Open the App

Subjects

AP Biology

Dec 13, 2025

36

2 pages

Understanding Enzyme-Coupled Reactions

Enzyme-controlled coupling reactions are fundamental to life processes, allowing cells to perform energy-requiring tasks efficiently. These reactions connect... Show more

Aim: why are enzyme-controlled reactions coupled?
Do now: The net amount of energy is collected as result of chemical process. Enzyme
lower

Coupling Reactions Energy Transfer

Ever wonder how your body powers complex functions? The answer lies in coupling reactions! These ingenious processes connect energy-releasing reactions with energy-requiring ones.

The First Law of Thermodynamics tells us energy cannot be created or destroyed, only transferred. This means reactions that need energy can "borrow" it from reactions that release energy. Your body runs on this energy-sharing economy!

There are two main types of biological reactions. Exergonic reactions release energy to the environment (like breaking down food) while endergonic reactions require energy input (like building proteins). Catabolic reactions break down molecules, releasing energy, while anabolic reactions build complex molecules, requiring energy.

Think of it this way Imagine breaking down a Lego castle (exergonic) gives you enough energy to build a Lego spaceship (endergonic). That's coupling!

Remember that complex macromolecules represent order, and breaking them down increases disorder. The Second Law of Thermodynamics states that natural reactions increase disorder. Dehydration synthesis (combining molecules) requires energy and decreases disorder, while hydrolysis (breaking molecules apart) releases energy and increases disorder.

Aim: why are enzyme-controlled reactions coupled?
Do now: The net amount of energy is collected as result of chemical process. Enzyme
lower

ATP and Enzyme Properties

ATP is your body's energy currency! When ATP is hydrolyzed (broken down), it releases approximately 30.5 kJ/mol of energy that can power other reactions. For example, transporting 9 sodium ions requires about 91.5 kJ of energy, meaning 3 ATP molecules must be hydrolyzed to power this process.

Similarly, synthesizing sucrose from glucose and fructose requires 27.2 kJ of energy. One ATP hydrolysis provides 30.5 kJ, which is more than enough! This demonstrates how cells couple energy-releasing reactions (ATP breakdown) to energy-requiring reactions (sucrose synthesis).

Enzymes make these coupling reactions possible, but they're picky about their working conditions. Enzymes require specific conditions to function properly. When conditions aren't ideal, enzymes begin to denature, changing their structure and losing function. Once human enzymes denature, they cannot properly couple reactions anymore.

Important to know The second level of protein folding (involving hydrogen bonds) is the weakest and most easily disrupted by environmental changes. This makes enzymes sensitive to factors like temperature and pH.

Different levels of protein folding contribute to enzyme stability. The third level involves hydrogen bonds and can change under stress, while the fourth level involves multiple polypeptides bonding together. Understanding these structures helps explain why enzymes work only under specific conditions.

We thought youโ€™d never ask...

What is the Knowunity AI companion?

Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.

Where can I download the Knowunity app?

You can download the app in the Google Play Store and in the 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 โ€“ all at your fingertips.

Can't find what you're looking for? Explore other subjects.

Students love us โ€” 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

I think itโ€™s very much worth it and youโ€™ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still donโ€™t get it!!! In the end I think itโ€™s worth it ๐Ÿ˜Š๐Ÿ‘ โš ๏ธAlso DID I MENTION ITS FREEE YOU DONโ€™T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLYโ—๏ธโ—๏ธโš ๏ธ

Thomas R

iOS user

Knowunity is the BEST app Iโ€™ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades

Brad T

Android user

Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help๐Ÿค๐Ÿค

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

I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend

Aubrey

iOS user

Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.๐Ÿ˜‹๐Ÿฉท๐ŸŽ€

Marco B

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 ๐Ÿ˜๐Ÿ˜๐Ÿ˜ฒ๐Ÿค‘๐Ÿ’—โœจ๐ŸŽ€๐Ÿ˜ฎ

Elisha

iOS user

This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as Iโ€™ve seen! Geometry too!

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

I think itโ€™s very much worth it and youโ€™ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still donโ€™t get it!!! In the end I think itโ€™s worth it ๐Ÿ˜Š๐Ÿ‘ โš ๏ธAlso DID I MENTION ITS FREEE YOU DONโ€™T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLYโ—๏ธโ—๏ธโš ๏ธ

Thomas R

iOS user

Knowunity is the BEST app Iโ€™ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades

Brad T

Android user

Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help๐Ÿค๐Ÿค

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

I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend

Aubrey

iOS user

Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.๐Ÿ˜‹๐Ÿฉท๐ŸŽ€

Marco B

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 ๐Ÿ˜๐Ÿ˜๐Ÿ˜ฒ๐Ÿค‘๐Ÿ’—โœจ๐ŸŽ€๐Ÿ˜ฎ

Elisha

iOS user

This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as Iโ€™ve seen! Geometry too!

