Anaerobic Respiration Overview
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Questions and Answers

What is the final acceptor of electrons in anaerobic respiration?

Inorganic compounds other than oxygen

What are the two electron acceptors that are involved in anaerobic respiration?

Nitrate (NO3) and sulfate (SO4)

What are the two products produced by the oxidation process in E. coli bacteria when they grow anaerobically?

Nitrate derivatives (NO2) and nitrogen gas (N2)

Which anaerobic bacteria reduces sulfates?

<p>Desulfovibrio sulfuricans</p> Signup and view all the answers

What is the final product of sulfate reduction by Desulfovibrio sulfuricans?

<p>Sulfide ions (S) in the form of H2S or atomic sulfur (S)</p> Signup and view all the answers

What causes the blackening of mud and the blackish color of the Black Sea?

<p>Hydrogen sulfide reacting with ferrous ions to form black ferrous sulfide salt</p> Signup and view all the answers

Anaerobic respiration does not involve an electron transport chain.

<p>False</p> Signup and view all the answers

The electron transport chain in anaerobic respiration is identical to the one in aerobic respiration.

<p>False</p> Signup and view all the answers

What is an alternative anaerobic pathway for breaking down glucose?

<p>Fermentation</p> Signup and view all the answers

What conditions do microbes require to either lack or suppress the synthesis of electron transport chains?

<p>Anaerobic conditions</p> Signup and view all the answers

In fermentation, pyruvate continues through the citric acid cycle.

<p>False</p> Signup and view all the answers

What is the role of pyruvate or one of its derivatives in fermentation?

<p>To act as an electron acceptor for the reoxidation of NADH</p> Signup and view all the answers

What are the two types of fermentation?

<p>Lactic acid fermentation and alcoholic fermentation</p> Signup and view all the answers

Which bacteria are involved in lactic acid fermentation?

<p>Bacillus and Lactobacillus</p> Signup and view all the answers

What is the final product of lactic acid fermentation?

<p>Lactate</p> Signup and view all the answers

Which organisms are responsible for alcoholic fermentation?

<p>Yeast is known for its role in alcoholic fermentation, leading to the production of beverages like beer and wine.</p> Signup and view all the answers

What two products are formed when pyruvate is broken down during alcoholic fermentation?

<p>Ethanol and carbon dioxide</p> Signup and view all the answers

What is the role of NADH in alcoholic fermentation?

<p>It donates its electrons to a derivative of pyruvate, producing ethanol in a two-step process</p> Signup and view all the answers

What is removed from pyruvate in the first step of alcoholic fermentation?

<p>Carboxyl group</p> Signup and view all the answers

What is the two-carbon molecule product after the carboxyl group is removed from pyruvate?

<p>Acetaldehyde</p> Signup and view all the answers

What happens to acetaldehyde in the second step of alcoholic fermentation?

<p>It is reduced to ethanol in the presence of NADH</p> Signup and view all the answers

What is the main product besides lactic acid that can be created during heterolactic fermentation?

<p>Ethanol</p> Signup and view all the answers

Which bacteria are involved in butyric fermentation?

<p>Clostridium bacteria</p> Signup and view all the answers

What are the products of butyric fermentation?

<p>CO2, butyrate, and gas (acid)</p> Signup and view all the answers

What is involved in propionic fermentation?

<p>The addition of propionic acid, resulting in trace amounts of carbon dioxide and acetic acid by Propionibacterium</p> Signup and view all the answers

What is the primary end product of butanediol fermentation?

<p>2,3-butanediol</p> Signup and view all the answers

What other products are beside 2,3-butanediol produced during the process?

<p>Ethanol, lactic acid, and formic acid</p> Signup and view all the answers

What is the test used to identify butanediol fermentation?

<p>Voges-Proskauer test</p> Signup and view all the answers

Which of the following monosaccharides are included in the catabolic pathways?

<p>Galactose</p> Signup and view all the answers

What is the process that the monosacchardies glucose, fructose, and mannose undergo in the catabolic pathways?

<p>Interconversion to glucose or glucose derivatives</p> Signup and view all the answers

Which monosaccharide requires a different conversion process?

<p>Galactose</p> Signup and view all the answers

Which pathway can glucose, fructose, and mannose enter after phosphorylation?

