why living things need energy

Why Do Living Organisms Need Energy? The Role of Energy

To fulfill activities, all living organisms require energy. Metabolism is the series of chemical events that provide energy for cellular operations. Every movement or action performed by an organism consumes energy. Thus, by reading a book, going on a walk, or running; the body is constantly in need of energy.

There are even some activities that our bodies perform that we are unaware require energy. For example, our heart continues to beat and continually, we breathe all the time. We are digesting and absorbing our meals in the blood for different activities in the body. Therefore, all of these processes, as well as many others that occur in the body, necessitate the use of energy.

Types of Energy

Energy is a property that may be manipulated or transmitted, but not destroyed. Organisms use energy to survive, grow, respond and reproduce. Likewise, all other biological processes use energy.

Kinetic Energy

The energy associated with moving objects is kinetic energy. For example, while an airplane is in flight, it is rapidly moving through the air. The labor it does affects change in its surroundings. Jet engines convert potential energy in fuel to kinetic energy of motion. Lastly, even when going slowly, a wrecking ball can cause significant damage.

A stationary wrecking ball, on the other hand, cannot perform any work and hence has no kinetic energy. Kinetic energy is available in a fast bullet, a walking human, and a quick movement of heat-producing, electromagnetic radiation molecules. In conclusion, sunshine is one best example of kinetic energy.

Potential Energy

Potential energy has the ability to accomplish work. Likewise, it is conceivable for a thing to do work in a particular state. Objects exchange energy between potential and kinetic states. The wrecking ball has 0 percent kinetic energy and 100 percent potential energy as it hangs stationary.

So the ball’s kinetic energy grows as it accelerates. In reaching the earth, the ball loses energy. Similarly, a parachute jumper jumping off from an airplane is also an example of potential energy.

Chemical Energy

Potential energy is connected to both location and structure of matter. A squeezed spring on the ground has potential energy. Likewise, with atoms, when molecular bonds that hold atoms together have potential energy. Chemical energy is a form of potential energy.

Cars run on chemical energy present in gasoline molecules. Breaking chemical bonds produces energy that drives the pistons when gas ignites. The energy held in chemical bonds can be used to power biological activities.

In conclusion, different metabolic processes degrade organic molecules, releasing energy for an organism to develop and thrive.

How Living Organisms Make Use of Energy?

Almost everything consumes sunlight – or consumes something that consumes sunlight. The sun is the primary source of energy for species and the environments that they inhabit. Plants and algae, for example, use sunlight energy to create food energy by mixing carbon dioxide and water. Moreover, this process initiates the transfer of energy through virtually all food webs.

Similarly, humans. It is through the breakdown of food molecules that cells are able to store energy. It carries out the numerous functions that cells, and consequently the entire organism, perform.

Energy is a property that can perform everyday functions in all living beings. It is essential for growth, survival, reaction to stimuli, reproduction, and all other biochemical functions. Therefore, living things require energy to function, because of that they cannot survive on their own.

So, how do living organisms make use of energy? Here are some examples:

1. Tissues and Cells of Living Things Needs Energy to Grow and Repair

The availability of energy is critical for cell growth and development. Every step of the process of assembling larger molecules from smaller ones requires the use of energy. Therefore, when cells lack energy, it makes it difficult for them to grow and repair themselves.

2. Living Organisms Uses Energy to Transport Nutrients Throughout the Cells

Plants need energy in order for nutrients to circulate through them. Likewise, substances are also transported into and out of cells similarly. To get carbs, proteins, lipids, and other complex molecules from the gut to the circulation, animals need energy.

3. Living Organisms Generate Energy Through Movement

All living things are in motion. Hence, It is necessary to put out some effort in order for things to happen. Energy is expended in cell division, muscle contraction, heartbeat, walking, running, talking, and reading.

4. Living Organisms Make Use of Energy to Regulate Temperature

Animals must expend a lot of heat energy to keep their internal temperature steady. Similarly, humans use about 70% of the energy retained from breathing to maintain their body temperature. Smaller animals must utilize nearly all of their respiratory energy to maintain a steady body temperature.

How Do Living Organisms Obtain Energy?

Energy is the ability to perform tasks. This power is produced in several ways, but the Sun is the main energy source. Food provides energy to living beings. They either prepare their own food or rely on others to prepare it for them.

The three sources of food are as follows:


Autotrophic organisms are primary consumers that generate their own food. Likewise, all other animals require food. Green plants are autotrophs. Hence, autotrophs produce food by a process called photosynthesis.

Photosynthesis is the process whereas green plants use chlorophyll in their cells. This is in conjunction with solar energy to synthesize glucose from water, air, and carbon dioxide. Photosynthesis cannot occur without the energy of the sun, and green plants cannot create food. As a result, secondary consumers would be unable to obtain food if plants did not produce food. There would be no energy if there was no food, and without energy, that living thing would perish.


