Cellular-respiration-featured

Cellular Respiration, Aerobic & Anaerobic Respiration

Abstract

Life’s essential activities are fueled by energy, sourced through cellular respiration—a series of metabolic reactions converting chemical energy from oxygen or food into adenosine triphosphate (ATP) while generating waste products.

Glucose serves as the cell’s primary fuel for this process, and its metabolism is contingent on oxygen availability. The initial step, glycolysis, initiates the breakdown.

ATP molecules, integral for diverse cellular functions like substance synthesis, membrane transport, muscle contraction, and nerve conduction, are subsequently produced.

Additionally, biological oxidation, involving hydrogen elimination catalyzed by dehydrogenases and specific coenzymes, is a facet of cellular respiration, fundamentally characterized as an oxidation reaction.

Respiration at the Cell Level

Living organisms require energy to carry on their essential life activities. This energy is provided within the cells by the phenomenon of respiration. Respiration is the universal procedure by which organisms breakdown complex compounds containing carbon in a manner that permits the cells to collect a maximum of useable energy.

In biology, the term respiration is used in two ways. More familiarly the term respiration means the exchange of breathing gases (CO2 and O2) in between the organism and its environment. This exchange is called external respiration. Cellular respiration is the process by which energy is provided to cells in a step by step breakdown of C-chain molecules in the cells.

Cellular respiration

Cellular respiration is a set of metabolic reactions and procedures that occur in the cells of organisms to transform chemical energy from oxygen molecules or food into adenosine triphosphate and after that release waste products.

Types of Cellular respiration

The most typical fuel used by the cell to offer energy by cellular respiration is glucose. The way glucose is metabolized depends upon the availability of oxygen. Prior to going into a mitochondrion, the glucose molecule is divided to form two molecules of pyruvic acid (3 Carbon molecules). This reaction is called glycolysis (glycolysis literally suggests splitting of sugar), and occurs in the cytosol and is represented by the equation:

Cellular-respiration-equation

This reaction happens in all the cells and biologists think that a similar reaction might have happened in the very first cell that was arranged in the world.

Cell processes pyruvic acid in three significant methods, alcoholic fermentation, lactic acid fermentation, and aerobic respiration. The first two reactions happen in the absence of oxygen and are described as anaerobic (without oxygen). The total breakdown of the glucose molecule happens just in the presence of oxygen, i.e. in aerobic respiration. Throughout aerobic respiration glucose is oxidized to CO2 and water and energy are released.

krebs-cyclen

Aerobic Respiration

” Aerobic respiration is the process of producing cellular energy in the presence of oxygen.”

The chemical equation for aerobic respiration is:

Aerobic-Respiration

The energy is released by splitting the glucose molecules with the help of oxygen gas. At the end of the chemical reaction, energy, water molecules, and carbon dioxide gas are released as the by-products or end products of the reactions.

The 2900 kJ of energy is released during the procedure of breaking the glucose molecule and in turn, this energy is used to produce ATP– Adenosine Triphosphate molecules which are utilized by the body for various purposes. Aerobic respiration procedure happens in all multicellular organisms consisting of animals, plants, and other living organisms.

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During the respiration process in plants, the oxygen gas enters the plant cells through the stomata, which is present in the epidermis (mesophyll cells) of leaves and stem of a plant. With the help of the photosynthesis procedure, all green plants manufacture their food and thus release energy.

Role of Mitochondria in Aerobic Respiration

Mitochondria are large granular or filamentous organelles that are dispersed throughout the cytoplasm of animal and plant cells. Each mitochondrion is consisting of an external enclosing membrane and an inner membrane with intricate folds or cristae that extend into the interior of the organelle.

Mitochondria play a role in cellular respiration by transferring the energy of the organic molecules to the chemical bonds of ATP. A big “Battery” of enzymes and coenzymes gradually release energy from the glucose molecules. Thus, mitochondria are the “Power houses” that produce the energy necessary for numerous cellular functions.

Mitochondria-role

Adenosine Triphosphate and its Significance

Adenosine triphosphate, normally abbreviated ‘ATP’ is a compound found in every living cell and is one of the necessary chemicals of life. It plays a crucial function in the majority of biological energy changes. Traditionally, ‘P’ represents the whole phosphate group.

The second and third phosphate represent the so-called “high energy” bonds. If these are broken by hydrolysis, much more totally free energy is released as compared to the other bond in the ATP molecule. The breaking of the terminal phosphate of ATP releases about 7.3 Kcal of energy. The high energy ‘P’ bond enables the cell to collect a great quantity of energy in a very small area and keeps it ready for use as soon as it is needed.

