Topic 3 - Cell Structure

Question 1

What are Eukaryotic organelles?

Answer 1

• Nucleus - Ribosomes
• Cytoplasm - Lysosomes
• Plasma membrane - Golgi apparatus
• Mitochondria - Endoplasmic reticulum

Question 2

What do monomorphic and pleomorphic mean?

Answer 2

Monomorphic means it has just one shape which is what bacteria usually is.
Pleomorphic has many shapes which is rare in bacteria.

Question 3

What are the basic shapes of microbes?

Answer 3

There is - bacillus, coccus and spiral.

Spiral shapes can be either vibrio, spirillum or spriochete.

Question 4

What are the arrangements of microbes and why are they important?

Answer 4

There is Diplo = pairs, tetra = 4 and sarcinae = 8.
There is also clusters = staphlo and chains = strepto.
These are important in the identification of the micro-organism but they also help determine is they are actively metabolising, i.e. in chains they are actively metabolising.

Question 5

What does glycocalyx mean?

Answer 5

It means sugar coating.

Question 6

Is a glycocalyx found in both Eukaryotes and Prokaryotes?

Answer 6

Yes.

Question 7

What is a glycocalyx used for in both eukaryotes and prokaryotes?

Answer 7

Eukaryotes- for self recognition in regards to the immune system.
Prokaryotes- they form biofilms and allow for binding with surfaces.

Question 8

What are some features of prokaryotic glycocalyx’s?

What are some examples?

Answer 8

• Capsule (which prevents phagocytosis and is organised).
• Slimy layer (unorganised)
• Extracellular polysaccharides
• Sticky
• Outside the cell

Some examples include plague on teeth, soil bacterial film and shower scum

Question 9

What are prokaryotic flagellum’s used for?

What are some properties?

Answer 9

They are used to propel and move bacteria. They are usually seen in gram-negative bacteria.

• outside cell
• propel my rotating
• are made of chains of protein and attached by protein hooks
• anchored to wall and membrane by basal bodies

Question 10

What kinds of prokaryotic flagellums are there?

Answer 10

Peter Always Makes Annie Lie 
Peri - around
A - none
Mono - one
Amphi - both (sides)
Lopho - tuft

Question 11

What are some differences between Prokaryotes and Eukaryotes?

Answer 11

Pros- no organelles, one circular chromosome, ribosomes small at 70s, no histone proteins, peptiglycan walls and binary fission.
Eu- organelles, paired chromosomes in membrane, ribosomes 80s, histone proteins, polysacchride cell walls and meiosis/mitosis.

Question 12

What are axial filaments and what are the properties?

Answer 12

• Endoflagella
• Anchored to one end of cell
• in spirochetes
• moves by rotation (like corkscrew)
• attached to one end

Question 13

What is a pili?

Answer 13

A pili is used for the transfer of genetic material and it consists of the protein pilian. It also transfers antibody resistance in proteins. It allows for mating in different environments and is what is referred to in conjugation.

Question 14

What is a fimbraie?

Answer 14

Fimbraie is attached to the cells surface and allows for movements.

Question 15

What is the difference between chemotaxis and phototaxis and why are they important?

Answer 15

Chemotaxis is when micro-organisms use chemicals to determine which direction or where they need to either go or get away from.
Phototaxis is when they use light to determine their direction.

It is important for a microorganisms’ survival to use metabolite (environmental signal) in order to get away from something or be drawn to something.

Question 16

What is the difference between flagella and cilia?

Answer 16

Flagella’s are usually seen in prokaryotes and mainly in rods, not cocci. Propulsion is by rotating both clock and anti-clockwise and they make the micro-organism ‘run and tumble’ along.
Cilia is in eukaryotes and it’s propulsion is beating not rotation. The structures are very small microtubules.

Question 17

What are bacterial cell walls made of?

Answer 17

peptidoglycan.

Question 18

What are bacterial cell wall properties?

Answer 18

• Rigid due to cross over and repeats of polymer polysaccharides.
• Prevent osmotic lysis.
• Polymer polysaccharides = n-acetylglucosamine (NAG) and n-acetlymuramic acid (NAM).

Question 19

How do are gram positive and gram negative bacteria differentiated?

Answer 19

By gram staining, gram positive is purple and gram negative is pink.

Question 20

Why does gram positive stain purple and gram negative not?

Answer 20

Gram positive cell well retains the crystal violet dye within the cell wall whereas gram negative bacteria’s outer membrane stops this.

Question 21

If penicillin was used on bacteria what kind would show drastic effects?

Answer 21

Gram positive are more susceptible to penicillin.

Question 22

What is the endosymbiotic theory?

Answer 22

The endosymbiotic theory is the theory that prokaryotes were engulfed or invaded by ancient/primitive eukaryotes. This gave the organisms an advantage when surviving and reproducing in their niche.

Question 23

What are the endosymbiotic organelles and why?

Answer 23

The mitochondria and chloroplast.
They have bacterial features, i.e:
- One round chromosome 
- Small ribosome (same size as bacterial ribosomes). 
- Thick membrane walls 
- Binary fission