Catabolism: Definition, Processes, Hormones and Stages of Catabolism

Definition of Catabolism   – Thanks to energy, humans can carry out all daily activities. But have you ever thought about how the body produces energy? Energy in the body is produced by a biochemical process called catabolism.

Catabolism is a metabolic pathway that breaks down a complex substrate of organic molecules into its constituent components while releasing energy, generally in the form of ATP.

In the catabolic pathway, large molecules such as polysaccharides, lipids, nucleic acids and proteins will be broken down into several smaller molecules such as monosaccharides, fatty acids, nucleotides and amino acids. Check out a more complete explanation of Catabolism below, Sinaumed’s!

A. Definition of catabolism

Through catabolic reactions, food that has been consumed and enters the digestive organs will be broken down by enzymes in our digestive system. Protein is broken down into amino acids.

This amino acid can be used as a source of energy when the body needs it. Amino acids can also be recycled to make proteins or oxidized to urea. In addition to breaking down protein, catabolism can also break down glycogen into glucose. These simple carbohydrates will then go through an oxidation process called glycolysis. It is from this reaction that energy is produced. Meanwhile, fat will go through a breakdown process called hydrolysis.

This process produces fatty acids and glycerol, which will then go through glycolysis and other biochemical reactions to form energy. The energy generated from the above processes is stored as the molecule adenosine triphosphate (ATP). Many aspects of cellular metabolism, both anabolism and catabolism, are closely related to the production and consumption of ATP as a source of energy, which also serves as fuel in all metabolic processes.

B. Catabolic Process

The main processes of catabolism include the citric acid cycle, glycolysis, oxidative deamination, breakdown of muscle tissue and breakdown of fat. We will briefly look at each of the main aspects of catabolism below.

1. Glycolysis

Is a very important process of catabolism, because it is the process that breaks down sugars (eg, glucose) into pyruvate, together with the production of ATP and NADH. Starting with one molecule of glucose, glycolysis is a 10-step reaction that will give two molecules of pyruvate as products.

Using a variety of enzymes, including kinases, mutases, dehydrogenases, isomerases and lyases, as well as the consumption of two ATPs, this basic glucose molecule can be broken down into 2 pyruvate molecules, 2 NADH (which are then used for the subsequent generation of ATP) and 4 ATP. Since two ATP are consumed during the energy consumption part of this process, the net gain from breaking down a glucose molecule is 2 ATP.

2. Citric Acid Cycle

Also known as the Krebs Cycle, the citric acid cycle uses several products of glycolysis for further energy production, starting with the pyruvate molecule. Again, enzymes play a key role in manipulating these pyruvate molecules and binding them with other molecules to release energy in a controlled manner and perpetuate the cycle.

The product of one turn of the citric acid cycle (using 2 molecules of pyruvate) consists of 4 molecules of carbon dioxide, 6 molecules of NADH, 2 molecules of FADH2, and 2 molecules of GTP. NADH and FADH2 will continue on to the electron transport chain for the production of even more ATP.

3. Oxidative Deamination

When it comes to breaking down proteins and amino acids, and accessing the energy within them, a lesser known process called oxidative deamination is required. Protein is usually broken down and used as a substrate for further molecular development (anabolic processes).

However, when there is a shortage of carbohydrates or normal sources of energy, the body will start breaking down proteins into their amino acids, through a process called proteolysis. Unlike other sources of energy, amino acids have nitrogen, so they require a different catabolic process – oxidative deamination.

When the nitrogen group is removed, the basic carbon skeleton is left behind, which is known as a ketoacid. Similar to normal glucose molecules, ketoacids can enter the Krebs Cycle to produce energy, or they can be further synthesized into free fatty acids.

Ammonia is a by-product of this type of deamination, which is fine in small amounts, but high levels are toxic. The body fights this by converting ammonia to urea in the liver, where it can be transferred from the liver to the kidneys and excreted in our urine.

Humans need energy in activities that can be fulfilled by the process of carbohydrate metabolism. You can learn about the series of reactions in this metabolic process in the book Biochemistry: Enzymes and Carbohydrate Metabolism for MIPA and Health Students.