<p>Embden-Meyerhof pathway</p> Signup and view all the answers

Galactose can directly enter the Embden-Meyerhof pathway.

<p>False</p> Signup and view all the answers

What must be done before galactose can enter the Embden-Meyerhof pathway?

<p>It must be converted to uridine diphosphate galactose after initial phosphorylation and then changed into glucose 6-phosphate</p> Signup and view all the answers

How are disaccharides cleaved into monosaccharides?

<p>Through two mechanisms: hydrolysis and phosphorolysis.</p> Signup and view all the answers

What three disaccharides can be directly hydrolyzed to their constituent sugars?

<p>Maltose, sucrose, and lactose</p> Signup and view all the answers

Name three disaccharides that can be split by phosphorolysis.

<p>Maltose, cellobiose, and sucrose</p> Signup and view all the answers

What is the process that cleaves disaccharides by adding a phosphate group to the bond joining the two sugars?

<p>Phosphorolysis</p> Signup and view all the answers

Polysaccharides can be cleaved by both hydrolysis and phosphorolysis, just like disaccharides.

<p>True</p> Signup and view all the answers

What is the mechanism used by procaryotes and fungi to degrade external polysaccharides?

<p>Secreting hydrolytic enzymes</p> Signup and view all the answers

What are the enzymes that are secreted by procaryotes and fungi to degrade external polysaccharides called?

<p>Exoenzymes</p> Signup and view all the answers

What do exoenzymes do to polysaccharides?

<p>They cleave them into smaller molecules that can be assimilated</p> Signup and view all the answers

What is the process that starch and glycogen undergo?

<p>They are hydrolyzed by amylases</p> Signup and view all the answers

Name two products of the hydrolysis of starch and glycogen.

<p>Glucose and maltose</p> Signup and view all the answers

Which organisms produce extracellular cellulases?

<p>Many fungi and a few bacteria</p> Signup and view all the answers

What happens to cellulose when it is hydrolyzed by cellulases?

<p>It is broken down into cellobiose and glucose</p> Signup and view all the answers

What is pectin?

<p>A component of plant cell walls</p> Signup and view all the answers

What are the organisms that degrade pectin?

<p>Soil bacteria and bacterial phytopathogens</p> Signup and view all the answers

What is the breakdown product of pectin?

<p>Units of galacturonic acid</p> Signup and view all the answers

What can degrade lignin?

<p>Certain fungi that release peroxide-generating enzymes</p> Signup and view all the answers

What is the enzyme that degrades agar?

<p>Agarase</p> Signup and view all the answers

What organisms produce agarase?

<p>Some actinomycetes and members of Cytophaga</p> Signup and view all the answers

Microorganisms can catabolize intracellular stores of substances like glycogen, starch, and poly-β-hydroxybutyrate in the absence of exogenous nutrients.

<p>True</p> Signup and view all the answers

What is the process by which glycogen and starch are degraded?

<p>Phosphorolysis</p> Signup and view all the answers

What is the enzyme that catalyzes phosphorolysis?

<p>Phosphorylases</p> Signup and view all the answers

What is the product of phosphorolysis?

<p>Glucose 1-phosphate</p> Signup and view all the answers

Which bacterium hydrolyzes PHB?

<p>Azotobacter</p> Signup and view all the answers

What is the first step in the breakdown of PHB by Azotobacter?

<p>Hydrolysis of PHB to 3-hydroxybutyrate</p> Signup and view all the answers

What happens to 3-hydroxybutyrate in the second step of PHB breakdown?

<p>It is oxidized to acetoacetate</p> Signup and view all the answers

Study Notes

Anaerobic Respiration

  • Anaerobic respiration is a type of cellular respiration that does not require oxygen.

  • The final electron acceptor in anaerobic respiration is an inorganic molecule other than oxygen.

  • The electron transport chain is similar to aerobic respiration, but the final oxidizer is different.

  • Nitrate (NO₃⁻) and sulfate (SO₄²⁻) are common electron acceptors in anaerobic respiration.

  • E. coli bacteria can use nitrate as the final electron acceptor when glucose is oxidized.

  • This process produces nitrate derivatives (NO₂⁻) and nitrogen gas (N₂).

