Metabolic pathways are like the cell's factory assembly lines -... Show more
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8 Dec 2025
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Understanding Key Metabolic Pathways
Jessica Jarvis
@jessjarvs0
1 / 8
Metabolic Pathways Basics
Think of metabolic pathways as interconnected motorways in your cells, where enzymes act like traffic controllers directing chemical reactions. These pathways aren't just straight lines - they've got reversible steps (like roundabouts), irreversible steps , and alternative routes that can bypass certain reactions when needed.
Anabolic reactions are your body's construction workers - they build large, complex molecules from smaller, simpler ones. This process requires energy input, just like construction work needs power tools.
Catabolic reactions work like demolition crews, breaking down large molecules into smaller pieces and releasing energy in the process. Your body uses this released energy to power other cellular activities.
Key Point: Remember "Ana = Add up" and "Cata = Cut apart" to distinguish between these reaction types!
Cell Membrane Transport
Your cell membranes aren't just barriers - they're sophisticated gatekeepers made of phospholipid bilayers with embedded proteins. These proteins include pores, pumps, and enzymes that control what gets in and out of your cells.
Diffusion is the lazy river approach - molecules naturally flow from high concentration areas to low concentration areas through channel-forming protein pores. No energy required, just going with the flow.
Active transport is like swimming upstream - it moves molecules against the concentration gradient (from low to high) and requires ATP energy. The sodium-potassium pump is a perfect example of this energy-demanding process.
Some membrane proteins, like ATP synthase in mitochondria, act as molecular factories. ATP synthase specifically creates ATP (your cell's energy currency) from ADP and phosphate.
Remember: Diffusion = downhill (no energy), Active transport = uphill (needs ATP energy)!
How Enzymes Control Reactions
Enzymes are the ultimate reaction facilitators - they don't change what happens, but they make it happen much faster and easier. They work by lowering the activation energy, which is like reducing the height of a hill you need to climb to start a reaction.
The induced fit model shows that enzymes aren't rigid - they're flexible and change shape slightly when substrates bind. It's like a handshake where both hands adjust to fit together perfectly.
Substrate affinity works brilliantly - substrates have high affinity (stick easily) to enzyme active sites, whilst products have low affinity (leave easily). This ensures the reaction flows smoothly in one direction.
Top Tip: Think of enzymes as molecular matchmakers - they bring reactants together, help them react, then let the products go!
Reaction Direction and Control
Metabolic reactions are surprisingly flexible - many can run forwards or backwards depending on what your cell needs. The presence of substrates or removal of products drives reactions in particular directions, like water flowing downhill.
When one metabolite builds up, it activates the next enzyme in the pathway, creating a domino effect. If metabolite levels get out of balance, enzymes can work in reverse to restore equilibrium.
Enzyme and substrate concentrations directly affect reaction rates - more enzymes or substrates mean faster reactions, but only up to a point. Once all active sites are occupied, adding more substrate won't speed things up further.
Real-World Connection: This is like checkout queues in shops - more cashiers (enzymes) serve customers (substrates) faster, but extra customers can't be served if all tills are full!
Enzyme Inhibition
Sometimes your cells need to slow down or stop certain reactions, and inhibitors are the perfect molecular brakes. There are two main types that work in completely different ways.
Competitive inhibitors are like molecular imposters - they have similar shapes to substrates and compete for the same active site. Increase substrate concentration, and you can outcompete these inhibitors.
Non-competitive inhibitors are sneakier - they bind to a different site (allosteric site) and change the enzyme's shape, making the active site unusable. No amount of extra substrate can reverse this type of inhibition.
Feedback inhibition is your cell's quality control system. When the end product of a pathway builds up too much, it inhibits an earlier enzyme, effectively shutting down production until levels drop.
Memory Aid: Competitive = competing for the same parking space (active site), Non-competitive = changing the shape of the parking space itself!
