B6 Learning objectives
a: Understanding bacteria
Yeast can be used to deal with water contaminated by
Parts of a bacterial cell:
sugars from food processing factories.
Yeast growth rate doubles for every 10°C rise in
• flagellum for movement;
• cell wall to maintain shape, and to stop it from bursting;
temperature.
• bacterial DNA to control cell’s activities and replication.
Recognise that yeast can undergo aerobic or anaerobic
Identify simple differences between bacterial cells and
respiration and the implications of this to the fermentation
plant and animal cells.
process.
Bacterial cells lack:a nucleus; mitochondria; chloroplasts;
Interpret data on breakdown of sugar by yeast in different
vacuole.
conditions such as changing temperature, presence or
The main shapes of bacteria: spherical; rod; spiral, curved
absence of oxygen.
rods.
Describe the main stages in brewing beer or wine to
Since some bacteria can consume organic nutrients and
include:
others can make their own, this means that:
• extracting sugar from source material;
• they can survive on an enormous range of energy
• adding hops for beer flavouring;
sources;
• adding yeast, keeping it warm;
• they can exploit a very wide range of habitats.
• preventing entry of air and other microorganisms;
Bacteria reproduce by a type of asexual reproduction
• clarifying/clearing drawing off the wine/beer;
called binary fission and they can be grown in large
• pasteurising, casking or bottling.
fermenters.
State what is meant by the term pasteurisation and
Recognise the consequences of very rapid reproduction in
understand why this needs to be done in the case of
terms of food spoilage and disease.
bottled beers.
Describe the main stages in making yoghurt including:
Recall the sources of spirits: rum (cane sugar); whisky
• sterilisation of equipment;
(malted barley); vodka (potatoes).
• pasteurisation of milk;
Describe the process of distillation to increase the
• incubation of culture;
alcoholic concentration, and understand that this
• sampling;
commercial process needs licensed premises.
• addition of flavours, colours then packaging.
Fermentation is limited by the increasing level of alcohol
Explain reasons for the safe handling of bacteria.
eventually killing the yeast.
Different strains of yeast can tolerate different levels of
b: Harmful microorganisms
alcohol.
Recall that some bacteria are pathogens (disease
d: Biofuels
causing).
Describe the stages in an infectious disease, to include:
Marshes, septic tanks and animal digestive systems
• entry into the body;
produce a mixture of gases called biogas, which contains:
• rapid growth, the incubation period;
• mainly methane;
• production of many toxins;
• some carbon dioxide;
• appearance of symptoms such as fever.
• traces of hydrogen, nitrogen and hydrogen sulphide.
Recall the organisms involved in: food poisoning
Biogas containing more than 50% methane burns easily
(Salmonella and E.coli bacteria); cholera (Vibrio bacteria);
and a lower percentage of about 10% is explosive.
dysentery (the protozoan Entamoeba); influenza (virus)
Different types of bacteria are needed to break down
and describe their transmission.
organic material.
Interpret data on the incidence of various diseases.
Describe the uses of biogas such as:
Diseases such as dysentery, cholera and food poisoning
• burned to generate electricity;
can be a major problem following a natural disaster.
• burned to produce hot water and steam for central
Describe how natural disasters cause a rapid spread of
heating systems;
diseases:
• used as a fuel for buses.
• damaged sewage systems and water supplies;
Methane can be produced on a large scale using a
• damaged electrical supplies causing rapid food decay;
continuous flow method of providing organic waste and
• disrupted health services.
removing the gas and remaining solids.
Describe the pioneering work of the following scientists:
Describe how and explain why biogas production is
• Pasteur and the germ theory of disease;
affected by temperature.
• Lister and the development of antiseptics;
Biogas is a cleaner fuel than diesel and petrol but does
• Fleming and the discovery of penicillin.
not contain as much energy as natural gas.
Describe how antiseptics and antibiotics can be used in
Describe the advantages of using biofuels such as:
the control of disease.
• alternative source to fossil fuels;
• less carbon dioxide produced than in fossil fuels;
c: Microorganisms –factories for the future?
• no particulates produced.
State the word and balanced chemical equations for
Explain the advantages of producing and using biofuels
fermentation (anaerobic respiration in yeast).
instead of fossil fuels in terms of: greenhouse gases;
Yeast can reproduce at a fast rate, its optimum growth
conservation of resources, and sustainability.
rate being controlled by: food availability; temperature; pH,
e: Life in soil
and removal of products.
