PL - Enzymes Flashcards
What are enzymes?
Biological catalysts.
What do enzymes do?
Speed up chemical reactions by acting as biological catalysts.
They catalyse many essential reactions in the bodies of living organisms.
What type of molecule are enzymes?
Proteins.
Enzymes are proteins but what do some of them have?
Non-protein components.
What are substrates?
The molecules that enzymes act on to speed up reactions.
What do all enzymes have?
An active site.
What is the active site of an enzyme?
The part of the enzyme that the substrate fits into so that it can interact with the enzyme.
Which part of the enzyme does the substrate fit into?
The active site.
Describe the structure of the active site
It is 3D - it’s part of the tertiary structure of the enzyme protein.
Which level of structure is the active site part of and why?
The tertiary structure of the enzyme protein because it is 3D.
How do enzymes have high specificity?
They only work with specific substrates - usually only one.
Why do enzymes usually work with only one substrate?
Because, for the enzyme to work, the substrate has to fit into the active site. Substrates are 3D, and if their shape doesn’t match the active site’s shape, then the reaction won’t be catalysed.
What is the model that explains how a reaction will only be catalysed if the substrate is a specific shape to fit the active site called?
The ‘lock and key’ model.
What does the ‘lock and key’ model explain?
How a reaction will only be catalysed if the substrate is a specific shape to fit the active site.
Because, for the enzyme to work, the substrate has to fit into the active site. Substrates are 3D, and if their shape doesn’t match the active site’s shape, then the reaction won’t be catalysed.
How is the substrate held in the active site in the lock and key model?
By temporary bonds such as hydrogen bonds and instantaneous dipole-induced dipole forces.
Where do the temporary bonds form between in the lock and key model when explaining how enzymes work?
Between the substrate and ‘R’ groups of the enzyme’s amino acids.
What is formed when the substrate has fit into/bonded to the enzymes active site?
An enzyme-substrate complex.
What conditions have to be right for enzymes to work?
pH and temperature.
What has to be right about the temperature and pH for enzymes to work at their best?
There has to be optimal pH and optimal pH levels for enzymes to work at their best.
Why is there an optimum temperature and pH?
Because in these conditions, the enzyme works best and the reaction rate is at a maximum.
What happens to enzyme activity/reaction rate at low temperatures and why?
The reaction is slow because the reactant molecules have low kinetic energy.
What happens to enzyme activity/reaction rate at higher temperatures, or at higher or lower pH values and why?
The reaction rate drops off dramatically because the enzyme becomes denatured. It stops working properly and can no longer effectively catalyse the reaction.
What happens to enzymes at higher temperatures, or at higher or lower pH values?
The enzyme becomes denatured - it stops working properly and can no longer effectively catalyse the reaction.
The bonds that define the shape of the active site break, changing the tertiary structure of the enzyme molecule. The active site is no longer the correct shape for the substrate to fit into.
Explain what happens to an enzyme when it becomes denatured.
The bonds that define the shape of the active site break, changing the tertiary structure of the enzyme molecule. The active site is no longer the correct shape for the substrate to fit into.