bacteria & viruses
TRANSCRIPT
BACTERIA VIRUSES&
Monera
Protist
PlantAnimalFungi
Bacteria belong to
the Kingdom:
MONERA or
PROKARYOTA
BACTERIA are among the smallest organisms
about 1/1000 mm
occur in the: soil air water inside
organisms
Bacteria have different shapes
Staphilococcus(cluster)
Flagella are used for locomotion
Structure of a bacterium [learn to draw]
Slime capsule
Flagella
Cytoplasm
Food store/glycogen granule
Chromosome /DNACell membraneCell wall
Two types of cells:
PROKARYOTIC bacterial cells
EUKARYOTICall other cells
Monera
Protist
PlantAnimalFungi
Differences between prokaryotic and eukaryotic cells
PROKARYOTES EUKARYOTES1. No proper nucleus is
present, that is their DNA is NOT enclosed in a nuclear membrane but lies free in the cytoplasm
1. Have a proper nucleus, that is their genetic material is enclosed within a nuclear membrane
PROKARYOTES EUKARYOTES
2. Smaller cells 2. Larger cells
3. Their organelles are NOT membrane-bound
3. Their organelles are membrane-bound
A eukaryotic cell is generally 10x greater.
SPORE FORMATION bacteria produce a thick protective
wall around them in adverse conditions e.g.
heat drought presence of poisons
they are now known as SPORES: can survive for many years [anthrax spores, 1,300 years old can cause disease]
the wall breaks when favourable conditions return
ASEXUAL REPRODUCTION
bacteria reproduce by BINARY FISSION
A single bacterial cell inside the human body can reproduce every 20 minutes.
Mention three conditions inside the human body that provide bacteria with the ideal environment.
1.Temperature is warm 2.Food3.Water4.pH is ideal
Question: SEP, 2009
Why are bacteria classified as prokaryotic organisms? (2)Lack a proper nucleus i.e. chromosomes are nor enclosed in a nuclear membrane. There are no membrane-bound organelles. Name the type of reproduction that takes place in bacteria. (2)Asexual reproduction by binary fission.
A group of bacteria is called a colony
How can bacteria respire?
AEROBICALLY use oxygen e.g. nitrogen fixing bacteria
ANAEROBICALLY do not use oxygen e.g. denitrifying bacteria
FEEDING
1) PHOTOSYNTHETIC build up their food by a chemical like
chlorophyll2) SAPROTROPHIC
decay dead material3) PARASITIC
get food from living organisms, causing them harm
Bacteria and other organisms which cause disease are called:
PATHOGENIC
BENEFICIAL BACTERIA
1) Decay bacteria (in soil)
saprophytic bacteria break down dead organisms to return essential nutrients to the soil
2) Decay bacteria (in sewage) bacteria decompose sewage before it is
thrown into the sea
3) Genetic engineering bacteria can be used to produce useful
chemicals such as insulin
Question: MAY, 2009
Give the biological explanation of each of the following statements.Most bacteria are saprophytes but some are mutualistic bacteria. (3)Saprophytes feed on dead and decaying material and live freely. Some live in a close association with another organism where both benefit. E.g. bacteria in rumen of cow.
Most bacteria feed on dead and decaying matter and so are saprophytes. Help in recycling nutrients.Mutualistic bacteria: Some bacteria form a relationship within
intestines of mammals where both help each other. Digest cellulose in herbivores. Produce vitamins B and K in humans.
Nitrogen-fixing bacteria in root nodules of leguminous plants get food and shelter from plant and give the plant ammonium compounds.
4) Vinegar production bacteria are used to
convert:
ethanol to ethanoic acid
Acetobacter aceti
5) Making silagesilage is:
undecayed grass used for feeding livestock in winter
the newly cut grass: is allowed to wilt (to remove water and so
concentrate the sugar in grass) but is not dried before conversion to silage
newly cut grass
the grass: is prevented from decaying by lactic acid produced
by anaerobic bacteria is covered by plastic sheeting to exclude oxygen and
rain
A silo in which silage is made and then stored.
