# data[].attributes.attachment_link.description
The version of the browser you are using is no longer supported. Please upgrade to a supported browser. Dismiss

# data[].attributes.body
Nur Azira Jannah Bt Manaf
D20202096436
ISMP Biologi
Sem 4
From Besut, Terengganu.

# data[].attributes.body
https://docs.google.com/spreadsheets/d/1K--DY32zrpb_E0Dh0hx17GHgluW4D48EWZAeijnFWHc/edit#gid=0

# data[].attributes.attachment_link.title
A HEALTHY LIFESTYLE - REDESIGNING ME: PRBL GROUP

# data[].attributes.body
Noor Syahira Bt Mohd Fauzi
D20202096439
ISMP Biologi
Sem 4
From Gemas, Negeri Sembilan.

# data[].attributes.body
https://flip.com/ea7940c2

# data[].attributes.attachment_link.description
Flip is where social and emotional learning happens! The leading video discussion platform for millions of PreK to PhD educators, students, and families.

# data[].attributes.body
https://flip.com/3f2ce0e2

# data[].attributes.attachment_link.description
Flip is where social and emotional learning happens! The leading video discussion platform for millions of PreK to PhD educators, students, and families.

# data[].attributes.body
https://flip.com/55c1a136

# data[].attributes.attachment_link.description
Flip is where social and emotional learning happens! The leading video discussion platform for millions of PreK to PhD educators, students, and families.

# data[].attributes.body
https://flip.com/a44ceda6

# data[].attributes.attachment_link.description
Flip is where social and emotional learning happens! The leading video discussion platform for millions of PreK to PhD educators, students, and families.

# data[].attributes.body
https://docs.google.com/spreadsheets/d/1i2ZN-SDqmkzNGy75FnUsFTXsZT4lJH_3z6Iqv6OzjNI/edit#gid=0

# data[].attributes.body
Nur Aliah Bt Zailani
D20201095528
ISMP Sains
Sem 5
From Changkat Lada, Perak.

# data[].attributes.body
Prisila Rhina Anak Nang
D20201095533
ISMP Sains
Sem 5
From Saratok, Sarawak.

# data[].attributes.body
https://padlet.com/fluidnationcorp/8mgqmd44kka67oiw

# data[].attributes.headline
Sample for this experiment (Peanut, Biscuit, Corntoz)

# data[].attributes.subject
Sample for this experiment (Peanut, Biscuit, Corntoz)

# data[].attributes.headline
3 sample for this lab (Oat, Biscuit and Anchovies) 

# data[].attributes.subject
3 sample for this lab (Oat, Biscuit and Anchovies) 

# data[].attributes.headline
After add 5ml of acetone and swirl gently the beaker 

# data[].attributes.subject
After add 5ml of acetone and swirl gently the beaker 

# data[].attributes.headline
Place the petri dish into fume hood to evaporate 

# data[].attributes.subject
Place the petri dish into fume hood to evaporate 

# data[].attributes.headline
After evaporation, we will see the fat extraction

# data[].attributes.subject
After evaporation, we will see the fat extraction

# data[].attributes.headline
Hey there! here is my psychomotor skills for this course of SBK3013 Principles in Biochemistry lab sessions. <3

# data[].attributes.subject
Hey there! here is my psychomotor skills for this course of SBK3013 Principles in Biochemistry lab sessions. <3

# data[].attributes.attachment_link.title
SBK 3013 - PRINCIPLES IN BIOCHEMISTRY (PSYCHOMOTOR SKILLS)

# data[].attributes.attachment_link.description
Check out this Presentation designed by NOOR RAIHANA.

# data[].attributes.attachment_link.description
This is a guide to preparing your report.
You are encourage to prepare it creatively

# data[].attributes.attachment_caption
''Education is not the filling of a pail, but the lighting of a fire''

# data[].attributes.headline
Hi, this part is all about my psychomotor skills during every lab session (enzyme, carb, lipid & proteins) with my groupmates. A lot of things I have learnt regarding the laboratory and experiments. Lets explore together !

# data[].attributes.subject
Hi, this part is all about my psychomotor skills during every lab session (enzyme, carb, lipid & proteins) with my groupmates. A lot of things I have learnt regarding the laboratory and experiments. Lets explore together !

# data[].attributes.attachment_link.title
Lipid Metabolism | Anatomy and Physiology II

# data[].attributes.attachment_link.embed_code
Lipid Metabolism

# data[].attributes.attachment_link.readable_text
Respiration is a metabolic biochemical reaction wherein the complex food material is converted into the form of cellular energy molecules (ATP) inside living cells. It is a series of oxidation-reduction reactions where an electron is transformed from an electron donor to an acceptor, and ultimately energy is released and conserved in form of the adenosine triphosphate (ATP) molecule. In general concept, respiration is considered inhaling oxygen and exhaling carbon dioxide gas. But, this is termed breathing instead of respiration.

