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Cellular Respiration Explained: Aerobic and Anaerobic Processes
Katrina Stone
@katrinastone02
1 / 3
Understanding Cellular Respiration
Ever wonder how your body extracts energy from the food you eat? That's cellular respiration at work. This process allows organisms to break down glucose using oxygen to produce energy in the form of ATP, along with carbon dioxide and water as waste products.
Organisms can be classified by how they obtain energy. Autotrophs like plants produce their own organic molecules through photosynthesis, while heterotrophs like humans rely on consuming organic compounds produced by other organisms. Regardless of type, all organisms use cellular respiration to extract energy from these organic molecules.
At its core, cellular respiration involves redox reactions - chemical reactions where electrons are transferred from one molecule to another, carrying energy with them. These reactions are often dehydrogenations, where hydrogen atoms (consisting of one electron and one proton) are removed. An important electron carrier called NAD+ accepts electrons and hydrogen to become NADH, storing energy for later use.
Energy Tip: Cellular respiration releases energy in small, controlled steps rather than all at once. If all 686 kcal/mol of glucose were released simultaneously, it would damage cells. Think of it like slowly releasing water through a dam instead of letting it burst!
Cellular respiration comes in different forms. Aerobic respiration uses oxygen as the final electron acceptor, while anaerobic respiration uses other inorganic molecules. Fermentation is another oxygen-free pathway that uses organic molecules as the final electron acceptor. Each pathway has different energy yields and occurs in different cellular locations.
Glycolysis and Pyruvate Oxidation
Glycolysis is your body's first step in extracting energy from glucose, and it happens right in the cytoplasm of your cells. This 10-step biochemical pathway converts one glucose molecule (6 carbon atoms) into two pyruvate molecules (3 carbon atoms each).
The process occurs in three main stages: energy investment, cleavage reactions, and energy production. During the energy investment phase, the cell actually uses 2 ATP molecules to "prime" the glucose. This investment pays off later when the pathway generates 4 ATP molecules, giving a net gain of 2 ATP. Glycolysis also produces 2 NADH molecules, which store additional energy.
What happens to pyruvate next depends entirely on oxygen availability. When oxygen is present, pyruvate moves into the mitochondria and undergoes pyruvate oxidation. During this process, each pyruvate molecule loses a carbon atom (released as CO₂), and the remaining two-carbon fragment attaches to Coenzyme A to form acetyl-CoA. This reaction also produces another NADH molecule.
Connection Alert: Think of pyruvate as being at a metabolic crossroads. With oxygen, it enters the high-energy pathway of the Krebs cycle. Without oxygen, your cells resort to fermentation, which produces much less ATP but allows glycolysis to continue.
The acetyl-CoA now enters the Krebs cycle (also called the citric acid cycle), which occurs in the mitochondrial matrix. This cycle begins when the acetyl group combines with oxaloacetate to form citrate, and then proceeds through several steps. For each glucose molecule, the Krebs cycle produces 2 ATP, reduces 6 NAD+ to 6 NADH, and reduces 2 FAD to 2 FADH₂. It also releases the remaining carbon atoms as CO₂.
Electron Transport Chain and Energy Yield
The final stage of cellular respiration is where most of your ATP is produced. The electron transport chain (ETC) consists of a series of protein complexes embedded in the inner mitochondrial membrane. NADH and FADH₂ molecules (created during earlier stages) deliver their high-energy electrons to these complexes.
As electrons move through the chain, they gradually lose energy. Rather than wasting this energy, the complexes use it to pump protons from the mitochondrial matrix into the intermembrane space. This creates a proton gradient - essentially a stored form of energy, like water behind a dam. The concentration of protons creates pressure, driving them to flow back into the matrix through special channels in ATP synthase.
ATP synthase works like a molecular turbine. As protons flow through it, the enzyme rotates and uses this mechanical energy to attach phosphate groups to ADP, creating ATP. This process is called chemiosmosis and generates most of the ATP from cellular respiration.
Energy Insight: While theoretical yields suggest 36-38 ATP molecules per glucose molecule, the actual yield is closer to 30 ATP in most eukaryotic cells. Some energy is lost due to "leaky" membranes and other cellular processes that tap into the proton gradient.
Cellular respiration is carefully regulated through feedback inhibition. When ATP levels are high, key enzymes in glycolysis and the Krebs cycle are inhibited, slowing down the process. Without oxygen, cells can still generate some energy through anaerobic respiration (using alternative electron acceptors) or fermentation (like lactic acid fermentation in your muscles during intense exercise). These processes regenerate NAD+ to keep glycolysis running, though they produce much less ATP than aerobic respiration.
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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.
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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 help🤍🤍
David K
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Paul T
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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
I think it’s very much worth it and you’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 don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’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 help🤍🤍
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.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. 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 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 I’ve seen! Geometry too!
