Visual Guide: Stages of Cellular Respiration Explained
A set of metabolic reactions and processes that helps the organisms to convert chemical energy into adenosine triphosphate from nutrients or oxygen molecules is called cellular respiration. The catabolic reactions are involved in the respiration process that helps to break down large molecules into smaller particles.
The visual representation of the known information either in the form of graphs or charts or tables or Venn diagrams. By analyzing the meaning of the concept map we will learn the definition of the cellular respiration concept map, it is a graphic representation of the complete process of cellular respiration.
Let us see the cellular respiration map and analyze it by following the steps mentioned below.
Steps Involved in Cell Respiration Concept Map
During the process of cellular respiration, the glucose molecule is broken down into water and carbon dioxide. In the reactions that transfer glucose, some of the ATP molecules are produced along the way. But the maximum number of ATP is produced in the process called oxidative phosphorylation. A series of proteins are embedded in the mitochondria, the movement of the electrons takes place in the electron transport chain reaction during which oxidative phosphorylation occurs.
The electrons that are traveled to the electron transport chain are directly derived from the glucose molecule by some of the electron carriers such as NAD⁺ and FAD and when the gain in the electrons takes place these carriers get converted to form NADH and FADH₂. In the cellular respiration map where ever it is mentioned as “+NADh and + FADH₂”, the molecules are not being added from the scratch instead they are being converted from the electron carriers.
Equations:
NAD⁺ + 2e⁻ + 2H⁺ → NADH + H⁺
FAD + 2e⁻ + 2H⁺ → FADH₂
We will see how the carbon dioxide is obtained from the glucose molecule and how the energy is harvested as NADH/FADH₂ and ATP. Cellular respiration consists of four stages, they include:
Glycolysis is the first process in the cell respiration concept map, in this process a six-carbon sugar molecule called glucose undergoes various forms of chemical transformations to convert as two pyruvate molecules at the end. The pyruvate molecule is an organic three-carbon molecule. The end product of this process is ATP and NADH which is converted from NAD⁺.
The second step that is involved in the cellular respiration concept map is pyruvate oxidation. In this process, the pyruvate that is obtained from the process of glycolysis is transferred to the innermost compartment of mitochondria called the mitochondrial matrix. In the mitochondrial matrix, each of the pyruvate molecules gets converted into a two-carbon molecule that is bound to coenzyme A called acetyl CoA. The end product of this process is the generation of NADH molecules by the release of carbon dioxide.
Citric acid cycle: The acetyl coenzyme that is obtained in the previous step of a cellular respiration mind map combines with the four-carbon molecule to undergo several cycles of reactions to obtain the regenerated four-carbon starting molecule. The final product of this process yields ATP, NADH, and FADH₂ by the release of carbon dioxide.
Oxidative phosphorylation: The NADH and FADH₂ generated in the previous steps, deposit the electron molecules in the electron transport chain by obtaining their original forms such as NAD⁺ and FAD. When these electrons are traveled down the chain the release of energy takes place and this energy is utilized to pump the protons out of the mitochondrial matrix by forming an electron gradient. To form an ATP molecule the protons are transferred back to the matrix with the help of an enzyme called ATP synthase. The end product of the electron transport chain is the formation of water with the acceptance of electrons and protons by oxygen molecules.
The final equation at the end of the cellular respiration is
Glucose + Oxygen → ATP + Carbon dioxide + Water
[Image will be Uploaded Soon]
If the process of glycolysis takes place in the absence of oxygen it is called fermentation. Cellular respiration includes other three steps that require oxygen, they are pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation. Among these, oxygen is directly utilized only in the case of oxidative phosphorylation, but the remaining two processes are dependent on oxidative phosphorylation for the consumption of oxygen.
Conclusion:
The process which is used by all the living organisms in the formation of energy from glucose molecules is cellular respiration. While the autotrophs produce their own glucose molecules by the process of photosynthesis and the heterotrophs obtain their glucose from another organism. However, the process of cellular respiration is the collection of metabolic processes such as glycolysis, citric acid cycle or Krebs cycle, and electron transport chain. While moving from glycolysis to the citric acid cycle the pyruvate molecules obtained from glycolysis are oxidized by a process called pyruvate oxidation. Practice cellular respiration concept maps to understand the process easily and efficiently. Remembering the end products of each step involved is necessary as it can appear in the examination in the form of objectives.
