5- use of biological resources

Question 1

what conditions can be manipulated in a greenhouse to increase photosynthesis

Answer 1

Artificial heating (enzymes controlling photosynthesis can work faster at slightly higher temperatures - only used in temperate countries such as the UK)
Artificial lighting (plants can photosynthesise for longer)
Increasing carbon dioxide content of the air inside (plants can photosynthesise quicker)
Regular watering

Question 2

polythene tunnels

Answer 2

More commonly called polytunnels, these are large plastic tunnels that cover crops
They can protect crops grown outside from the effects of the weather, including excessive wind, rain and extreme temperatures
They also increase the temperature slightly inside the tunnel
They can prevent the entry of pests that can damage plants or diseases that can kill plants

Question 3

fertilisers

Answer 3

fertilisers increase the amount of key nutrients in the soil for crop plants, meaning that they can grow larger and are more healthy, which increases yields

Question 4

pesticides

Answer 4

these chemicals kill off unwanted insects and weed species, meaning that there is less damage done to crop plants by insects, as well as reducing competition from other plant species, which increases yields

Question 5

how can fertiliser increase crop yield

Answer 5

Fertilisers are used to replace these mineral ions
They can make crops grow faster and bigger so that yields are increased
Fertilisers can be in the form of organic fertiliser or chemical fertiliser
Organic fertilisers commonly used by farmers include farmyard manure and compost
Chemical fertilisers are often applied to the soil as dry granules or can be sprayed on in liquid form
They mainly provide crop plants with nitrogen, phosphorus and potassium:

Question 6

using pest control to increase crop yields

Answer 6

Pests such as insects and other animals can damage crops by eating them
Weeds can outcompete crop plants for space, water and soil nutrients
Fungi can infect crop plants and spread disease which can affect growth and yield
All of these can be controlled by using pesticides (chemical control) or by introducing other species (biological control)

Question 7

advantages of pesticides

Answer 7

easily accessible and cheap, have an immediate affect, kills entire population of pests

Question 8

disadvantages of pesticides

Answer 8

organisms they are meant to kill can develop resistance to kill them, they sometimes kill beneficial organisms, need to be rapidly applied

Question 9

biological control

Answer 9

Can happen naturally – for example, ladybirds eat aphids
Usually, a species is introduced specifically to prey on the pest species – for example, parasitic wasps can control whitefly in glasshouse tomato crops
As they are based on a predator-prey cycle, they do not completely remove a pest, but keep it at lower levels

Question 10

advantages of biological control

Answer 10

no pollution, no resistance, can target specific species, long lasting, doesn’t need to be applied rapidly

Question 11

disadvantages of biological control

Answer 11

may eat other organisms instead of pests, takes longer, can’t kill entire population, may not adapt to new environment, may become a pest

Question 12

yeast is

Answer 12

a single celled fungus that can carry out both aerobic and anaerobic respiration

Question 13

how is bread made

Answer 13

When yeast carries out anaerobic respiration, it produces an alcohol (ethanol) and carbon dioxide
Yeast will respire anaerobically if it has access to plenty of sugar, even if oxygen is available
This is taken advantage of in bread making, where the yeast is mixed with flour and water
The yeast produces enzymes that break down the starch in the flour, releasing sugars that can then be used by the yeast for anaerobic respiration
The carbon dioxide produced by the yeast during anaerobic respiration is trapped in small air-pockets in the dough, causing the dough to rise (increase in volume)
The dough is then baked in a hot oven to form bread
During baking, any ethanol produced by the yeast (as a waste product of anaerobic respiration) is evaporated in the heat
This is why bread doesn’t contain any alcohol
The yeast is killed by the high temperatures used during baking
This ensures there is no further respiration by the yeast
Once cooled, the bread is ready to be eaten

Question 14

anaerobic respiration in yeast

Answer 14

Yeast can respire anaerobically (without oxygen), breaking down glucose in the absence of oxygen to produce ethanol and carbon dioxide
Anaerobic respiration in yeast cells is called fermentation
Fermentation is economically important in the manufacture of bread (where the production of carbon dioxide makes dough rise) and alcoholic drinks (as ethanol is a type of alcohol)
It is possible to investigate the effect of temperature on yeast fermentation, by seeing how temperature affects the rate of anaerobic respiration in yeast

Question 15

apparatus needed to investigate the role of anaerobic respiration by yeast in different conditions

