← All notesBiology · Biotechnology & genetic modification⬇ Download PDF
IGCSE Biology 0610 · Chapter 15 notes · ~18 min read

Biotechnology & genetic modification

How bacteria, yeast and fungi make useful products, how enzymes are used in fruit juice, washing powders and milk, how fermenters work, and how a gene is cut out, moved and used to make human insulin and better crops.

Bacteria & yeastEnzymes in industryFermentersGenetic modification
ASby Aiza Ma'am
mentorriyaz.in
No tag = Core (everyone)EXTENDED Extended onlyhighlight = comes up again and againTest yourself at the end

In 30 seconds

  • Biotechnology uses living organisms or their enzymes to make useful products. Bacteria (fast breeders), yeast (ethanol and bread) and fungi (penicillin, mycoprotein) are grown in fermenters under controlled conditions.
  • Enzymes are used in industry: pectinase in fruit juice, protease, lipase and amylase in washing powders, and lactase in lactose-free milk.
  • Genetic modification moves a gene into another organism. Restriction enzymes cut, ligase joins, and a plasmid carries the gene into bacteria, which then make human insulin. GM crops can resist herbicides and pests or contain extra nutrients.

By the end you can

  • Explain why bacteria are useful in biotechnology and genetic modification.
  • Describe how yeast is used to make ethanol for biofuel and in bread-making.
  • Describe the use of pectinase in fruit juice and of enzymes in biological washing powders.
  • Define genetic modification and give examples of GM bacteria and GM crops.
  • Explain why bacteria are suitable for biotechnology: rapid reproduction, few ethical concerns and plasmids. EXT
  • Describe the use of lactase to make lactose-free milk. EXT
  • Describe how fermenters are used to make insulin, penicillin and mycoprotein, and which conditions are controlled. EXT
  • Outline how a gene is transferred, using restriction enzymes, sticky ends, DNA ligase and recombinant plasmids. EXT
  • Discuss the advantages and disadvantages of GM crops. EXT

1Microorganisms in biotechnology

Bacteria, yeast and fungi

BACTERIAplasmidreproduce very fast; make complexmolecules such as human insulin(after genetic modification)YEASTrespires without oxygen:sugar → ethanol (biofuel) + CO₂,so bread dough risesFUNGIPenicillium makes the antibioticpenicillin; Fusarium makesmycoprotein (a protein-rich food)ENZYMESpectinase: fruit juiceprotease, lipase, amylase:washing powderslactase: lactose-free milkAll are grown or used in carefully controlled conditions, often in FERMENTERS.
Bacteria, yeast, fungi and enzymes all do useful jobs for people, often in controlled conditions.

Biotechnology — the use of living organisms (or parts of them, such as enzymes) to make useful products or carry out useful processes.

  • Why bacteria are useful: they reproduce very fast (some divide about every 20 minutes), so large numbers grow cheaply and quickly. They can also make complex molecules, such as proteins, that are very hard to make in any other way.
  • EXT Why bacteria suit genetic modification: (1) fewer ethical concerns than using animals; (2) they contain plasmids, which are easy to cut open and put genes into; (3) the genetic code is the same in all living things, so a bacterium can read a human gene and make the human protein.

Plasmid — EXT a small circular ring of DNA in a bacterium, separate from the main chromosome.

Common mistake"All bacteria are harmful germs." No. Most bacteria are harmless and many are very useful (making insulin, enzymes and food). Only some cause disease (pathogens).
Worked example

One bacterium divides every 30 minutes. How many bacteria could there be after 5 hours if there are no limits?

  1. 5 hours = 300 minutes
  2. 300 ÷ 30 = 10 divisions
  3. each division doubles the number: 210 = 1 024 bacteria
  4. in a real culture food and space run out first (growth curve)