Based on oxygen requirement, respiration can be classified into two types; aerobic and anaerobic respiration. More precisely, this classification is based on the use of oxygen or any other molecules as the electron acceptor in the respiratory process.

Anaerobic respiration is the cellular respiration process that takes place in the absence of oxygen. It is the process where an electron is transferred to molecules other than an oxygen molecule. It is a quicker method, but there is an incomplete breakdown of glucose, releasing fewer ATP molecules. It mainly occurs in microorganisms.

Aerobic Respiration.

Aerobic respiration is the cellular respiration process that occurs in the presence of oxygen.
It is the respiratory process where the electron is transferred to dioxygen molecules (O ₂), generating water molecules and energy molecule ATP. Here glucose molecule is completely oxidized into energy (ATP), carbon dioxide, and water. The general process of aerobic respiration can be expressed as:
C₆H₁₂O₆ (Glucose) + O₂ (Oxygen) → 6CO₂ (Carbondioxide) + 6H₂O (water) + ATP (Energy)
One molecule of glucose is oxidized to 6 molecules of carbon dioxides, 6 molecules of water, and 32 molecules of ATP.

It occurs in most living organisms, including every higher plant and animal, and most microorganisms in the aerobic and facultative mode of respiration. It occurs in the mitochondria of eukaryotes and the cytoplasm of prokaryotes' cells. It is slower compared to the anaerobic type but has a higher yield of ATP molecules. A total of 32 ATP molecules are generated from a single glucose molecule. In this process, glucose, amino acids, and fatty acids are used as substrates and metabolized in the presence of oxygen.

It is a complex multistep enzymatic reaction process that occurs in four steps; glycolysis, pyruvate oxidation, Krebs cycle, and oxidative phosphorylation. Each step is already a complex multistep enzymatic chemical reaction process.

Steps of Aerobic Respiration.

Etymology: Derived from the Greek words meaning "sugar", and meaning "dissolution".

Glycolysis is the sequence of catabolic reactions converting glucose (or glycogen) molecule to pyruvic acid using several enzymes. In the process, a glucose molecule is catalyzed to yield two molecules of pyruvic acids, two molecules of NADH, and two molecules of ATP. It is also called "Embden-Meyerhof-Parnas Pathway" or "EMP Pathway".

The overall reaction can be expressed as:
Glucose + 2NAD⁺ +2ADP + 2Pi → 2Pyruvate + 2NADH + 2ATP + 2H₂O + 2H⁺
It occurs in the cytoplasm of every cell of a body. It occurs in both aerobic and anaerobic conditions. In aerobic conditions, pyruvic acid is produced, whereas lactic acid is produced in anaerobic conditions.

Glycolysis Diagram

It is the first step of the aerobic respiration process. It is a multistep reaction process. The sequence of reaction can be divided into three distinct phases;

A. Energy Investment Phase (Preparatory Phase)

It is the first phase where glucose is converted to Fructose-1, 6-bisphosphate using two molecules of ATP (hence called the energy investment phase) in a three-step reaction, viz.:

1. Phosphorylation of glucose: Here glucose is phosphorylated to glucose - 6 - phosphate by the enzyme "hexokinase" using an ATP molecule.

2. Isomerization of glucose - 6 - phosphate (G-6-P): Here, the enzyme "glucose - 6 - phosphate isomerase" catalyzes the reversible isomerization of G-6-P to fructose - 6 - phosphate in presence of Mg⁺² ion.

3. Phosphorylation of fructose - 6 - phosphate (F-6-P): Here, F-6-Pis phosphorylated by the "phosphofructokinase" enzyme to yield fructose- 1,6 - bisphosphate. It is called the committed step of glycolysis.

B. Splitting Phase

It is a two-step reaction where the 6-carbon fructose - 1,6 - bisphosphate molecule is split into two 3 - carbon compounds glyceraldehyde - 3 - phosphate.

1. Cleavage of fructose - 1,6 - bisphosphate: Fructose - 1,6 - bisphosphate is converted to two triose phosphate; glyceraldehyde - 3 - phosphate (G - 3 - P) and dihydroxyacetone phosphate, by an enzyme called "aldolase (fructose bisphosphate aldolase)".

2. Triosephosphate isomerization: The enzyme "triosephosphate isomerase" reversibly converts dihydroxyacetone phosphate to G - 3 - P.

C. Energy Generation Phase

It is the final phase where the glyceraldehyde - 3 - phosphate molecules are converted to pyruvate. It comprises the following reaction sequence:

1. Oxidation of glyceraldehyde - 3 - phosphate (G-3-P): G - 3 - P is oxidized to 1,3 - bisphosphoglycerate by the enzyme "glyceraldehyde - 3 - phosphate dehydrogenase" producing a molecule of NADH.