FAQs on Cellular Respiration Concept Map: Pathways & Processes
1. What is the fundamental concept of cellular respiration?
Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy from oxygen molecules or nutrients into adenosine triphosphate (ATP), and then release waste products. It is a catabolic process, meaning it breaks down large molecules like glucose into smaller ones to release energy.
2. What are the major pathways or stages involved in aerobic cellular respiration?
Aerobic cellular respiration is typically divided into four main stages, each occurring in a specific part of the cell:
- Glycolysis: The initial breakdown of glucose in the cytoplasm.
- Pyruvate Oxidation (or Link Reaction): Conversion of pyruvate to acetyl-CoA in the mitochondrial matrix.
- Krebs Cycle (or Citric Acid Cycle): A series of reactions in the mitochondrial matrix that oxidises acetyl-CoA.
- Electron Transport Chain (ETC) and Oxidative Phosphorylation: A process on the inner mitochondrial membrane where the majority of ATP is produced.
3. How does a concept map visually represent the process of cellular respiration?
A concept map of cellular respiration visually illustrates the entire process by connecting its key components. It typically shows glucose as the starting input, branching into glycolysis. The products of glycolysis, like pyruvate, are shown entering the mitochondria for the Krebs Cycle. Arrows indicate the flow of energy-carrying molecules like NADH and FADH₂ from these stages to the Electron Transport Chain, culminating in the production of ATP. This visual roadmap helps clarify the sequence and interconnection of these complex pathways.
4. What is the overall chemical equation for aerobic cellular respiration?
The balanced chemical equation that summarises the entire process of aerobic cellular respiration is:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (approx. 36-38 ATP)
This equation shows that one molecule of glucose (C₆H₁₂O₆) reacts with six molecules of oxygen (O₂) to produce six molecules of carbon dioxide (CO₂), six molecules of water (H₂O), and a significant amount of energy in the form of ATP.
5. What are the key differences between aerobic and anaerobic respiration?
The primary difference lies in the requirement for oxygen. Aerobic respiration requires oxygen as the final electron acceptor, occurs in both the cytoplasm and mitochondria, and yields a large amount of ATP (around 36-38 molecules). In contrast, anaerobic respiration (or fermentation) does not require oxygen, occurs entirely in the cytoplasm, and produces a much smaller amount of ATP (only 2 molecules from glycolysis) along with byproducts like lactic acid or ethanol.
6. Why is the Krebs Cycle often described as an amphibolic pathway?
The Krebs Cycle is considered an amphibolic pathway because it involves both catabolism (breaking down molecules) and anabolism (building up molecules). While it catabolises acetyl-CoA for energy release, its intermediates (like α-ketoglutarate and oxaloacetate) can be drawn off and used as precursors for the synthesis of essential molecules such as amino acids and fatty acids, making it a central hub in cellular metabolism.
7. How are the different locations within a cell specialised for the stages of cellular respiration?
The compartmentalisation of the cell is crucial for the efficiency of cellular respiration. Glycolysis occurs in the cytoplasm, where glucose-splitting enzymes are readily available. The subsequent stages move into the mitochondria; the Krebs cycle takes place in the mitochondrial matrix where necessary enzymes are concentrated, and the Electron Transport Chain is embedded in the inner mitochondrial membrane, which allows for the creation of a proton gradient essential for ATP synthesis.
8. What happens if oxygen is unavailable to a cell after glycolysis?
If oxygen is not present, the cell cannot proceed with the Krebs cycle and electron transport chain. Instead, it undergoes fermentation. The primary purpose of fermentation (e.g., lactic acid or alcoholic fermentation) is to regenerate the NAD+ that was converted to NADH during glycolysis. This regeneration allows glycolysis to continue, ensuring a small but continuous supply of ATP for the cell even in anaerobic conditions.