Yeast: ethanol and bread

ETHANOL FOR FUELBREADsugarsolution+ yeastairlock:CO₂ out,no O₂ inCO₂glucose → ethanol + carbon dioxide(yeast, no oxygen, 30–40 °C)Ethanol is used as a biofueldough + yeastdough risesbakingYeast respires the sugar in the dough.CO₂ bubbles make it rise; bakingexpands them and kills the yeast.
Yeast ferments sugar without oxygen, making ethanol and carbon dioxide. Ethanol is a fuel and CO₂ makes dough rise.
  • Yeast is a single-celled fungus. With no oxygen it respires anaerobically, turning sugar into ethanol and carbon dioxide (anaerobic respiration). This is fermentation.
glucose → ethanol + carbon dioxide
anaerobic respiration in yeast (fermentation)
  • Biofuel: yeast ferments sugars from crops such as sugar cane or maize. The ethanol is separated and used as a fuel, often mixed with petrol. It is renewable, because the crop can be grown again.
  • Bread-making: yeast respires the sugar in the dough. The CO₂ bubbles make the dough rise. Baking makes the bubbles expand (and kills the yeast), giving a light texture.
Exam tipYeast works best when warm (about 30–40 °C). If it is too cold it is slow. If it is too hot its enzymes denature and it dies.
Worked example

Yeast is added to sugar solution at four temperatures and the CO₂ bubbles in 1 minute are counted: 20 °C = 15, 30 °C = 32, 40 °C = 48, 70 °C = 0. Describe and explain the results.

  1. from 20 to 40 °C the bubbles increase (15 → 32 → 48), so the rate of fermentation rises with temperature
  2. enzymes and sugar have more kinetic energy, so more collisions
  3. at 70 °C there are no bubbles: the enzymes are denatured and the yeast has died
  4. the rate at 40 °C is 48 ÷ 15 = 3.2 times the rate at 20 °C

2Enzymes in industry

Pectinase and fruit juice

WITHOUT PECTINASEWITH PECTINASEpectin holdscells togetherpectin brokendown: cellsseparate28 cm³cloudy,thick juice45 cm³clearer,more juicePectinase breaks down pectin, the “glue” between plant cells.
Pectinase breaks down the pectin that holds plant cells together, so more juice runs out.

Pectinase — an enzyme that breaks down pectin.

  • Pectin is a carbohydrate that holds plant cells together. When pectinase is added to crushed fruit, the cells separate and release more juice.
  • Benefits: more juice (a higher yield), clearer juice, and juice that is less thick, so it is easier to filter.
Worked example

Crushed apple pulp gives 28 cm³ of juice without pectinase and 45 cm³ with pectinase. Calculate the percentage increase in juice.

  1. increase = 45 − 28 = 17 cm³
  2. % increase = 17 ÷ 28 × 100
  3. = 61% (to the nearest whole number)
Exam tipIn a pectinase investigation use the same mass of pulp, same temperature and same time. The only difference is whether the enzyme is added (enzymes).

Enzymes in washing powders

protein stainPROTEASEamino acidssoluble: dissolve andare washed awayfat or greaseLIPASEfatty acids + glycerolsoluble: dissolve andare washed awaystarch stainAMYLASEsugarssoluble: dissolve andare washed awayBiological washing powders work at 30–40 °C: this saves energy and protects fabrics.At high temperatures the enzymes denature and stop working.
Biological washing powders contain enzymes that break stains into small soluble molecules that wash away.
  • Biological washing powders contain protease (breaks down protein stains such as blood and egg), lipase (breaks down fats and oils) and amylase (breaks down starch from food).
  • The enzymes turn the stains into small, soluble molecules, which dissolve in the water and are washed away.
  • They work at low temperatures (30–40 °C), which saves energy and protects fabrics. At high temperatures the enzymes denature and stop working.
Common mistake"Enzymes work best in a boiling wash." No. High temperatures denature enzymes. Biological powders are used at 30–40 °C.
EnzymeBreaks downIntoUse
pectinasepectinsmaller carbohydrate moleculesfruit juice
proteaseproteinamino acidswashing powder
lipasefats and oilsfatty acids and glycerolwashing powder
amylasestarchsugarswashing powder
lactase EXTlactoseglucose and galactoselactose-free milk

Lactase and lactose-free milkEXTENDED

LACTASE BREAKS DOWN LACTOSEglugalLACTOSE (milk sugar)lactaseglugal+GLUCOSE + GALACTOSEtwo sugars joinedtwo separate sugarsMILKlactose+ lactaseLACTOSE-FREE MILKSome people make too little lactaseso cannot digest lactose.Lactose-free milk lets them drink milk.It also tastes sweeter, because glucoseand galactose are sweeter than lactose.
EXT Lactase splits lactose into glucose and galactose, so people who cannot digest lactose can drink the milk.
  • EXT Lactose is the sugar in milk. The enzyme lactase breaks lactose down into glucose and galactose.
  • EXT Some people are lactose intolerant (they make too little lactase). Milk treated with lactase is lactose-free, so they can drink it.
  • EXT Glucose and galactose taste sweeter than lactose, so less sugar needs to be added to some milk products.

