Prokaryotic Cells and Viruses

Question 1

Give information about prokaryotic cells

Answer 1

Are single-celled organisms eg. bacteria (E. coli)

Question 2

What is the size of bacteria?

Answer 2

0.1-10 um (micrometres) - eukaryotic cells can be up to 50 times bigger, about 0.1 mm

Question 3

What is the main difference between the organelles in a prokaryotes and those in a eukaryotes?

Answer 3

Eukaryotes have many, membrane bound organelles whereas prokaryotes have few organelles, none bound by membranes.

Question 4

Give information about the cytoplasm in a bacteria cell.

Answer 4

Contains smaller 70s ribosomes which are free in the cytoplasm.

Question 5

Give information about the cell surface membrane in a bacteria cell.

Answer 5

Mainly made up of lipids and proteins, controls the movement of substances in and out of the cell.

Question 6

Give information about the cell wall in a bacteria cell.

Answer 6

90% have a cell wall, supports and prevents the cell from changing shape, made of a glycoprotein (made up of polysaccharides and peptides - a protein with a carbohydrate attached) called MUREIN.

Question 7

What is a slime capsule?

Answer 7

SOME have a slime capsule which is a polysaccharide layer that lies outside the cell wall.

Question 8

What is the function of a slime capsule in a bacteria cell?

Answer 8

Sticks cells together.
Acts as a food reserve (nutrients)
Protects the cells from digestion enzymes and chemicals.
Prevents the detection of antigens of the bacteria’s surface therefore increasing its virulence (prominence/ability to cause damage) in the body.
Protects the bacteria from the unfavourable environment eg. extreme pH, dehydration.

Question 9

Give information about the plasmids in a bacteria cell.

Answer 9

SOME bacteria have plasmids - small loops of DNA that aren’t part of the main circular DNA molecule, foreign DNA is easily inserted into them (eg. insulin production),, plasmids are not always present however some cells have many, plasmids contain genes for things like antibiotic resistance and can be passed between prokaryotes.

Question 10

Give information about the genetic material in a bacteria cell.

Answer 10

Bacteria cells contain free floating, circular DNA (no nucleus), presents as one long coiled up strand, not attached to any histone proteins (not associated with proteins).

Question 11

Give information about the flagella in a bacteria cell.

Answer 11

SOME bacteria have flagella, some have not and some have more than one. It is a basal body (has a long, hair-like structure) which acts like a small motor, which rotates the flagellum causing movement.

Question 12

How are food reserves stored in bacteria cells?

Answer 12

As glycogen granules and oil droplets.

Question 13

How do bacteria divide?

Answer 13

By binary fission.

Question 14

What are the three organelles that only some bacteria have?

Answer 14

1 or more plasmids, slime capsule, flagella

Question 15

Give information about the respiratory membranes in a bacteria cell.

Answer 15

In bacteria cells there are infoldings in the membrane called mesosomes (if something ends in some it always has something to do with the membrane) where respiration is carried out in bacteria cells (has no mitochondria).

Question 16

What type of reproduction is binary fission?

Answer 16

Asexual reproduction (one parent cell)

Question 17

What is the first step of binary fission?

Answer 17

Circular DNA and plasmids replicate - the main DNA is only replicated once but the plasmids can be replicated multiple times.

Question 18

What is the second step of binary fission?

Answer 18

Cell Elgonation - cell gets bigger and the circular DNA moves to opposite pole (ends) of the cell.

Question 19

What is the third step of binary fission?

Answer 19

Septum formation - cytoplasm divides, new cells walls form.

Question 20

What is the fourth step of binary fission?

Answer 20

Cell separation - two daughter cells are formed each with a single copy of the circular DNA and a variable number of plasmids.

Question 21

Give examples of viruses.

Answer 21

Influenza, mumps, measles, HIV, AIDS, herpes and small pox, rhinoviruses (cause colds)

Question 22

Are viruses cells?

Answer 22

No, they are acellular - they cant keep themselves in a stable state, they aren’t living because they have no energy metabolism, dont’ produce waste, don’t grow, don’t respond to stimuli, don’t reproduce independently.

Question 23

Can diseases caused by viruses be cured?

Answer 23

No cures, only prevention methods.

Question 24

How big are viruses?

Answer 24

20-300 nm (nanometres) - even smaller than bacteria, are the smallest and simplest of the microbes.

Question 25

What three things do you need to label when talking about virus structure?

Answer 25

Capsid, attachement proteins, genetic materail.

Question 26

Give information about the structure of a virus.

Answer 26

Contain nucleic acids such as DNA OR RNA as genetic material. The nucleic acid (viral genetic material) is enclosed within a protein coat (capsid). The capsid has attachment proteins which identify and allow the virus to cling onto host cells.

Question 27

What additional structure can SOME viruses have?

Answer 27

Some viruses eg. human immunodeficiency virus are also surrounded by a lipid envelope to assist entry to host cells. Some also have glycoproteins and enzymes.

Question 28

Give information about the capsid in a virus.

Answer 28

Composed of subunits called capsomers which have several complex shapes - polyhedral, rod or complex.

Question 29

What is the function of the capsid in a virus?

Answer 29

Primary function - to protect the viral genetic material from damage.
Secondary function - can assist the virus in infecting the host.

Question 30

How do viruses reproduce?

Answer 30

Are not living so can’t undergo cell division so replicate by invading other living cells - host cells - which get damaged and then killed in the process.

Question 31

What is the first stage of virus replication?

Answer 31

The virus attaches to the host cells surface, by using its attachment proteins to bind to complementary receptor proteins (antigens) on the cell-surface membrane of the host cells.

Question 32

Give information about the attachment proteins on viruses.

Answer 32

Different viruses have different attachment proteins so require different receptor proteins (antigens) on host cells. Resultantly, some viruses can infect one specific type of cell whereas others can infect lots of different cells. Viruses have evolved to have antigens specific to specific cells.

Question 33

What is the second stage of virus replication?

Answer 33

Virus penetrates cell membrane and injects nucleic acid (DNA or RNA) into the cell.

Question 34

What is the third stage of virus replication?

Answer 34

Viral nucleic acid replicates using the host cellular machinery.

Question 35

What is the fourth stage of virus replication?

Answer 35

New viral nucleic acids are packaged into virus particles and released (burst) from the cell. The host cell may be destroyed in the process.