2. Phosphoryl Transfer from 1,3 - bisphosphate to ADP: Enzyme "phosphoglycerate kinase" reversibly catalyze the conversion of 1,3 - bisphosphate to 3 - phosphoglycerate. A molecule of ATP is synthesized in the process.

3. Conversion of 3 - phosphoglycerate to 2 - phosphoglycerate: The enzyme "phosphoglycerate mutase" catalyzes the conversion of 3 - phosphoglycerate to 2 - phosphoglycerate.

4. Dehydration of 2 - phosphoglycerate: In a reversible reaction, 2 - phosphoglycerate is dehydrated to phosphoenolpyruvate by the enzyme "enolase".

5. Formation of Pyruvate: The final transfer of the phosphoryl group from phosphoenolpyruvateto ADP yields a pyruvate molecule. It is catalyzed by the enzyme "pyruvate kinase".

It is the second step where pyruvate is converted to Acetyl-CoA which can then enter the Krebs cycle. This step results in the oxidative decarboxylation of pyruvate produced by glycolysis.

First, the pyruvate is transferred to the mitochondrial matrix by the "pyruvate translocase" enzyme. The enzyme "pyruvate dehydrogenase complex" irreversibly catalyzes the conversion of pyruvate to Acetyl - CoA. There is a loss of an atom of carbon from pyruvate, forming a molecule of CO ₂. Additionally, NAD⁺ is reduced to NADH in the process.

The overall reaction can be summarized as:
Pyruvate + NAD⁺ + CoA → Acetyl CoA + CO₂ + NADH + H⁺
It is a sequence of reactions where Acetyl - CoA is oxidized to CO ₂ and H ₂O inside the mitochondrial matrix generating energy in the form of ATP and reduced coenzymes NADH and FADH ₂. 20 ATP molecules are produced in this stage. This is the central aerobic pathway that connects all the individual metabolic pathways and utilizes about 2/3 rd of the total oxygen consumed by the body.

It was discovered by German biologist and biochemist Sir Hans Adolf Krebs, hence got the name "Krebs cycle".

It occurs in the mitochondrial matrix because all the required enzymes are located inside the mitochondria. It has catabolic and anabolic reactions, hence regarded as a cyclic amphibolic aerobic oxidative metabolic pathway. It is involved in gluconeogenesis, transamination, and delamination processes.

Krebs cycle

Citric acid is produced in the first step of the reaction. Hence it is also called the "Tricarboxylic Acid Cycle (TCA Cycle)" or "Citric Acid Cycle".

It is a multistep oxidative reaction cycle including the following steps:

1. Formation of Citrate: acetyl - CoA and oxaloacetate are condensed by the enzyme "citrate synthase" resulting production of citric acid.

2. Isomerization of Citrate: enzyme "aconitase" isomerizes the citrate to isocitrate (isocitric acid) through an intermediate process forming cis-aconitate which further rehydrates to form isocitrate.

3. Formation of - ketoglutarate: isocitrate is first dehydrogenated to oxalosuccinate and then decarboxylated to - ketoglutarate by an enzyme "isocitrate dehydrogenase". A molecule of CO₂ and NADH is formed in the process.

4. Conversion of - ketoglutarate to Succinyl CoA: oxidative decarboxylation of - ketoglutarate by the enzyme - ketoglutarate dehydrogenase results in the formation of succinyl CoA and CO2. NADH is released as NAD+ serves as an electron acceptor.

5. Formation of Succinate: Succinyl CoA is converted to succinate by "succinate thiokinase". A molecule of GDP is phosphorylated to GTP which is, in turn, converted to ATP by enzyme nucleoside diphosphate kinase.

6. Oxidation of Succinate: "Succinate dehydrogenase" oxidizes succinic acid (succinate) to fumarate (fumaric acid). A molecule of FADH2 is produced in the process.

7. Hydration of Fumarate: "Fumarase" catalyze the hydration of fumarate to malate (malic acid).

8. Oxidation of Malate: Finally, the enzyme "malate dehydrogenase" oxidize malate to oxaloacetic acid (oxaloacetate). The third and final synthesis of NADH occurs in this stage.

It is the series of biochemical reactions catalyzed by several enzymes, in which electrons are transferred from electron carriers like NADH and FADH to an oxygen molecule (O ₂), releasing ATP molecules in the process.

Generally, oxidative phosphorylation is understood as an electron transport chain. Broadly, oxidative phosphorylation is coupled reaction series including electron transport chain (ETC) and chemiosmosis.

The ETC transfers the electrons and generates a proton gradient, and the ATP is synthesized by using ATP synthase, ADP, and the energy generated by the proton gradient in a process called chemiosmosis.

