Chap 4 p 2 Microbial Metabolism Overview
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Questions and Answers

What primarily describes catabolism?

  • It uses the products of anabolism for growth.
  • It requires energy to synthesize cellular components.
  • It involves the building of complex organic molecules.
  • It releases energy through the breakdown of complex compounds. (correct)

Which statement accurately describes anabolism?

  • It produces energy as a primary output.
  • It is an exergonic reaction.
  • It requires water to break chemical bonds.
  • It uses ATP or reducing powers to build cellular components. (correct)

Which of the following is a result of catabolic reactions?

  • Production of complex sugars.
  • Formation of nucleic acids.
  • Release of energy captured in ATP. (correct)
  • Building of cellular structures.

What is a common characteristic of anabolic reactions?

<p>They consume more energy than they produce. (C)</p> Signup and view all the answers

Which process converts light energy into chemical energy in the form of sugars?

<p>Photosynthesis. (A)</p> Signup and view all the answers

Which of the following statements regarding metabolic reactions is true?

<p>Catabolism is centered around energy release and breakdown. (C)</p> Signup and view all the answers

What does 'reducing power' generated from catabolism typically include?

<p>NADH, FADH, and NADPH. (A)</p> Signup and view all the answers

What is the main objective of catabolic reactions?

<p>To generate energy and reducing power. (D)</p> Signup and view all the answers

What is the preferred pH range for bacterial growth?

<p>6.5 - 7.5 (A)</p> Signup and view all the answers

Which of the following factors is considered an intrinsic parameter affecting microbial growth?

<p>pH (A)</p> Signup and view all the answers

What does the term 'Water Activity' (aw) refer to?

<p>The pure water quantity available for biological growth (C)</p> Signup and view all the answers

How is the Oxidation-Reduction Potential (OR) of a substrate primarily characterized?

<p>By its ability to lose or gain electrons (A)</p> Signup and view all the answers

What is the significance of buffering pH in material preservation?

<p>It stabilizes the pH level (A)</p> Signup and view all the answers

Which condition typically favors anaerobic microbial growth?

<p>Negative OR potential (D)</p> Signup and view all the answers

Which of the following describes a favorable nutritional condition for microbial growth?

<p>Sufficient nutrient sources (B)</p> Signup and view all the answers

What role does drying or desiccation play in material preservation?

<p>It reduces the water activity (A)</p> Signup and view all the answers

What is the primary role of Nicotinamide adenine dinucleotide (NAD) in microbial metabolism?

<p>Carrying high energy electrons (B)</p> Signup and view all the answers

Which of the following best describes the aerobic pathway of bacterial metabolism?

<p>Uses oxygen as the final electron acceptor and generates high energy (B)</p> Signup and view all the answers

In anaerobic metabolism, what acts as the final electron acceptor?

<p>Intermediary carbohydrates (D)</p> Signup and view all the answers

What is a characteristic of facultative organisms?

<p>They can thrive both in presence and absence of oxygen. (A)</p> Signup and view all the answers

How much ATP do bacteria typically generate from one glucose molecule in anaerobic respiration?

<p>2 ATP (D)</p> Signup and view all the answers

Which of these substances can serve as the final electron acceptor in anaerobic respiration?

<p>Nitrate (A)</p> Signup and view all the answers

Which type of metabolic pathway generates the least amount of energy?

<p>Anaerobic pathway (B)</p> Signup and view all the answers

What is the primary function of superoxide dismutase in microbial metabolism?

<p>To detoxify superoxide radicals (A)</p> Signup and view all the answers

Which of the following is NOT one of the basic needs for biological life?

<p>Source of carbon dioxide (C)</p> Signup and view all the answers

What factor primarily affects the spoilage of materials by microorganisms?

<p>Chemical constituents of the material (C)</p> Signup and view all the answers

Which of the following is an example of a natural antimicrobial constituent?

<p>Eugenol from cloves (B)</p> Signup and view all the answers

What is NOT an extrinsic parameter affecting microbial growth?

<p>Presence of nutrients (D)</p> Signup and view all the answers

How does temperature influence microbial growth?

<p>Microorganisms grow over a wide range of temperatures (B)</p> Signup and view all the answers

Which preservation method would be least effective in controlling microbial growth?

<p>Applying high relative humidity (C)</p> Signup and view all the answers

What role does relative humidity play in microbial growth?

<p>Low humidity can inhibit growth (C)</p> Signup and view all the answers

What impact does the presence of gases have on microbial growth?

<p>Gaseous content contributes to growth capacity (B)</p> Signup and view all the answers

Flashcards

Catabolism

The breakdown of complex organic compounds into simpler ones, releasing energy.

Anabolism

The building of complex organic molecules from simpler ones, requiring energy.

Metabolism

All the chemical reactions in a living organism.

ATP

Adenosine triphosphate; the main energy currency of cells.

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Enzymes

Biological catalysts that speed up chemical reactions.

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Cellular Respiration

A catabolic process that breaks down glucose to produce ATP.

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Biosynthesis

The synthesis of complex molecules from simpler ones.

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Reducing power

Electron carriers like NADH and FADH2, storing energy for use in later reactions.

