Enzymes Flashcards
What do enzymes do?
Enzymes speed up chemical reactions by acting as biological catalysts. They catalyse metabolic reactions.
What can enzymes affect in an organism?
Structures as well as functions.
Where can enzyme activity occur?
Intracellular - within cells.
Extracellular - outside cells.
What are enzymes?
Proteins.
What do enzymes have?
An active site, which has a specific shape.
What is the purpose of the active site?
It is the part of the enzyme where the substrate molecules bind to.
Why are enzymes highly specific?
Due to their tertiary structure.
What is the activation energy?
The lowest amount of energy required for a reaction to occur.
What do enzymes do to the activation energy?
Enzymes lower the activation energy required, speeding up the rate of reaction.
What is an enzyme-substrate complex?
When a substrate fits into the enzyme’s active site. this is what lowers the activation energy.
Why does an enzyme-substrate complex lower the activation energy?
If two substrate molecules need to be joined, being attached to the enzyme holds them close together, reducing any repulsion between the molecules so they can bond more easily.
If the enzyme is catalysing a breakdown reaction, fitting into the active site puts strain on bonds in the substrate, so the substrate molecule breaks up more easily.
What is the ‘lock and key; model?
The substrate fits into the enzyme like a key fits into a lock. The active site and the substrate have a complementary shape.
Why is the ‘lock and key’ model no longer used to illustrate how enzymes work?
New evidence showed when the substrate binds to the active site, the enzyme substrate-complex changed shape slightly to complete the fit. The substrate has to be the right shape and cause the active site to change shape in the right way, in order to lock the substrate in to the enzyme tightly.
What is the new model of how an enzyme works called?
The ‘induced fit’ model.
What are enzyme properties related to?
Their tertiary structure.