It occurs inside the mitochondria in its inner membrane. It is the final step in aerobic cellular respiration.

The ETC is a series of complexes that transfer the electrons from the electron donors (NADH and FADH) to the electron acceptors (O ₂) via oxidation-reduction reactions, and couples this electron transfer with the transfer of proton (H⁺) across the mitochondrial membrane.

ETC involves five distinct enzyme complexes denoted I, II, III, IV, and V. The complexes I - IV are electron carriers while complex V is responsible for ATP synthesis. Besides, there are other mobile electron carriers like NADH, coenzyme - Q, Cytochrome - C, and oxygen.

Electron Transport Chain

The overall reactions in the ETC can be listed as:

1. Delivery of electrons; substrates like NADH and FADH transfer their electrons to the prosthetic group FMN coenzyme. The coenzyme FMN accepts 2 electrons and a proton to form FMNH ₂.

2. Transport of electrons; one iron-sulfur (FeS) protein participates in electron transfer from FMNH ₂ to coenzyme Q. There are 6 FeS identified that exist in either oxidized Fe ³⁺ or reduced Fe ²⁺ form. All these FeS proteins are associated with cytochromes (b, c1, c, a, a3) and take part in transporting electrons.

3. Formation of the water molecule; in the final stage, the transported electrons are accepted by the oxygen molecule. This splits the O ₂ into two O ⁻ radicles and combines with the free proton (H⁺) to form a water molecule. This reaction is exergonic and produces energy which is used to produce ATP.

B. Chemiosmosis

It is the process where the energy generated from the proton gradient is used to produce ATP. The transfer of electrons in the ETC is coupled with the translocation of the proton (H⁺) which develops a proton gradient.

The movement of H⁺ ions down their electrochemical gradient activates the ATP synthase enzyme which will catalyze the phosphorylation of ADP forming ATP molecule.

During the aerobic respiration process, ATPs are generated in oxidative phosphorylation at two levels; first at the substrate level, and the second at the ETC level.

The first is called substrate-linked oxidative phosphorylation, occurring in the glycolytic pathway and TCA cycle. In the glycolytic pathway, oxidation of G-3-P by G-3-P dehydrogenase enzyme adds a high energy phosphate group which is transferred to ADP in the next reaction generating ATP molecule.

Substrate-linked oxidative phosphorylation

In another reaction, the energy released during dehydration of 2-phosphoglycerate converts the low energy phosphate bond into a high energy phosphate bond which is transferred to ADP in the next reaction producing an ATP molecule.

Dehydration of 2-phosphoglycerate

In the TCA cycle energy released during the oxidation of α-ketoglutarate is used to form a high energy bond between succinate and CoA. In the next reaction, CoA is separated, and the energy is released, which is used to phosphorylate GDP to GTP.

Oxidation of α-ketoglutarate

The second level is called oxidative phosphorylation at the ETC level. Reducing equivalents formed during glycolysis and TCA cycles are oxidized in the ETC coupled with the phosphorylation of ADT to generate ATP in chemiosmosis.

Total ATP yield per glucose molecule in aerobic respiration can be summarized as:

In Glycolysis
ATP consumed = 2 ATP
ATP produced = 4 ATP
NADH produced = 2 NADH = 2 x 2.5 = 5 ATPs

In Oxidative Decarboxylation of Pyruvate
NADHproduced = 2 NADH = 2 x 2.5 = 5 ATPs

In (TCA) Krebs Cycle
Since 2 Acetyl CoA are formed by one glucose molecule, the number of ATP production is double of ATP produced in one TCA cycle.
Total NADH produced = 2 x 3 NADH = 6 x 2.5 = 15 ATPs
Total FADH ₂ produced = 2 x 1 FADH 2 = 2 x 1.5 = 3 ATPs
Total direct ATPs produced = 2 ATPs

In Oxidative Phosphorylation the NADH and FADH ₂ are converted to ATPs which are already included above.

TOTAL ATP YIELD = 7 (in glycolysis) + 5 (in oxidative decarboxylation) + 20 (in TCA)
= 32 ATPs

First and foremost, it is used for the production of energy in the form of ATP in cells of aerobic organisms.

CO₂ released during the process is used in photosynthesis by green plants.

Several intermediate compounds, coenzymes, and organic acids are produced.

They are used in the production of proteins from amino acids during anabolic reactions.

They are used in aerobic composting and biodegradation processes.

