Key difference - photosynthesis vs. cellular respiration

Photosynthesis and cellular respiration are two fundamental metabolic processes that take place in the energy conversion of ecosystems. Photosynthesis uses carbon dioxide and water to synthesize organic compounds with the help of sunlight. These organic compounds can be used by cells as food. During cell respiration, energy is generated in the form of ATP through the breakdown of food. The main difference between photosynthesis and cellular respiration is that photosynthesis is an anabolic process in which the synthesis of organic compounds takes place and stores energy, while cellular respiration is a catabolic process in which the stored organic compounds are used to produce energy .

This article examines

1. What is photosynthesis - definition, properties, types, process 2. What is cellular respiration - definition, properties, types, process 3. What is the difference between photosynthesis and cellular respiration?

What is photosynthesis?

Photosynthesis is the production of glucose from carbon dioxide and water by extracting energy from sunlight. Oxygen gas is a by-product of photosynthesis. Pigments like chlorophyll, carotenoids and phycobilins are used to capture the light energy. Therefore, during photosynthesis, light energy is converted into potential chemical energy. Glucose then provides the metabolic energy for all cellular processes in the cell.

Types of photosynthesis

Oxygen photosynthesis and anoxygen photosynthesis are the two types of photosynthesis that occur on earth. Plants, algae and cyanobacteria carry out photosynthesis containing oxygen, while purple sulfur bacteria and green sulfur bacteria carry out anoxygenic photosynthesis. The electron donor in oxygen-containing photosynthesis is water, while the electron donor in anoxygenic photosynthesis is a variant such as hydrogen sulfide and not water. As a result, no oxygen gas is released as a by-product during anoxygenic photosynthesis. The chemical reactions of both oxygenated and anoxygenic photosynthesis are shown below.

Figure 1: Photosynthesis in a plant

In plants, photosynthesis takes place in specialized plastids called chloroplasts , which are found in the cytoplasm of photosynthetic cells. Photosynthesis occurs in thylakoid membrane and stromal regions of chloroplasts. The first stage of photosynthesis is the light reaction . In Grana's thylakoid membrane there are photo centers that organize the photosynthetic pigments in it. The light is absorbed by photosystems I and II , the two protein complexes found in the thylakoid membrane, and the absorbed light is transmitted to photo centers. The generating high-energy electrons are transferred to the third protein complex, the cytochrome bf complex. The high energy electrons in PSI are transferred to a series of ferrodoxin carriers and eventually these electrons are transferred to NADP + by the NADPH reductase enzyme, thereby forming NADP. During the light reaction, oxygen gas is generated by splitting water, while NADP and ATP are produced.

The second stage of photosynthesis is the dark reaction , in which the NADPH and ATP formed during the light reaction are used as energy sources for the synthesis of glucose. A dark reaction occurs in the stroma. The dark reaction is also called the Calvin cycle . In addition to glucose, 18 ATP and 12 NADPH are produced during the Calvin cycle. The 18 ATPs are used by the Calvin cycle itself. The 12 NADPH contain 24 electrons that are transported into the electron transport chain , which is the third stage of photosynthesis. The ATP synthase enzyme on the thylakoid membrane transfers the 24 electrons into 12 water molecules, producing 6 oxygen molecules. This process of electron transport is called photophosphorylation . The process of photosynthesis is shown in Figure 2 .

Figure 2: Photosynthetic mechanism

What is cellular respiration

Cellular respiration is the process that converts the biochemical energy in ATP into energy, eliminating carbon dioxide and water as waste products. It occurs in all organisms living on earth. Stored foods such as carbohydrates, fats and proteins are used in organisms in the form of glucose through cell respiration.

Types of cellular respiration

Aerobic breathing and anaerobic breathing are the two types of breathing on earth. In aerobic respiration , the oxidizing agent, or the last electron acceptor, is molecular oxygen. One glucose molecule contains enough energy to produce 30 ATPs through oxidative phosphorylation. During anaerobic respiration , the last electron acceptor is either inorganic sulfates or nitrates. Anaerobic respiration takes place in hydrothermal springs in the deep sea. Fermentation is also a type of anaerobic respiration that occurs when pyruvate is metabolized in the cytoplasm without oxygen. Lactic acid fermentation in muscle cells and ethanol fermentation in yeast are the two types of fermentation among organisms. During fermentation, only two ATPs are produced per glucose molecule. The chemical reaction of cellular respiration is shown below.

Figure 3: Cellular respiration in humans

In eukaryotes , cell respiration takes place in specialized organelles, the mitochondria . In prokaryotes , it occurs in the cytoplasm itself. Cell respiration also takes place in the matrix, the inner membrane of the mitochondria, and in the cytoplasm. The first stage of cellular respiration is glycolysis . Glycolysis breaks down glucose (C6) in the cytoplasm into two pyruvate (C3) molecules. Then two pyruvate molecules are imported into the mitochondria. In the presence of oxygen, pyruvate combines with oxaloacetate (C4) to form citrate (C6) and eliminates acetyl-CoA during the citric acid cycle. The citric acid cycle is the second phase of cellular respiration, also known as the Krebs cycle . During the Krebs cycle, carbon dioxide is eliminated as waste, while NAD is reduced to NADH. 6NADH, 2FADH ₂ and 2ATPs per one glucose molecule are produced by the Krebs cycle. Oxidative phosphorylation , the third stage of cell respiration, takes place in the mitochondrial cristae by the enzyme ATP synthase, which produces 30ATPs. The process of cell respiration is shown in Figure 4 .