Paul T

iOS user

ย 

AP Biology

โ€ข

36

โ€ข

Dec 13, 2025

โ€ข

2 pages

Understanding Enzyme-Coupled Reactions

Enzyme-controlled coupling reactions are fundamental to life processes, allowing cells to perform energy-requiring tasks efficiently. These reactions connect energy-releasing processes with energy-demanding ones, creating a biological energy economy that powers cellular functions.

Aim: why are enzyme-controlled reactions coupled?
Do now: The net amount of energy is collected as result of chemical process. Enzyme
lower

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Coupling Reactions: Energy Transfer

Ever wonder how your body powers complex functions? The answer lies in coupling reactions! These ingenious processes connect energy-releasing reactions with energy-requiring ones.

The First Law of Thermodynamics tells us energy cannot be created or destroyed, only transferred. This means reactions that need energy can "borrow" it from reactions that release energy. Your body runs on this energy-sharing economy!

There are two main types of biological reactions. Exergonic reactions release energy to the environment (like breaking down food) while endergonic reactions require energy input (like building proteins). Catabolic reactions break down molecules, releasing energy, while anabolic reactions build complex molecules, requiring energy.

Think of it this way: Imagine breaking down a Lego castle (exergonic) gives you enough energy to build a Lego spaceship (endergonic). That's coupling!

Remember that complex macromolecules represent order, and breaking them down increases disorder. The Second Law of Thermodynamics states that natural reactions increase disorder. Dehydration synthesis (combining molecules) requires energy and decreases disorder, while hydrolysis (breaking molecules apart) releases energy and increases disorder.

Aim: why are enzyme-controlled reactions coupled?
Do now: The net amount of energy is collected as result of chemical process. Enzyme
lower

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

ATP and Enzyme Properties

ATP is your body's energy currency! When ATP is hydrolyzed (broken down), it releases approximately 30.5 kJ/mol of energy that can power other reactions. For example, transporting 9 sodium ions requires about 91.5 kJ of energy, meaning 3 ATP molecules must be hydrolyzed to power this process.

Similarly, synthesizing sucrose from glucose and fructose requires 27.2 kJ of energy. One ATP hydrolysis provides 30.5 kJ, which is more than enough! This demonstrates how cells couple energy-releasing reactions (ATP breakdown) to energy-requiring reactions (sucrose synthesis).

Enzymes make these coupling reactions possible, but they're picky about their working conditions. Enzymes require specific conditions to function properly. When conditions aren't ideal, enzymes begin to denature, changing their structure and losing function. Once human enzymes denature, they cannot properly couple reactions anymore.

Important to know: The second level of protein folding (involving hydrogen bonds) is the weakest and most easily disrupted by environmental changes. This makes enzymes sensitive to factors like temperature and pH.

Different levels of protein folding contribute to enzyme stability. The third level involves hydrogen bonds and can change under stress, while the fourth level involves multiple polypeptides bonding together. Understanding these structures helps explain why enzymes work only under specific conditions.

We thought youโ€™d never ask...

What is the Knowunity AI companion?

Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.

Where can I download the Knowunity app?

You can download the app in the Google Play Store and in the 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 โ€“ all at your fingertips.

Can't find what you're looking for? Explore other subjects.

Students love us โ€” 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

I think itโ€™s very much worth it and youโ€™ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still donโ€™t get it!!! In the end I think itโ€™s worth it ๐Ÿ˜Š๐Ÿ‘ โš ๏ธAlso DID I MENTION ITS FREEE YOU DONโ€™T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLYโ—๏ธโ—๏ธโš ๏ธ

Thomas R

iOS user

Knowunity is the BEST app Iโ€™ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades

Brad T

Android user

Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help๐Ÿค๐Ÿค

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

I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend

Aubrey

iOS user

Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.๐Ÿ˜‹๐Ÿฉท๐ŸŽ€

Marco B

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 ๐Ÿ˜๐Ÿ˜๐Ÿ˜ฒ๐Ÿค‘๐Ÿ’—โœจ๐ŸŽ€๐Ÿ˜ฎ

Elisha

iOS user

This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as Iโ€™ve seen! Geometry too!

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

I think itโ€™s very much worth it and youโ€™ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still donโ€™t get it!!! In the end I think itโ€™s worth it ๐Ÿ˜Š๐Ÿ‘ โš ๏ธAlso DID I MENTION ITS FREEE YOU DONโ€™T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLYโ—๏ธโ—๏ธโš ๏ธ

Thomas R

iOS user

Knowunity is the BEST app Iโ€™ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades

Brad T

Android user

Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help๐Ÿค๐Ÿค

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

I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend

Aubrey

iOS user

Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.๐Ÿ˜‹๐Ÿฉท๐ŸŽ€

Marco B

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 ๐Ÿ˜๐Ÿ˜๐Ÿ˜ฒ๐Ÿค‘๐Ÿ’—โœจ๐ŸŽ€๐Ÿ˜ฎ

Elisha

iOS user

This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as Iโ€™ve seen! Geometry too!

Paul T

iOS user