Topic 2 - 2.2 Prokaryotic Cells

Question 1

What is a hypertonic solution?

Answer 1

It is a solution with a higher concentration of solutes and lower concentration of water than the surrounding solution.

Question 2

What is peptidoglycan?

Answer 2

It is a large net like structure found in all bacterial cell walls made up of many parallel polysaccharide chains with short peptide cross linkages

Question 3

What are pili/fimbriae?

Answer 3

They are thread-like protein projections found on the surface of some bacteria. They seem to be used for attachment to the host cell or for sexual reproduction.

Question 4

What is the purpose of a bacterial cell wall? What is it made of?

Answer 4

The bacterial cell wall maintains the shape of the bacteria (water moves into the cell via osmosis the wall stops it from bursting) it also helps protect the insides.
All bacterial cell walls consist of a layer of peptidoglycan, it is made up of many parallel polysaccharide chains with short peptide cross linkages forming an enormous molecule.

Question 5

What is a flagella?

Answer 5

Some bacteria can move themselves using flagella. These are a little bigger than one of the microtubules used in prokaryotic cells. They are made of long strands of flagellin.

Question 6

Describe the cell surface membrane for prokaryotic cells.

Answer 6

Bacteria have nome mitochondria so the cell membrane is also the site of some of the respiratory enzymes. In some cells there are unfolding called mesosomes which may be for this purpose.

Question 7

What are plasmids?

Answer 7

Plasmids code for the phenotype in addition to the genetic information in the nucleoid for example resistance to a antibiotic. These plasmids can reproduce themselves and be passed on to other bacteria through the pili in sexual reproduction.

Question 8

What is the nucleoid?

Answer 8

It is where the coil of genetic information is found.

Question 9

Describe a gram positive cell wall.

Answer 9

They have a thick layer of peptidoglycan which can help it be resistant to some antibiotics however some antibiotics inhibit the formation of peptidoglycan and so are very affective.

Question 10

Gram negative cell walls?

Answer 10

They are hidden and have a small peptidoglycan layer.

Glycopeptide and polypeptide antibiotics are good at treating this type of bacteria.

Question 11

What are bacteriophages?

Answer 11

Are viruses that attack bacteria

Question 12

What is gram staining?

Answer 12

Is a staining technique used to distinguish different types of bacteria through the structure of their cell wall.

Question 13

What is teichoic acid?

Answer 13

Is a chemical found in the cell walls of gram positive bacteria

Question 14

What are cocci?

Answer 14

Are spherical bacteria

Question 15

What are bacilli?

Answer 15

Are rod shaped bacteria.

Question 16

What are spirilla?

Answer 16

Are bacteria with a twisted or spiral shape.

Question 17

What are vibrios?

Answer 17

Are comma-shaped bacteria

Question 18

What are obligate aerobes?

Answer 18

Are organisms that need oxygen for respiration

Question 19

What are facultative anaerobes?

Answer 19

Are organisms that use oxygen if it is available, but can respire and survive without it.

Question 20

What are obligate anaerobes?

Answer 20

Are organisms that can only respire in the absence of oxygen and are killed by oxygen

Question 21

Describe DNA viruses

Answer 21

The genetic material is DNA. The viral DNA acts directly as a template for both new viral DNA and for mRNAs needed to induce synthesis of viral proteins

Question 22

Describe RNA viruses

Answer 22

70% of viruses have RNA as their genetic material and they are more likely to mutate. They never produce DNA as part of their life cycle

Question 23

What are Positive ssRNA viruses?

Answer 23

They have RNA that can act directly as messenger RNA and can be translated at the ribosomes

Question 24

What are negative ssRNA viruses?

Answer 24

They cannot be directly translated. The RNA strand must be transcribed before it is translated at the ribosomes

Question 25

What are RNA retroviruses?

Answer 25

A type of RNA virus, they have the ability to produce an enzyme called reverse transcriptase which goes onto make viral DNA. This DNA can can then be incorporated into the host cells genome and used as a template for new viral proteins

Question 26

Describe the basic parts of a virus.

Answer 26

Nucleus acid- Double or single stranded DNA or RNA
Capsomere- repeating protein unit that makes up the protein coat
Capsid - protein coat
Envelope- lipid derived from host cell, not always present
Receptors or tail- involved in attachment to host cell

Question 27

What is the lysogenic pathway?

Answer 27

Most viruses are non-virulent when they first Exeter the cell. They insert their DNA Into the hosts DNA so it replicates every time the cells divide. This is called the provirus. The virus doesn’t affect the host in any way at this stage.
During this period of lysogeny the virus is latent

Question 28

What is the lytic pathway?

Answer 28

Sometimes the viral genetic material is replicated independently of the host DNA. They enter a hosts cell multiply, burst and infect a number of other cells. The virus is said to be virulent at this stage.
Some viruses have Boothe lysogenic and lytic parts to their lifecycle

Question 29

Describe the stages of the lysogenic pathway.

Answer 29

1) virus attaches to host cell
2) virus DNA is injected into host cell leading to synthesis of viral enzymes
3) viral DNA is incorporated into host cell DNA
4) Viral DNA is replicated each time the bacterium divides without causing any damage
5) it then joins the lytic pathway.

Question 30

Describe the stages of the lytic pathway

Answer 30

1) virus attaches to host cell
2) virus DNA is injected into host cell leading to synthesis of viral enzymes
3) viral DNA is incorporated into host cell DNA
4) Viral DNA is replicated each time the bacterium divides without causing any damage
5) Viral DNA is replicated
6) new viral particles are assembled as new protein coats are made around viral DNA
7) lysis- the virus bursts out

Question 31

What is a pandemic?

Answer 31

Is an epidemic that take place in several countries at once