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0
T
Tara Vidal
05/12/2025
Biology
Digestion and enzymes
112
•
5 Dec 2025
•
Understanding Digestion and Enzymes
T
Tara Vidal
@taravidal_jrny
1 / 6
Cells, Tissues and the Digestive System
Your body is brilliantly organised, starting with specialised cells that are perfectly adapted for their jobs. Muscle cells, for example, contain protein fibres for contracting and loads of mitochondria to provide the energy needed for movement.
When similar cells group together, they form tissues - basically a team of cells working towards the same goal. Take it up a level, and you get organs, where different tissues collaborate to perform specific functions like digestion.
Digestion is your body's way of breaking down massive food molecules into tiny bits your cells can actually use. The process starts in your mouth with mechanical digestion (chewing) and chemical digestion (saliva breaking down starch), then moves through your oesophagus via peristalsis - those wave-like muscle contractions that push food along.
Quick Tip: Remember that digestion happens both mechanically (physical breakdown) and chemically (using enzymes) throughout your digestive tract.
Digestive Organs and Their Adaptations
Your stomach is basically a muscular acid bath with some clever adaptations. It produces hydrochloric acid and pepsin to break down proteins, has strong muscular walls for mixing, and secretes a thick mucus layer to stop it digesting itself - pretty smart!
The small intestine is where the magic really happens - it's your main absorption organ that soaks up most nutrients and releases digestive enzymes. Meanwhile, your large intestine focuses on absorbing water from whatever's left over.
Your liver produces bile, which gets stored in your gallbladder. Bile does two crucial jobs: it neutralises the acid from your stomach and emulsifies lipids (breaks fat droplets into smaller ones) to make them easier to digest.
Enzymes are your digestive superstars - they're large protein molecules that act as catalysts, each with a specific active site that fits perfectly with its target substrate. Think of the lock and key theory: each enzyme (lock) only works with its specific substrate (key).
Remember: Different enzymes work in different parts of your digestive system - protease breaks down proteins in your stomach, pancreas, and small intestine.
Enzymes and How They Work
Understanding what enzymes break down makes digestion much clearer. Proteins are long chains of amino acids that get broken down by protease enzymes. Starch consists of glucose molecule chains and gets digested by carbohydrase enzymes like amylase.
Lipid molecules contain one glycerol and three fatty acids, and they're broken down by lipase enzymes. This is where bile becomes essential - it emulsifies fats, increasing their surface area so lipase can work more effectively.
Temperature massively affects enzyme activity. As temperature increases, reaction rates speed up until you hit the optimal temperature. Beyond that point, enzymes start to denature - the high energy makes enzyme molecules vibrate, changing the shape of their active sites so substrates no longer fit.
Enzymes also denature in conditions that are too acidic or alkaline, which explains why different enzymes work in different parts of your digestive system where pH levels vary.
Exam Tip: Remember that denatured enzymes can't be 'fixed' - once the active site changes shape, that enzyme is permanently damaged.
Movement Across Cell Membranes
Diffusion is the movement of molecules from areas of high concentration to low concentration - it's how substances naturally spread out. Your lungs' alveoli are perfectly adapted for this with their large surface area, thin membranes, and excellent blood supply for rapid gas exchange.
Osmosis is specifically about water movement through partially permeable membranes, always moving from high to low water concentration. You can investigate this using potato cylinders in different sugar solution concentrations - the potatoes will gain or lose water depending on the solution strength.
Understanding concentration terminology helps loads: isotonic means equal concentrations on both sides, hypertonic means higher concentration outside the cell, and hypotonic means lower concentration outside the cell.
Sometimes cells need to move substances against the concentration gradient, which requires active transport. This process needs energy (from mitochondria) and happens in places like plant roots absorbing nitrate ions and your small intestine absorbing nutrients.
Practical Tip: When doing osmosis experiments, always peel potatoes first as the skin can interfere with water movement and affect your results.
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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.
