section 1. (1) Identify the role of enzymes in metabolism, describe their chiemical compositions and use a simple model to describe their specificity on substrates Flashcards
Define metabolism
Metabolism is all of the chemical processes which occur within an organism
What is an anabolic reaction?
the synthesis of smaller molecules to form larger molecules. They are usually endergonic (require energy input)
What is a catabolic reaction?
complex organic compounds break down into smaller/ simpler ones. They are usually exergonic (release energy)
What role do enzymes play in metabolic reactions?
enzymes usually act as biological catalysts. they are not used up in the reactions and hence can be reused
How do enzymes carry out their role as biological catalysts?
Lower the activation energy required for the reactions to occur. Do this by bringing specific molecules together/ breaking specific molecules apart to reduce the need for random interaction.
Why do enzymes exist in living organisms and not in non-living organisms?
in non-living organisms, heat can be used to activate reactions, but heat damages tissue and hence enzymes are used.
What is the basic chemical composition of an enzyme?
Most enzymes are protein molecules (organic), consist of long chains/ sequences of amino acids that are folded in a particular shape; Globular
What is an active site?
An active site is the particular point on the enzyme surface where the substrate fits. Some enzymes have a section that is non-protein and binds with the protein to form the active site, forms an enzyme-cofactor complex
What is the difference between a Coenzyme and a cofactor?
o A Coenzyme is an organic molecule (mineral etc)
o A Cofactor is inorganic (ions etc)
Why must an optimum internal temperature and pH be maintained?
An optimum temperature and pH must be maintained otherwise the enzymes could become denatured and hence ineffective- functions would stop
What suffix do enzyme names usually end with?
‘-ase’
What is a substrate?
A substrate is the molecule on which an enzyme acts, Enzymes are highly specific; one enzyme will only catalyse one chemical reaction/ work on one substrate
Who proposed the lock and key model and when?
First postulated in 1894 by Emil Fischer
What are the advantages and disadvantages of the lock and key model?
- Advantages: explains enzyme specificity
- Disadvantages: does not show rate of reaction, required conditions for reaction or molecular nature of substrates/ products
What differentiates the induced fit model from the lock and key model?
- Induced-fit theory assumes that the substrate plays a role in determining the final shape of the enzyme and that the enzyme is partially flexible
- Model covers why certain compounds can bind to the enzyme but do not react because the enzyme has been distorted too much.