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
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This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
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Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
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Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Understanding Key Metabolic Pathways
Jessica Jarvis
@jessjarvs0
Metabolic pathways are like the cell's factory assembly lines - integrated networks of enzyme-controlled reactions that keep your cells running. Understanding how these pathways work, along with the enzymes that drive them, is crucial for grasping how your body builds... Show more
Metabolic Pathways Basics
Think of metabolic pathways as interconnected motorways in your cells, where enzymes act like traffic controllers directing chemical reactions. These pathways aren't just straight lines - they've got reversible steps (like roundabouts), irreversible steps , and alternative routes that can bypass certain reactions when needed.
Anabolic reactions are your body's construction workers - they build large, complex molecules from smaller, simpler ones. This process requires energy input, just like construction work needs power tools.
Catabolic reactions work like demolition crews, breaking down large molecules into smaller pieces and releasing energy in the process. Your body uses this released energy to power other cellular activities.
Key Point: Remember "Ana = Add up" and "Cata = Cut apart" to distinguish between these reaction types!
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Cell Membrane Transport
Your cell membranes aren't just barriers - they're sophisticated gatekeepers made of phospholipid bilayers with embedded proteins. These proteins include pores, pumps, and enzymes that control what gets in and out of your cells.
Diffusion is the lazy river approach - molecules naturally flow from high concentration areas to low concentration areas through channel-forming protein pores. No energy required, just going with the flow.
Active transport is like swimming upstream - it moves molecules against the concentration gradient (from low to high) and requires ATP energy. The sodium-potassium pump is a perfect example of this energy-demanding process.
Some membrane proteins, like ATP synthase in mitochondria, act as molecular factories. ATP synthase specifically creates ATP (your cell's energy currency) from ADP and phosphate.
Remember: Diffusion = downhill (no energy), Active transport = uphill (needs ATP energy)!
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How Enzymes Control Reactions
Enzymes are the ultimate reaction facilitators - they don't change what happens, but they make it happen much faster and easier. They work by lowering the activation energy, which is like reducing the height of a hill you need to climb to start a reaction.
The induced fit model shows that enzymes aren't rigid - they're flexible and change shape slightly when substrates bind. It's like a handshake where both hands adjust to fit together perfectly.
Substrate affinity works brilliantly - substrates have high affinity (stick easily) to enzyme active sites, whilst products have low affinity (leave easily). This ensures the reaction flows smoothly in one direction.
Top Tip: Think of enzymes as molecular matchmakers - they bring reactants together, help them react, then let the products go!
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Reaction Direction and Control
Metabolic reactions are surprisingly flexible - many can run forwards or backwards depending on what your cell needs. The presence of substrates or removal of products drives reactions in particular directions, like water flowing downhill.
When one metabolite builds up, it activates the next enzyme in the pathway, creating a domino effect. If metabolite levels get out of balance, enzymes can work in reverse to restore equilibrium.
Enzyme and substrate concentrations directly affect reaction rates - more enzymes or substrates mean faster reactions, but only up to a point. Once all active sites are occupied, adding more substrate won't speed things up further.
Real-World Connection: This is like checkout queues in shops - more cashiers (enzymes) serve customers (substrates) faster, but extra customers can't be served if all tills are full!
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Enzyme Inhibition
Sometimes your cells need to slow down or stop certain reactions, and inhibitors are the perfect molecular brakes. There are two main types that work in completely different ways.
Competitive inhibitors are like molecular imposters - they have similar shapes to substrates and compete for the same active site. Increase substrate concentration, and you can outcompete these inhibitors.
Non-competitive inhibitors are sneakier - they bind to a different site (allosteric site) and change the enzyme's shape, making the active site unusable. No amount of extra substrate can reverse this type of inhibition.
Feedback inhibition is your cell's quality control system. When the end product of a pathway builds up too much, it inhibits an earlier enzyme, effectively shutting down production until levels drop.
Memory Aid: Competitive = competing for the same parking space (active site), Non-competitive = changing the shape of the parking space itself!
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We thought you’d never ask...
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.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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Most popular content: Enzymes
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English - inspector calls quotes and analysis
Quotes from every main character
English Literature10
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user