This is based on the OCR A Gateway spec for A level biology, Chapter 22 from module 6. Specification reference: 6.2.1
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Bulbs e.g. daffodils
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Leaf bases contain stored food, buds develop internally and make new shoots.
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Runners e.g.strawberry
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Lateral stem grows, eventually withers away.
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Rhizomes e.g. marram grass
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Specialised horizontal growth, stem develops buds -which becomes new plant.
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Stem tubers e.g. potatoes
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Tip of underground stem becomes swollen with stored nutrients. Buds develop on that storage organisms and form new shoots.
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Uses in horticulture:
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Can take cuttings from bulbs/runners to increase the yield because it is faster than growing seeds.
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This also guarantees quality (because genetically identical).
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e.g. used in sugar cane cloning.
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Micropropagation:
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Sample taken from meristem (sterile conditions).
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Sterilised. Collected tissue = explant.
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Placed in sterile culture medium containing plant hormones. Cells form Mass of identical cells (callus).
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Callus is divided and transferred to different medium. This stimulates the development of genetically identical plantlets.
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Plantlets are planted in compost and grow.
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Young plants planted out to grow as crops.
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Artificial twinning
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Animal w/ desired trait is given hormones for super-ovulation.
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Ova is fertilised in vitro or by insemination (by desired male).
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Before 6 days, cells are split (still totipotent).
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Each cell becomes an embryo.
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Embryos are inserted in surrogates.
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Develop into foetuses and born normally.
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Somatic Cell Nuclear Transfer (SCNT)
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Transfer nucleus from adult somatic cell into enucleated egg cell (no nucleus).
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Nucleus and egg are fused with an electric shock
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OR electrofusion - Cells are left next to each other with constant current running through.
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+ More offsprings than usual
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+ Guarantees desirable genes from sire.
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+ Useful in pharming
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+ Can clone rare and endangered animals
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- SCNT = inefficient -- many eggs required to successfully produce one offspring.
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- Cloned embryos fail to develop, produced deformed offsprings...
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- Most clones have a shorter lifespan, which also means we have not been successful in cloning extinct species yet.
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Biotechnology:
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Applying biological organisms / enzymes to the synthesis / breakdown / transfer of materials in the service of people
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e.g. foods, penicillin, insulin...
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Pros / cons of using microorganisms:
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+ No ethics
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+ Easily manipulated genetically
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+ Short life cycles
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+ Simple + cheap nutrient requirements
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+ Growth conditions = low temperatures / oxygen / food...
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- Can produce toxins
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- Have to be separated from nutrient and processed.
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- Sterile conditions needed (increases cost).
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- Less natural flavour.
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Indirect food prod
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Use microorganisms for their effects on other foods.
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e.g. bread -- yeast caused it to rise.
yoghurt -- bacteria make it sour. |
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Direct food prod
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Grow microorganisms to eat
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e.g. Quorn, fusarium venetatum (grown on glucose syrup).
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Indirect food production
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Yeast anaerobically respires.
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Optimum temp about 20-28oC, but can also be genetically modified to function at lower temperatures.
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Malting - Barley germinates and digests starch into sugars so yeast respires.
Mashing - Malt + hot water. Enzymes break down starch, worth is formed. Fermentation - Wort + yeast. pH a lowered as yeast runs out of O2 and produces ethanol. Maturation - Low temperatures for about a month. Finishing - Filtered, pasteurised and bottled with CO2. |
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Indirect food prod
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Yeast feeds on sugars and ferments them into ethanol and CO2 which makes the bread rise
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Optimum temp. of 38-46oC
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Optimum pH - 5.0 / 5.5
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Yeast requires O2 and sugars for fermentation.
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Indirect food prod
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Bacteria feed on lactose, inhibit growth of bacteria which makes milk go off.
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Pasteurised - 95oC for 20 seconds.
Mixed with bacteria culture and enzymes. The milk is separated into solid curds and liquid whey. Cheese - Curds are separated and cooked in whey, sometimes pressed and dried. |
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Indirect food prod
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Skimmed milk powder, milk is pasteurised and cooked.
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L. bulgarius / S. thermopilus bacteria added to the milk and milk is stored at cool temepratures.
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Inoculating broth
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Bacteria suspension, mixed with sterile nutrient broth. Incubated and shook.
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Inoculating agar
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Inoculating loop Sterile and dipped in suspension. Streaks made across a Petri dish.
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Microorganisms are used to break down pollutants and contaminants in soil / water.
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Natural organisms
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Used on crude oil / sewage.
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GM microorganisms
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Break down material they don't normally encounter (e.g. mercury in water).
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Lag phase
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Bacteria adapting to environment.
Growing and synthesising enzymes. |
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Exponantial phase
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Close to / at theoretical max.
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Stationary phase
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Growth rate = zero --> Cells formed cancelled out by cells dying.
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Death phase
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Reproduction almost stopped, death rate increases (resources used up).
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Alternative to using microorganisms is to isolated their enzymes.
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Immobilised enzymes are when those enzymes are fixed so substrate washes over them.
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+ Reusable so cheaper, greater temperature tolerance, less downstream processsing.
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Surface immobilisation - Surface adsorption (sticking to the surface) to inorganic carrier.
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+ Simple and cheap.
+ Activity virtually unchanged. |
- Enzymes can be lost from matrix easily.
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Surface immobilisation - covalent / ionic binding to inorganic carrier.
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+ Enzymes bound strongly, unlikely lost.
+ Accessible to substrate. + pH / substrate concentration = little effect on activity. |
- Cost varies
- Active site may be modified. |
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Entrapment - in matrix.
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+ Applicable to different processes.
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- Expensive.
- Difficult to entrap. - Diffusion can be slow. |
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Entrapment - encapsulation or semi-permeable membrane.
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+ Relatively simple to do.
+ Small effect on enzymes activity. + Applicable to different processes. |
- Expensive.
- Diffusion can be slow. |
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