Bacterial Cell Structure And Function

Question 1

What’s the importance of Microorganisms ?

Answer 1

1. Oldest form of life
2. Largest mass of living material on Earth
3. Carry out major processes for biogeochemical cycles
4. Other life forms require microbes to survive
5. Can live in places unsuitable for other organisms
6. Microbes play important roles in medicine, agriculture and industry

Question 2

What’s the positive and negative impacts of microorganisms and food ?

Answer 2

POSITIVE -
1. Microbial transformation yield
2. Diary products
3. Other food products

NEGATIVE
1. Food spoilage by microorganisms requires specialised preservation of many food.

Question 3

What’s the positive and negative impacts of microorganisms and agriculture ?

Answer 3

POSITIVE
1- Nitrogen-fixing bacteria
2- Cellulose-degrading microbes in the rumen
3. Regeneration of nutrients in soil and water

NEGATIVE
1- Diseases in plants and animals

Question 4

What are 4 positive impacts microorganisms have on humans ?

Answer 4

1- The role of microbes in biofuels production
2- The role of microbes in cleaning up pollutants
3. Exploitation of microbes for production of antibiotics, enzymes, and various chemicals.
4. Genetic engineering of microbes to generate products of value to humans, such as insulin

Question 5

What’s a Glycoalyx and what’s its function ?

Answer 5

1. Polymers of sugars surrounding some bacterial cells to form capsule or slime layer
2. Protects cell against dehydration
3. Promotes adhesion to inert surfaces
4. Protects cell from macrophages attack
5. Protects cells against viral attack

Question 6

What is a flagella and its function ?

Answer 6

1. Large hair-like structures which rotate and allow bacteria to swim.
2. Not all bacteria have flagella
3. cocci are rarely motile
4. pff across cm used to turn motor
5. Direction of swimming influenced by environment.

Question 7

What is a pili and what’s its function ?

Answer 7

1. Many species of bacteria have pili
2. They are small hair like structures on the outside of the cell - used for attaching to surfaces and other cells
3. Pili necessary for many pathogenic bacteria to attach to host tissue and infect cells
4. Specialized pili are used for transferring plasmid DNA between cells

Question 8

What is clostridium botulinum and what are symptoms ?

Answer 8

1. Spores are heat resistant and germinate in cooled food
2. Vegetative cells produce potent neurotoxin during growth, but toxin is heat sensitive
   - Associated with meat dishes or canned goods no reheated before eating
   - onset of symptoms within 12-36 hr - death within 24 hrs
   - Symptoms include headache, dizziness, diarrhoea, muscle paralysis and blurred vision.

Question 9

What are all the structures of the bacterial cell wall from plasma membrane onwards ?

Answer 9

1. Plasma membrane
2. Periplasmic space
3. peptidoglycan
4. Outer membrane
5. plasma membrane
6. Peptidoglycan

Question 10

What is the plant cell wall made of ?

Answer 10

its made out of peptidoglycan which is a major polymer giving bacterial cell wall its rigidity
The cell wall helps maintain the cell shape

Question 11

What’s the structure of peptidoglycan ?

Answer 11

Polysacccharide of repeating sugar units linked by b-1,4 glycosidic bonds polysaccharide chains cross-linked via peptide bridges

Question 12

What’s the Peptidoglycan like in gram negative cells?

Answer 12

only 10-20nm wide and is surrounded by a second membrane which is anchored to it by lipoproteins
Outer layer is composed of lipopolysaccharide which is highly variable and antigenic
It also acts as an endotoxin in humans

Question 13

What is an endotoxin and the effects of it ?

Answer 13

ENDOTOXIN - parts of the structural components of the bacterial cell structure. Some of the symptoms of bacterial infection caused by natural toxicity of cell compartments.
EFFECTS
- Interacts with cells an molecules of inflammation, immunity and homeostasis
- Septic shock occurs during severe infection with gram negative organisms when bacteria or lipopolysaccharide enter the bloodstream

Question 14

What is the cytoplasmic membrane and its functions ?

Answer 14

Is a thin barrier which separates the cytoplasm from the cell’s environment
- The hydrophobic core acts as a barrier to most H20 - soluble molecules
- Protein permeates allow selective transport of small molecules into cell
-

Question 15

What is the function of the cytoplasmic membrane when it separates the cytoplasm of unicellular organism from the environment ?

Answer 15

• Prevents release of cell components
• Allows uptake of nutrients
• allows excretion of by-products
  -acts as a sensor of the environment
  -Allows generation of a proton motive force.

Question 16

How does gas enter the cell and water ?

Answer 16

GAS - Enters the cell by simple diffusion
WATER - tends to move into the cell by osmosis

Question 17

What does it mean if the cells are usually in a hypotonic medium ?

Answer 17

• High conc of compounds found in the cytoplasm
• Tugor pressure helps maintain cell shape

Question 18

What did CARL WOESE discover ?

Answer 18

He realised rRNA sequences could be used to infer evolutionary relationships, discovered rRNA from methanogens distinct from Bacteria and Eukarya
Named new group ARCHEAE
Found relationships can be be deduced by comparing genetic info in the different specimens

Question 19

What are cell inclusions and function ?

Answer 19

Inclusions function as energy reserves, carbon reservoirs, and have special functions
Enclosed by thin membrane
Reduces osmotic stress

Question 20

What are megnetosomes ?

Answer 20

Magnetic iron oxides - allow cell to undergo magneto taxis - migration along magnetic field lines

Question 21

What are surface appendages archaella ?

Answer 21

They play an important role in spatial organisation of cells, from initial surface attachment to the development of mature community structures.
- Mixed communities in aggregates and complex biofilms
- Possible these structures may have role in locally increasing the conc of substrates around the cell, movement, and co-aggregation with other microorganisms

Question 22

What is the S-layer ?

Answer 22

Most common cell wall of ARCHAEA
consists of protein or glycoprotein
Withstand osmotic bursting

Question 23

Explain properties of the cell wall of archaea - what’s it made of ?

Answer 23

• No peptidoglycan
• No outer membrane
• made of PSEUDOMURIEIN
• Cell wall plays a crucial role in survival of bacteria and archaea in extreme environments
• Able to grow in high temp due to the chemical stability of their membrane lipids

Question 24

What are some properties of extreme thermophiles ?

Answer 24

• Isolated from depth of 2,600 m
• Growth range of 50-86 degrees
• Produces methane