Introduction to Metabolism - Online Tutor, Practice Problems & Exam Prep

Metabolism encompasses all chemical reactions within an organism, organized into metabolic pathways that convert substrates through multiple steps, ultimately yielding a final product. There are two primary types of pathways: catabolic pathways, which release energy by breaking down larger molecules into smaller ones (exergonic processes), and anabolic pathways, which require energy to synthesize larger molecules from smaller ones (endergonic processes). Understanding these pathways is crucial for grasping how organisms manage energy and build cellular structures.

Introduction to Metabolism

In this video, we're going to begin our introduction to metabolism. Metabolism is a term that refers to all of an organism's chemical reactions. When we talk about all the chemical reactions inside an organism, that is what metabolism is referring to. Now, metabolic pathways are defined as a series of chemical reactions that ends up altering a substrate multiple times before the final product is released. Notice in the example image below, we're showing you an image of an example metabolic pathway. Metabolic pathways have multiple steps. Notice that the very first substrate here, substrate A, is being converted into product B by enzyme number 1, but notice that product B is not the final product. Instead, B is going to be converted into C by enzyme 2, and C is further going to be converted into D by enzyme 3, and then last but not least, D is going to be converted into E by enzyme 4. Here, it is molecule E that is acting as the final product to this pathway, and all these other molecules that we see here are acting as substrates to enzymes. What we can see here is that enzymes can work together in a series of steps in order to convert one substrate into another until the final product is released. When enzymes work together in this fashion, we refer to it specifically as a metabolic pathway. There are two main types of metabolic pathways that you should be aware of, and we'll introduce those two in our next video. So, I'll see you all there.

Catabolic & Anabolic Pathways

In this video, we're going to distinguish between Catabolic and Anabolic Pathways. And so really there are 2 main types of metabolic pathways. The first type are going to be catabolic pathways or catabolism, and the second are going to be anabolic pathways or anabolism. And so catabolic pathways or catabolism are going to be pathways that release energy into the environment by breaking down molecules into smaller ones. And anabolic pathways are pretty much the exact opposite, so instead of releasing energy into the environment, they are going to be spending energy or requiring an energy input, and they use that energy in order to build up larger molecules such as DNA and proteins, for instance. And so catabolic pathways, because they release energy into the environment, they are going to be associated with exergonic processes. And anabolic pathways, because they spend energy or require an energy input, they're going to be associated with endergonic processes. And so let's take a look at our image down below to further distinguish between catabolic and anabolic reactions and pathways. And so notice over here on the left-hand side, we're focusing on catabolism, and over here on the right-hand side, we're focusing on Anabolism. Now, Catabolism is all about breaking down molecules, large molecules, into smaller pieces, their smaller components. Whereas, Anabolism is all about building up, building larger molecules using smaller molecules. And so when you think about catabolism, you can see the word cat that is embedded inside of catabolism, and so when you see catabolism, you could think about a cat, And that's because cats, really all they can do is pounce on a pyramid like this one and break it down into its smaller components. But a cat can't really do the opposite. A cat cannot build this pyramid like what we see here. If you ever see a cat build a pyramid like this, please give me a call. I'd like to see that. But when you think about catabolism, you can think about cats and you can think about cats pouncing on pyramids and breaking down the pyramids like what we see here. Now Anabolism doesn't have the word cat in it, and so if there's no cat to break it down, then it's going to allow for building up. And so over here, notice that we've got, for metabolism, the cat is breaking down the molecules into their smaller components, and here we have an enzyme breaking down a larger molecule into its smaller components. And then over here on the right for Anabolism, we're showing building up. So notice that the building blocks are being built up into the larger, more structured pyramid. And here we're taking the smaller building blocks and the enzyme is converting it into a larger piece here, building up. And so really this is the main difference between Catabolism and Anabolism. Catabolism is going to break down and Anabolism is going to build up. And so that concludes our introduction to catabolic and anabolic pathways, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.

Which of the following terms specifically describes the metabolic process of breaking down large molecules?

a) Catabolism. 

b) Metabolism.

c) Anabolism.

d) Dehydration.

• A. Catabolism.
• B. Metabolism.
• C. Anabolism.
• D. Dehydration.

Which of the following statements is TRUE regarding anabolic pathways?

a) They are used for digesting sugars.

b) They consume energy to build up polymers from monomers.

c) They release energy by breaking down polymers into monomers.

d) They increase the entropy of the organism.

• A. They are used for digesting sugars.
• B. They consume energy to build up polymers from monomers.
• C. They release energy by breaking down polymers into monomers.
• D. They increase the entropy of the organism.

Here’s what students ask on this topic:

What is metabolism and why is it important for living organisms?

Metabolism refers to all the chemical reactions that occur within a living organism to maintain life. These reactions are organized into metabolic pathways, where substrates are converted into products through a series of enzymatic steps. Metabolism is crucial because it enables organisms to grow, reproduce, maintain their structures, and respond to environmental changes. It encompasses both catabolic pathways, which break down molecules to release energy, and anabolic pathways, which build larger molecules and require energy input. Understanding metabolism helps us grasp how organisms manage energy and resources for growth and maintenance.

What are catabolic pathways and how do they differ from anabolic pathways?

Catabolic pathways, or catabolism, involve the breakdown of larger molecules into smaller ones, releasing energy in the process. These pathways are associated with exergonic reactions, which release energy into the environment. In contrast, anabolic pathways, or anabolism, involve the synthesis of larger molecules from smaller ones, requiring an input of energy. These pathways are associated with endergonic reactions, which consume energy. Essentially, catabolism breaks down molecules to release energy, while anabolism builds up molecules and requires energy input.

How do enzymes function in metabolic pathways?

Enzymes are biological catalysts that speed up chemical reactions in metabolic pathways. They work by lowering the activation energy required for a reaction to occur. In a metabolic pathway, each enzyme is specific to a particular substrate and catalyzes a specific step in the pathway. For example, in a series of reactions converting substrate A to final product E, enzyme 1 converts A to B, enzyme 2 converts B to C, and so on. This sequential action ensures that substrates are efficiently converted into final products, facilitating the organism's metabolic processes.

What is the role of energy in anabolic and catabolic pathways?

Energy plays a crucial role in both anabolic and catabolic pathways. In catabolic pathways, energy is released as large molecules are broken down into smaller ones. This released energy can be harnessed for various cellular activities. In contrast, anabolic pathways require an input of energy to build larger molecules from smaller ones. This energy is often derived from ATP (adenosine triphosphate) generated during catabolic processes. Thus, the energy released in catabolism is used to drive the energy-consuming reactions in anabolism, maintaining a balance within the organism's metabolism.

Can you provide an example of a metabolic pathway and explain its significance?

An example of a metabolic pathway is glycolysis, which is the process of breaking down glucose into pyruvate, releasing energy in the form of ATP. Glycolysis is a catabolic pathway that occurs in the cytoplasm of cells and is the first step in cellular respiration. It is significant because it provides the cell with a quick source of energy and intermediates for other metabolic pathways. The ATP produced during glycolysis is essential for various cellular functions, and the pyruvate generated can be further processed in the mitochondria to produce even more ATP through the citric acid cycle and oxidative phosphorylation.