What is the difference between competitive and non-competitive enzyme inhibition?

The active site of an enzyme is the place on the enzyme molecule where the substrate (the substance which participates in the reaction catalysed by the enzyme) normally binds. 

Competitive inhibitors slow down enzyme action by acting at the active site - they bind to the active site of the enzyme molecule to prevent the substrate binding, so that that the reaction cannot be catalysed by the enzyme. The name "competitive" comes from the idea that the inhibitor "competes" to bind to the active site with the substrate. You can overcome the effect of a competitive inhibitor by simply adding more substrate so that the "competition" tips in favour of the substrate instead of the inhibitor.

Non-competitive inhibitors act at a site other than the active site on the enzyme molecule, so they don't actually "compete" with the substrate to bind to the active site. They act by changing the shape of an enzyme molecule once they bind to it, which also changes the shape of the active site. So, the substrate cannot bind to the active site anymore. You cannot overcome the effect of a non-competitive inhibitor by adding more substrate - the shape of the enzyme is changed permanently and the substrate will not bind to the active site no matter how much is present.

Krithi R. Mentoring -Medical School Preparation- tutor, Uni Admission...

2 years ago

Answered by Krithi, an A Level Biology tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist


£20 /hr

Zoe B.

Degree: Bsc Psychology (Bachelors) - Exeter University

Subjects offered: Biology, Psychology


“Who am I? Hi there, my name is Zoe. I am currently in my first year at the University of Exeter studying Psychology. I have for a long time had a great interest and passion for Psychology and love to read into different areas. Somethi...”

£20 /hr

Ed S.

Degree: Biology (Masters) - Sheffield University

Subjects offered: Biology, Spanish+ 2 more

Extended Project Qualification
-Personal Statements-

“Hello Parents & Students! My name is Ed and I'm a biology student at the University of Sheffield. In short, I'm mad about all things animal, with a particular interest in the field of marine conservation. Additionally, I have a real p...”

MyTutor guarantee

£20 /hr

Emma W.

Degree: Veterinary Medicine (Bachelors) - Liverpool University

Subjects offered: Biology, Science+ 2 more

-Personal Statements-

“Who am I? I am a veterinary student at the University of Liverpool. From a young age I have always had a keen interest in science - and animals of course! I want to share my passion for science and maths with others, and show that it'...”

About the author

Krithi R.

Currently unavailable: until 29/05/2016

Degree: Medicine (Bachelors) - Oxford, St Anne's College University

Subjects offered: Biology, Maths+ 5 more

.BMAT (BioMedical Admissions)
-Personal Statements-
-Medical School Preparation-

“Medical student at Oxford University, ready to offer practical advice and strategies to help you feel more confident with your subjects and university applications!”

You may also like...

Posts by Krithi

What extracurriculars should i do to get into medical school?

What is the difference between competitive and non-competitive enzyme inhibition?

Other A Level Biology questions

What is meant by the semi-conservative replication of DNA?

What is a mutation and what are they caused by?

How does an action potential cause contraction in skeletal muscle?

In genetics, what does co-dominance mean?

View A Level Biology tutors


We use cookies to improve our service. By continuing to use this website, we'll assume that you're OK with this. Dismiss