Chapter 4: Enzymes Flashcards
Define ‘enzymes’.
They are proteins that function as biological catalysts.
What do enzymes do?
They speed up the rate of chemical reactions
Why are enzymes required in a small amount in our body?
Enzymes remain chemically unchanged at the end of the reaction thus it can be reused.
How do enzymes lower activation energy?
They provide an alternative pathway with lower activation energy required to start a chemical reaction.
How do enzymes speed up chemical reactions?
By lowering the activation energy.
Why are enzymes needed?
Enzymes are needed to break down large molecules that cannot diffuse through the cell membrane into simpler and smaller substances so that they are soluble in water and are small enough to diffuse through the cell membrane.
What can enzyme-catalysed reactions be classified into?
Anabolic and catabolic reactions
What are anabolic reactions?
Reactions that build up complex substances.
What are catabolic reactions?
Reactions that break down complex susbtances.
How do enzymes work?
- Enzymes are highly specific in their action.
- This enzyme specificity means that each chemical reaction in a cell is catalysed by a unique enzyme.
- They are this specific due to their three-dimensional shape.
According to the lock-and-key hypothesis, what do enzyme reactions depend on?
They depend on the presence of active sites.
What can fit into the active site of a specific enzyme?
The substrate molecules with the matching shape to their enzyme’s active site.
What happens when the substrate binds to the active site of an enzyme?
An enzyme-substrate complex is formed
What is an enzyme-substrate complex?
It is a temporary molecule formed when the substrate binds to the enzyme.
What happens at the active site of an enzyme when the substrate fits into it?
Reactions take place at the active site to convert the substrate molecules to the product molecules.
What happens after the reactions that took palce at the active site of an enzyme?
The product molecules then separate from the enzyme.
Tell me about the specific nature of an enzyme using the lock-and-key hypothesis.
- An enzyme has a specific three-dimensional shape and it has an active site.
- Only the substrate complementary to that active site can fit into the enzyme. This results in the formation of an enzyme-substrate complex.
- The enzyme is just like a lock and the substrate is just like a key. The substrate fits into the enzyme just like a key fits into a lock.
- While the substrate is attached to the active site, a chemical reaction occurs. The substrate is converted to other products.
- Later, the products leave the active site. The enzyme remains unchanged and it can catalyze another reaction.