Read Also:

1. Nelson, D. L., & Cox, M. M. (2017). Lehninger principles of biochemistry (7th ed.). W.H. Freeman.

2. Satyanarayana, U. (2013). Biochemistry. Elsevier Health Sciences. https://books.google.com.np/books?id=Bd9XAwAAQBAJ

3. Respiration- Types and Phases Of Respiration In Organisms (byjus.com)

4. Respiration - Definition, Types, Flow Chart & Stages (vedantu.com)

5. Respiration and gas exchange - KS3 Biology - BBC Bitesize - BBC Bitesize

6. Patwa, A., & Shah, A. (2015). Anatomy and physiology of respiratory system relevant to anaesthesia. Indian journal of anaesthesia, 59(9), 533-541. https://doi.org/10.4103/0019-5049.165849

7. Kelly DJ, Hughes NJ, Poole RK. Microaerobic Physiology: Aerobic Respiration, Anaerobic Respiration, and Carbon Dioxide Metabolism. In: Mobley HLT, Mendz GL, Hazell SL, editors. Helicobacter pylori: Physiology and Genetics. Washington (DC): ASM Press; 2001. Chapter 10. Available from: https://www.ncbi.nlm.nih.gov/books/NBK2411/

8. Qusheng Jin, American Journal of Science June 2012, 312 (6) 573-628; DOI: https://doi.org/10.2475/06.2012.01

9. (14) (PDF) Difference Between Aerobic and Anaerobic respiration (researchgate.net)

10. Aerobic Respiration: Definition, Process & Significance (embibe.com)

11. Aerobic Respiration - The Definitive Guide | Biology Dictionary

12. Aerobic Respiration - Definition, Process and Steps | Biology (vedantu.com)

13. What Is Aerobic Respiration? - Definition, Diagram and Steps (byjus.com)

14. Wilson D. F. (2017). Oxidative phosphorylation: regulation and role in cellular and tissue metabolism. The Journal of physiology, 595(23), 7023-7038. https://doi.org/10.1113/JP273839

15. Oxidative Phosphorylation - Definition, Oxidative Phosphorylation Steps (byjus.com)

16. Importance of Aerobic Respiration and Anaerobic Respiration - QS Study

17. Real-life applications - Respiration - Anaerobic Respiration, Anaerobic bacteria, Humans and anaerobic respiration (scienceclarified.com)

About Author

# data[].attributes.attachment_link.title
Aerobic Respiration- Definition, Steps, ATP Yield, Diagram, Uses

# data[].attributes.attachment_link.description
Respiration is a metabolic biochemical reaction wherein the complex food material is converted into the form of cellular energy molecules (ATP) inside living cells. It is a series of oxidation-reduction reactions where an electron is transformed from an electron donor to an acceptor, and ultimately energy is released and conserved in form of the adenosine triphosphate (ATP) molecule.

# data[].attributes.attachment_link.readable_text
Respiration is the metabolic process of breaking down the simple organic nutrients (food material) releasing the cellular energy in form of ATP (Adenosine Triphosphate) inside the living cell. It is a series of oxidation-reduction reactions where an electron is transformed from an electron donor to an acceptor. Ultimately, energy is released and conserved in the form of the ATP molecule. It is different from breathing which is the inhalation of atmospheric air (O ₂) and exhalation of CO 2. It is often termed " cellular respiration ".

Based on the type of terminal electron acceptor in the respiration cycle, respiration can be classified as aerobic and anaerobic respiration. In aerobic respiration, oxygen (O ₂) is used as a terminal electron acceptor. In anaerobic respiration, molecules other than oxygen are used as terminal electron acceptors.

Simply, Anaerobic Respiration can be defined as the cellular respiration process occurring in an anoxic environment i.e. in the absence of oxygen. Anaerobic Respiration is the respiration process where the terminal electrons released during oxidation-reduction of nutrients are transferred to several organic and inorganic electron acceptors other than oxygen molecules to produce the energy molecule ATP. The usual terminal electron acceptors used in the anaerobic respiration process are sulfur (S), sulfate (SO4⁻²), ferric ion (Fe ³⁺), nitrate (NO ₃⁻), DMSO, etc. Hence, it is the production process of ATP molecules in the absence of oxygen.

Unlike aerobic respiration which takes place in the cytoplasm and mitochondria, anaerobic respiration occurs only in the cytoplasm. It usually occurs in two stages; anaerobic glycolysis and fermentation. The end products are either organic acids (lactic acid) or ethanol and ATP molecules (energy). The overall reaction of anaerobic respiration of a glucose molecule can be expressed as follows;

Glucose + electron acceptors (other than O₂) → Lactic acid / ethanol + 2 ATP molecules

Anaerobic Respiration

It is shown by several anaerobic bacteria, yeasts, protozoans, helminths, and even animal cells. During severe muscle contraction and expansion, anaerobic respiration occurs in human muscle cells producing lactate. Besides, it also occurs in brain cells, retina, and RBCs.

The anaerobic respiration process results in the incomplete breakdown of the substrate (nutrients). Hence it is less efficient than aerobic respiration in terms of ATP generation. Only two molecules of ATP are generated in the process. However, it is a quicker process and produces essential intermediate products like ethanol and organic acids.