Adenosine-Triphosphate

The ATP particle is utilized by cells as a source of energy for various functions, for instance, synthesis of more complex substances, active transport across the cell membrane, muscular contraction and nerve conduction, etc.

Anaerobic Respiration

The respiration in the absence of oxygen is called anaerobic respiration. It might be:

  • Alcoholic Fermentation: In primitive cells and in some eukaryotic cells such as yeast, pyruvic acid is more broken down by alcoholic fermentation into alcohol (C2 H5 OH) and CO2.

Anaerobic-equation

Fermentation is commonly used for the production of alcohol and bread making. When sugar, yeast, flour, and water are integrated to form the dough, yeast breaks down the sugar and produces carbon dioxide, which triggers the bread to rise.

  • Lactic acid fermentation: In lactic acid fermentation, each pyruvic acid molecule is converted into lactic acid C3 H6 O3 in the absence of oxygen gas:

Lactic-acid-equation

Lactic acid fermentation is used to flavor or maintains dairy products and vegetables, for instance, yogurt and pickles.

This type of anaerobic respiration occurs in muscle cells of human beings and other animals during extreme physical activities and heavy exercises, such as sprinting when oxygen can not be carried to the cells as quickly as it is required. Both alcoholic and lactic acid fermentation yield fewer percentages of energy from the glucose molecules. Only about 2% of the energy present within the chemical bonds of glucose is converted into adenosine triphosphate (ATP).

Biological oxidation

The maintenance of the living system needs a continuous supply of totally free energy which is eventually originated from numerous oxidation-reduction reactions. Except for photosynthetic and some bacterial chemosynthetic processes, which are themselves oxidation-reduction reactions, all other cells depend ultimately for their supply of totally free energy on oxidation reactions in respiratory processes.

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Sometimes biological oxidation includes the elimination of hydrogen, a reaction catalyzed by the dehydrogenase attached to specific coenzymes. Cellular respiration is basically an oxidation reaction.

FAQs related to Cellular Respiration, Aerobic and anaerobic Respiration

1. What is cellular respiration, and why is it essential for living organisms?

  • Cellular respiration is a set of metabolic reactions that occur in cells to convert chemical energy from oxygen or food into adenosine triphosphate (ATP). It is essential for providing energy for various cellular functions.

2. How does respiration occur at the cell level?

  • Respiration at the cell level involves the breakdown of complex carbon-containing compounds to collect usable energy for cells to function.

3. What are the types of cellular respiration?

  • Cellular respiration can be categorized into aerobic respiration, which occurs in the presence of oxygen, and anaerobic respiration, which occurs in the absence of oxygen.

4. What is glycolysis, and when does it occur in cellular respiration?

  • Glycolysis is the initial step in cellular respiration where a glucose molecule is split to form two molecules of pyruvic acid. It occurs in the cytosol before entering the mitochondrion.

5. Explain the process of aerobic respiration.

  • Aerobic respiration is the process of producing cellular energy in the presence of oxygen. It involves the breakdown of glucose into carbon dioxide and water, releasing energy that is used to produce ATP.

6. What is the role of mitochondria in aerobic respiration?

  • Mitochondria play a crucial role in cellular respiration by transferring the energy of organic molecules to ATP through a series of enzymatic reactions. They are often referred to as the “powerhouses” of the cell.

7. What is adenosine triphosphate (ATP) and its significance in cellular processes?

  • ATP is a compound found in every living cell and serves as a key player in biological energy changes. The high-energy bonds in ATP release energy for various cellular functions, including synthesis, active transport, muscular contraction, and nerve conduction.

8. How does anaerobic respiration differ from aerobic respiration?

  • Anaerobic respiration occurs in the absence of oxygen and includes processes like alcoholic fermentation and lactic acid fermentation. It yields less energy compared to aerobic respiration.

9. What are the two types of anaerobic fermentation, and where do they commonly occur?

  • Alcoholic fermentation, found in primitive cells and yeast, produces alcohol and carbon dioxide. Lactic acid fermentation, occurring in muscle cells during intense physical activities, produces lactic acid.

10. Why is biological oxidation important in cellular respiration? – Biological oxidation, involving the removal of hydrogen, is a key aspect of cellular respiration. It provides a continuous supply of free energy needed for various oxidation-reduction reactions in living systems.

