By: Annie Hu
When people hear the word “metabolism,” they straightaway think about weight gain and loss. Often we hear people talk about metabolism in conjunction with diets and weight loss trends. While there is a link between the two topics in popular culture, in reality, metabolism is more multifaceted than that. Metabolism is extremely important in helping maintain the energy levels of your body, as it is the sum of the chemical reactions that change our food into energy. Our bodies need energy in order to function, and because of that, metabolism is involved in everything we do.
Your body is made of trillions of cells that are your building blocks. All of the chemical processes that take place within the cells are referred to as your cellular metabolism. The digestion of food in the stomach and intestines breaks it down into molecules that are crucial to the body’s metabolic reactions.
Enzymes in your mouth and stomach are responsible for breaking foods down into amino acids, fatty acids, and glucose. From there, they can enter the intestines and then the bloodstream, where they are transferred to cells to fuel chemical reactions.
To simplify these processes, the chemical reactions that occur in cells are divided up into two big categories; anabolic metabolism (anabolism) and catabolic metabolism (catabolism). Anabolic metabolism involves chemical reactions that build larger molecules from smaller molecules, which build tissue and energy stores. New cells/cell parts can be formed and tissues are maintained or newly formed by anabolic reactions powered by the small molecules from food. When there are extra molecules, anabolism turns them into larger molecules for storage. The larger molecules that are commonly formed to store this energy are carbohydrates and fats, and sometimes proteins are formed to create new cell parts.
Catabolic metabolism are the processes which access this stored energy. By breaking down large molecules (such as carbs and fats) into smaller molecules, the energy stored within them can be released and provided to your body’s cells.
The body doesn’t just run these processes, but the anabolic vs. catabolic processes need to be controlled and balanced between each other as well. For example, the pancreas gland and insulin hormones are relevant to diabetes. The pancreas has the ability to secrete the hormone insulin, which is important for allowing sugar in the bloodstream to be absorbed into cells to make energy. It can also signal for excess glucose to be stored in the liver as glycogen. Diabetes occurs when the body uses insulin improperly or doesn’t have enough insulin. The pancreas and the hormone insulin are also important in regulating whether at any one time, the body is using mainly anabolism or catabolism. Logically, after you finish a meal and have digested the food, your body goes into more anabolic metabolism because it needs a way to store all the surplus of molecules produced after digesting the food. This is called the absorptive state where all the food is being stored. The postabsorptive state, like you could assume, is when the body has to run off of the stored molecules rather than those eaten, and occurs when there is no recent food in the gastrointestinal tract (stomach and intestines). This essentially translates into a shift from anabolic processes to catabolic ones as the large stored molecules are broken down for energy to keep the body running. The reason why the pancreas gland and insulin hormones are so important in shifting the processes is that the pancreas secretes insulin to shift processes to become more anabolic rather than catabolic if there are higher blood sugar levels sensed from recently ingested food. Thus, insulin is very important in controlling the balance of anabolic and catabolic reactions. That is why in diabetes, where there is an insulin imbalance, blood sugar levels rise unchecked and the molecules are not absorbed into the cells where they can be converted into usable energy, causing imbalance metabolism as well between the anabolic and catabolic processes.
It is common to hear about the “rate” of metabolism when it is mentioned. You may have heard people refer to a faster natural metabolism as the reason for a lower body weight. This is not always necessarily true though, because weight is affected by genetics, diet, and lifestyle as well. Your body’s natural set weight (defined by genetics) is majorly involved in determining weight. So while the rate of metabolism isn’t the complete reason for weight, it does provide for some general understanding of how our bodies function.
So how does the rate of metabolism affect our bodies? The rate that a person’s body can burn calories (which measure the amount of energy food can provide the body) at rest is called basal metabolic rate, or BMR. The BMR is purely an “at rest” rate (think bed rest), and doesn’t include regular daily activities. The BMR is a biological process that can play a role in weight management, and is affected by factors like genetics, body size and composition, sex, and age.
People who are larger or have more muscle mass burn calories faster, men tend to burn calories faster, and younger people also require more calories. This is where popular culture caught the idea that people with a faster basal metabolism don’t gain fat easily, as the bodies burn more calories that will be used as energy and not stored as body fat. However, exercise (which takes the body out of rest) can help increase the rate of metabolism from the basal rate, and also affects the number of calories burnt up in a day, so it is not just basal metabolism that affects weight.
Metabolism affects everything that we do because it provides energy from the food we eat to keep our bodies running. Through anabolic and catabolic processes, energy and molecules are stored and used by the body in a symbiotic process that is regulated with hormones. These two categories of processes are extremely broad, and provide a lot of room for new information to be discovered about metabolic processes. For now, much research has been done into how metabolism impacts weight, and there are certainly a diverse number of factors that affect that as well.
Hopefully you had fun learning about the interesting topic of metabolism!
Citations:
Images:
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What Did You Learn?
Questions:
1. What two broad categories is metabolism commonly divided into?
Anabolism and Catabolism. Anabolism sums up the metabolic processes where larger molecules are formed from smaller ones during the chemical reactions (carbohydrates and fats may be formed). This also involves the creation of new cell parts and formation of tissue to store excess molecules as energy for later. Catabolism breaks down these larger stores to access and use the energy.
2. Why are the pancreas and the secretion of insulin so important in metabolism?
Metabolism must occur at a balance between anabolic and catabolic processes. The secretion of insulin helps to direct a shift between the two types of processes when it is needed. After eating, blood sugar levels are higher than normal, and to maintain balance, insulin is released into the bloodstream to help absorb the energy into the cells to be used. Excess may even be stored into the liver as glycogen. In short, anabolic processes become more prominent after insulin is released to use the energy from any recently ingested food. The pancreas is important to secreting the insulin in the first place.
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