Heterotrophs are secondary consumers. They rely on green plants to create the food that they ultimately devour in order to gain their own energy. Heterotrophs either directly or indirectly absorb plant nourishment. Herbivores, carnivores, and omnivores are among them. Herbivores get their energy from plants, whereas carnivores devour other herbivorous animals or lesser carnivores. Omnivores receive their energy by consuming both herbivorous and carnivorous creatures.


Chemotrophs are organisms that get their energy from chemical reactions other than those used by plants. The oxidation of electron contributors located around them helps them to acquire their energy. Thus, a chemotroph is something like a bacterium.

Living Organisms : Energy Production and Utilization

All living organisms need the energy to be able to develop, reproduce, conserve their structures and react to their environments.

Metabolism is a collection of chemicals that enables organisms to convert molecular-based chemical energy into energy. Thus, allowing the living thing to use it for cellular activity. Animals eat to replenish their energy stores; their metabolism breaks down carbs, lipids, proteins, and nucleic acids to create chemical energy for these functions. Photosynthesis converts solar light energy into chemical energy contained in molecules.


Metabolism refers to the chemical reactions that occur in the cells of living creatures in order to sustain life. Metabolic processes drive development and reproduction, allowing living creatures to maintain their structures and respond to their surroundings. Metabolism includes all chemical reactions that occur in living organisms. Starting from digestion to the movement of chemicals from cell to cell.

Categories of Metabolism: Catabolism and Anabolism

Catabolism is the breakdown of organic matter. On the other hand, anabolism is the utilization of energy to produce cell components such as proteins and nucleic acids.

Metabolic pathways organize metabolic processes. Thus, a single molecule undergoes multiple chemical changes. Enzymes aid in this process by facilitating and catalyzing reactions. Enzymes, which respond to cell signals and govern metabolic pathways, are required for the processes. The metabolic rate is how quickly the body burns calories.

A live organism’s metabolism helps it to identify which compounds are nutritional and beneficial and which are toxic. Substances and organism parts involved in the metabolic process include amino acids, proteins, lipids, carbohydrates, nucleotides, coenzymes, minerals, and cofactors.

Let us further explore the two categories of metabolism below.


Anabolism is the process through which the body uses catabolic energy to create complex compounds. These complicated compounds are then used to construct small and basic cellular structures.

Stages of Anabolism

Anabolism is divided into three stages.

  • Production of precursors such as amino acids, monosaccharides, isoprenes, and nucleotides happens in first stage.
  • Second Stage entails converting these precursors into reactive forms with the help of ATP energy.
  • Assembly of precursors into complex molecules like proteins, polysaccharides, lipids, and nucleic acids happens in the last stage.

Energy Sources for Anabolic Processes

Different organisms rely on different sources of energy. Autotrophs, such as plants, may use sunlight to produce complex organic compounds in cells such as polysaccharides and proteins. It originates from simple molecules such as carbon dioxide and water.

In contrast, heterotrophs require sources of complex molecules, such as monosaccharides and amino acids. These can be produced from more complex components.

Photoautotrophs and photoheterotrophs derive their energy from light, whereas chemoautotrophs and chemoheterotrophs derive their energy from inorganic oxidation reactions.

Anabolism in Carbohydrates

It turns simple organic acids into monosaccharides like glucose, which are then utilized to build polysaccharides like starch. The process of gluconeogenesis involves pyruvate, lactate, glycerol, glycerate 3-phosphate, and amino acids. Gluconeogenesis uses intermediates from glycolysis to convert pyruvate to glucose-6-phosphate.

Gluconeogenesis cannot usually convert adipose tissue fatty acids to glucose because these organisms cannot convert acetyl-CoA to pyruvate. The brain cannot metabolize fatty acids. Therefore, humans and other animals must create ketone bodies from fatty acids to replace glucose.

Plants and bacteria use the glyoxylate cycle to bypass the decarboxylation phase in the citric acid cycle. It then converts acetyl-CoA to oxaloacetate. This produces glucose.

Glycans and polysaccharides are sugar compounds. Glycosyltransferase transfers a reactive sugar-phosphate donor, like UDP-glucose, to an acceptor hydroxyl group on the developing polysaccharide. The hydroxyl groups on the substrate’s ring can act as acceptors, resulting in straight or branched polysaccharides. Oligosaccharyltransferases can transfer these polysaccharides to lipids and proteins.

Anabolism of Proteins

Amino acids make proteins. Most species can produce a few of the 20 amino acids. Most microorganisms and plants can synthesize all twenty, while mammals can only synthesize 10.

Peptide bonds connect amino acids to produce polypeptide chains. This is the fundamental structure of each protein. To make a protein, the polypeptide chain is folded and restructured.

It takes a lot of energy to make nucleotides from amino acids, CO2, and formic acid.

Purine nucleosides (bases attached to ribose). Inosine monophosphate produces adenine and guanine. Glycine, glutamine, and aspartic acid atoms generate these, as does formate from coenzyme tetrahydrofolate.

They are made from orotate, which is made from glutamine and aspartate.