3Fermenters EXT

Making products in fermenters

motornutrients incooling water outcooling water insterile air inwastegas outpH andtemperatureprobesstirrerpaddlesproduct outCONTROLLED:temperaturepHoxygennutrientsmixingsterile (no germs)
EXT A fermenter keeps temperature, pH, oxygen, nutrients and mixing at the best level for the microorganisms.

Fermenter — EXT a large vessel in which microorganisms are grown under controlled conditions to make a product.

  • EXT Products: insulin (made by genetically modified bacteria), the antibiotic penicillin (made by the mould Penicillium, antibiotics) and mycoprotein (a protein-rich food made from the fungus Fusarium, used as a meat substitute).
  • EXT The conditions are controlled so that the microorganisms grow fastest and make the most product.
ConditionHow it is controlledWhy
temperaturewater jacket with cooling water; temperature proberespiration releases heat; the right temperature keeps the enzymes working
pHpH probe; acid or alkali addedthe wrong pH denatures enzymes
oxygensterile air bubbled inmost of the microorganisms need oxygen for aerobic respiration
nutrientsadded (glucose, nitrogen source, minerals)for energy, growth and making the product
mixingstirrer (paddles)spreads nutrients, oxygen and heat evenly
sterile conditionsvessel steam-cleaned; air filteredother microorganisms would compete with the culture and spoil the product
wastewaste gases and product removeda build-up of waste can poison the microorganisms
Common mistake"A fermenter must have no oxygen." No. That is true for yeast making ethanol, but many fermenters (for example for penicillin) are supplied with sterile air for aerobic respiration.
Exam tipFor a fermenter question, link every condition to a reason: "temperature kept at the optimum so enzymes work fastest", "sterile so that other microbes do not compete".

4Genetic modification

What is genetic modification?

herbicide-resistantsoya××sprayresistance gene: the cropsurvives the weedkiller,but the weeds dieinsect-resistantmaize×pesta bacterial gene makes theplant toxic to pests, soless insecticide is usednutritional rice(golden rice)normalGMan extra gene makesbeta-carotene, which thebody turns into vitamin AIn each case the new gene is inserted into the crop’s cells.GM crops are grown for higher yield, lower costs or better nutrition.
Genes can be inserted into crops to give them useful new features.

Genetic modification — changing the genetic material of an organism by removing, changing or inserting individual genes.

  • A gene from one species can be put into another species. All living things use the same genetic code, so the cell can read the new gene and make the protein.
  • Human proteins in bacteria: the gene for human insulin is put into bacteria, which make insulin for people with diabetes (diabetes).
  • Crops with new features: herbicide resistance (soya survives the weedkiller), pest resistance (maize with a bacterial gene that makes it toxic to pest insects) and extra nutrients (golden rice makes beta-carotene, which the body turns into vitamin A).
  • GM is not the same as selective breeding, which only mixes genes that are already in the species.
Selective breedingGenetic modification
what changes?the whole set of genes, over many generationsone chosen gene, in one step
where do the genes come from?the same speciesany species (for example a bacterium or a human)
examplecattle that give more milkbacteria that make human insulin

Making human insulin in bacteriaEXTENDED

1Cut out the genecutcuthuman DNArestriction enzymecuts out the humaninsulin gene2Cut the plasmidplasmidthe same enzymecuts open abacterial plasmid3Join themplasmidsticky ends pair up;ligase joins them:recombinant plasmid4Put into bacteriathe bacterium takesup the recombinantplasmid5Grow in a fermenterbacteria divide fast:millions of copiesof the gene6Collect the productinsulinthe bacteria makehuman insulin, whichis then purified
EXT The gene is cut out, joined into a plasmid, put into bacteria and the bacteria are grown in a fermenter.

Restriction enzyme — EXT an enzyme that cuts DNA at a specific sequence of bases, often leaving sticky ends.

DNA ligase — EXT an enzyme that joins pieces of DNA together.