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4. Fat Breaker (Lipolysis)

Breaking down stored triglyceride fat stores in adipose tissue is another way to generate energy. Triglycerides consist of a glycol backbone, three fatty acid tails, and three ester bonds that link the two previous components. Three ester bonds must be broken to release their energy, which is done by a hydrolysis reaction. In three separate steps, each of these bonds is broken.

After each fatty acid is removed through the introduction of water (HO), the end products include a glycerol molecule, the two free fatty acids, and usable energy. Hormones that stimulate this process include cortisol, adrenaline and glucagon; insulin acts against this process, stimulating the anabolic processes that produce triglycerides.

5. Breakdown of Muscle Tissue

Although most people try to avoid degrading their muscle mass at all costs, it can often be difficult. Immediately after a workout, or in the morning after a long period without nutritional intake, the body may start catalyzing muscle tissue because it lacks the anabolic processes needed to build more muscle tissue. This definitely sounds counterintuitive, but this transformation of tissue into energy is in response to not providing the body with sufficient basic energy, either from protein or carbohydrate sources.

C. Catabolic Hormones

Did you know, sports such as running, swimming, and cycling are types of activities that are catabolic or cardio exercises. When doing this activity, heart rate, blood pressure, and breathing will increase. The process of catabolism itself plays an important role, with the energy produced, the heart can beat so that all body tissues receive blood supply. The function of the lungs, kidneys, digestion, and cell metabolism will also work optimally, to maintain the body’s survival and health. Hormones that play a role in the process of catabolism, including:

  • Cortisol – This hormone helps regulate protein, fat and carbohydrate metabolism. This hormone, known as the ‘stress’ hormone, is produced by the adrenal glands.
  • Cytokines – These are substances that regulate interactions between cells and play a role in regulating the immune system. Several types of cytokines function to stimulate the immune system, while several other types of cytokines function to suppress the activity of the immune system.
  • Glucagon – This hormone is produced by the pancreas, and together with insulin it functions to maintain blood sugar levels.
  • Adrenaline – This hormone known as epinephrine increases heart rate, strengthens heart contractions, and increases blood flow to muscles.


D. Catabolism Exercise to Improve Health

Exercise can help the catabolic process go well. Sports that can increase the process of catabolism are called catabolic sports. Catabolic exercise is known to reduce weight by burning more fat and building more muscle mass as well.

Sometimes, these catabolic processes are often used as a reference for whether the body can lose or gain weight quickly or not. Catabolic sports, such as cycling, swimming and running can be beneficial exercises for the health of the body, especially the heart.

Catabolic exercise is believed to increase heart rate and blood pressure. That way, the lungs and heart will also become healthier. In order to always be fit, follow the exercise guidelines with the following time settings: 150 minutes a week at moderate intensity, 75 minutes a week at high intensity, you can divide these exercise times into three to five days of training schedules in 1 week. If you have a history of certain health conditions, consult your doctor first before starting the sport.

During this catabolic exercise, heart rate, blood pressure, and respiration will increase. In this process, the body will break down glycogen (the result of breaking down carbohydrates) into energy to use as fuel during exercise.

If the carbohydrates in the body have been used up and nothing else can be converted into energy, the hormone cortisol in the body will use amino acids to create energy. This causes catabolism to run slowly. In addition, other factors that cause the body’s catabolism to run slowly.

Causes of Slow Catabolism

1. Lack of Activity

Catabolism is the process of producing energy. Exercise helps the process run more quickly. When you don’t move much, your body burns less (or slower) carbohydrates so that less energy is created.

2. Lack of Calories

Limiting the amount of intake is often chosen as a way to lose weight. In fact, eating too little can make catabolic and anabolic processes decrease. As a result, the body cannot produce energy as it should. When reducing total calorie intake to very little than usual, the body will assume someone is starving. In that condition, the body will slow down the burning of calories in the body.

3. Lack of sleep

Lack of sleep can increase the risk of various diseases and fatigue the next day. In addition, several studies have also shown that sleep deprivation can slow down metabolism and can lead to weight gain.