 

Multiple-Choice Question (MCQ)

  1. What is the primary purpose of cellular respiration?
    • A) Synthesis of DNA
    • B) Breakdown of carbon compounds for energy
    • C) Production of carbohydrates
    • D) Facilitation of cell division
    • Answer: B) Breakdown of carbon compounds for energy
  2. Where does glycolysis occur in the cell?
    • A) Nucleus
    • B) Endoplasmic reticulum
    • C) Mitochondria
    • D) Cytosol
    • Answer: D) Cytosol
  3. Which fuel is most commonly used by cells for energy production in cellular respiration?
  4. What is the term for the total breakdown of the glucose molecule in the presence of oxygen?
    • A) Glycolysis
    • B) Fermentation
    • C) Krebs cycle
    • D) Aerobic respiration
    • Answer: D) Aerobic respiration
  5. In which organelle does aerobic respiration take place in eukaryotic cells?
    • A) Nucleus
    • B) Golgi apparatus
    • C) Mitochondria
    • D) Endoplasmic reticulum
    • Answer: C) Mitochondria
  6. What is the role of mitochondria in aerobic respiration?
    • A) Synthesis of proteins
    • B) ATP production
    • C) Photosynthesis
    • D) Lipid storage
    • Answer: B) ATP production
  7. Which molecule is considered the “high-energy” molecule in cellular processes?
    • A) DNA
    • B) RNA
    • C) ATP
    • D) NADH
    • Answer: C) ATP
  8. What is the main by-product of aerobic respiration?
    • A) Carbon monoxide
    • B) Oxygen
    • C) Water
    • D) Nitrogen
    • Answer: C) Water
  9. What is the term for respiration in the absence of oxygen?
    • A) Anaerobic respiration
    • B) External respiration
    • C) Aerobic respiration
    • D) Mitochondrial respiration
    • Answer: A) Anaerobic respiration
  10. Which of the following is a by-product of lactic acid fermentation?
    • A) Ethanol
    • B) Carbon dioxide
    • C) Lactic acid
    • D) Acetic acid
    • Answer: C) Lactic acid
  11. In which cellular location does lactic acid fermentation primarily occur?
    • A) Nucleus
    • B) Cytoplasm
    • C) Mitochondria
    • D) Endoplasmic reticulum
    • Answer: B) Cytoplasm
  12. What is the significance of the high-energy bonds in ATP?
    • A) They store genetic information
    • B) They facilitate cell division
    • C) They release energy for cellular functions
    • D) They are involved in photosynthesis
    • Answer: C) They release energy for cellular functions
  13. What is the primary purpose of biological oxidation in cellular respiration?
    • A) Synthesis of lipids
    • B) Removal of carbon dioxide
    • C) Supply of free energy
    • D) DNA replication
    • Answer: C) Supply of free energy
  14. What is the product of alcoholic fermentation in yeast cells?
    • A) Lactic acid
    • B) Carbon dioxide
    • C) Water
    • D) Ethanol
    • Answer: D) Ethanol
Further Reading:  Water Absorption in Plants

 

Summary

The tutorial covers the following key points:

  1. Aerobic Respiration:
    • Describes the process of producing cellular energy in the presence of oxygen.
    • Presents the chemical equation for aerobic respiration, emphasizing the release of energy, water molecules, and carbon dioxide as by-products.
    • Highlights the vital role of ATP (Adenosine Triphosphate) molecules produced during aerobic respiration in various cellular functions.
  2. Role of Mitochondria in Aerobic Respiration:
    • Discusses the significance of mitochondria, organelles within cells, in the aerobic respiration process.
    • Describes mitochondria as “Power houses” responsible for transferring energy from organic molecules to ATP through a battery of enzymes and coenzymes.
  3. Adenosine Triphosphate (ATP) and its Significance:
    • Explains the structure of ATP and its crucial role as a compound found in every living cell.
    • Highlights the “high-energy” bonds in ATP, which, when broken by hydrolysis, release a significant amount of free energy for cellular functions.
  4. Anaerobic Respiration:
    • Defines anaerobic respiration as respiration in the absence of oxygen.
    • Details two types of anaerobic respiration: Alcoholic Fermentation and Lactic Acid Fermentation.
    • Provides equations for both types of anaerobic respiration and mentions their applications, such as in the production of alcohol and the flavoring of dairy products.
  5. Biological Oxidation:
    • Emphasizes the continuous need for a free energy supply in living systems, primarily derived from oxidation-reduction reactions.
    • Highlights the role of dehydrogenases and specific coenzymes in biological oxidation, a process integral to cellular respiration.