Enzymes are the biochemical workhorses that make life possible -... Show more
Biology162 views·Updated May 22, 2026·2 pagesUnderstanding Enzyme Action for Efficient Learning
Frankie <3@franki3.s
1
of 2![# 1.7 Enzyme Action
[AQA Biology A level]
Notes
What are enzymes?
→ Enzymes are proteins that act as catalysts [they speed up metabolic r](/_next/image?url=https%3A%2F%2Fcontent-eu-central-1.knowunity.com%2FCONTENT%2FJxCpmvaUkzZxDQVBdkeL_image_page_1.webp&w=2048&q=75)
What Are Enzymes and How Do They Work?
Think of enzymes as molecular speed boosters - they're proteins that act as catalysts, dramatically speeding up metabolic reactions without getting used up in the process. You only need tiny amounts of them, and they can work over and over again.
The magic happens because enzymes lower the activation energy needed for reactions to occur. Activation energy is like the initial push you need to get a boulder rolling downhill - enzymes reduce this energy barrier so reactions can happen much faster at body temperature.
Every enzyme has an active site - this is the business end where all the action happens. The molecule that the enzyme works on is called the substrate, and when they come together, they form an enzyme-substrate complex.
Quick Tip: Remember that enzymes are highly specific - each one typically works with just one type of substrate, which is why we have thousands of different enzymes in our bodies.
2
of 2![# 1.7 Enzyme Action
[AQA Biology A level]
Notes
What are enzymes?
→ Enzymes are proteins that act as catalysts [they speed up metabolic r](/_next/image?url=https%3A%2F%2Fcontent-eu-central-1.knowunity.com%2FCONTENT%2FJxCpmvaUkzZxDQVBdkeL_image_page_2.webp&w=2048&q=75)
Two Models of Enzyme Action
The induced fit model is the current explanation for how enzymes work, and it's much more dynamic than you might expect. Rather than being rigid, the active site actually moulds around the substrate as they bind together - think of it like a flexible glove adjusting to fit your hand perfectly.
This flexibility is crucial because the enzyme puts strain on the substrate, weakening its bonds and making it easier to break apart. However, this also means that any changes in the enzyme's environment can alter its shape and denature it, destroying its function.
The older lock and key model suggested that substrates fit perfectly into pre-shaped active sites, like a key fitting into a lock. Whilst this helps visualise enzyme specificity, we now know it's too simplistic - enzymes aren't rigid structures.
Remember: The induced fit model explains why enzyme inhibitors work - they can actually change the shape of the active site, preventing the enzyme from functioning properly.
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Biology162 views·Updated May 22, 2026·2 pagesUnderstanding Enzyme Action for Efficient Learning
Frankie <3@franki3.s
Enzymes are the biochemical workhorses that make life possible - they're specialised proteins that speed up every chemical reaction in your body. Understanding how these molecular machines work is crucial for grasping metabolism, digestion, and countless other biological processes you'll... Show more
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What Are Enzymes and How Do They Work?
Think of enzymes as molecular speed boosters - they're proteins that act as catalysts, dramatically speeding up metabolic reactions without getting used up in the process. You only need tiny amounts of them, and they can work over and over again.
The magic happens because enzymes lower the activation energy needed for reactions to occur. Activation energy is like the initial push you need to get a boulder rolling downhill - enzymes reduce this energy barrier so reactions can happen much faster at body temperature.
Every enzyme has an active site - this is the business end where all the action happens. The molecule that the enzyme works on is called the substrate, and when they come together, they form an enzyme-substrate complex.
Quick Tip: Remember that enzymes are highly specific - each one typically works with just one type of substrate, which is why we have thousands of different enzymes in our bodies.
2
of 2Sign up to see the content. It's free!
- Access to all documents
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Two Models of Enzyme Action
The induced fit model is the current explanation for how enzymes work, and it's much more dynamic than you might expect. Rather than being rigid, the active site actually moulds around the substrate as they bind together - think of it like a flexible glove adjusting to fit your hand perfectly.
This flexibility is crucial because the enzyme puts strain on the substrate, weakening its bonds and making it easier to break apart. However, this also means that any changes in the enzyme's environment can alter its shape and denature it, destroying its function.
The older lock and key model suggested that substrates fit perfectly into pre-shaped active sites, like a key fitting into a lock. Whilst this helps visualise enzyme specificity, we now know it's too simplistic - enzymes aren't rigid structures.
Remember: The induced fit model explains why enzyme inhibitors work - they can actually change the shape of the active site, preventing the enzyme from functioning properly.
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What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
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Stefan SiOS user
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