1.4 Enzymes Abd Biological Reactions Flashcards
What type of bonds in enzymes allow them to withstand high temperatures?
Disulphide bonds- allowing them enzymes found in bacteria to live in hot volcanic springs
What is an enzyme substrate complex?
An intermediate structure formed during an enzyme-catalysed reaction in which the substrate and enzyme bind temporarily, such that the substrates are close enough to react.
What is activation energy?
The minimum energy that must be put into a chemical system for a reaction to occur
What happens to the substrate during a catabolic reaction?
Binds to the active site, forming the enzyme-substrate complex.
The reaction proceeds and products are released meaning the active site is now free to catalyse another reaction
What happens to substrates in an anabolic reaction?
Several substrates bind, and one or more products are released.
How are chemical reactions speed up by enzymes?
They lower the activation energy needed to start a reaction by providing energy to break bonds in existing molecules, so new ones can start in new molecules.
Give an example of when enzymes act intracellularly
During protein synthesis, where the formation of a peptide bond between two amino acids is catalysed
Give an example of when enzymes act extracellulary
When pancreatic amylase is released from the pancreatic cells and travels to the small intestine via the pancreatic duct where it then catalysed the breakdown of starch to maltose
What is the lock and key model?
The substrate has a complementary shape to the enzymes active site, like a key fitting into a lock. This explains the specificity of many enzymes i.e that many only catalyse one substrate
What is the induced fit model?
The enzymes active site is altered by the binding substrate molecule. The induced fit theory suggests that the active site is able to change slightly to accommodate the substrate a bit like a latex glove stretching to accommodate a handy this change places strain on the substrate molecules helping to break bonds and so lowering the activation energy.
This explains why in some cases several molecules with similar shapes are able to bind to the active site. This is shown by the enzyme lysozyme, which is an anti-bacterial enzyme found in human tears and saliva.
The active site consists of a groove, which closes over the polysaccharides found in the bacterial cell walls, and the enzyme molecules changes shape, which allows hydrolysis to occur.
What are 5 factors affecting the rate of enzyme reaction?
Substrate concentration Temperature PH Enzyme concentration Presence of inhibitors
How does substrate concentration affect the rate in enzyme action?
Greater chance of successful collisions between the substrate and the enzyme. This results in more enzyme-substrate complexes forming, which increases the rate of reaction.
When all the enzyme active sites are occupied, a plateau is reached which represents the maximum rate of reaction for the conditions.
What is denaturing?
Results in permanent changes to the shape of the active site, preventing the substrate from binding
What is kinetic energy of an object?
The energy that it possesses due to its motion
How does temperature affect the rate of enzyme action?
Both the enzyme and substrate molecules gain kinetic more energy=move faster= increased chance of a successful collision between them.
As more enzyme-substrate complexes are formed, rate of reaction increases up to an optimum. Above this the rate of reaction decreases rapidly as hydrogen bonds in the tertiary stucture break due to increased vibrations resulting in a change to the shape of the active site (denaturing)
