|Biology||A Level||£20 /hr|
There are four methods of enzyme immobilisation: adsorption, covalent bonding, entrapment and membrane separation.
Adsorption involves mixing the enyzme with an immobilsing support so the enzyme molecules will bind to it because of hydrophobic interactions and ionic links. The support is called an adsorbing agent and could be porous carbon, glass beads or clays.
Covalent bonds between enzyme molecules and an insoluble material, such as clay, are formed using cross-linking agents (e.g. sepharose).
Entrapping the enzyme molecules in a network or gel beads or cellulose fibres allows the enzyme to be immobilised in their natural state (not attached to another molecule).
Membrane separation physicially separates the enzyme and substrate solutions with a partially permeable membrane. Both the substrate and product molecules are small enough to pass through the membrane.see more
The myelin sheath is a layer of insulating, fatty material that encases some neurones. The sheath is composed of Schwann cells that have gaps called nodes of Ranvier between them. Potassium and sodium ions can only diffuse in and out of the neurone at these gaps. This allows saltatory or 'jumping' conduction where the local currents are elongated as the sodium ions have to diffuse further along the neurone before the action potential can occur. The action potential appears to 'jump' from one node of Ranvier to another.see more
Tonality describes what key a piece is in or what tonal relationships are used. When asked to talk about tonality you should discuss whether the key is major or minor and the different modulations used during the piece e.g. in bar 60 the music moved from C major to the dominant (G) major.see more