Based on the type of end product of respiration, anaerobic respiration can be classified into several types like; organic acid fermentation (lactic acid fermentation, butyric acid fermentation, propionic acid fermentation, mixed acid fermentation, etc.), methanogenesis, acetogenesis, denitrification, sulfur reduction, alcohol (ethanol) fermentation, butanediol fermentation, etc. The major types of anaerobic respiration are:

It is a type of anaerobic respiration where sugar molecules (glucose and other six-carbon sugars) are metabolized to lactate, releasing the chemical energy in the form of ATP molecules. It is the fermentation process where pyruvate is produced at the end of glycolysis and is converted to lactate by the lactate dehydrogenase enzyme. It is also called 'Lacto-fermentation'.

Lactic Acid Fermentation

The general equation of lactic acid fermentation can be expressed as:

Glucose + ADP + NADH → Lactic acid + ATP + NAD⁺

It is one of the most common fermentation widely used in food preservation and fermented food production. Since ancient times, it has been in practice to ferment fruits, vegetables, cereals, milk (production of fermented dairy products), and meat and preserve them for later use.

It mainly occurs in the bacterial cytoplasm. Bacteria fermenting glucose to lactic acid are called "Lactic Acid Bacteria" (LAB), and they are widely used in the food industry and biotechnology. Common LAB are; Lactobacillus, Lactococcus, Leuconostoc, Streptococcus, Pediococcus, Enterococcus, etc.

Besides, it also occurs in the cytoplasm of higher animals, including humans. During strenuous muscular activities, lactic acid fermentation occurs in our body muscles due to the shortage of oxygen supply. This will result in muscle cramps or pain and fatigue sensation in our muscles after laborious muscular activities. Apart from muscles, this type of respiration is common in RBCs also as they lack mitochondria.

It is another common type of anaerobic respiration process where the sugar molecules (glucose and other six-carbon sugars) are metabolized to ethanol, releasing the chemical energy in the form of ATP molecules. The pyruvate produced by the glycolytic cycle is converted to ethanol in the presence of the alcohol dehydrogenase enzyme. It is also called 'alcoholic fermentation'.

Alcohol Fermentation

The general equation of ethanol fermentation can be expressed as:

It is used universally for the production of alcoholic beverages. It is performed by yeasts like Saccharomyces cerevisiae, Schizosaccharomyces, Zygosaccharomyces, Candida, Pichia, etc. Besides, fungi like Aspergillus oryzae, bacteria like Zymomonas, etc., are also used. It also occurs in higher animals like Goldfish.

Anaerobic respiration occurs in two steps; the first is glycolysis, and the second is fermentation.

Glycolysis is defined as the sequence of catabolic reactions converting glucose (or glycogen) molecule to pyruvic acid using several enzymes inside the cytoplasm of every cell. In the process, a molecule of glucose is catalyzed to yield two molecules of pyruvic acids, two molecules of NADH, and two molecules of ATP. It occurs in the cytoplasm of every living cell in both aerobic and anaerobic respiration. It is also called "Embden -Meyerhof - Parnas (EMP) Pathway".

It is a 10 step complex catabolic process where six-carbon sugar (glucose) is splitted into two 3 - carbon pyruvate molecules. The overall reaction is divided into three stages viz.;

1. Energy Investment Phase

It is the first phase where glucose is converted to Fructose - 1, 6 -bisphosphate using 2 molecules of ATP (hence called the energy investment phase) in a three-step reaction.

First, glucose is phosphorylated to glucose - 6 - phosphate (G-6-P) by the enzyme "hexokinase". The G - 6 - P is reversibly isomerized to fructose - 6 - phosphate (F-6-P) in the next step by the enzyme "glucose - 6 - phosphate isomerase" in presence of Mg⁺⁺ ion.

Finally, the F - 6 - P is phosphorylated to fructose - 1,6 - bisphosphate by the "phosphofructokinase" enzyme.

Glycolysis

2. Splitting Phase

It is the second phase where the 6-carbon fructose - 1,6 - bisphosphate molecule is split into two 3 - carbon compounds glyceraldehyde - 3 - phosphate (G - 3 - P).

It is 2 step reaction where the fructose - 1,6 - bisphosphate is first enzymatically broken down to G - 3 - P and dihydroxyacetone phosphate by an enzyme called " aldolase (fructose bisphosphate aldolase)". In the next step, dihydroxyacetone phosphate is reversibly isomerized to G - 3 - P by the enzyme "triosephosphate isomerase".

3. Energy Generation Phase

It is the final phase of glycolysis where G - 3 - P is finally oxidized to pyruvate releasing two molecules of ATP.