Recombinant plasmid — EXT a plasmid that contains DNA from another organism.

  • EXT Step 1. A restriction enzyme cuts out the human insulin gene from human DNA.
  • EXT Step 2. The same restriction enzyme cuts open a bacterial plasmid. Both pieces now have matching sticky ends.
  • EXT Step 3. The gene and the plasmid are mixed. The sticky ends pair up, and DNA ligase joins them to make a recombinant plasmid. The plasmid is the vector that carries the gene.
  • EXT Step 4. The recombinant plasmid is put into bacteria.
  • EXT Step 5. The bacteria are grown in a fermenter. They divide quickly, copying the plasmid, and make human insulin.
  • EXT Step 6. The insulin is collected and purified for use by people with diabetes.
Memory trickRestriction enzyme = scissors (it cuts). Ligase = glue (it joins).
Common mistake"DNA ligase cuts out the gene." No. The restriction enzyme cuts and the ligase joins.

Restriction enzymes, sticky ends and ligaseEXTENDED

1 A restriction enzyme cuts DNA and leaves “sticky ends”CTGAATTCAGGACTTAAGTCcut here (the red line)CTGGACTTAAAATTCAGGTCsticky ends: short singlestrands of unpaired bases2 A piece cut with the same enzyme has matching sticky ends, so they pair upCTGAATTCGAGACTTAAGCTDNA ligase joins the backbones(green) to make one strand of DNA■ plasmid DNA■ inserted genebase pairs: A–T and C–G
EXT A restriction enzyme cuts both strands off-set, leaving single-stranded sticky ends that can pair with matching ones.

Sticky ends — EXT short single-stranded pieces of unpaired bases at the cut ends of DNA. They pair with matching sticky ends made by the same enzyme.

  • EXT The enzyme recognises one sequence of bases and cuts the two strands at different places. This leaves single-stranded overhangs.
  • EXT Sticky ends join by complementary base pairing: A with T and C with G. DNA from any organism cut with the same enzyme has matching ends, so the gene fits into the plasmid.
  • EXT At first the pieces are held together only by base pairs. DNA ligase joins the sugar–phosphate backbones to make them permanent.
Worked example

One sticky end has the bases A A T T. Which bases must the matching sticky end have?

  1. bases pair up as A with T and C with G
  2. A–T, A–T, T–A, T–A
  3. so the matching sticky end is T T A A

GM crops: advantages and disadvantagesEXTENDED

AdvantagesDisadvantages
higher yield because the crop resists pests or weedkiller, so more food from the same landthe gene may spread to wild plants by pollen (for example herbicide resistance in weeds)
less insecticide is needed (insect-resistant maize), which saves money and reduces pollutionharm to other organisms (for example useful insects) and so to biodiversity
herbicide-resistant soya makes weed control easierlong-term effects on human health are not fully known, which worries some people
extra nutrients (golden rice has vitamin A), which helps prevent deficiency diseasesthe seeds are expensive, so farmers depend on the companies that sell them
Worked example

The yield of a GM maize crop is 9.6 tonnes per hectare and of ordinary maize 8.0 tonnes per hectare. Calculate the percentage increase.

  1. increase = 9.6 − 8.0 = 1.6 t/ha
  2. % increase = 1.6 ÷ 8.0 × 100
  3. = 20%
Exam tipFor a "discuss" question give at least one advantage and one disadvantage, each with a reason. Avoid saying GM crops are "unsafe" or "perfectly safe": say that long-term effects are still being studied.

5Test yourself

Test yourself — cover the answers first

Quick check

  1. Define biotechnology.
  2. Give two reasons why bacteria are useful in biotechnology.
  3. What does yeast make when it respires without oxygen?
  4. Write the word equation for fermentation in yeast.
  5. Why does bread dough rise?
  6. What is bioethanol used for?
  7. What does pectinase do?
  8. Give two benefits of adding pectinase to crushed fruit.
  9. Which enzymes in washing powders break down protein, fats and starch?
  10. Why do biological washing powders work well at 30–40 °C?
  11. Define genetic modification.
  12. Name one human protein made by GM bacteria.
  13. Give one example of a useful feature given to a GM crop.
  14. EXT What is a plasmid?
  15. EXT Give two reasons why bacteria are suitable for genetic modification.
  16. EXT What does lactase do?
  17. EXT Name two products made in fermenters.
  18. EXT Why must a fermenter be sterile?
  19. EXT Why is cooling water used in a fermenter?
  20. EXT Which enzyme cuts DNA at a specific sequence of bases?
  21. EXT What are sticky ends?
  22. EXT Which enzyme joins DNA fragments together?
  23. EXT What is a recombinant plasmid?
  24. EXT Give one advantage and one disadvantage of GM crops.