6) Biogas formation
Biogas is a mixture of: methane carbon dioxide
Biogas is produced when anaerobic
bacteria breakdown:
Anaerobic bacteria
sewage manure plant material
Effluent
A biogas plant is built underground: to keep a constantly cool temperature –
overheats if above ground
A biogas plant as used by a family in
China.
What can biogas be used for?
When biogas is burnt, it can be used for: heating the home cooking to generate electricity
Question: SEP, 2003A major concern for most people these days is the use and availability of energy. Fossil fuels are non-renewable forms of energy. One excellent source of energy is Biogas. This is a mixture of methane (CH4) and carbon dioxide (CO2). This can be produced in a laboratory using the simple set-up shown below.
a) Name:i) One suitable material which can be placed in
the flask to generate Biogas;Plant material/animal manure
ii) The organisms that must be present in the flask together with this material to produce Biogas;
Bacteriaiii) The process occurring within the flask
Anaerobic respiration
7) Cheese, butter & yoghurt making all require:
lactic acid
bacteriaBacteria convert
LACTOSE[sugar in milk]
LACTIC ACID
Lactic acid is: made by the process called lactic acid
fermentation : lactose lactic acid
The manufacture of cheese, butter & yoghurt depend on the curdling (coagulation) of milk.
lactic acid is needed to make the milk curdle
Milk pasteurised at 73C for 15 sec to kill most microbes
Special strain of cheese-making bacteria added to convert sugar
in milk to lactic acid
Curds cut into blocks and piled up
Blocks chopped and mixed with salt to slow down
bacterial growth
Flavour gradually develops and bacterial action makes cheese
more digestible
Enzyme (rennin) added to separate into curds & whey
Cheese packed into moulds and left to ripen
Huge vat
Cheese making
1
2
3
4
5
6
6
Huge vat
Rennet for cheese making can be made by:
bacteria
animals
Whey poured off
Curds cut into blocks Ripening
Moulds in press
[seen better in this picture]
Yoghurt production
Lactic acid is produced during fermentation by special strains of bacteria added to the milk
SphericalStreptococcus
Rod-shapedLactobacillus
Yoghurt production
The following list gives five of the steps involved in the commercial production of a well known
brand of yoghurt.A)Milk heated to 73C for at least 30 seconds to make it
virtually sterile.B)‘Sterilised’ milk is cooled to 44C.C) Special ‘yoghurt’ bacteria added to ‘sterilised’ milk.D)Milk kept at 44C for four hours to allow bacteria to
convert it to yoghurt by making lactic acid.E) Yoghurt stored in cartons at 4C to slow down further
bacterial action.
Question: MAY, 2012Humans use different micro-organisms including bacteria to produce useful substances and food stuffs. Bacteria are added to pasteurised milk to produce yoghurt.Explain why milk is pasteurised before producing yoghurt. (2)
To kill living microbes so that yoghurt can have a longer shelf-life.
Butter making
Churning
Fermentation
Butter-making machine
Bacteria are added to cream
This culture has 4 bacteria — 2 which seem to primarily drive the acidification and 2 which drive the flavour.
The cream is beaten/churned
Churning the milk
Butter can be made at home.What forms after 5 minutes beating the
cream?
Soft butter and a liquid called
buttermilk form.
The buttermilk is strained out.
The butter is squeezed to remove the
remaining liquid.
Question: SEP, 2008 Milk is used in the production of butter and cheese. Below is a simplified flow diagram which describes the production of butter:
Fermentation
Churning
i) Why is bacteria added to the cream? (2)Bacteria produce lactic acid which makes milk curdle. Also to add flavour.
ii) Write a word equation to show the fermentation process in which cream is converted to sour cream. (3)
Lactose Lactic acid
Question: [MAY, 2010]Give a biological explanation for each of the following statements:In cheese making when the enzyme rennin is added to milk, the temperature of the curding (clotting) milk is kept in the region of 40C. (3)
Enzymes must be kept at their optimum temperature to work fast. Increasing the temperature above the optimum denatures the enzyme and the reaction slows down or even stops.
Question: [SEP, 2009]
A group of biology students investigated a type of yoghurt. Some yoghurt samples were taken.
The pH of yoghurt samples was tested. Would you expect the pH to be acidic, neutral or alkaline? Give a reason for your answer. (3)Acidic. Bacteria change the sugar in milk called lactose into lactic acid.
