Co-factors, co-enzymes, and vitamins | MCAT | Khan Academy

Summary

In this Khan Academy video on MCAT preparation, the roles of co-factors, co-enzymes, and vitamins in enzymatic reactions are explained. Enzymes increase reaction speed by reducing activation energy and binding substrates at an active site. However, not all enzymes can catalyze reactions independently and may require co-factors or co-enzymes. Co-enzymes, like NADH and CoA, are organic carrier molecules, while co-factors, such as magnesium ions, assist directly in catalysis. Vitamins and minerals act as dietary sources of these co-enzymatic and co-factoring agents, crucial for maintaining health as the body cannot synthesize them.

Highlights

• Enzymes speed up reactions by lowering the activation energy and binding to substrates at the active site 🔥.
• Co-factors and co-enzymes are key in helping enzymes catalyze reactions more efficiently.
• NADH, a co-enzyme, acts as an electron carrier vital in processes like lactic acid fermentation 🧪.
• Co-enzyme A (CoA) transfers acyl or acetyl groups in metabolic reactions.
• Co-factors, unlike co-enzymes, are directly involved in the catalysis process, often stabilizing the substrates.
• Magnesium functions as an essential co-factor in DNA synthesis, stabilizing the negative charge of DNA 📜.
• Vitamins and minerals are critical as dietary sources of co-factors and co-enzymes needed by the body to function properly.

Key Takeaways

• Enzymes need help too! Co-factors and co-enzymes assist in making reactions happen smoother 😎.
• Co-enzymes, such as NADH and CoA, carry molecules to aid in enzymatic processes 🔄.
• Co-factors, like magnesium, directly help stabilize and convert substrates during reactions 🚀.
• Vitamins B3 (niacin) and B5 are actually precursors for the essential co-enzymes NAD and CoA 💊.
• Minerals are usually inorganic co-factors; magnesium helps DNA polymerase, while calcium strengthens bones 🦴.
• You need dietary co-factors and co-enzymes to stay healthy because the body can't make them on its own 🥗.

Overview

In this insightful video, Khan Academy delves into the world of co-factors and co-enzymes, exploring how they are essential in helping enzymes perform their tasks efficiently. Not all enzymes can function autonomously; some require additional help through co-factors or co-enzymes, which are responsible for either carrying elements needed in the reactions or directly stabilizing the catalytic processes.

Co-enzymes like NADH and CoA play pivotal roles in our body's metabolic functions by acting as transporters for electrons and acyl groups respectively. Meanwhile, co-factors such as magnesium ions contribute by providing necessary support to enzymes like DNA polymerase, ensuring that DNA synthesis and other crucial biochemical reactions are completed seamlessly.

Adding another layer of importance, the video highlights how vitamins and minerals serve as dietary sources of these critical co-factors and co-enzymes. Since the human body cannot produce these nutrients, a balanced diet is essential to maintain optimal health and support enzymatic activity. From Vitamin B3 aiding in forming NAD to calcium strengthening bones, understanding these elements' roles makes clear their importance to our health.

Chapters

• 00:00 - 00:30: Introduction to Enzymes and Their Function This chapter provides an introduction to enzymes, emphasizing their role in accelerating reactions by lowering activation energy. It discusses the concept of the active site where enzyme-substrate binding occurs and highlights the necessity of co-factors and co-enzymes for some enzymatic functions.
• 00:30 - 02:00: Co-factors and Co-enzymes Role The chapter introduces the concept of enzymes requiring assistance to function effectively, specifically through co-factors and co-enzymes. It explains that co-enzymes are organic carrier molecules essential for the efficient functioning of enzymes. Details on how these co-enzymes assist in enzymatic reactions are promised to be covered. The chapter sets up a discussion on the definitions and functionalities of co-enzymes and co-factors.
• 01:00 - 02:00: Details on Co-enzyme Function The chapter discusses the function of co-enzymes, which assist enzymes by holding onto certain elements to facilitate catalytic processes. An example provided is NADH, which acts as an electron carrier. NADH can dissociate into its oxidized form, NAD+, and a hydride ion, essentially a pair of electrons available for another molecule to capture.
• 02:30 - 04:00: Differences Between Co-factors and Co-enzymes NAD+ can accept electrons and convert into NADH to carry electrons for an enzyme.
• 04:00 - 05:30: Examples of Minerals and Vitamins as Co-factors and Co-enzymes This chapter discusses various examples of minerals and vitamins serving as co-factors and co-enzymes in biochemical reactions. It specifically highlights the role of specific co-enzymes, such as NADH and co-enzyme A (CoA). NADH functions as an electron carrier, while CoA carries acyl or acetyl groups, frequently appearing in metabolic reactions to transport two-carbon acetyl groups between molecules.
• 05:00 - 05:30: Conclusion and Summary This chapter provides a conclusion and summarization of the concepts covered, focusing on the difference between co-factors and co-enzymes. It explains that while co-enzymes are mainly involved in transferring components between molecules, co-factors play a direct role in an enzyme's catalytic process by stabilizing enzymes or substrates and aiding in substrate transformation. An example given is the function of DNA polymerase.