In the first step, the G - 3 - P is oxidized to 1,3 - bisphosphoglycerate by the enzyme "glyceraldehyde - 3 - phosphate dehydrogenase" producing a molecule of NADH. The enzyme "phosphoglycerate kinase" reversibly catalyzes the conversion of 1,3 - bisphosphate to 3 - phosphoglycerate releasing an ATP molecule which will then be catalyzed to 2 - phosphoglycerate by another enzyme, "phosphoglycerate mutase".

In a reversible reaction by "enolase" 2 - phosphoglycerate is dehydrated to phosphoenolpyruvate. Phosphoenolpyruvate will in turn, be dephosphorylated by "pyruvate kinase" producing a "pyruvate" and ATP molecule.

The overall chemical reaction can be summarized as following equation;

Glucose + 2 ATP + 2 ADP + 2Pi + 2 NAD⁺ → 2 Pyruvate + 2 NADH + 2 ATP

It is the process where pyruvate produced in glycolysis is reduced to an end product of anaerobic respiration (mainly ethanol or lactic acid). In the process, NADH is oxidized to NAD+, and the released proton is used to reduce the pyruvate in the presence of a different enzyme.

Fermentation may be homo-fermentation, i.e., producing only one type of product by reducing pyruvate, or maybe hetero-fermentation, i.e., producing two or more end products while reducing the pyruvate.

The end product of pyruvate reduction depends on the enzyme involved and the types of fermentation. In lactic acid fermentation, the end product is lactic acid, and in alcohol fermentation, the end product is ethanol.

1. Lactic Acid Fermentation

In this type, the pyruvate is reduced to L-lactate (the conjugate base of lactic acid). The reduction is catalyzed by the "lactate dehydrogenase" enzyme, and in the process, NADH is oxidized to NAD.

The equation of lactic acid fermentation is expressed as:

Lactic Acid Fermentation

2. Ethanol Fermentation

In this type, the pyruvate is reduced to ethanol in a two-step reaction. At first, pyruvate is decarboxylated into acetaldehyde in the presence of TPP (Thymine pyrophosphate) by the enzyme "pyruvate decarboxylase". A molecule of CO ₂ is released in this process. In the next step, acetaldehyde is reduced to ethanol by the enzyme "alcohol dehydrogenase". A molecule of NADH is oxidized to NAD⁺ in this reaction.

Ethanol Fermentation

Step I: Glucose + 2 ATP + 2 ADP + 2 Pi + 2 NAD → 2 Pyruvate + 4 ATP + 2 NADH

Step II: 2 Pyruvate + 2 NADH → 2 Lactate (lactic acid) + 2 NAD

∴ Glucose + 2ADP + 2Pi → 2 Lactate + 2 ATP

Step I: Glucose + 2 ATP + 2 ADP + 2 Pi + 2 NAD → 2 Pyruvate + 4 ATP + 2 NADH

Step II: 2 Pyruvate → 2 Acetaldehyde + 2 CO ₂

Step III: 2 Acetaldehyde + 2 NADH → 2 Ethanol + 2 NAD

∴ Glucose + 2 ADP + 2 Pi → 2 Ethanol + 2 ATP + 2 CO2 ↑

Based on the types of electron acceptors used in the respiration process, products of anaerobic respiration vary. Lactic acid, ethanol, CO2, and ATP are the common products of anaerobic respiration. Other compounds produced are acetic acid, butyric acid, methane, Fe(II), H ₂S, halide ions, succinate, NO ₂⁻ and N ₂, U (IV), etc.

1. It plays a critical role during biogeochemical cycles like Nitrogen Cycle, Iron Cycle, Sulfur Cycle, and Carbon Cycle. Several steps in these cycles require an anaerobic respiration process. For e.g., denitrification, sulfur reduction, methanogenesis, etc. are anaerobic respiration processes.

2. It is used in sewage treatment plants and waste management systems. The denitrification step is used in the treatment of sewage to remove nitrate. Chlorinated chemicals, arsenic wastes, radioactive wastes, petroleum wastes, etc., are anaerobically reduced in bioremediation processes.

3. Power generation through microbial fuel cells is an anaerobic respiration process.

4. Production of organic acids like lactic acid, propionic acid, acetic acid, butyric acid, etc. for commercial and household uses.

5. Alcohol fermentation is the most widely applied sector of anaerobic respiration. Production of alcoholic beverages (beer, wine, distilled alcohols, etc.) has a long history, and still, it covers a very large sector of business.

6. Lactic acid fermentation, acetic acid fermentation, and other organic acid fermentation processes are used to produce fermented foods. Fermented dairy products, soya sauce, sourdough bread, Indian Idli and Dosa, fermented mustard green, pickled vegetables, sauerkraut, etc. are produced as a result of the organic acid fermentation process.

7. Anaerobic lactic acid fermentation in our gut converts ammonia to ammonium ions. This prevents from harmful effects of ammonia in our body system.

