Everything from the 4 lessons of this topic on a few pages: the key idea of each lesson, the diagram to remember, the points to learn and the traps examiners set. Read it, cover it, test yourself.
Bacteria are useful in biotechnology and genetic modification because of their rapid reproduction rate and their ability to make complex molecules, such as proteins. Extended: there are few ethical concerns over their manipulation and growth, and they contain plasmids, small circular pieces of DNA that can be cut open and used to carry new genes into them.
Doubling is not adding. After 1 hour there are 8 bacteria, not 3 or 4: each 20 minutes the number is multiplied by 2 (1, 2, 4, 8, ...).
A plasmid is not the bacterial chromosome and it is not a nucleus. Bacteria have no nucleus: the chromosome lies free in the cytoplasm, and plasmids are extra small rings of DNA.
Yeast respires anaerobically: glucose → ethanol + carbon dioxide. In biofuel production the ethanol is the useful product; in bread-making the carbon dioxide makes the dough rise. Pectinase breaks down pectin in fruit cell walls, so more juice is released and it is clearer. Biological washing powders contain enzymes that digest stains into small soluble molecules at low temperatures. Extended: lactase breaks lactose into glucose and galactose to make lactose-free milk.
In bread-making the dough rises because of carbon dioxide, not ethanol and not oxygen. For biofuel, the useful product is ethanol.
Very hot water does not help a biological powder: above about 60 °C its enzymes are denatured, so it cleans no better than a non-biological powder.
Lactase does not remove the sugar from milk. It breaks lactose into two smaller sugars, glucose and galactose, which the body can absorb.
Extended. Fermenters are large, sterile vessels used to grow bacteria and fungi on a large scale so they make useful products such as insulin (genetically modified bacteria), penicillin (the fungus Penicillium) and mycoprotein (the fungus Fusarium). The conditions are controlled: temperature, pH, oxygen, nutrient supply and removal of waste products, so the microorganisms grow fast and give a high yield.
The water jacket cools the fermenter. The microorganisms release heat by respiration, so without cooling the temperature would rise and denature their enzymes.
Genetic modification is changing the genetic material of an organism by removing, changing or inserting individual genes. Examples: human genes inserted into bacteria to produce human proteins such as insulin; genes inserted into crop plants to give resistance to herbicides or insect pests, or to improve nutritional qualities. Extended: a human gene is cut out with restriction enzymes, leaving sticky ends; a plasmid is cut with the same enzyme; DNA ligase joins them into a recombinant plasmid, which is put into bacteria that multiply and express the gene.
Genetic modification is not the same as selective breeding. Selective breeding mixes whole sets of genes over many generations; genetic modification moves or changes individual genes, often between different species.
Restriction enzymes cut DNA; DNA ligase joins it. The same restriction enzyme must cut both the gene and the plasmid, or the sticky ends will not be complementary.
In a 'discuss' question give both sides: at least one advantage and one disadvantage, each linked to a named crop where you can (soya, maize, rice).