Co-factors, co-enzymes, and vitamins | MCAT | Khan Academy Transcription

• 00:00 - 00:30 Today, we're going to talk about co-factors and co-enzymes and how sometimes they can be essential to proper enzymatic function. But first, let's review the idea that enzymes make reactions go faster. And they do this by lowering the activation energy peak of their respective reactions. Let's also review the idea that enzymes bind their substrates at a location on the enzyme called the active site, which is where most of the reaction takes place. Now, not all enzymes are able to catalyze reactions
• 00:30 - 01:00 on their own. And some need a little help. So if we have our enzyme here, trying to react with our substrate over here, sometimes something called a co-factor or a co-enzyme will be needed, which will also need to bind to the enzyme in order for it to function properly. And we're going to go over what co-enzymes and co-factors are and exactly how they work. So first, we'll talk about what a co-enzyme is. Well, co-enzymes are organic carrier molecules. And what I mean by "organic" is that they're primarily
• 01:00 - 01:30 carbon-based molecules. And by "carrier," I mean that co-enzymes hold on to certain things for an enzyme to make the catalysis run a little more smoothly. And a great example of a co-enzyme is NADH, which acts as an electron carrier. And here, I've shown NADH dissociating into its oxidized form, NAD+, as well as to a hydride ion, which basically just exists as a pair of electrons that some other molecule would be grabbing.
• 01:30 - 02:00 So NAD+ can accept electrons, causing the molecule to be converted to NADH, which could then carry electrons for an enzyme. Now if you remember the lactic acid fermentation reaction, where pyruvate is converted to lactic acid, you'd see that the enzyme catalyzing this reaction, lactate dehydrogenase, uses NADH as a co-enzyme in order to transfer electrons to the pyruvate molecule, in order to turn it into lactic acid. And in this sense, NADH is acting
• 02:00 - 02:30 as an electron-carrying co-enzyme. Another example of a co-enzyme is co-enzyme A, which like NADH acts as a carrier molecule. But instead of carrying electrons like NADH does, co-enzyme A, which we sometimes call CoA, holds on to acyl or acetyl groups instead. And you'd see CoA appear quite often in metabolic reactions, where it will carry these two carbon acetyl groups from one molecule to another.
• 02:30 - 03:00 Now, co-factors are a little different from co-enzymes. While co-enzymes are only really involved in transferring different things from one molecule to another, co-factors are directly involved in the enzyme's catalytic mechanism. They don't strictly carry something like a co-enzyme would, but might be stabilizing the enzyme or the substrates or helping the reaction convert substrates from one form to another. A great example of this is with the enzyme DNA polymerase. Remember that DNA polymerase is responsible for helping out
• 03:00 - 03:30 with synthesizing new DNA during DNA replication. Now, you may remember that DNA is a very negatively charged molecule because of all the negatively charged phosphate groups that you'll find around it. Well, DNA polymerase uses a magnesium ion as a co-factor, which can use its big positive charge to stabilize all that negative charge on DNA. And you can see how this is different from a co-enzyme. Becomes instead of acting as a carrier molecule, the magnesium
• 03:30 - 04:00 ion co-factor is stabilizing the DNA and is more directly involved in the actual catalysis. Now, interestingly, what people normally called vitamin and minerals, like the kinds that a doctor would tell you to make sure you get enough of in your diet, are often different co-factors and co-enzymes. And what's special about vitamins and minerals is that your body can't build them up from scratch. And you need to get them from your diet in order to stay healthy. So when we say vitamins, we typically
• 04:00 - 04:30 refer to organic co-factors and co-enzymes. So two great examples are ones we just discussed. Vitamin B3, which you may see being called niacin on a food label, is actually just a precursor for NAD. And vitamin B5 is just a precursor for co-enzyme A. Minerals, on the other hand, are inorganic, meaning they aren't carbon based. And minerals are usually just co-factors in our body. So magnesium would be a great example of a mineral co-factor
• 04:30 - 05:00 that an enzyme like DNA polymerase would use. Now, not all minerals act only as co-factors. Some minerals, like calcium, which can act as a co-factor, is also a critically important component of bone and teeth. And it doesn't strictly act as an enzyme co-factor here. It's actually an important part of the structure itself. So what did we learn? Well, first we learned that not all enzymes are able to function alone and some need a little help.
• 05:00 - 05:30 And next, we learned that this help can come from co-enzymes, which usually act as carrier molecules, or co-factors, which directly assist with the catalysis that the enzyme is doing. And finally, we learned that the vitamins and minerals generally refer to dietary co-factors and co-enzymes.