What are the similarities and differences between the processes of photosynthesis and cellular respiration?

When you go through the concepts of cellular respiration and photosynthesis, you are bound to find some striking similarities. Nonetheless, fundamentally they are quite different from one another.

Before we head straight to the differences between respiration and photosynthesis, let’s become familiar with the concepts. In turn, it will help to differentiate the two more effectively.

What is Photosynthesis?

It occurs only in cells that have chlorophyll and can only take place in the presence of sunlight. The said process uses water and carbon dioxide and produces oxygen and carbohydrates as by-products. 

It is noteworthy that light energy is changed into chemical energy during photosynthesis. Also, hydrogen released through photolysis is absorbed by NADP, which in turn gets reduced into NADPH2. 

It is expressed as 6CO2 + 6H2O \[\longrightarrow\] C6H12O6 + 6O2

Hence, Calvin Cycle forms an integral part of photosynthesis.

What is Cellular Respiration?

Essentially, it is an ongoing catabolic process. The process uses carbohydrates and oxygen and releases water and carbon dioxide as end products. Notably, on oxidation, the energy released through carbohydrates and other vital substrates gets absorbed in ATP. Nevertheless, a fraction of energy is lost as heat amidst the process.

Furthermore, during the simultaneous process of oxidative phosphorylation, ATP molecules are produced from the oxidation of carbohydrates. Subsequently, synthesized ATP is used during various stages of the metabolic process. Additionally, glycolysis and oxidation of pyruvic acid take place during cellular respiration. 

It is expressed as C6H12O6 + 6O2 \[\longrightarrow\] 6CO2 + 6H2O

Are you still wondering - “How are photosynthesis and cellular respiration different?” Check below to know more.

Differences between Photosynthesis and Respiration

It must be noted that despite being a similar process, photosynthesis and respiration takes place in reverse. For instance, in photosynthesis, the input, namely, water and carbon dioxide, generates glucose and oxygen as by-products. On the other hand, in cellular respiration, oxygen and Glucose release water and carbon dioxide as by-products.

Also, in photosynthesis, the sun’s light energy is first converted into chemical energy and is then stored in glucose bonds. Conversely, in cellular respiration, the chemical energy in Glucose is released to yield ATP. Likewise, both follow a different metabolic process. For instance, photosynthesis follows an anabolic process. In the metabolic process, the carbon dioxide and energy produced from NADPH and ATP are utilized to create Glucose molecules. 

Similarly, cellular respirations follow a catabolic process. Glucose is broken down for the production of ATP, FADH2, NADH, and carbon dioxide. 

Look at the table below to check out the fundamental difference between photosynthesis and respiration in a nutshell.

DIY: What are photosynthesis and cellular respiration? Explain in your own words. 

Similarities between Photosynthesis and Respiration

Despite the difference between photosynthesis and respiration, both processes are interdependent. Let’s take a quick look at the comparison between photosynthesis and respiration from the figure below. 

It also answers the query of – “What is the difference between respiration and photosynthesis?” in brief. 

Conclusion

This is all about the meaning, explanation, and difference between photosynthesis and respiration. Learn how both biological processes are different from each other in different aspects. Concentrate on the features of these biochemical processes to understand the differences perfectly. 

Photosynthesis vs. Cellular respiration

Photosynthesis and cellular respiration are complementary processes by which living things obtain needed substances. They both consume and create the same substances (water, glucose, oxygen, and carbon dioxide) but in different ways. Through these processes, plants obtain the carbon dioxide they need and living organisms obtain the oxygen they need. They are also necessary to the energy exchange that living things need to survive.

Photosynthesis is the process by which green plants create their own food by turning light energy into chemical energy. Chlorophyll in the leaves transform carbon dioxide, water, and minerals into oxygen and glucose. Photosynthesis takes place in the chloroplasts of cells. This process is what gives energy to all living organisms either directly or indirectly. Without it, life on Earth would cease to exist.

Cellular respiration, on the other hand, is the process by which living things convert oxygen and glucose to carbon dioxide and water, thereby yielding energy. It does not require the presence of sunlight and is always occurring in living organisms. Cellular respiration takes place in the mitochondria of cells.

While photosynthesis requires energy and produces food, cellular respiration breaks down food and releases energy. Plants perform both photosynthesis and respiration, while animals can only perform respiration.

In many respects, photosynthesis and cell respiration are complementary reactions within the environment

• The products of photosynthesis function as the inputs of cell respiration (oxygen and glucose)
• The products of cell respiration function as the inputs of photosynthesis (carbon dioxide and water)

Most producers (i.e. photoautotrophs) undertake both photosynthesis and cell respiration to survive

• Consumers (i.e. heterotrophs) only undertake cell respiration, but will ingest or absorb photosynthetic products

Interrelationship Between Processes

Similarities

Photosynthesis and cell respiration both involve the production of chemical energy (ATP)

• In photosynthesis, ATP is produced via light energy (photophosphorylation) and used to make organic molecules
• In cell respiration, ATP is produced by breaking down organic molecules (oxidative phosphorylation)

In both cases, the production of ATP involves an electron transport chain and chemiosmosis

• In photosynthesis, electrons are donated by chlorophyll and protons accumulate within the lumen of the thylakoid
• In cell respiration, electrons are donated by hydrogen carriers and protons accumulate in the intermembrane space

Comparison of ATP Production

Differences

Photosynthesis and cell respiration are in many respects the reverse of one another

• Photosynthesis is an anabolic process, whereas cell respiration is a catabolic process

Photosynthesis:

• Water is broken down to oxygen to release electrons for an electron transport chain
• Electrons from the transport chain are taken up by hydrogen carriers (NADPH specifically)
• Uses the Calvin cycle to synthesise glucose (requires hydrogen carriers and carbon dioxide)

Cell Respiration:

• Uses the Krebs cycle to break down glucose (releases hydrogen carriers and carbon dioxide
• Hydrogen carriers release electrons for an electron transport chain (NADH and FADH2 specifically)
• Electrons from the transport chain are taken up by oxygen (to form water)

Differences Between Photosynthesis and Cell Respiration