This is a legacy topic. View the most up to date content by selecting the exam board in the dropdown to the left.
Enzymes are proteins which catalyse (speed up) metabolic reactions. Like all other catalysts (e.g. in chemistry), enzymes achieve this by lowering the activation energy (energy needed for a reaction to occur) of a reaction, by forming an enzyme-substrate complex.
This can be described by the lock and key, and induced fit models of enzyme action. The lock and key model is based on complementary shapes between the enzyme and substrate. The substrate fits into the enzyme.
The induced fit model: (the enzyme changes shape to “hug” the substrate)
The enzyme’s shape is not exactly matched to the substrate, but it is able to accommodate the substrate with a close enough shape into an enzyme-substrate complex and carry out catalysing that reaction. Here is a video of an enzyme catalysing a reaction between two molecules into one molecule. This is different to the above scenario in the diagrams, where one molecule is broken down into two molecules.
I got A* in A-level biology (Cambridge), thanks! I love your videos
Sherif Negm Facebook
OFF TOPIC : I just want to say that your website is brilliant, thank you!!
You explain everything so simply!
SecretDuck The Student Room
Thank you!! Your site is so helpful!
Good topic notes and cool videos. I'll definitely recommend it to my students.
Seema Sehgal AQA Examiner and biology teacher on LinkedIn