Describe a typical food web in a soil to include:
• herbivores such as slugs, snails, wire worms;
• detritivores such as earthworms, millipedes, springtails;
• carnivores such as centipedes, spiders and ground
beetles.
Explain why most life in soil depends on a supply of
oxygen and water.
Describe why aerating and draining will improve soils.
Describe why neutralising acid soils and mixing up soil
layers is important.
Describe the importance of earthworms to soil structure
and fertility to include:
• burying organic material for decomposition by bacteria
and fungi;
• aerating and draining the soil;
• mixing up soil layers;
• neutralising acid soil.
Recognise the part played by Charles Darwin in
highlighting the importance of earthworms in agriculture.
Recognise why it is important that elements such as
nitrogen, carbon, sulfur and phosphorus are recycled.
These cycles depend on different types of bacteria.
Explain the part played by bacteria in the nitrogen cycle:
• saprophytic soil bacteria start the decomposition;
• nitrifying bacteria such as Nitrobacter;
• nitrogen fixing bacteria such as Rhizobium.
f: Microscopic life in water
Describe the advantages of life in water:
• no problem of water shortage and dehydration;
• less variation in temperature;
• more support;
• easy disposal of waste products.
State the disadvantages of life in water:
• regulating water content;
• resistance to movement.
Some organisms such as insects and frogs spend part of
their life cycle in water and part on land to exploit both
habitats.
Explain the problems of water balance caused by
osmosis.
Describe the action of contractile vacuoles in microscopic
animals such as Amoeba.
Describe the problems for animals (such as salmon)
moving from salt water to fresh water.
Phytoplankton are capable of photosynthesis.
Describe how seasonal changes in light, temperature and
availability of nitrates and phosphates cause changes in
the population of plankton (algal blooms).
Describe how sewage and fertiliser run-off can cause
eutrophication,:
• rapid growth of algae;
• resulting death and decay;
• using up oxygen;
• causing the death of animals unable to respire.
Describe how certain species of organisms are used as
biological indicators for pH and oxygen levels.
Understand the accumulative, long term effect of PCBs
and DDT on animals such as whales.
g: Enzymes in Action
State that enzymes in biological washing powders include:
• amylases (digest carbohydrates such as starch);
• lipases (to digest fatty stains);
• proteases (to digest protein stains).
Explain why biological washing powders may not work in
acidic or alkaline tap water.
Explain that the soluble products of amylase, lipase and
protease activity are sugars, fatty acids and glycerol and
amino acids, and that these products will then easily wash
out of clothes.
Describe how sucrose can be broken down by the use of
an enzyme called invertase (sucrase).
Explain that because invertase converts sucrose into
glucose and fructose, which are much sweeter than the
sucrose, foods can be sweetened without adding so much
sugar (e.g. in low calorie foods).
Describe advantages of immobilising enzymes:
• that the mixture does not become contaminated with the
enzyme;
• that immobilised enzymes in alginate beads can be used
in continuous flow processing.
Explain the principles behind the production of lactose free
milk for lactose intolerant people:
• immobilised lactase converts lactose in milk into glucose
and galactose;
• these simple sugars can then be absorbed.
The same idea is used to produce cat milk since cats
cannot digest lactose in milk bacteria in the cat’s gut
ferment the lactose producing diarrhoea and wind.
h: Genetic engineering
Recall that genetic engineering alters the genetic code of
an organism by inserting genes.
Recall that the new type of organism is called a transgenic
organism.
Describe the main stages in genetic engineering:
• identification of a desired gene in one organism;
• removal of gene from DNA;
• cutting open the DNA in another organism;
• inserting the new gene into the DNA;
• gene works in transgenic organism;
• transgenic organism is then cloned to produce identical
copies.
Describe how bacteria can be used in genetic
engineering, e.g, to produce human insulin:
• gene for producing human insulin cut out of human DNA;
• loops of bacterial DNA called plasmids cut open;
• insulin gene inserted into plasmid;
• transgenic bacteria cultured by cloning;
• large quantities of insulin harvested.
Describe how restriction enzymes cut open DNA and
ligase enzymes rejoin DNA strands.
Assaying techniques are used to check that the new gene
has been correctly transferred.
Describe how genetic engineering can improve crops by:
• increasing yield;
• making them resistant to weed killers;
• making plants produce other chemicals such as vitamins;
• helping plants survive in poor conditions.
Describe how genetic engineering improves plants by:
• making them able to grow bigger/faster;
• making them able to grow in conditions such as salty
water or drought;
• making them able to resist disease/weed killers.
Discuss the advantages and disadvantages of genetic
engineering.