Anabolism of Fatty Acids

To make fatty acids, acetyl-CoA units are polymerized, then depolymerized. The acyl chains of these fatty acids are expanded into an alkaline group. Dehydration converts them to alkanes.

In mammals and fungi, a single multifunctional type I protein performs all of these functions. Separate type II enzymes perform each step in the route in plants, plasmids, and bacteria.

Carotenoids are the largest class of natural plant compounds, together with other lipids such as terpenes and isoprenoids. Thus, the reactive precursors isopentenyl pyrophosphate and pyrophosphate assemble and modify isoprene units. The mevalonate pathway produces acetyl-CoA in mammals and archaea.


Catabolism is the breakdown of big molecules like polysaccharides, nucleic acids, and proteins.

Energy is produced by smaller molecules such as monosaccharides, nucleotides, and amino acids. It is the destructive branch of metabolism that results in energy release. Each living cell relies on energy to survive. Catabolism and anabolism coexist to make metabolism.

Stages of Catabolism

Catabolism is not a one-step process that occurs in a cell. It is critical to understand where catabolism takes place. The mitochondrial complex is the primary site of catabolism in the cell. It is a multi-step procedure. So, first, let’s go over the stages of catabolism.

Step 1 is the digestion stage.

Outside the cells are discharged monomerized polysaccharides, lipids, and proteins. Absorption of these complex chemicals is not possible. It is necessary to break down these critical molecules into smaller components for absorption.

The second stage is the release of energy.

More readily, the absorption of smaller molecules (monomers) by cells. Subsequently, they are transformed into smaller, energy-releasing molecules like acetyl-coenzyme A (acetyl-CoA).

Stage 3 – Energy Capture & Storage

CoA’s acetyl group is finally reduced to water and CO2. In this phase, the stored energy is released by reducing NAD+ to NADH.

Prokaryotic Catabolism

Prokaryotes need energy and carbon to survive. Most prokaryotes, known as chemoheterotrophs, rely on other species for energy and carbon.

Prokaryotes get their carbon and energy from:

Prokaryotes are classified by their carbon source:

  • Autotrophs, as previously mentioned, are organisms that utilize carbon dioxide as a source of carbon. Photoautotrophs are food producers who use light to prepare their products.
  • Heterotrophs are creatures that utilize carbon from other living species.
  • Lithotrophs are organisms that feed on inorganic materials.

Based on their energy metabolism, prokaryotes are classified as:

  • Phototrophic organisms use sunlight to generate chemical energy in their cells.
  • Chemoautotrophs utilize inorganic chemicals to provide cell energy and carbon dioxide as a source of carbon.

As a consequence, all animals fall into four categories:

  1. Photoheterotrophs utilize sun energy to create chemical energy in their cells, using other species’ carbon as a carbon source. Purple-green bacteria, non-sulfur bacteria, and heliobacteria are among examples.
  2. Chemoheterotrophs are organisms that get both their energy and carbon from organic sources. This method is widespread in eukaryotes, such as humans.
  3. Photoautotrophs, such as cyanobacteria, derives their carbon from sunlight.
  4. Chemoautotrophs utilize inorganic substances as a source of carbon energy to provide cell and carbon dioxide. Prokaryotes that degrade hydrogen sulfide and ammonia are two examples.

Catabolism in Prokaryotes

Nitrogen is an essential macronutrient for all biological processes and components, including protein and nucleic acid. Prokaryotes recycle ambient organic molecules via a variety of mechanisms to produce ammonia, ammonium ions, nitrate, nitrite, and nitrogen gas.

In the nitrogen cycle, Prokaryotes play an essential role. Plants, with the assistance of prokaryotes, convert atmospheric nitrogen into a useful form (ammonia). Thus, referred to as nitrogen fixation. Azotobacteria and archaea referred to as diazotrophs, perform nitrogen fixation in the soil.

Ammonia is formed when nitrogen-containing organic compounds decompose. Certain prokaryotes nitrify ammonia anaerobically to produce N2. Essentially, nitrification converts ammonium to nitrite and nitrate.

Nitrosomonas is a nitrifying bacteria found in soil. Nitrosomonas, Nitrobacter, and Nitrospira oxidize NH4+ to produce nitrite (NO2). Hence, the bacteria employ this chemical reaction to release energy. Rather, the microorganisms help with denitrification. It produces gaseous molecules like N2O, NO, and N2 from nitrate in the soil.

Bacteria and fungus break down plants, animals, and their organic components. Therefore, they constitute the decomposer family. Microbial decomposition of the dead matter is a significant source of ambient carbon dioxide.


All living organisms require energy to carry out their functions. Metabolism is a sequence of chemical reactions that generate energy for biological functions. Even when we aren’t aware of it, our bodies are constantly in need of energy.

Automobiles run on the chemical energy contained in gasoline molecules. To regulate their body temperature, animals must expend a lot of heat energy. Humans require energy in order to grow and repair themselves. All living organisms require energy to develop, reproduce, conserve their structures and respond to their surroundings.

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