Enzymes

Question	Answer
Define enzyme	Enzymes are very efficient catalysts for biochemical reactions. They speed up reactions by providing an alternative reaction pathway of lower activation energy. But they do not undergo permanent changes and so remain unchanged at the end of the reaction.
Describe the structure of an enzyme	Enzymes have a tertiary structure and are globular proteins. They are known as bond breakers.
Are enzymes selective?	In contrast enzymes are usually highly selective, catalysing specific reactions only. This specificity is due to the shapes of the enzyme molecules.
What factors effect a chemical reaction?	For two molecules to react they must collide with one another. They must collide in the right direction (orientation) and with sufficient energy. Sufficient energy means that between them they have enough energy to overcome the energy barrier to reaction. This is called the activation energy.
Define anabolic reactions	Reactions that build up molecules.
Define catabolic reactions.	Reactions that break down molecules.
Define metabolism.	A balance between anabolic and catabolic reactions.
Define catalyst.	A substance that lowers the activation energy of a reaction so the rwaction speeds up.
Define metabolic pathway.	A series of enzyme controlled reactions.
Define specificity.	An enzymes ability to only catalyse certain reactions.
Define substrate	The molecule that the enzyme works on.
Define product.	This is what is produced in a reaction. Molecules produced by an enzyme.
How does an enzyme work?	The enzyme's active site holds the substrate molecule, this puts stress on the bond that has to be broken.
What is the enzyme substrate complex?	This is when the enzyme and substrate fit together.
Name the 4 factors affecting catalytic activity of enzymes	Temperature pH Enzyme concentration Substrate concentration
State the two names of the hypotheses used to describe how enzymes work.	-Lock and key -Induced fit
How does temperature effect enzyme activity?	As the temperature rises, reacting molecules have more and more kinetic energy. This increases the chances of a successful collision between the substrate and enzyme's active site and so the rate of reaction increases. There is a certain temperature at which an enzyme's catalytic activity is at its greatest (optimum temperature)
What happens when the temperature rises too much?	Denaturing occurs, the hydrogen and disulphide bonds break on the enzymes active site. This means that the active site is no longer complementary to the substrate shape and so enzyme-substrate complex does not occur (decrease of rate of reaction)
How does pH effect enzyme activity?	Each enzyme has its own optimum pH level- highest ROR. -If pH increases/decreases too much ionisation may occur which changes the charge of the substrate decreasing the likelihood of enzyme-substrate complex occurring. -Extreme pH's cause bonds that maintain enzyme's tertiary structure to break, irreversible denaturing.
How does enzyme concentration effect rate of reaction?	Low enzyme concentration=more substrates than active sites. Increasing concenration=increased ROR as there are now more active sites available so enzyme-substrate complex more likely. Substrate concentration becomes limiing as more active sites than substrates.
How does substrate concentration effect rate of reaction?	Low substrate concentration=ROR is low as there aren't enough substrate molecules to fill active sites. High- ROR increases up to the point where all active sites are filled with substrates any added substrates will not increase ROR as there are no free active sites.
What are the types of inhibition on enzyme activity?	-Competitive inhibitor- slows ROR inhibitors that occupy the active site and prevent a substrate molecule from binding to the enzyme(prevents enzyme-substrate complex), reversible. -Non-competitive inhibitors- This inhibitor pulls on the allosteric site to alter the active sites shape so that it is no loner complementary with the substrate, reversible.

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	Created by Hannah 2nd year about 6 years ago