The production of wine, beer, and other distilled ethanol products is the result of alcohol fermentation. Yeast like Saccharomyces cerevisiae, Schizosaccharomyces, Zygosaccharomyces, etc., are commonly used for ethanol production.

The production of methane gas is an anaerobic fermentation process used for the digestion of organic waste. Methane gas is widely used as an alternative source of energy.

Swiss cheese has its distinct flavor and porous texture due to propionic acid fermentation. The acid gives the flavor, and the release of CO ₂ gas develops the characteristic holes in the cheese surface.

Vinegar used as a flavoring agent and food preservatives is a mixture of about 5 - 8% acetic acid. Its production is the double fermentation process. At first, alcohol fermentation produces ethanol. The ethanol is then oxidized by acetic acid bacteria (Acetobacter) to acetic acid.

The reduction of nitrate (NO 3 - ) to nitrite (NO ₂ - ) in the nitrogen cycle is an anaerobic respiration process called denitrification. Bacteria such as Pseudomonas, Clostridium, Geobacter, etc., perform denitrification.

Read Also:

1. Lactic Acid Fermentation. (2020, August 13). University of Kentucky. https://chem.libretexts.org/@go/page/58862

2. Electron Donors and Acceptors in Anaerobic Respiration. (2021, January 4). https://bio.libretexts.org/@go/page/8976

3. National Research Council (US) Panel on the Applications of Biotechnology to Traditional Fermented Foods. Applications of Biotechnology to Fermented Foods: Report of an Ad Hoc Panel of the Board on Science and Technology for International Development. Washington (DC): National Academies Press (US); 1992. 5, Lactic Acid Fermentations. Available from: https://www.ncbi.nlm.nih.gov/books/NBK234703/

4. Anaerobic Respiration: The Definitive Guide | Biology Dictionary

5. 5 Examples of Anaerobic Respiration | Life Persona

6. Anaerobic Respiration | Boundless Microbiology (lumenlearning.com)

7. https://byjus.com/biology/aerobic-anaerobic-respiration/

8. Anaerobic respiration | definition of anaerobic respiration by Medical dictionary (thefreedictionary.com)

9. What is Anaerobic Respiration? - Biology Wise

10. Anaerobic Respiration: Definition, Equation, and Examples (researchtweet.com)

11. Anaerobic Respiration - Process - Regulation - TeachMePhysiology

12. Anaerobic Respiration (With Diagram) (biologydiscussion.com)

13. Anaerobic respiration: Definition, Overview & Equation (studysmarter.us)

14. Glycolysis and Anaerobic Respiration - EONS LEARNING

15. What Is Fermentation? - Definition, Types, Anaerobic Respiration (byjus.com)

About Author

# data[].attributes.attachment_link.title
Anaerobic Respiration- Definition, Types, Steps, Equation, Products, Uses

# data[].attributes.attachment_link.description
Respiration is the metabolic process of breaking down the simple organic nutrients (food material) releasing the cellular energy in form of ATP (Adenosine Triphosphate) inside the living cell. It is a series of oxidation-reduction reactions where an electron is transformed from an electron donor to an acceptor.

# data[].attributes.body
PRISILA RHINA ANAK NANG
D20201095533

# data[].attributes.attachment_link.description
Check out this Presentation designed by PRISILA RHINA ANAK NANG.

# data[].attributes.body
Here I attached skills that I have learned while doing the lab work!

# data[].attributes.body
Holla! This is my artifacts for this 6 months studying this course! Lets share some knowledge 👏

# data[].attributes.body
PRISILA RHINA ANAK NANG
D20201095533

# data[].attributes.attachment_link.description
Check out this Presentation designed by PRISILA RHINA ANAK NANG.

# data[].attributes.body
1.  ENZYMES : https://anyflip.com/ptfrk/agux/

2.  CARBOHYDRATES METABOLISM : https://anyflip.com/ptfrk/lbue/

3.  LIPID METABOLISM : https://anyflip.com/ptfrk/yflq/

4.  PROTEIN METABOLISM : https://anyflip.com/ptfrk/bcvo/

5.  AEROBIC AND ANAEROBIC METABOLISM: https://anyflip.com/ptfrk/gkiu/

# data[].attributes.attachment_link.title
Choice Board Reflection - Dreamer World Cup 2022

# data[].attributes.body
Noor Raihana Bt Mujubir Rahman
D20202096438
ISMP Biologi
Sem 4
From Klang, Selangor.

# data[].attributes.body
PRISILA RHINA ANAK NANG
D20201095533

# data[].attributes.body
https://flip.com/d7c0c115

# data[].attributes.attachment_link.description
Flip is where social and emotional learning happens! The leading video discussion platform for millions of PreK to PhD educators, students, and families.