The key difference between photosynthesis and cellular respiration is that photosynthesis utilizes carbon dioxide and water to produce glucose and oxygen while cellular respiration utilizes glucose and oxygen to produce energy, carbon dioxide, and water.
Photosynthesis and cellular respiration are two cellular processes that occur in organisms in order to produce energy. Photosynthesis converts the light energy of the sun into chemical energy of sugar by releasing oxygen as a byproduct. On the other hand, cellular respiration is a biochemical process by which cells obtain energy from the chemical bonds of food molecules. Photosynthesis and cellular respiration are key processes of life. This article highlights the difference between photosynthesis and cellular respiration.
CONTENTS
1. Overview and Key Difference
2. What is Photosynthesis
3. What is Cellular Respiration
4. Similarities Between Photosynthesis and Cellular Respiration
5. Side by Side Comparison – Photosynthesis vs Cellular Respiration in Tabular Form
6. Summary
What is Photosynthesis?
Photosynthesis is a process that is carried out by photoautotrophs. Photoautotrophs produce their own food by this process. Plant, algae, and cyanobacteria are the main groups of photoautotrophs. During photosynthesis, using the light energy of sunlight, carbon dioxide, and water transform into glucose and oxygen when photosynthetic pigments are present. Oxygen, which is important to all living beings, is released to the atmosphere as a byproduct of photosynthesis. Photosynthesis is a very crucial process which allows life to continue on earth. Oxygen produced through photosynthesis is essential for the process of respiration of most living creatures on earth. Carbohydrate produced by photosynthesis is the simplest form of food that could be processed by living organisms to obtain energy.
Figure 01: Photosynthesis
The following equation is the most common form of summarizing photosynthesis:
Carbon Dioxide (6CO2) + Water (6H2O) —-converted with help of light energy -→ Glucose (C6H12O6) + Oxygen (6 O2)
Photosynthesis can be divided into two main processes: light dependent (light reaction) process and light independent (dark reaction) process. Light-dependent photosynthesis needs actual sunlight to react, whereas dark reaction only needs the products of the light reaction to proceed. Light reaction needs the photons and water to give out oxygen leading to the production of ATP and NADPH. NADPH is a reducing agent that can reduce its hydrogen molecule.
Dark reaction photosynthesis, also known as the Calvin cycle, use Carbone dioxide and the newly formed NADPH to produce phosphogylcerides; the three carbon sugars could combine later to form sugar and starch. Plants store these produced sugar and starch in the forms of fruits and yams, etc. for future use. Most other living organisms depend on these carbohydrates produced by plants through photosynthesis. Hence, photoautotrophs serve as primary producers in almost every food chain in an ecosystem.
What is Cellular Respiration?
Cellular respiration is a biochemical process by which cells convert the chemical energy of macromolecules into energy in the form of ATP. Cellular respiration uses carbohydrates, fats, and proteins as fuels. Glucose is the most commonly utilized energy source in cellular respiration. All living organisms carry out respiration: aerobic respiration in the presences of oxygen, and anaerobic respiration in the absence of oxygen. Prokaryotic cells carry out cellular respiration in the cytoplasm whereas eukaryotic cells carry out cellular respiration mostly inside the mitochondria of the cell. In aerobic respiration, one glucose molecule can generate 36-38 molecules of ATP, but in anaerobic respiration (through glycolysis and fermentation) only 2 ATP molecules could be derived.
Figure 02: Cellular Respiration
Moreover, cellular respiration can be divided into three metabolic processes as glycolysis, Krebs cycle and electron transport chain. Glycolysis occurs in the cytosol while Krebs cycle occurs in the mitochondrial matrix. Electron transport chain occurs at the inner mitochondrial membrane. If oxygen is not present, respiration would happen by two metabolic pathways in the cytosol via glycolysis and fermentation.
What are the Similarities Between Photosynthesis and Cellular Respiration?
- Photosynthesis and cellular respiration are vital processes of living organisms.
- Furthermore, both processes depend on each other.
- They are complementary to each other.
What is the Difference Between Photosynthesis and Cellular Respiration?
Photosynthesis is a process that converts light energy into chemical energy of carbohydrates in the presence of sunlight and chlorophylls. Whereas, cellular respiration is a process that converts the chemical energy of organic compounds into ATP (energy currency) in order to use it for all functions occurring in living organisms. So, this is the key difference between photosynthesis and cellular respiration. Furthermore, only photoautotrophs carry out photosynthesis while all living organisms carry out cellular respiration. Hence, this is also a difference between photosynthesis and cellular respiration.
Moreover, a further difference between photosynthesis and cellular respiration is that the photosynthesis utilizes carbon dioxide and water and produces glucose and oxygen while cellular respiration utilizes glucose and oxygen and produces carbon dioxide, water, and energy. Additionally, photosynthesis occurs via two steps: light reaction and dark reaction. In contrast, cellular respiration occurs via three steps: glycolysis, Krebs cycle and electron transport chain. Besides, the site of photosynthesis is chloroplasts while the sites of cellular respiration are cytoplasm and mitochondria. Therefore, we can consider this too as a difference between photosynthesis and cellular respiration.
Summary – Photosynthesis vs Cellular Respiration
In summary, both photosynthesis and cellular respiration are important processes occuring in living organisms in order to obtain energy. However, photosynthesis stores the energy of sunlight in the form of chemical energy in sugar and starch molecules while cellular respiration breaks down organic compounds such as sugar and starch in order to produce energy in the form of ATP (energy currency). Both these processes are dependent on each other; animals feed on fruits produced by plants to obtain organic compounds for their cellular respiration; they also use the oxygen released into the air to breath while plants in turn depend on carbon dioxide exhaled by animals into the air for the process of photosynthesis. In the absence of one, the chances of survival for the other drastically degrade. Thus, this concludes the summary of the difference between photosynthesis and cellular respiration.
Reference:
1. “Photosynthetic Cells.” Nature News, Nature Publishing Group, Available here.
2. “Cellular Respiration.” Wikipedia, Wikimedia Foundation, 22 Feb. 2019, Available here.
Image Courtesy:
1. “Photosynthesis en” By At09kg: originalWattcle : vector graphics – This file was derived from Photosynthesis.gif (CC BY-SA 4.0) via Commons Wikimedia
2. “Cellular respiration” By Darekk2 – Own work (CC BY-SA 3.0) via Commons Wikimedia