Bacterial structure

Question 1

Average bacterial size

Answer 1

0.2-1.o um by 2-8 um

Question 2

Main cell structures

Answer 2

-Flagella
-Fimbriae and pili
-Capsules, slime layers, S-layers
-Cell wall
-Plasma membrane
-Nucleoid
-Gas vacuoles
-Inclusion bodies
-Ribisomes
-Internal membrane system
NB not all found in bacteria: depends on type and environmental factors

Question 3

Capsule, slime and s-layers

Answer 3

layers of material outside CW
-Extracellular polymeric substances (EPS)

Types:
-polysaccharide (primarily): Capsule and slime layers
-protein

Question 4

Roles of slime layers, capsules and s-layers

Answer 4

-Determine cell shape (Archaea)
-Growth
-Enzymes
-Molecular sieves:
-Exclude molecular weights of 30 and 45 kD
-Pore diameter in range of 3.0 to 4.5 nm
-Maintenance of cell integrity
-Protective coat
-Contribute virulence
-Ion traps (prevent clogging of other layers)

Question 5

Nucleiod

Answer 5

-Irregular shaped dense region containing prokaryotic DNA
-single, circular dsDNA molecule

Question 6

Inclusion bodies

Answer 6

Reserve deposits
-Concentrated storage
-May be membrane bound

Store
-Polysaccharide granules- eg. glycogen
-Lipids
-Enzymes: Ribulose-1,5-bisphosphate carboxylase/oxygenase
-Nitrogen, Phosphate, Sulphur

Question 7

Gas vacuoles

Answer 7

Found in:
-Phososynthetic bacteria
-Aquatic bacteria

Purpose;

Question 8

Ribisomes

Answer 8

Smaller than Eu
-Subunits:
70s (svedburg unit)
50S
-> 5S rRNA and 23S rRNA
30s
-> 15S rRNA

Question 9

Intracytoplasmic membranes

Answer 9

Intracytoplasmic membranes (ICMs) are specialized internal membrane structures found within the cytoplasm of certain prokaryotic cells, especially in bacteria like photosynthetic or nitrifying bacteria

1.	Increased Surface Area for Metabolic Reactions
2.	Photosynthesis: In photosynthetic bacteria (like Cyanobacteria and Purple Bacteria), ICMs contain pigment-protein complexes that are essential for capturing light energy and conducting photosynthetic reactions.
3.	Respiration and Nitrogen Fixation: In other bacteria, ICMs may house enzymes and proteins for respiration or nitrogen fixation

Question 10

Origin of intracytoplasmic membranes

Answer 10

ICMs are thought to derive from the invagination of the plasma membrane. These invaginations form extended networks of membranes that remain continuous with the outer membrane but are more internalized, creating a larger surface area inside the cell.