OCR Biology F215: Biotechnology

OCR specification broken down into smaller pieces

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(a) State that Biotechnology is the industrial use of living organisms (or parts of living organisms) to produce food, drugs or other products

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(b) Explain why microorganisms are often used in biotechnological processes
--> Reproduce asexually - genetically identical & carry out the same metabolic processes
--> Have a fast life cycle & growth rate so large populations can be built up quicklyCan produce chemicals which are released into the growth medium which can be harvested
--> Can be genetically modified to produce specific products
--> Grow rapidly in favourable conditions - generation time can be as little as 30 mins
--> Can be grown on waste materials from industry which would be useless or towix to humans
--> Can be grown anywhere in the world, not climate dependant e.g. some bacteria has evolved and enzymes can work in hot environments
--> Tend to generate products that are in a more pure form than those generated via chemical processes
--> No ethical questions

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(c) Describe, with the aid of diagrams, and explain the standard growth curve of a microorganism in a closed culture
Sigmoid Growth Curve


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.. Explaining the sigmoid growth curve:

1) Lag Phase - Growth is slow, organisms are adjusting to the surrounding conditions. The cells are active but not reproducing. The length of this period depends on the growing conditions

2) Log Phase - Rapid rate of growth, dividing at max rate as each individual has enough space & nutrients. The limiting factor is their growth rate, this phase depends on how quickly the organisms reproduce

3) Stationary Phase - Birth rate = Death rate. Nutrients are being used up & waste products are building up

4) Death Phase - Nutrients become exhausted & a build up of toxic waste leads to the death rate to increase above the rate of reproduction. Eventually all organisms will die in a closed system

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(d) Describe how enzymes can be immobilised

--> Absorption - Enzyme molecules are mixed with the immobilising support & bind to it due to a combination of hydrophobic interactions & ionic links

--> Entrapment - Enzymes are trapped e.g. in a gel bead/network of cellulose fibres. Substrate & product can pass through the material to the enzyme, but the enzyme can't pass through to the solution

--> Covalent bonding - Enzyme molecules are covalently bonded to a support, often by covalently linking enzymes together to an insoluble material using a cross-linking agent

--> Encapsulation

--> Membrane separation

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(e) Explain why immobilised enzymes are used in large scale production
--> Enzymes can be recovered easily & used again many times
--> The product isn't contaiminated by the enzyme
--> Protection from the immobilising material means the enzyme is more stable in changing temps or pH
--> Enzyme activity can be controlled more easily

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(f) Compare & contrast the processes of continuous culture & batch culture

  • Nutrients added: only at start / continuously
  • Product removed: when fermentation stops / continuously (organisms held in log/growth phase giving higher productivity so can be on a smaller scale)
  • Growth rates & product fermentation are slower because of limiting factors
  • slower growth rates = larger vessels used
  • Easy to set up & maintain / an be difficult to maintain conditions for log phase
  • Contamination? Only one batch is wasted / can affect huge volumes
  • Less efficient / more efficient use of time
  • Quality can vary / quality is consistant
  • Useful for processes involving secondary metabolites / primary metabolites
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(g) Describe the differences between primary & secondary metabolites

Primary metabolites --> substances produced by an organism as part of its normal growth e.g. amino acids, proteins, enzymes, nucleic acids, ethanol & lactate. Production matched the growth in population of the organism.

Secondary metabolites --> substances produced by an organism that are not part of its normal growth phase. Production usually begins after main growth period of the organism & doesn't match the growth in population of the organism. Antibacterial chemicals are mainly secondary metabolites. Only a small mumber of micro-organisms produce secondary metabolites, often when there is a depletion in nutrients or a build up of waste products

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(h) Explain the importance of manipulating the growing conditions in a fermentation wessel in order to maximise yield of product required

Growing conditions can be manipulated & controlled in order to ensure that the microorganism is growing in its optimum conditions = maximisation of product:
--> Temperature - Too hot = enzymes denature. Too cold = growth will be slow
--> Type & addition of nutrient - depends on whether the product is a primary or secondary metabolite
--> Oxygen concentration - most organisms are grown under aerobic conditions so there must be a sufficient supply of oxygen to prevent the unwanted products of anaerobic respiration & a reduction in growth rate
--> pH - changes in pH can reduce the activity of enzymes & .'. reduce growth rates

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(i) Explain the importance of asepsis in the manipulation of microorganisms

Asepsis is the absence of unwanted microorganisms which could:
--> compete with the culture for nutrients & space
--> reduce the yield of useful products form the culture
--> spoil the product (contamination)
--> produce toxic chemicals
--> destroy the culture & their products

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brilliant resource!



love this, such a good idea! Thanks

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