Microbiology, part 17: Metabolism - Chemical Reactions & Energy Carriers

Hi, I'm Cathy with Level Up RN. In this video, I'm going to begin my coverage of topics from the microbial metabolism section of our microbiology flashcard deck. Specifically, I'll be talking about chemical reactions and energy carriers. And at the end of the video, I'm going to give you guys a quiz to test your understanding of some of the key points I'll be covering, so definitely stay tuned for that. And if you have our Level Up RN microbiology flashcards, go ahead and pull out your flashcards so you can follow along with me.

A chemical reaction is the process of either forming or breaking bonds between atoms. The starting substances in a chemical reaction are the reactants, and the substances that are formed from the reaction are the products, and then the arrow in between the reactants and the products indicates the direction of the reaction. Let's review the different types of chemical reactions. In a synthesis reaction, two or more substances are combined to form a more complex substance. In a decomposition reaction, a reactant is broken down into two or more products. In a single replacement reaction, one element replaces another in a compound. In a double replacement reaction, the two reactants exchange ions, forming two new compounds. And in a reversible reaction, the conversion of reactants to products happen simultaneously as products are converted to reactants.

When we talk about metabolism, this refers to all the chemical reactions that take place in a cell. Endergonic reactions are reactions that require energy to proceed, whereas exergonic reactions are reactions that release energy. Catabolism refers to the breakdown of complex molecules into simpler ones. So these are decomposition reactions that are exergonic, so energy is released. Anabolism involves endergonic reactions that combine simple molecules into more complex molecules, so synthesis reactions. These reactions require energy, which the cell can get from the breakdown of chemical bonds that occurs during catabolism. So in this way, we have a balance of catabolism and anabolism in the cell. The way I remember the difference between anabolism and catabolism is that with anabolism, we are adding molecules together. So anabolism and adding both start with A. And with catabolism, we have the catastrophic breakdown of molecules. So catastrophic and catabolism both start with cat.

Now let's talk about oxidation and reduction. With an oxidation reaction, we are removing a high-energy electron from a donor molecule, leaving that molecule oxidized. A reduction reaction is the opposite. With a reduction reaction, we are adding a high-energy electron to an acceptor molecule, leaving that molecule reduced. So oxidation and reduction reactions always occur together, so we refer to these as redox reactions. And the helpful way to remember these reactions in a way you have likely heard of is oil rig. So oxidation is loss of a high-energy electron, and reduction is gain of a high-energy electron.

When energy is released through the breakdown of chemical bonds, this energy can be stored through the reduction of electron carriers or in the bonds of ATP. So electron carriers are basically molecules that shuttle high-energy electrons from one molecule to another. Some important electron carriers to be familiar with include NAD, NADP, and FAD. Adenosine triphosphate, or ATP, is considered to be the energy currency of the cell. So when energy is released through catabolism, in addition to storing that energy through the reduction of electron carriers, we can also store that energy in the high-energy phosphate bonds of ATP, where it can be used later to drive processes that require energy.

All right. It's quiz time, and I have four questions for you. Question number one. Which type of reaction requires energy to proceed, an endergonic reaction or an exergonic reaction? The answer is an endergonic reaction. Question number two. Is catabolism an endergonic reaction or exergonic reaction? The answer is exergonic reaction. Question number three. Which molecule is referred to as the energy currency of the cell? The answer is ATP. And question number four. What type of reaction removes a high-energy electron from a donor molecule? The answer is an oxidation reaction. All right. That's it for this video. I hope it was helpful. Thank you so much for watching, and good luck with studying.

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Catabolism refers to [exerjonic?]-- [jonic?]. What the [inaudible]?