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Research also proves that sleep deprivation can lower the resting metabolic rate of healthy adults in the morning. Lack of sleep can disrupt the metabolism of carbohydrates in the body so that when you wake up your body still has high blood sugar levels. High blood sugar levels indicate that glucose, which should be broken down into energy in the body, continues to flow freely in the bloodstream.

4. Stress

Stress can increase the production of the hormone cortisol. This then makes your appetite increase. If this happens continuously, you will experience weight gain because carbohydrates that are not broken down into energy are stored as fat. This weight gain can eventually cause a decreased body metabolism.

5. Consumption of certain drugs

Certain drugs can also slow down the metabolism in the body. Some of them are antidepressants, diabetes drugs, steroids, and hormone therapy. If you feel that you have gained weight after taking the drug, maybe the drug has an impact on your body’s metabolism. If this condition bothers you, immediately discuss it with your doctor.

Less Calories The Body Intakes When you lower your total calorie intake to very little than usual, the body will think you are starving. Under these conditions, the body will slow down your body’s burning of calories.

Therefore, in order to keep catabolism running as optimally as possible, you can do regular exercise as well as various other healthy tips that you can learn from the book 50 Healthy Tips to Prevent Disease with Exercise.


E. Stage Catabolism

Catabolism is the process when the body digests food into small molecules in the body to be used as energy or to break down carbohydrates. The large and complex molecules in the body are then broken down into smaller and simpler ones.

Examples of catabolic processes are the same as carbohydrates from rice that enter the body. Carbohydrates are then converted into disaccharides and further broken down into monosaccharides (glucose). The causes of slow catabolism are lack of movement and activity, lack of calories absorbed by the body, lack of sleep, stress and taking certain drugs.

In the process of catabolism there is a process of cellular respiration or cellular respiration. Cellular respiration carries out the process of breaking down complex organic molecules that are rich in potential energy into lower energy waste products at the cellular level. Cellular respiration has four stages namely glycolysis, oxidative decarboxylation, Krebs cycle and electron transfer.

Catabolism is part of the body’s metabolism, namely the process of breaking down complex molecules into smaller molecules to obtain energy. Catabolism occurs in the digestive process of food. Living cells carry out catabolism to get energy to move, warm the body, and also think. Catabolism in living things occurs in several stages, namely glycolysis, oxidative decarboxylation, the Krebs cycle, and the electron transport chain.

1. Glycolysis

Glycolysis comes from two words namely “glucose” which means sugar, and “lysis” which means the breakdown of glucose. Reporting from the Britannica encyclopedia, glucose or the six-carbon sugar group (C6H12O6) is the most important source of energy for the body. Glycolysis is the process of breaking down sugar that takes place in the cytoplasm of cells. The process of glycolysis breaks down sugar into pyruvic acid, NADH, and energy in the form of ATP.

2. Oxidative decarboxylation

Oxidative decarboxylation is the stage of catabolism after glycolysis. Reporting from the Britannica encyclopedia, pyruvic acid from glycolysis is oxidized by the pyruvate dehydrogenase (PDC) enzyme complex to produce acetyl coenzyme A and carbon dioxide. NAD is converted to a higher energy form namely NADH. Oxidative decarboxylation converts pyruvic acid to be processed again in the Krebs cycle, this is why oxidative decarboxylation is called a transition reaction. This transition reaction takes place in the mitochondria of living cells.

3. Krebs cycle

Krebs cycle or tricarboxylic acid cycle is a stage of catabolism to produce higher energy. The Krebs cycle is called a cycle because it continues in a closed loop. Reporting from BCcampus Open Textbooks, the Krebs cycle processes acetyl coenzyme A as a result of oxidative decarboxylation to produce energy. The image above was discovered in 1937 by the biochemist Sir Hans Adolf Krebs. The Krebs cycle consists of 8 stages and each stage is assisted by 8 different enzymes. Reporting from the Encyclopaedia Britannica, that the molecules resulting from the Krebs cycle transfer their energy to the electron transfer chain.

4. Transport Chain

Electrons Reported from, the electron transport chain is a complex series of proteins and electron carrier molecules in mitochondria to. The electron transport chain aims to produce energy from NADH and FADH. The electron transport chain takes place in each stage of catabolism so that the energy produced is the accumulation of all catabolic processes, namely 30-32 ATP.