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ENZYMES - Coggle Diagram
ENZYMES
- Enzymes are biological catalysts
- They speed up chemical reactions without being used up during the reactions
- They are all 3D globular proteins with a specific tertiary structure
- They are specific - they only catalyse one type of reaction and can only work on one specific type of substrate molecule
- They have an active site that is the complementary shape to the shape of their specific substrate
- The active site lowers the activation energy require to start the reaction
- When an enzyme and a substrate bind at the active site, and enzyme substrate complex is formed
- The reaction then occurs and products are formed
- The name is usually derived from its substrate with the suffix '-ase' e.g. lipase breaks down lipids
- For an enzyme reaction to take place, there must be successful collisions between enzyme active sites and substrate molecules leading to the formation of enzyme - substrate complexes
Activation energy:
- The extra energy that is required to enable a reaction to occur is known as the activation energy
LOCK & KEY MODEL
- The lock and key model says that the active site is a specific shape which is complementary to the shape of its substrate
- The binding of the substrate to the active site allows bonds to break and form more easily
- This is because it allows for a different pathway that has a lower activation energy
INDUCED FIT MODEL
- The induced fit hypothesis says that the active site changes shape to allow the substrate to fully enter the active site e.g. lysozymes - found in tears and egg whites.
- Lysozyme is an anitbacterial enzyme because it hydrolyses the polysaccharide peptidoglycan in bacterial cell walls
- it does this by catalysing the hydrolysis of glycosidic bonds
- The chains of modified beta glucose molecules are broken
- The substrate collides with the active site
- The active site moulds around the substrate molecule and it is held in position by oppositely charged groups on the amino acids in the active site
- An enzyme - substrate complex is formed
- A change in the enzymes 3D shape places a strain on the substrate molecule/brings two reactants closer together allowing the reaction to occur more easily
- The strain on the substrate molecule weakens chemical bonds making them break more easily - lowering the activation energy
- An enzyme - product now forms
- The product no longer fits into the active site and is released
Types of reaction:
- Catabolic - involves the hydrolysis of larger molecules into smaller molecules
- Anabolic - Larger molecules being made by the condensation of smaller molecules
- All enzymes are made inside cells by protein synthesis but afterwards they can function as either:
- Intracellular - enzymes which remain inside the cell
- Extracellular - Enzymes which are secreted from cells to function
Turnover number: - An enzyme's turnover number is the maximum number of substrate molecules it can convert to product molecules per unit time
- Catalase has one of the highest turnover numbers of all enzymes - it can convert approx. 5 million molecules of hydrogen peroxide to water and oxygen each second
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INDUSTRIAL ENZYMES
- Enzymes are produced by culturing microbes in fermentation vessels, the microbes produce enzymes as part of their normal metabolic activity
- The microbes are then killed and the enzymes are extracted from the culture and purified
- The enzymes are then added to substrate molecules to catalyse reactions which would be difficult to carry out otherwise
- Enzymes are useful in industry as they are biological catalysts and speed up the rate of reaction
- They lower activation energies so reactions occur at lower temperatures saving energy and increasing efficiency
- There are few side reactions and so less waste products are formed which means fewer stages in the purification process.
IMMOBILISED ENZYMES
- These are enzymes which are held or stabilised in an INERT support or matrix e.g. celluloseImmobilised enzymes in a reactor vessels: - Substrates are trickled through the vessel from the top - Reaction occurs as the substrate passes the immobilised enzymes (immobilised in beads) - Products are collected from the bottom
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BIOSENSOR
- An instrument that can detect a SPECIFIC molecule in a mixture of molecule in a mixture of molecules
- The coupling of a biochemical reaction to an electronic meter
- Biosensors work because enzymes are specific. Therefore they can select one type of molecule from a mixture even at very low concentrations
- Biosensor can be used for medical and environmental monitoring
- The electrode probe which has specific immobilised enzyme - (glucos oxidas) on a membrane attatched, is places in the blood.
- If glucose is present it diffuses through the membrane to the enzyme and forms an enzyme substrate complex - the product gluconic acid is formed
- the reaction produces a small electrical current
- This is picked up by the electrode (transducer)
- The current is then read by the monitor and the blood glucose concentration is displayed
- normal levels are between 3.89 - 5.83 mmol/dm3
Testing for blood glucose - In urine - using Clinistix. This is a firm plastic strip with a test are containing glucose oxidase. When dipped inn urine, this test are changes colour according to the amount of glucose in the urine.
Advantages:
- Ability to detect very small concentrations of the target substance
- Very accurate
- Easy to use
- Quick to respond
- Versatile and cost affective
- Linked to data loggers and computers for online monitoring
- They can be used for continuous monitoring because the immobilised are retained in the matrix/inside the alginate beads
- the biological element can be regenerated and reused
Disadvantages:
- Require accurate calibration
- Require extensive and expensive research and development from skilled workforce