  • Desulfovibrio sulfuricans bacteria reduce sulfate (SO₄²⁻) to sulfide ions (S²⁻), which can be in the form of hydrogen sulfide (H₂S) or atomic sulfur (S).

  • This reduction process sometimes causes the blackening of mud, particularly in environments like the Black Sea, due to the reaction of hydrogen sulfide with ferrous ions (+Fe) to form black ferrous sulfide.

Diagram of Anaerobic Respiration

  • Diagram shows the electron transport chain components (cyt, Nir) and their arrangement in the cytoplasmic membrane.
  • Nitrate reduction is a key part of the electron transport chain.
  • The components of respiration are indicated in the diagram.

Fermentation

  • Fermentation is an anaerobic pathway that many microorganisms use to break down glucose, particularly if they lack an electron transport chain.
  • In fermentation, pyruvate produced in glycolysis doesn't proceed through the citric acid cycle and the electron transport chain.
  • Pyruvate or its derivatives act as electron acceptors for NADH reoxidation.

Lactic Acid Fermentation

  • This fermentation occurs in some Bacillus and Lactobacillus species.
  • NADH directly transfers electrons to pyruvate, resulting in lactate production.
  • This process is utilized in cheese production.
  • The overall reaction involves converting glucose to lactate.

Alcohol Fermentation

  • Yeast and certain bacteria perform this process, breaking pyruvate from glucose metabolism into ethanol and carbon dioxide.
  • NADH donates its electrons to pyruvate derivatives, producing ethanol in a two-step process.
  • The first step involves removing the carboxyl group from pyruvate to produce carbon dioxide and acetaldehyde.
  • The second step involves the reduction of acetaldehyde to ethanol using NADH.

Heterolactic Fermentation

  • This type of fermentation occurs under anaerobic conditions and produces not only lactic acid, but also ethanol, acetic acid, and CO₂ and glycerol.

Butyric Fermentation

  • Clostridium bacteria, including C. butyricum, are involved in this fermentation.
  • This process results in the production of CO₂, butyrate, and gas.

Propionic Fermentation

  • This fermentation process utilizes propionic acid and traces of carbon dioxide and acetic acid produced by Propionibacterium.

Butanediol Fermentation

  • This fermentation involves the production of 2,3-butanediol along with ethanol, lactic acid, and formic acid in some bacterial genera like Klebsiella and Enterobacter.
  • Use of the Voges-Proskauer test to identify this fermentation.

Catabolism of Carbohydrates (Other than Glucose)

  • The catabolic pathways for monosaccharides (glucose, fructose, mannose, and galactose) typically involve converting them to glucose derivatives.
  • Glucose, fructose, and mannose are readily phosphorylated using ATP and enter the Embden-Meyerhof pathway.
  • Galactose needs conversion to UDP-galactose before entering the pathway.

Disaccharides

  • Common disaccharides (maltose, sucrose, lactose, and cellobiose) are cleaved into monosaccharides via hydrolysis or phosphorolysis.
  • Hydrolysis uses water to break the bonds, while phosphorolysis uses a phosphate group.
  • Specific enzymes catalyze these reactions (e.g., maltase, sucrase, and lactase) .

Polysaccharides

  • Polysaccharides like starch and glycogen are broken down by enzymes like amylases into simpler sugars (e.g., glucose and maltose) via hydrolysis.
  • Certain fungi produce enzymes like cellulases to break down cellulose.
  • Soil bacteria, such as Azotobacter, can break down poly-β-hydroxybutyrate (PHB) and the components in the cell wall, such as pectin and lignin.

Reserve Polymers

  • Microorganisms synthesize and utilize reserve polymers like glycogen, starch, and poly-β-hydroxybutyrate (PHB) for energy storage.
  • The polymers are catabolized through phosphorolysis to glucose-1-phosphate to enter glycolytic pathways.
  • Degradation of PHB involves the hydrolysis to 3-hydroxybutyrate and subsequent oxidation to acetoacetate.

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Description

This quiz covers the essential concepts of anaerobic respiration, a process that occurs without oxygen. It includes details about electron acceptors, specific bacteria like E. coli and Desulfovibrio sulfuricans, and the outcomes of anaerobic processes. Test your knowledge on how these mechanisms work and their environmental implications.

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