Exam-style

  1. Describe how yeast is used in bread-making. [3]
  2. Describe how biological washing powders remove stains, and explain why they are used at low temperatures. [4]
  3. Describe the use of pectinase in making fruit juice. [3]
  4. State two reasons why bacteria are used to make human proteins. [2]
  5. EXT Explain why lactase is added to milk. [3]
  6. EXT Describe how the conditions in a fermenter are controlled and why. [5]
  7. EXT Describe how a bacterium can be genetically modified to make human insulin. [6]
  8. EXT Discuss the advantages and disadvantages of growing herbicide-resistant soya. [4]
Show answers
  1. the use of living organisms (or parts of them, such as enzymes) to make useful products
  2. they reproduce very quickly; they can make complex molecules such as proteins
  3. ethanol and carbon dioxide
  4. glucose → ethanol + carbon dioxide
  5. yeast respires the sugar and the carbon dioxide bubbles make the dough rise
  6. as a biofuel (mixed with petrol)
  7. it breaks down pectin, which holds plant cells together
  8. more juice, clearer juice, easier to filter
  9. protease, lipase, amylase
  10. this saves energy and protects fabrics, and the enzymes work without being denatured
  11. changing the genetic material of an organism by removing, changing or inserting individual genes
  12. insulin
  13. herbicide resistance, pest resistance, extra vitamin A
  14. a small circular ring of DNA in a bacterium, separate from the main chromosome
  15. fewer ethical concerns, they have plasmids, the genetic code is the same in all organisms, they reproduce fast
  16. it breaks lactose down into glucose and galactose
  17. insulin, penicillin, mycoprotein
  18. so other microorganisms do not compete with the culture and spoil the product
  19. respiration releases heat and the temperature must stay at the optimum for the enzymes
  20. a restriction enzyme
  21. short single-stranded pieces of unpaired bases at the ends of cut DNA that pair with matching ends
  22. DNA ligase
  23. a plasmid containing DNA from another organism
  24. advantage: higher yield or less insecticide or extra nutrients; disadvantage: gene may spread to wild plants or harm other organisms or seeds are expensive
  25. yeast is mixed into dough that contains sugar
    the yeast respires the sugar and makes carbon dioxide
    the carbon dioxide bubbles make the dough rise and baking makes the bubbles expand
  26. they contain protease, lipase and amylase
    these break down protein, fat and starch stains
    into small soluble molecules that wash away
    low temperatures save energy and prevent the enzymes being denatured
  27. pectinase is added to crushed fruit
    it breaks down pectin that holds the cells together
    so more juice is released and the juice is clearer
  28. they reproduce very quickly
    they can make complex molecules such as proteins
  29. lactase breaks lactose into glucose and galactose
    some people cannot digest lactose
    so the milk becomes lactose-free and they can drink it
  30. temperature is controlled with a water jacket so that enzymes work at their optimum
    pH is monitored and adjusted so enzymes are not denatured
    sterile air supplies oxygen for respiration
    nutrients are added for growth
    a stirrer mixes everything and the vessel is kept sterile so other microorganisms do not compete
  31. a restriction enzyme cuts out the human insulin gene
    the same enzyme cuts open a plasmid, leaving matching sticky ends
    the gene and plasmid are joined by DNA ligase
    this makes a recombinant plasmid
    the plasmid is put into bacteria
    the bacteria are grown in a fermenter and make insulin
  32. advantage: weeds can be killed without harming the crop, giving a higher yield
    advantage: lower costs of weed control
    disadvantage: the resistance gene may spread to wild plants (weeds)
    disadvantage: harm to other organisms and biodiversity or unknown long-term effects
Practise this chapter
BiotechnologyGenetic modification
Stuck on a question?

Send it to us on WhatsApp. We read every message.

Want regular help? Send this to your parent →
Share with a friendAsk on WhatsApp