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

http://biology.clc.uc.edu/fankhauser/Cheese/Cheese_5_gallons/29_decant_whey_3_P3120306md.jpg

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

THE END