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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
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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
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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 Digestion and Enzymes
T
Tara Vidal
@taravidal_jrny
Ever wondered how your body breaks down that sandwich you had for lunch and gets all the nutrients to your cells? This topic covers everything from how your digestive system works to how substances move in and out of cells... Show more
Cells, Tissues and the Digestive System
Your body is brilliantly organised, starting with specialised cells that are perfectly adapted for their jobs. Muscle cells, for example, contain protein fibres for contracting and loads of mitochondria to provide the energy needed for movement.
When similar cells group together, they form tissues - basically a team of cells working towards the same goal. Take it up a level, and you get organs, where different tissues collaborate to perform specific functions like digestion.
Digestion is your body's way of breaking down massive food molecules into tiny bits your cells can actually use. The process starts in your mouth with mechanical digestion (chewing) and chemical digestion (saliva breaking down starch), then moves through your oesophagus via peristalsis - those wave-like muscle contractions that push food along.
Quick Tip: Remember that digestion happens both mechanically (physical breakdown) and chemically (using enzymes) throughout your digestive tract.
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Digestive Organs and Their Adaptations
Your stomach is basically a muscular acid bath with some clever adaptations. It produces hydrochloric acid and pepsin to break down proteins, has strong muscular walls for mixing, and secretes a thick mucus layer to stop it digesting itself - pretty smart!
The small intestine is where the magic really happens - it's your main absorption organ that soaks up most nutrients and releases digestive enzymes. Meanwhile, your large intestine focuses on absorbing water from whatever's left over.
Your liver produces bile, which gets stored in your gallbladder. Bile does two crucial jobs: it neutralises the acid from your stomach and emulsifies lipids (breaks fat droplets into smaller ones) to make them easier to digest.
Enzymes are your digestive superstars - they're large protein molecules that act as catalysts, each with a specific active site that fits perfectly with its target substrate. Think of the lock and key theory: each enzyme (lock) only works with its specific substrate (key).
Remember: Different enzymes work in different parts of your digestive system - protease breaks down proteins in your stomach, pancreas, and small intestine.
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Enzymes and How They Work
Understanding what enzymes break down makes digestion much clearer. Proteins are long chains of amino acids that get broken down by protease enzymes. Starch consists of glucose molecule chains and gets digested by carbohydrase enzymes like amylase.
Lipid molecules contain one glycerol and three fatty acids, and they're broken down by lipase enzymes. This is where bile becomes essential - it emulsifies fats, increasing their surface area so lipase can work more effectively.
Temperature massively affects enzyme activity. As temperature increases, reaction rates speed up until you hit the optimal temperature. Beyond that point, enzymes start to denature - the high energy makes enzyme molecules vibrate, changing the shape of their active sites so substrates no longer fit.
Enzymes also denature in conditions that are too acidic or alkaline, which explains why different enzymes work in different parts of your digestive system where pH levels vary.
Exam Tip: Remember that denatured enzymes can't be 'fixed' - once the active site changes shape, that enzyme is permanently damaged.
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Movement Across Cell Membranes
Diffusion is the movement of molecules from areas of high concentration to low concentration - it's how substances naturally spread out. Your lungs' alveoli are perfectly adapted for this with their large surface area, thin membranes, and excellent blood supply for rapid gas exchange.
Osmosis is specifically about water movement through partially permeable membranes, always moving from high to low water concentration. You can investigate this using potato cylinders in different sugar solution concentrations - the potatoes will gain or lose water depending on the solution strength.
Understanding concentration terminology helps loads: isotonic means equal concentrations on both sides, hypertonic means higher concentration outside the cell, and hypotonic means lower concentration outside the cell.
Sometimes cells need to move substances against the concentration gradient, which requires active transport. This process needs energy (from mitochondria) and happens in places like plant roots absorbing nitrate ions and your small intestine absorbing nutrients.
Practical Tip: When doing osmosis experiments, always peel potatoes first as the skin can interfere with water movement and affect your results.
Sign up to see the contentIt's free!
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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?
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Is Knowunity really free of charge?
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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
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
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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