Enzymes and biological reaction (general properties of enzymes (The…
Enzymes and biological reaction
general properties of enzymes
anaobolic-building up, catabolic-breaking down
Enzymes are globular proteins and biological catalysts. They speed up reactions without being used up, they are not changed and have a high turnover number.
They have tertiary structure, folded into a spherical shape with hydrophilic R groups on the outside making enzymes soluble in water.
The active site is a small area with a specific 3D shape.
A substrate makes temporary bonds with the active site, forming an enzyme-substrate complex. When the reaction is complete, products are released.
Lock and key model says that the unique shape of the active site means that it can only catalyse one type of reaction, enzyme specifity means that it is only specific for one substrate.
Induced fit means that the enzyme changes shape when the substrate binds to it, so it is flexible eg. lysozyme.
Sites of enzyme action
extracellular- secreted from cells by exocytosis and catalyse extracellular reactions
Intracellular-act in a solution inside cellls
Intracellular-membrane bound- attached to be membranes in cells eg on the cristae of a mitochondria.
Activation energy is the minimum amount of energy required for a reaction to take place, enzymes lower this activation energy.
Factors affecting enzyme action
The number of molecules that an enzyme can turn into a product in a given time is called the turnover number. Catalase has a turnover number of 40 million a second.
Competitive inhibition is when a molecule has a shape complementary to the active site so can fill the active site, preventing the substarte from being converted into product
Non competitive inhibitors bind to the allosteric site of an enzyme affecting the bonds In the enzyme and changing the shape of the active site, this prevents an enzyme substrate complex from being formed and the enzyme is denatured.
When enzymes are fixed, bound or trapped onto an inert matrix such as sodium alginate beads or cellulose microfibrils. Substrate is added to the top of the column and as it flows down, its molecules bind to the active sites. They column can b e used repeatedly and the enzyme doesn't contaminate the products, more than one enzyme can be used and they can be easily recovered.
uses include making lactose free milk, biosensors