Figure 4: Cell respiration mechanism

Difference between photosynthesis and cellular respiration

presence

Photosynthesis: Photosynthesis is only found in chlorophyll cells.

Cellular respiration : Cellular respiration is found in all cells on earth.

definition

Photosynthesis: Photosynthesis is the production of glucose from carbon dioxide and water by extracting energy from sunlight.

Cellular respiration : Cellular respiration is the process that converts the biochemical energy in ATP into energy, eliminating carbon dioxide and water as waste products.

Organelles

Photosynthesis: Photosynthesis takes place in the thylakoid membrane and in the stroma of chloroplasts in plants.

Cellular respiration : Cellular respiration takes place in the matrix and inner membrane of mitochondria and cytoplasm in eukaryotes.

Darkness / light

Photosynthesis: Photosynthesis only takes place in light.

Cellular respiration : Cellular respiration occurs in both light and dark.

steps

Photosynthesis: light reaction, dark reaction and photolysis are the three steps of photosynthesis.

Cellular respiration: glycolysis, citric acid cycle and electron transport chain are the three steps of cellular respiration.

Oxygen / carbon dioxide / water

Photosynthesis: During photosynthesis, carbon dioxide and water are used and oxygen is released.

Cellular respiration: Oxygen is used and carbon dioxide and water are released during cellular respiration.

metabolism

Photosynthesis: Photosynthesis is an anabolic process that synthesizes complex organic compounds.

Cellular respiration : Cellular respiration is a catabolic process that breaks down organic compounds.

carbohydrates

Photosynthesis: Carbohydrates are synthesized during photosynthesis.

Cellular respiration : Carbohydrates are used during cellular respiration.

energy

Photosynthesis: During photosynthesis, energy is stored. Therefore photosynthesis is an endothermic process.

Cellular respiration : During cellular respiration, energy is released. Therefore cell respiration is an exothermic process.

Form of energy

Photosynthesis: Chemical energy is stored in the bonds of the organic compounds that are formed.

Cellular respiration: Energy is released in the form of ATP, which can be used by other cell processes.

Dry weight

Photosynthesis: The dry weight of the plant is increased during photosynthesis.

Cellular respiration : The dry weight of the organism is reduced during cellular respiration.

Type of phosphorylation

Photosynthesis: Photophosphorylation occurs during photosynthesis.

Cellular respiration : Oxidative phosphorylation occurs during cellular respiration.

Energy conversion

Photosynthesis: During photosynthesis, light energy is converted into potential energy.

Cellular respiration : In cellular respiration, potential energy is converted into kinetic energy.

Final electron acceptor

Photosynthesis: The last electron acceptor is water.

Cellular respiration: the last electron acceptor is molecular oxygen.

Pigments

Photosynthesis: Chlorophyll is the main type of pigment involved in photosynthesis.

Cell respiration : Pigments are not involved in cell respiration.

Coenzymes

Photosynthesis: NADP is the coenzyme used in photosynthesis.

Cellular respiration : NAD and FAD are the coenzymes used in cellular respiration.

diploma

Photosynthesis and cell respiration are the two most important metabolic processes that take place in organisms and drive all cell processes in the body. Photosynthesis only takes place in organisms that are soluble in chlorophyll. It has the highest contribution to the production of food for all living things on earth. Therefore photosynthetic organisms are found as primary producers in food chains. Photosynthesis uses the energy of sunlight to produce glucose from carbon dioxide and water. Photosynthetic organisms contain special pigments such as chlorophyll and carotenoids to capture light. In contrast, cell respiration occurs in all living things on earth. During breathing, food is oxidized in order to preserve the potential energy stored in the form of ATP. ATP drives almost all cellular processes in the cell. Carbon dioxide and water are produced as waste during cell respiration. Photosynthesis releases oxygen gas that can be used in cell respiration. Hence, the main difference between photosynthesis and cellular respiration is their contribution to a cell's metabolism.

Reference: Cooper, Geoffrey M. "Photosynthesis". The cell: a molecular approach. 2nd Edition. US National Library of Medicine, January 1, 1970. Web. April 03, 2017. Berg, Jeremy M. “The Citric Acid Cycle”. Biochemistry. 5th edition. US National Library of Medicine, January 1, 1970. Web. April 04, 2017. Cooper, Geoffrey M. "Metabolic Energy". The cell: a molecular approach. 2nd Edition. US National Library of Medicine, January 1, 1970. Web. April 04, 2017.

Image courtesy: 1. "Photosynthesis pictures" by Masroor.nida.ns - Own work (CC BY-SA 4.0) via Commons Wikimedia 2. "Photosynthesis" by Cykl_Calvina.svg: PisumThylakoid_membrane.svg: YikrazuulThylakoide.png: Tameeria pour la version Anglaise, Pascal la traductionderivative work: Marek M (lecture) - Cykl_Calvina.svgThylakoid_membrane.svgThylakoide.png (CC BY-SA 3.0) via Commons Wikimedia 3. "Energy and Life" By Mikael Häggström - All images are from the public domain license .File: Pikilia. JPG (Public Domain) via Commons Wikimedia 4. “CellRespiration” By RegisFrey - Own work (CC BY-SA 3.0) via Commons Wikimedia