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Lactose-free milk
An important industrial use is in making lactose-free/lactose-reduced milk. Milk is passed down a column containing immobilised lactose. The lactose bind to its active site & is hydrolysed into its components, glucose & galactose.
Detecting blood glucose
The enzyme glucose oxidise, immobilised on a selectively permeable membrane placed in a blood sample that binds glucose. This produces a small electric current, detected by the electrode & read ona screen-biosensor.
The enzymes can also be immobilised onto test strips. The strips detect a variety of molecules. Testing strips with glucose oxidise immobilised onto them are used to detect glucose in urine(e.g pregnancy tests).
Biosensors
Turn a chemical signal into an electrical signal.They rapidly & accurately detect, identify & measure even very low conc. of important molecules. They work on the principle that enzymes are specific and are able to select one type of molecule from a mixture. One particular use of a biosensor is in the detection of blood glucose.

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Enzymes are 'immobilised' when they're fixed, bound or trapped in an inert matrix such as sodium alginate beads or cellulose microfibrils, which can be packed into glass columns. Substrate is added to the column & as it flows down, its molecules bind to the enzymes active sites, both on the bead surface and inside the beads as the substrate molecule diffuses in. Columns can be used repeatedly. The enzyme is fixed & doesn't contaminate the products, making products east ro purify.
Advantages:

products aren't contaminated with enzymes

enzymes are easily reused

enzymes can be easily added/removed, giving greater control over the reaction

they work better at low temperatures

sequence of columns, several enzymes with differing pH or temperature optimum can be used in one process

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E.g Arsenic
They bind to the enzyme at an 'allosteric site' i.e a site other than the active site, so they don't compete with the substrate. They affect bonds within the enzyme molecule & alter the shape of the active site, and no enzyme-substrate complexes form. As the inhibitor concentration increases, more enzyme molecules are denatured & so the RAR and final mass of product decrease.

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E.g Cyanide
They have a molecular shape complementary to the active site & similar to that of the substrate, soothes compete for the active site(e.g in the mitochondria matrix).
It can be reversed by increasing the concentration of the substrate.

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Enzyme concentration
The number of substrate molecules that one enzyme can turn into a product in a given time is call the turn-over number. As the enzyme conc. increases there are more active sights available causing the rate to increase.
Temperature
Increase in temperature gives molecules more kinetic energy which increases the chance of collisions & successful enzyme-substrate complexes. Increased temp. means increased ROR, generally the rate of reaction double for every 10° rise. The optimum for most enzymes is 40°.
Substrate concentration
The rate of an enzyme-catalysed reaction varies with change in substrate concentration. If the enzyme conc. is constant, the ROR increases as the substrate conc. increases. At low substrate conc. the enzyme molecules have only a few substrate molecules to collide with so the active sites are not working at full capacity. With more substrate, more active sites are filled. The conc. of substrate is controlling the ROR & so it is a limiting factor. As even more substrate is added, at a critical concentration, all the active sites become occupied & the rate is at its maximum. When all active sites are full, the enzyme is saturated. The line plateaus when more substrate is added because the reaction can't be catalysed any faster. The substrate conc. is no longer controlling the rate so it's no longer a limiting factor.
Enzyme concentration
Once a product leaves the active site, the enzyme molecule can be reused, so only a low enzyme conc. is needed to catalyse the a large number of reactions. The number of substrate molecules that one enzyme molecule can turn into product in a given time is the turn-over number. One of the fastest-acting enzymes known is catalyse, with a turn-over number of 40million molecules per second. It breaks down the highly toxic waste, hydrogen peroxide. As the enzyme conc. increases, there are more active sites available and therefore the ROR increases.

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The minimum energy requires for molecules to react, breaking existing bonds in the reactants & making new ones, is the activation energy. A way of making chemicals react is by increasing their kinetic energy, to make successful collisions between them more likely. Increasing temperature above 40° causes irreversible damage to proteins, and they denature.

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This model suggests that the enzyme shape alters slightly to accommodate the substrate. An example, the enzyme lysosome(an antibacterial enzyme in human saliva, mucus & tears). The active site is a groove & sugars on the bacterial cell wall fit into it. The grooves close over the sugars & the lysosome molecule changes shape around the sugar & hydrolyses the bonds holding them together. The cell wall is weakened; the bacteria absorbs water by osmosis & bursts.

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Unique shape of active site means enzymes can only catalyse one type of reaction. 'Enzyme specificity' means that an enzyme is specific for its substrate. The shape of a lock & key are specific to one another.

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1. Extracellular - enzymes secreted from the cells by exocytosis & catalyse extracellular reactions. E.g amylase in salivary gland, moves down the salivary ducts to the mouth.

2. Intracellular, in solution - act inside of cells, e.g enzymes that catalyse glucose breakdown in glycolysis.

3. Intracellular, membrane-bound - may be attached to membranes, e.g cristae of mitochondria & grana of chloroplasts.

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Enzymes are globular proteins that are catalysts - biological catalysts because they're made of cells.

Speed up reactions

Not used up

Not changed

High turn-over number

Without enzymes, reactions in cells would be too slow to be compatible with life. Enzymes are proteins with tertiary structure, the chains fold up into spherical/globular shapes with a hydrophobic R groups on the outside of the molecule(making them soluble). Each enzyme has a particular sequence of amino acids & the elements in the R group determine the bonds the amino acids make. A small area with a specific 3D shape is the active site & gives then enzyme its properties.

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Metabolism refers to reactions in the body. Reactions occur in the metabolic pathway, including:

anabolic reactions; building up molecules(protein synthesis)

catabolic reactions; breaking down molecules(digestion)

The pathways are controlled by enzymes, the product of one reaction becomes the reactant in the next