Answer 15

Boiling tubes
Capillary tubes
Bungs
Yeast
Sugar solution
Oil
Stopwatch
Water bath
Limewater

Question 16

aerobic respiration in yeast equation

Answer 16

glucose -> alcohol + carbon dioxide

Question 17

method to investigate aerobic respiration in yeast experiment

Answer 17

Mix yeast with sugar solution in a boiling tube
The sugar solution provides the yeast with glucose for anaerobic respiration
Carefully add a layer of oil on top of the solution
This prevents oxygen from entering the solution (prevents aerobic respiration in the yeast)
Using a capillary tube, connect this boiling tube with another boiling tube that is filled with limewater
Place the boiling tube with yeast and sugar solution into a water bath at a set temperature and count the number of bubbles produced in a fixed time (e.g. 2 minutes)
The rate that carbon dioxide is produced by yeast can be used to measure the rate of anaerobic respiration (i.e. the rate of fermentation)
Change the temperature of the water bath and repeat

Question 18

results and analysis of investigating aerobic respiration in yeast experiment

Answer 18

Compare results at different temperatures to find out at which temperature yeast respires fastest
The higher the temperature, the more bubbles of carbon dioxide should be produced as higher temperatures will be closer to the optimum temperature of enzymes in yeast, increasing enzyme activity
As respiration is an enzyme controlled reaction, as enzyme activity increases, the rate of anaerobic respiration will increase
If the temperature is too high (beyond the optimum temperature), the enzymes will denature causing carbon dioxide production to slow down and eventually stop

Question 19

corms of investigating aerobic respiration in yeast experiment

Answer 19

C – We are changing the temperature in each repeat
O – The type (species) of yeast we are using must be the same
R – We will repeat the investigation several times at each temperature to make sure our results are reliable
M1 – We will measure the number of bubbles (of carbon dioxide) produced
M2 – in a set time period (e.g. 2 minutes)
S – We will control the concentration, volume and pH of the sugar solution, as well as the mass of yeast added

Question 20

how is yogurt produced

Answer 20

Yoghurt is made in a process that relies on the presence of a specific type of bacterium – in this case, Lactobacillus
First, all equipment is sterilised to kill other, unwanted bacteria and to prevent chemical contamination
Milk is then pasteurised (heated) at 85-95°C to kill other, unwanted bacteria
Contamination with other bacteria could slow production of the yoghurt by competing with the Lactobacillus for the lactose in the milk
It could also spoil the taste of the yoghurt
The milk is then cooled to 40-45°C and Lactobacillus bacteria is added
The mixture is incubated at this temperature for several hours, while the Lactobacillus bacteria digest milk proteins and ferment (digest) the sugar (i.e. the lactose) in the milk
The Lactobacillus bacteria convert the lactose into lactic acid and this increased acidity sours and thickens the milk to form yoghurt
This lowering of the pH also helps to prevent the growth of other microorganisms that may be harmful, so acts as a preservative
This means the yoghurt can be kept for a longer time (compared to fresh milk)
The yoghurt is then stirred and cooled to 5°C to halt the action of the Lactobacillus bacteria
Flavourings, colourants and fruit may be added before packaging

Question 21

industrial fermentation

Answer 21

Fermenters are containers used to grow (‘culture’) microorganisms like bacteria and fungi in large amounts
These can then be used for brewing beer, making yoghurt and mycoprotein and other processes not involving food, like producing genetically modified bacteria and moulds that produce antibiotics (e.g. penicillin)
The advantage of using a fermenter is that conditions can be carefully controlled to produce large quantities of exactly the right type of microorganism

Question 22

aseptic precautions in industrial fermenter

Answer 22

FERMENTER IS CLEANED BY STEAM TO KILL
MICROORGANISMS AND PREVENT CHEMICAL
CONTAMINATION, WHICH ENSURES ONLY THE
DESIRED MICROORGANISMS WILL GROW

Question 23

nutrients in industrial fermenter

Answer 23

NUTRIENTS ARE NEEDED FOR USE IN RESPIRATION
TO RELEASE ENERGY FOR GROWTH AND TO ENSURE
THE MICROORGANISMS ARE ABLE TO REPRODUCE

