Biology Revision

1
Biology Revision

• B6 Beyond the Microscope

2
6a Understanding Bacteria

• Bacteria smaller than animal or plant cells,
  typically a few microns long (1000 of a mm)
• Flagellum for movement
• Cell wall for maintaining
• shape stop it bursting
• Bacterial DNA for
• cell replication control of cell
• Bacteria lack
• A true nucleus
• Mitochondria
• Chloroplasts
• A vacuole

Main shapes Spherical Rod Spiral Curved rods
3
6a Understanding Bacteria

• Food sources some consume organic nutrients
  like carbohydrates proteins, some make their
  own using sunlight
• Survival extreme habitats e.g. hot springs,
  inside humans
• Reproduction by binary fission
• Rapid reproduction
• causes fast spread of
• disease food
• spoilage, but can be
• useful

4
6a Understanding Bacteria

• Making Yoghurt
• In large steel fermenters
• Equipment sterilised
• Raw milk pasteurised heated to 80C, then
  cooled rapildy
• Heated to 40C
• Live bacterial culture added incubated
• Bacteria feed on lactose make lactic acid
• Manufacturer samples yoghurt
• Flavours colours added

5
6b Harmful Microorganisms

• Pathogens microbes that cause disease

Pathogen Illness caused Transmission method
Bacteria Cholera (Vibrio) Contaminated water
Bacteria TB Airborne droplets
Bacteria Food poisoning (salmonella E. coli) Contaminated food
Bacteria Septic wound Contact with wound
Protozoa Dysentery (Entamoeba) Contaminated food/water
Protozoa Malaria Mosquito bite
Viruses Flu Airborne droplets
Viruses Chickenpox/smallpox Direct contact or airborne droplets
Fungi Athletes foot Direct contact
6
6b Harmful Microorganisms

• Natural Disasters
• Rapid spread of disease because
• Sewage systems water supplies damaged
• Electrical supplies damaged -gt food decay
• Disrupted health services
• Dysentery, cholera food poisoning common

7
6b Harmful Microorganisms

• History of Disease Treatment
• Pasteur 1860s Germ Theory microbes in the
  air cause food decay passed from person to
  person causing disease
• Lister 1865 development of antiseptics use
  of carbolic acid during surgery
• Fleming 1928 Penicillin discovered
  accidentally that this mould killed bacteria

8
6c Microorganisms factories for the future?

• Yeast single celled fungus
• Asexual reproduction budding
• Conditions for reproduction
• Lots of sugar
• Optimum temperature (rate doubles for every 10C
  rise, above 40C?) pH
• Removal of waste products e.g. alcohol

9
6c Microorganisms factories for the future?

• Fermentation anaerobic respiration in yeast
• Sugar -gt Alcohol Carbon Dioxide
• Uses
• Cleaning sugar in water from food processing
  factories
• Making alcohol e.g. beer from barley, wine from
  grapes, cider from apples

10
6c Microorganisms factories for the future?

• Brewing Beer
• Mashing extraction of sugar from source
  material
• Hops added for flavour
• Yeast added to ferment (keep warm)
• Tank sealed to cause anaerobic respiration
  prevent unwanted microbes entering
• Clarifying/clearing to leave a clear liquid
• Pasteurising to kill harmful microbes
• Bottling or casking

11
6c Microorganisms factories for the future?

• Distilling spirits
• Rum from cane sugar
• Whisky form malted barley
• Vodka from potatoes
• Process
• Liquid heated to evaporate alcohol
• Concentrated alcohol trapped and condensed into a
  liquid
• Fermentation is limited by increasing levels of
  alcohol that eventually kill yeast

12
6d Biofuels

• Biogas contains mainly methane (50 burns
  easily 10 is explosive), some carbon dioxide,
  traces of hydrogen, nitrogen hydrogen sulphide
• Biogas produced by decomposer bacteria in
  marshes, septic tanks, animals digestive systems
• Uses
• Burned to generate electricity
• Burned to produce hot water steam for central
  heating
• Fuel for buses (cleaner than diesel petrol, but
  doesnt produce as much energy)

13
6d Biofuels

• Large scale production of methane
• Continuous flow method in a digester organic
  material added daily gas siphoned off
• Optimum temperature too low, little gas
  produced above 45c enzymes denatured, no gas
  produced
• Advantages of biofuels
• Alternative source to fossil fuels reduce
  greenhouse effect
• No particulates produced
• Cheap
• Renewable/sustainable
• Conservation of resources

14
6e Life in Soil

• Composition of soil
• Rock particles
• Humus (dead organic matter)
• Water
• Living organisms e.g. fungi, microscopic
  protozoans, nematode works, earthworms, bacteria
• Importance of worms
• Burying organic material for decomposition
• Mixing soil layers
• Aerating draining soil
• Neutralising acid soil

15
6e Life in Soil

• Soil Food Webs

Detritivores e.g. earthworms Decomposers e.g.
fungi
16
6e Life in Soil

• Nitrogen Cycle

Nitrogen fixing e.g. Azobacter, Rhizobium
Clostridium
Nitryfying e.g. Nitrosomonas Nitrobacter
convert ammonia to nitrates
Saprophytic bacteria start decomposition make
ammonia
17
6f Microscopic life in water
Advantages of living in water Disadvantages of living in water
No problem of water shortage or dehydration Water is dense so resists movement
Less variation in temperature Difficult to control the absorption release of water from living cells
Water gives more support so organisms grow bigger without increases in skeleton size
Waste is easily disposed
Amoeba use active transport to pump water into
small vacuoles which join into one contractile
vacuole which empties out of the cell
Salmon move from salt to fresh water they alter
their urine concentration to counteract osmosis
in or out of cells
18
6f Microscopic life in water

• Plankton
• Phytoplankton microscopic plants capable of
  photosynthesis
• Zooplankton microscopic animals
• Have limited movement/rely on currents
• Seasonal variation in population due to changes
  in
• Light
• Temperature
• Nitrates
• Can cause algal blooms

19
6f Microscopic life in water

• Water Pollution
• Sewage - cause eutrophication
• Oil
• Fertilisers cause eutrophication
• Pesticides e.g. DDT - bioaccumulate
• Detergents
• Acid rain
• PCBs (chemical used to insulate electrical
  equipment) bioaccumulate
• Biological Indicators of pollution/cleanliness

20
6g Enzymes in action

• Uses
• Biological washing powders enzymes digest food
  stains
• Cheese making separate curds whey
• Fruit juice extraction
• Alter food flavour
• Reagent sticks e.g. glucose/urine test stick