Energy in Biological Systems

Energy is a fundamental concept in all areas of biology, particularly in understanding the processes of respiration and other metabolic activities. It’s important to understand how energy operates in biological systems, how it’s transferred and converted, and how it propels various life-sustaining processes.

Forms of Energy

Biological systems utilise different forms of energy including chemical, heat, light, and mechanical energy.
Chemical energy is stored in the bonds between atoms in molecules. This is the prime energy used in biological systems.
Thermal / heat energy is commonly a byproduct of energy conversions in organisms.
Light energy is crucial for photosynthetic organisms as it’s used to convert carbon dioxide and water into glucose and oxygen.

Energy Conversion

Energy is often converted from one form to another in biological systems, a process known as energy transduction.
An example of this is in photosynthesis where light energy is converted into chemical energy.
Another example is in cell respiration where chemical energy in glucose is converted into a form useable by the cell (ATP).
Note that in energy conversions, no energy is lost but some may be converted into less useful forms, primarily heat, following the “Law of Energy Conservation”.

ATP: The Energy Currency

Adenosine triphosphate (ATP) is often referred to as the ‘energy currency’ of the cell.
ATP is characterized by high-energy phosphate bonds. The breakdown of ATP into adenosine diphosphate (ADP) and inorganic phosphate (Pi) releases energy for cellular work.
ATP formation happens during cell respiration, specifically in the mitochondria via a process called oxidative phosphorylation.
It can also form during glycolysis and the Krebs cycle, both of which are stages of cellular respiration.

Energy Storage

Organisms store energy for future use. In plants, energy is prominently stored as starch while in animals it’s stored as glycogen.
Another form of energy storage in animals is fat stored in adipose tissue. This is a long-term storage system and is tapped into during periods of starvation.

Energy Flow in Ecosystems

Energy flow in ecosystems follows the ‘Ecosystem Energy Flow’ model where energy from the sun is absorbed by plants (producers) and transferred up the food chain to herbivores (primary consumers), carnivores (secondary consumers), and on to apex predators (tertiary consumers).
This flow is often depicted as a flow diagram or a pyramid of energy.
Note, at each level of the energy flow, there is notable loss of energy, primarily as heat, leading to the energy pyramid being narrower at the top.

Remember, understanding the role and behavior of energy in biological systems is essential for understanding fundamental processes such as respiration, photosynthesis, energy storage and ecologic systems.