2.2 prokaryotic cells

Question 1

describe the structure and function of a bacterial cell wall

Answer 1

consists of a layer of peptidoglycan
water tends to move into bacterial cells by osmosis and the cell wall prevents them from swelling and bursting
it also helps them to maintain their shape and give support and protection to the contents of the cell

Question 2

what’s the function of the slime capsule

Answer 2

protects bacterium from phagocytosis, covers the cell markers on the membrane that help identify the cell

Question 3

name the dna tangle found in bacterial cells

Answer 3

nucleoid

Question 4

what are the type and functions of ribosomes in bacterial cells

Answer 4

70S ribosomes that carry out protein synthesis

Question 5

describe the process of gram staining bacteria

Answer 5

bacteria are often colourless and a crystal violet/ iodine complex is added to the bacteria

Question 6

what would the different results be in gram positive bacteria and gram negative bacteria

Answer 6

the gram positive bacteria have a thick peptidoglycan walls and would be purple/blue after

gram negative have thin peptidoglycan walls and the cells would appear red

Question 7

what are antibiotics

Answer 7

drugs that are used against bacterial pathogens

Question 8

how do antibiotics work ?

Answer 8

different antibiotics affect different types of bacteria (gram positive/negative)
some inhibit the formation of the peptidoglycan layer of the cell wall (gram positive) which is vital to their wall structure

Question 9

what are the alternative ways of classifying bacteria

Answer 9

can be identified by their shape
-spherical, comma shaped, rod shapes, twisted ect.

can be identified by their respiratory requirements

Question 10

what is a virus

Answer 10

obligate intracellular parasites, that only exist and reproduce in the cells of other living organisms
usually cause damage or disease

Question 11

describe the structure of a virus

Answer 11

usually made of geometric shapes and of similar structures but VARY in genetic material
centre is double or single stranded DNA or RNA, surrounded by a capsid, made of capsomeres, sometimes have an envelope (derived from host cell) then receptors on the outside

Question 12

what is a virus’ protein coat made up of

Answer 12

it is a capsid made up of capsomeres

Question 13

how are viruses classified, and describe the different forms

Answer 13

-classified by their genome and mode of replication
-DNA viruses, genetic material is DNA, used as a template for new DNA and RNA
-RNA viruses 70%, more likely to mutate
-RNA retroviruses, special type of RNA virus that have a capsid and lipid envelope

Question 14

what is a bacteriophage

Answer 14

a virus that attacks bacteria

Question 15

describe how viruses get into the cell

Answer 15

taken into the body by endocytosis, host cell digests the capsid and releases the genetic material , viral envelope fuses with cell surface, releasing the rest of the virus into the membrane

Question 16

describe the process of infection (latency) the lysogenic pathway

Answer 16

viruses are non virulent through the lysogenic pathway
insert their dna into the host dna (provirus), so its replicated when the cell divides
virus doesn’t affect the host cell, virus is said to be latent

Question 17

describe the process of infection; the lytic pathway

Answer 17

genetic material is replicated independently of the host dna
host cell bursts, releasing large numbers of new virus particles that invade other cells

Question 18

what is a positive ssRNA virus

Answer 18

viruses that contain a single strand of RNA, that is a sense strand, used directly as mRNA for translations into proteins

Question 19

what is a negative ssRNA virus

Answer 19

contain a single strand of RNA that is an antisense strand, and before it can be used it must be transcribed into a sense strand

Question 20

what is an RNA retrovirus

Answer 20

they have viral RNA as their genetic material and is translated into DNA by the enzyme reverse transcriptase

Question 21

how do viruses cause the symptoms of disease

Answer 21

they cause symptoms by the lysis of the host cells, causing them to release their own lysosomes, or by the production of toxins that inhibit cell metabolism

Question 22

why are viruses often specific to particular tissues

Answer 22

due to the presence or absence of cell markers on the surface of the host cell
each cell has specific markers and each virus only binds to a certain marker

Question 23

describe foot and mouth disease and how it’s spread

Answer 23

weakens and kills a high percentage of young animals and spread through body secretions and transmitted in breath and faeces

Question 24

describe ebola and how it’s spread

Answer 24

severe illness caused by ebola virus and spreads to humans through faeces, blood and meat of infected animals
spreads from human to human through contact of skin

Question 25

why are viruses hard to kill

Answer 25

live inside cells and are not living cells that can be killed

Question 26

describe ways in which antiviral treatments can work

Answer 26

-they target virus replication
-target receptors that help viruses recognise host cells
-target enzymes that help translate or replicate DNA or RNA
-inhibit enzymes that allow the virus to bud from host membranes

Question 27

what is an epidemic

Answer 27

when the levels of people with a disease are much higher than expected

Question 28

name 6 ways that people can control the spread of disease

Answer 28

-rapid identification of disease
-nursing in isolation
-preventing transmission from one individual to another by handwashing, disposal of bodily fluids ect.
-sterilising or disposing of equipment after use
-wearing of protective clothing
-identifying those who have come in contact with the disease

Question 29

describe the process of the development of a new medicine

Answer 29

-chemicals go through research and testing on animal tissue and cultures
-animal testing
-three phases of human testing

Question 30

name the factors that are taken into account if a drug were to be fast tracked

Answer 30

-severity of the disease
-availability of other treatments
-community consent

Question 31

name reasons against fast tracking untested drugs

Answer 31

-not ethical
-could produce unexpected side effects
-hard decision on who gets the drug

Question 32

why do gram positive bacteria appear their colour when they’re stained

Answer 32

they have a thick layer of peptidoglycan which contains chemicals like teichoic acid. the crystal violet/ iodine complex gets trapped by these chemicals so it resists decolouring when it is dehydrated using alcohol

Question 33

why do gram negative appear their colour when they’re stained

Answer 33

-they have a thin layer of peptidoglycan
no teichoic acid, the outer membrane made up of lipopolysaccharides. after the crystal violet/ iodine complex is applied, it’s dehydrated in ethanol, complex is washed out
peptidoglycan takes up the red counterstain

Question 34

what are the different types of bacteria according to their respiratory requirements

Answer 34

-obligate aerobes need oxygen to respire
-facultative anaerobes use oxygen if it’s available, but can manage without it
-obligate anaerobes can only respire in the absence of oxygen- oxygen will kill them