Question: [MAY, 2010]Give a biological explanation for the following statement:Bacteria are involved in making yoghurt. (5)Certain types of bacteria are needed to make yoghurt.Bacteria change lactose into lactic acid by fermentation.The lactic acid makes the milk curdle.Flavour , colouring & fruit may be added.
1) Cause diseases in animals and plants, e.g. Tuberculosis in man, cause tooth decay
2) Spoil food3) Denitrifying bacteria reduce the nitrate
content in the soil
HARMFUL BACTERIA
Question: MAY, 2004
a) i) Name one organism that has a mutually beneficial symbiotic relationship with a bacterium.
ii) Explain what each organism benefits from the symbiotic relationship. (1, 2)
e) Describe one saprophytic activity of bacteria that is:i) useful to humans; ii) harmful to humans. (2)
Question: MAY, 2007Explain how bacteria inside the body may have both beneficial and harmful effects. (4)Beneficial effects: digest cellulose in herbivores as they produce
cellulase produce vitamins B and K in intestines of
humans
Harmful effects: cause disease
RESISTANCE TO DISEASE
1) The skin forms a barrier to bacteria.
2) Chemicals e.g. hydrochloric acid in the
stomach lysozyme in tear fluid
destroy bacteria
3) Body fluids such as saliva, contain antibodies.
4) White blood cells can:i) engulf bacteria
ii) produce antibodies to kill bacteria
FOOD PRESERVATION[this section acts as background knowledge
about bacteria].
1) COLD TREATMENT freezing does not kill
microbes, but stops them multiplying and slows their action
2) DRYING microbes need moisture and if the food is
dried, they become dormant dried food lasts indefinitely food is dried by blowing air over it
Grapes soon go bad BUT raisons can be stored
for a long time.
3) HEAT TREATMENTheat: kills many of the microbes can STERILISE food
Explain the following statement:In food preparation, a clean sterile surface is necessary. (2)
Question: MAY, 2012
To avoid contamination of food with harmful microbes.
Method used to find out which is the most effective antibiotic to kill
microbes
VIRUSES
Viruses consist of: a strand of DNA or RNA surrounded by
a protein coat (capsid)
Protein coat (made of capsomeres)
Genetic material(DNA or RNA)
Viruses are NOT cells as they lack the usual cell components
Different shapes of virusesAIDS virus
Tobacco mosaic virus which causes
tobacco mosaic disease in tomato plants.
Different shapes of viruses
Influenza virus
Virus that attacks bacteria.
Bacterium attacked by viruses.
Viruses: are smaller than bacteria (measured in nm,
1nm = 1/1000 000 mm) reproduce only when inside living organisms
virus
bacterium
Viruses are borderline between living & non-living things
Living Non-living
Carry out all 7 vital functionsMade of cells
Can be crystallised
Viruses: REPRODUCE and CAN BE CRYSTALLISED
Explain why viruses are always considered parasitic. (2)
Always cause harm to the cell in which they have reproduced.
Cell bursts and dies.
Question: MAY, 2007
Question: SEP, 2008a) The diagram below shows the generalized
structure of a virus.Label the parts A and B. (2)
Question: SEP, 2008a) The diagram below shows the generalized
structure of a virus.Label the parts A and B. (2)
Protein coat / capsid
DNA or RNA / genetic material
Question: SEP, 2008
b)Viruses are not usually considered to be living organisms. Why? (2)Are not composed of cells.Do not carry out all of the seven vital functions.
Question: SEP, 2008The diagram below shows the reproductive stages of a virus in an incorrect order. Fill in the table to indicate the correct order in which these events take place. (3)
Step
1 2 3 4 5 6
Letter
Step
1 2 3 4 5 6
Letter B F D E A C
Question: June, 1998
Explain clearly, how viruses differ from bacteria in their structure and in their mode of life. (Present your answer in the form of a table.)
(8)
Viruses Bacteria1. No cell membrane 1. Cell membrane
present2. No organelles 2. Organelles present3. Never present 3. May have flagella4. Never present 4. May have a slime
capsule5. No food stores 5. Store food granules6. Do not respire 6. Respire 7. Do not excrete 7. Excrete8. Do not grow 8. Grow