Question 24

optimum temperature in industrial fermenter

Answer 24

TEMPERATURE IS MONITORED USING PROBES
AND MAINTAINED USING THE WATER JACKET TO
ENSURE AN OPTIMUM ENVIRONMENT FOR ENZYMES
TO INCREASE ENZYME ACTIVITY (ENZYMES WILI
DENATURE IF THE TEMPERATURE IS TOO HIGH OF
WORK TOO SI OWl Y IF IT Is ToOlOW

Question 25

optimum pHin industrial fermenter

Answer 25

PH INSIDE THE FERMENTER IS MONITORED USING
A PROBE TO CHECK IT IS AT THE OPTIMUM VALUE
FOR THE PARTICULAR MICROORGANISM BEING
GROWN. THE PH CAN BE ADJUSTED, IF NECESSARY
USING ACIDS OR ALKALIS.

Question 26

oxygenation in industrial fermenter

Answer 26

OXYGEN IS NEEDED FOR AEROBIC RESPIRATION TC

TAKE PLACE

Question 27

agitation in industrial fermenter

Answer 27

STIRRING PADDLES ENSURE THAT
MICROORGANISMS, NUTRIENTS, OXYGEN,
TEMPERATURE AND PH ARE EVENLY DISTRIBUTED
THROUGHOUT THE FERMENTER

Question 28

selective breeding is

Answer 28

selecting individuals with desirable characteristics and breeding them together

Question 29

natural selection

Answer 29

occurs naturally, results in development of populations with features that are better adapted to their environment and survival, takes a long time

Question 30

artificial selection

Answer 30

only occurs when humans intervene, results in development of population with features that are useful to humans and not necessarily to survival of the individual, takes less time

Question 31

problems with selective breeding

Answer 31

Selective breeding can lead to ‘inbreeding’
This occurs when only the ‘best’ animals or plants (which are closely related to each other) are bred together
This results in a reduction in the gene pool – this is a reduction in the number of alleles (different versions of genes) in a population
As inbreeding limits the size of the gene pool, there is an increased chance of:
Organisms inheriting harmful genetic defects
Organisms being vulnerable to new diseases (there is less chance of resistant alleles being present in the reduced gene pool)

Question 32

process of genetic engineering

Answer 32

Restriction enzymes are used to isolate the required gene, leaving it with ‘sticky ends’ (a short section of unpaired bases)
A bacterial plasmid is cut by the same restriction enzyme leaving it with corresponding sticky ends (plasmids are circles of DNA found inside bacterial cells)
The plasmid and the isolated gene are joined together by DNA ligase enzyme
If two pieces of DNA have matching sticky ends (because they have been cut by the same restriction enzyme), DNA ligase will link them to form a single, unbroken molecule of DNA
The genetically engineered plasmid is inserted into a bacterial cell
When the bacteria reproduce the plasmids are copied as well and so a recombinant plasmid can quickly be spread as the bacteria multiply and they will then all express the gene and make the human protein
The genetically engineered bacteria can be placed in a fermenter to reproduce quickly in controlled conditions and make large quantities of the human protein

Question 33

genetic modification of bacteria to produce human insulin

Answer 33

The gene that is to be inserted is located in the original organism – the gene for insulin production is located within a human chromosome
Restriction enzymes are used to isolate or ‘cut out’ the human insulin gene, leaving it with ‘sticky ends’ (a short section of unpaired bases)
A bacterial plasmid is cut by the same restriction enzyme leaving it with corresponding sticky ends (plasmids are circles of DNA found inside bacterial cells)
The plasmid and the isolated human insulin gene are joined together by DNA ligase enzyme
If two pieces of DNA have matching sticky ends (because they have been cut by the same restriction enzyme), DNA ligase will link them to form a single, unbroken molecule of DNA
The genetically engineered (recombinant) plasmid is inserted into a bacterial cell
When the bacteria reproduce the plasmids are copied as well and so a recombinant plasmid can quickly be spread as the bacteria multiply and they will then all express the human insulin gene and make the human insulin protein
The genetically engineered bacteria can be placed in a fermenter to reproduce quickly in controlled conditions and make large quantities of the human protein
Bacteria are extremely useful for genetic engineering purposes because:
They contain the same genetic code as the organisms we are taking the genes from, meaning they can easily ‘read’ it and produce the same proteins
There are no ethical concerns over their manipulation and growth (unlike if animals were used, as they can feel pain and distress)
The presence of plasmids in bacteria, separate from the main bacterial chromosome, makes them easy to remove and manipulate to insert genes into them and then place back inside the bacterial cells