Paul T
iOS user
Cellular Respiration Explained: Aerobic and Anaerobic Processes
Katrina Stone
@katrinastone02
Cellular respiration is the essential process by which organisms convert nutrients into usable energy. This biochemical pathway breaks down glucose molecules to produce ATP, the energy currency of cells, through a series of carefully controlled reactions. Understanding cellular respiration helps... Show more
Understanding Cellular Respiration
Ever wonder how your body extracts energy from the food you eat? That's cellular respiration at work. This process allows organisms to break down glucose using oxygen to produce energy in the form of ATP, along with carbon dioxide and water as waste products.
Organisms can be classified by how they obtain energy. Autotrophs like plants produce their own organic molecules through photosynthesis, while heterotrophs like humans rely on consuming organic compounds produced by other organisms. Regardless of type, all organisms use cellular respiration to extract energy from these organic molecules.
At its core, cellular respiration involves redox reactions - chemical reactions where electrons are transferred from one molecule to another, carrying energy with them. These reactions are often dehydrogenations, where hydrogen atoms (consisting of one electron and one proton) are removed. An important electron carrier called NAD+ accepts electrons and hydrogen to become NADH, storing energy for later use.
Energy Tip: Cellular respiration releases energy in small, controlled steps rather than all at once. If all 686 kcal/mol of glucose were released simultaneously, it would damage cells. Think of it like slowly releasing water through a dam instead of letting it burst!
Cellular respiration comes in different forms. Aerobic respiration uses oxygen as the final electron acceptor, while anaerobic respiration uses other inorganic molecules. Fermentation is another oxygen-free pathway that uses organic molecules as the final electron acceptor. Each pathway has different energy yields and occurs in different cellular locations.
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Glycolysis and Pyruvate Oxidation
Glycolysis is your body's first step in extracting energy from glucose, and it happens right in the cytoplasm of your cells. This 10-step biochemical pathway converts one glucose molecule (6 carbon atoms) into two pyruvate molecules (3 carbon atoms each).
The process occurs in three main stages: energy investment, cleavage reactions, and energy production. During the energy investment phase, the cell actually uses 2 ATP molecules to "prime" the glucose. This investment pays off later when the pathway generates 4 ATP molecules, giving a net gain of 2 ATP. Glycolysis also produces 2 NADH molecules, which store additional energy.
What happens to pyruvate next depends entirely on oxygen availability. When oxygen is present, pyruvate moves into the mitochondria and undergoes pyruvate oxidation. During this process, each pyruvate molecule loses a carbon atom (released as CO₂), and the remaining two-carbon fragment attaches to Coenzyme A to form acetyl-CoA. This reaction also produces another NADH molecule.
Connection Alert: Think of pyruvate as being at a metabolic crossroads. With oxygen, it enters the high-energy pathway of the Krebs cycle. Without oxygen, your cells resort to fermentation, which produces much less ATP but allows glycolysis to continue.
The acetyl-CoA now enters the Krebs cycle (also called the citric acid cycle), which occurs in the mitochondrial matrix. This cycle begins when the acetyl group combines with oxaloacetate to form citrate, and then proceeds through several steps. For each glucose molecule, the Krebs cycle produces 2 ATP, reduces 6 NAD+ to 6 NADH, and reduces 2 FAD to 2 FADH₂. It also releases the remaining carbon atoms as CO₂.
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Electron Transport Chain and Energy Yield
The final stage of cellular respiration is where most of your ATP is produced. The electron transport chain (ETC) consists of a series of protein complexes embedded in the inner mitochondrial membrane. NADH and FADH₂ molecules (created during earlier stages) deliver their high-energy electrons to these complexes.
As electrons move through the chain, they gradually lose energy. Rather than wasting this energy, the complexes use it to pump protons from the mitochondrial matrix into the intermembrane space. This creates a proton gradient - essentially a stored form of energy, like water behind a dam. The concentration of protons creates pressure, driving them to flow back into the matrix through special channels in ATP synthase.
ATP synthase works like a molecular turbine. As protons flow through it, the enzyme rotates and uses this mechanical energy to attach phosphate groups to ADP, creating ATP. This process is called chemiosmosis and generates most of the ATP from cellular respiration.
Energy Insight: While theoretical yields suggest 36-38 ATP molecules per glucose molecule, the actual yield is closer to 30 ATP in most eukaryotic cells. Some energy is lost due to "leaky" membranes and other cellular processes that tap into the proton gradient.
Cellular respiration is carefully regulated through feedback inhibition. When ATP levels are high, key enzymes in glycolysis and the Krebs cycle are inhibited, slowing down the process. Without oxygen, cells can still generate some energy through anaerobic respiration (using alternative electron acceptors) or fermentation (like lactic acid fermentation in your muscles during intense exercise). These processes regenerate NAD+ to keep glycolysis running, though they produce much less ATP than aerobic respiration.
We thought you’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 – all at your fingertips.
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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
I think it’s very much worth it and you’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 don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’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 help🤍🤍
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.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. 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 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 I’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 it’s very much worth it and you’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 don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’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 help🤍🤍
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.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. 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 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 I’ve seen! Geometry too!
Paul T
iOS user