star-shaped, pleomorphic

Question 3

What is the polysaccharide material that makes up the capsule called?

Answer 3

Glycocalyx
Most capsules are polysaccharide but some are proteins

Question 4

Capsule VS Slime layer

Answer 4

-If attached to cell and forms a rigid layer - capsule
-If not attached to cell and easily deformed - slime layer

Question 5

What is the lipopolysaccharides of Gram neg bacteria composed of?

Answer 5

O-Antigen that is recognised by the immune system
Core oligosaccharide
Lipid A - toxin

Question 6

What protein subunits are the flagella made of?

Answer 6

Flagellin

Question 7

How do flagella move?

Answer 7

The base region spin- due to hydrogen ions - causes top to spin

Question 8

Flagellar distribution - peritrichous

Answer 8

Flagella are all around the capsid

Question 9

Flagellar distribution - Polar monotrichous

Answer 9

Flagellum (SINGLE) come out one end

Question 10

Flagellar distribution - polar iophotrichous

Answer 10

Many flagella come out one end

Question 11

What do spirochetes have that are different to other bacteria with regards to motility?

Answer 11

Spirochetes have axial filaments which enable corkscrew motility - allowing penetration of tissues

Question 12

What are fimbriae, made of and func?

Answer 12

Fimriae are shorter than flagella and more numerous
Made of proteins
Not present in all bacteria
Used to adhee to surfeces like specific tissues

Question 13

What are pili?

Answer 13

Pili are longer than fimbriae
Fewer present on cell
Involved in attachment to tissues
Involved in motility and DNA transfer in some bacteria

Question 14

How do pili move the cell?

Answer 14

Type IV pili
Pili extension
Attachment to a surface
Retraction
-uses a motor for extension and retraction

Question 15

How is pili involved in DNA transfer?

Answer 15

Pilus makes contact with recipient cell, pulls cells together and DNA transfer occurs

Question 16

Where is the DNA aggregated in bacteria?

Answer 16

In a dense area called the nucleoid - no nuclear membrane

Question 17

What are bacterial chromosomes structurally?

Answer 17

Singular, circular, double stranded DNA molecule

Question 18

How is DNA packed into the nucleoid?

Answer 18

-Packed in an organised way to enable transcription- supercoiling

Question 19

What enzymes do the supercoiling of DNA?
What are these supercoiled domains stabilised by?

Answer 19

Supercoiling is done by enzymes called gyrases and topoisomerases.
These domains are stabilised by structural proteins

Question 20

What are plasmids and are they necessary for bacterial survival?

Answer 20

Circular double stranded pieces of DNA which replicate separately from chromosomal DNA
-Not essential for bacterial survival
-Capable of being transferred between bacteria

Question 21

Types of plasmids and their gene fuctions and examples

Answer 21

1. Resistance - antibiotic resistence - e-coli
2. Fertility - conjugation and DNA transfer between bacteria - e-coli
3. Killer - synthesis of toxins that kill other bacteria - e-coli
4. Degradative - enzymes for metabolism of unusual molecules - p.putida

Question 22

Combined prokaryotic ribosome - how much in each subunit?

Answer 22

70S ribosome total
- 30S small subunit composed of 16S rRNA + 21 proteins
-50S large subunit composed of 23S rRNA + 30 proteins

Question 23

What is the S when giving ribosomes a unit?

Answer 23

Svedberg units = a measure of how quickly particles sediment in an ultracentrifuge
-the larger the particle the greater its S value
-Smaller subunit of ribosome sinks slower than the larger subunit

Question 24

Why do bacteria have storage granules/inclusion bodies sometimes?

Answer 24

Most of time for energy storage or structural building blocks - use when environmental sources are depleted
-most common is poly-b-hydroxybutyrate (PHB)
-can also contain glycogen, polyphosphate, iron oxide or elemental sulphur

Question 25

What are magnetosomes and why do bacteria make them?

Answer 25

Magnetosomes are intracellular inclusions of the iron mineral magnetite
-Gives a permanent magnetic dipole to cell
-Enables bacteria to orient themselves and migrate along geomagnetic field lines

Question 26

What are gas vesicles made from and why do bacteria have them?

Answer 26

Gas vesicles are small gas-filled structures made of protein
They allow buoyancy on cells
Common in cyanobacteria

Question 27

What is the Bt toxin?

Answer 27

a crytalline protein that is produced by Bacillus thuringiensis - breaks down the cells lining gut in insects

Question 28

Features of endospores and examples of bacteria that produce endospores?

Answer 28

-Endospore formers are usually found in soil
- Normally triggered by environmental stress
-Very resistent to heat, drying, freezing, radiation, chemicals
-Can survive million sof years

Usually part of Bacillus or Clostridium genera

Question 29

What is sporulation and germination?

Answer 29

Sporulation = the production of an endospore

Germination = endospores converting back to vegetative cells

Question 30

What are the 3 categories of bacterial endospore formation

Answer 30

1. Terminal
2. Subterminal
3. Central