Metabolism

Your body is always working.

It uses food to make power. This power helps you grow. It also helps you fix your body.

Some parts break food down. This gives you energy. This is like taking things apart.

Other parts build things up. They use power to make new parts. This is like putting blocks together.

Special tools help these jobs happen. They make the work go fast. They help your body stay healthy.

All living things do this. Even tiny bugs and huge elephants.

Your body is a busy place!

Your body is a busy place! It uses metabolism to stay alive.

Metabolism is a set of chemical changes. These changes happen inside all living things. Metabolism has three main jobs. First, it turns food into power. Second, it turns food into building blocks. These blocks make parts like proteins and fats. Third, it gets rid of waste.

There are two main ways this works. One way is called catabolism. This is when the body breaks down large things. This process gives off power. The other way is called anabolism. This is when the body builds things up. This way uses power to work.

A special molecule called ATP acts like a tiny battery. It carries power between these two jobs.

Special tools called enzymes help these jobs. Enzymes make the changes happen much faster. They also help the body control the work. All living things use similar ways to do this. Tiny bacteria and huge elephants use the same basic steps. This shows how important metabolism is for life.

Metabolism is a set of life-sustaining chemical reactions. These reactions happen inside every living thing.

Metabolism has three main jobs to keep life going. It turns food into a form of energy cells can use. It also turns food into building blocks for parts like proteins and fats. Finally, it helps the body get rid of metabolic waste. These reactions allow living things to grow and reproduce. They also help organisms respond to their environments.

There are two main ways these reactions work. One way is called catabolism. This is the process of breaking down compounds, like turning glucose into pyruvate. Catabolism usually releases energy for the cell to use. The other way is called anabolism. This is the building up of compounds like proteins and lipids. Anabolism consumes energy to make these new parts.

These reactions are organized into metabolic pathways. In a pathway, one chemical changes into another through many steps. Each step in the path is helped by a specific enzyme.

Enzymes are very important tools for metabolism. They act as catalysts, which means they make reactions happen much faster. Without enzymes, many reactions would not occur by themselves. Enzymes also help regulate how fast a reaction goes. They can change the rate based on signals from other cells.

One central molecule is called adenosine triphosphate, or ATP. ATP is the energy currency of the cell. It acts as a bridge between catabolism and anabolism. Catabolic reactions generate ATP, and anabolic reactions use it. The human body can use about its own weight in ATP every day.

Living things are made of four basic classes of molecules. These are amino acids, carbohydrates, nucleic acids, and lipids.

Amino acids join together to make proteins. Proteins can act as enzymes or help with cell signaling. Carbohydrates, like glucose, are used to store and move energy. Nucleic acids, such as DNA and RNA, store genetic information. Lipids, or fats, are used for cell membranes and energy. Many of these molecules are built from small units called monomers.

All living things share many of the same metabolic pathways. This is true for very different species. For example, a tiny bacterium called E. coli uses similar steps to a huge elephant.

These pathways use the same intermediates, like those in the citric acid cycle. Scientists think these pathways are so common because they appeared early in history. They have stayed because they work so well. Even though metabolism is similar, it can be disrupted by diseases. This includes things like cancer or type II diabetes.

Metabolism refers to the complete set of life-sustaining chemical reactions within a living organism.

These reactions are essential for survival, growth, and reproduction. Metabolism performs three primary functions to maintain life. First, it converts energy from food into a usable form for cellular processes. Second, it transforms food into the building blocks of macromolecules, which are large biological molecules. Third, it handles the excretion of metabolic wastes produced during these processes. Beyond these roles, metabolism includes all chemical activities, such as digestion and the movement of substances between cells.

Metabolic reactions are organized into two main categories: catabolism and anabolism. Catabolism is the process of breaking down complex compounds into simpler ones. An example is cellular respiration, where glucose is broken down into pyruvate. This process typically releases energy. In contrast, anabolism is the biosynthesis or building up of compounds like proteins and lipids. Anabolism consumes energy to create these structures. These reactions occur in organized metabolic pathways. In a pathway, one chemical is transformed into another through a series of steps.

Enzymes are the essential tools that drive these metabolic pathways. They act as catalysts, which means they allow chemical reactions to proceed much more rapidly. Many reactions require energy to occur and would not happen on their own. Enzymes allow these reactions to proceed by coupling them to spontaneous reactions that release energy. They also regulate the rate of metabolism. This regulation allows a cell to respond to its environment or to signals from other cells. Without enzymes, the complex chemistry required for life would be too slow to sustain an organism.

One of the most important molecules in metabolism is adenosine triphosphate, or ATP.

ATP is often called the energy currency of the cell. It serves as a central bridge between catabolic and anabolic processes. Catabolic reactions generate ATP, while anabolic reactions consume it to build molecules. Although a cell only holds a small amount of ATP at any time, it is continuously regenerated. In fact, the human body uses about its own weight in ATP every single day.

Living organisms are constructed from four basic classes of biochemicals. These include amino acids, carbohydrates, nucleic acids, and lipids. Amino acids are the monomers that join to form proteins, which serve as enzymes or structural scaffolds. Carbohydrates, such as glucose, are the most abundant biological molecules and are used for energy storage and transport.

Nucleic acids, like DNA and RNA, are polymers of nucleotides that store and use genetic information. Finally, lipids are diverse molecules used to build cell membranes and store chemical energy.

Inorganic elements also play critical roles in maintaining metabolic functions. About 99% of human body weight consists of elements like carbon, nitrogen, oxygen, and hydrogen. Many of these act as electrolytes, such as sodium, potassium, and calcium. These ions are vital for maintaining osmotic pressure and pH levels within cells. They are also necessary for nerve and muscle function. For instance, muscle contraction depends on the movement of calcium, sodium, and potassium through ion channels in the cell membrane.

Metabolism shows a remarkable similarity across the entire tree of life. Basic metabolic pathways are found in vastly different species. For example, the citric acid cycle uses the same carboxylic acid intermediates in a tiny bacterium like E. coli as it does in a massive elephant.

Scientists believe these pathways are so widespread because they appeared very early in evolutionary history. They have been retained because they are highly effective. However, when these systems are disrupted, it can lead to diseases. Conditions such as cancer, type II diabetes, and metabolic syndrome all involve disruptions to normal metabolic processes.