A-Level Biology OCR Notes

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Cloning Plants

Vegetative propagation is asexual reproduction from the vegetative parts of a plant rather than through specialised sexual reproductive structures
- Overwinter organs such as bulbs and tubers
- Runners and rhizomes
- Stem cutting, with rooting hormones encouraging root growth
Micropropagation is the process of growing large numbers of cloned plants from meristem tissue taken from a sample plant.
- Explants from the meristem are acquired and sterilised
- They are placed on a sterile culture medium, forming a callus
- The callus is divided and moved onto separate culture mediums to stimulate the development of roots and shoots
- The plantlets developed are potted in soil
Tissue culture is the growth of tissues or cells in an artificial medium taken from tissues of a sample plant.

Cloning Animals

Embryo twinning is the process of splitting an early embryo in half to create two genetically identical embryos
Somatic cell nuclear transfer is the method of cloning that is achieved by transferring the nucleus from a somatic (body) cell of an adult animal into an egg cell
- Ovum is enucleated
- Somatic cell is enucleated and transferred to enucleated ovum
- An electric shock stimulated division
- It is implanted into the uterus of a surrogate mother
Non-reproductive cloning clones only tissues and cells

Microorganisms

In a batch culture, the microorganisms in a fermenter do not have any exchange of nutrients or gases with the external environment. A closed culture:
1 is the lag phase.
2 is the log phase.
3 is the stationary phase and
4 is the decline phase

Primary metabolites are produced during the log phase as they are made in continuous culture. In continuous culture the conditions are altered continuously to allow for optimal growth.

Secondary metabolites are produced during the stationary phase when there are not enough nutrients for the whole population. This is because they are produced in stressful conditions and are therefore made in closed culture
Microorganisms are used in biotechnology because theyre cheap, have a rapid growth rate, easily genetically modified, need simple nutrient, secrete products and make their own enzymes
Bioremediation is the process in which microorganisms are used to clear toxic pollutants by converting them to less harmful substances
Microorganisms are often used to produce drugs, such as in the production of penicillin. Commercial drug production takes place on a large-scale using fermenters, as this allows for certain conditions to be carefully controlled so that a high yield is obtained
The fungus Fusarium veneatum directly produces mycoprotein, also known as single cell protein (SCP).
Sterile conditions are necessary in order to prevent the growth of unwanted microorganisms which can reduce yield or produce toxins, killing the cultured microorganisms and destroying their products

Immobilised Enzymes

Immobilised enzymes are not free to diffuse through a solution as it is held in place. This can be by adsorption, covalent bonding, entrapment and membrane separation.
It reduces the cost of product separation from enzymes
Glucose isomerase is used to convert glucose to fructose for sweeteners
Glucoamylase converts dextrins to glucose
Penicillin acylase use in the formation of semi-synthetic penicillin which provides a barrier against antibiotic resistance
Aminoacylase synthesises L-amino acids from N-acyl amino acid, for use in the production of compounds.

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