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Intrinsic Parameters

Factors inherent to the substance itself that affect microbial growth. These include pH, moisture content, oxidation-reduction potential, nutrient availability, antimicrobial components, and biological structures.

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pH and Microorganisms

Bacteria generally prefer neutral to slightly acidic pH (6.5-7.5), while fungi prefer slightly alkaline pH (7.5-8.5).

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Water Activity (aw)

The amount of pure water available for microbial growth in a substance.

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Oxidation-Reduction Potential (OR)

The tendency of a substance to gain or lose electrons. A positive OR (Eh) indicates a more oxidized state, while a negative OR indicates a reduced state.

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Redox Potential and Microbial Growth

Microbes can prefer either oxidized or reduced environments. For example, anaerobic bacteria thrive in a reduced environment with a negative OR.

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Nutrient Content and Growth

The availability of nutrients in a substance significantly impacts microbial growth.

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Antimicrobial Constituents

Substances naturally present in a food or material that inhibit microbial growth.

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Biological Structures

The physical structure of a food or material can influence microbial growth. For example, porous structures can provide more surface area for colonization.

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Microbe's Food Needs

Microorganisms require water, energy sources, nitrogen, minerals, vitamins, and growth factors to survive and thrive.

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Simple Sugars: Spoilage Risk

Materials containing simple sugars are more vulnerable to microbial spoilage because they are easily broken down as an energy source.

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Antimicrobial Defense

Many natural and synthetic materials possess antimicrobial compounds that protect them from microbial spoilage.

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Biological Structures: Barriers

Protective structures like eggshells, skin, and resin help shield materials from microbial attack.

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Temperature's Role

The temperature surrounding a material significantly influences microbial growth and spoilage.

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Humidity's Impact

The relative humidity of the environment affects microbial growth as they need water to survive.

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Gas Content's Influence

The presence and concentration of gases like carbon dioxide, oxygen, and nitrogen in the surrounding atmosphere impact microbial growth.

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Precursor Metabolites

Small building blocks, like carboxylic acids (R-COOH), used for cell mass synthesis. They are obtained from the breakdown of nutrients.

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Aerobic Pathway

A metabolic pathway that breaks down nutrients in the presence of oxygen, generating the most energy for cells.

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Anaerobic Pathway

A metabolic pathway that breaks down nutrients without oxygen, producing less energy and sometimes forming alcohols or organic acids.

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Facultative Pathway

A metabolic pathway that allows organisms to thrive in both the presence and absence of oxygen.

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Anaerobic Respiration

A metabolic pathway that breaks down nutrients using an alternative electron acceptor (not oxygen or an intermediary carbohydrate), like nitrate or sulfate.

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What is the main difference between aerobic and anaerobic pathways?

The presence or absence of oxygen as the final electron acceptor. Aerobic pathways use oxygen, while anaerobic pathways use other molecules.

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Why do some organisms use anaerobic respiration?

Because they live in environments where oxygen is scarce or absent, and need a way to generate energy in those conditions.

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Study Notes

Microbial Metabolism

  • Metabolism is the sum of all processes that occur in living cells. It involves thousands of biosynthetic reactions, all governed by enzymes, that generate materials for growth.
  • Metabolism includes two types of reactions:
    • Catabolism: breakdown of complex molecules, releasing energy
    • Anabolism: building complex molecules from simpler ones, requiring energy
  • Catabolism is broken down into three key pathways:
    • Aerobic respiration: oxygen is the final electron acceptor; generates the most energy (often 36-38 ATP per glucose molecule)
    • Anaerobic respiration: an inorganic molecule other than oxygen is the final electron acceptor; produces less energy than aerobic respiration
    • Fermentation: an organic molecule acts as the final electron acceptor; produces the least energy (often 2 ATP per glucose molecule)
  • Factors affecting microbial growth include intrinsic and extrinsic factors:
    • Intrinsic: inherent properties of the substance (material)
      • pH: bacteria prefer neutral to slightly acidic (6.5-7.5), fungi prefer slightly alkaline (7.5-8.5)
      • Moisture content (water activity): the amount of water available for growth;
      • Oxidation-reduction potential (Eh): how readily a substrate/material gives or gains electrons.
      • Nutrient content: the availability of essential nutrients (water, energy source, nitrogen, minerals)
      • Antimicrobial constituents: naturally occurring substances that deter microbial growth (e.g., spices)
      • Biological structures: protective structures that make certain materials less susceptible to spoilage (e.g. egg shells, plant cell walls)
    • Extrinsic: characteristics of the surrounding environment
      • Temperature: microorganisms have varying temperature ranges for growth.
      • Relative Humidity: influences water availibility for microbial growth
      • Gaseous contents: the presence and concentration of gases (oxygen, carbon dioxide) may influence microbial growth

Learning Outcomes

  • Students should be able to explain catabolism and anabolism reactions.
  • Students should be able to differentiate the three forms of microbial metabolism.
  • Students should be able to discuss the intrinsic and extrinsic factors affecting microbial growth.

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Chapter 4 Microbial Metabolism (MIC461) PDF

Description

Explore the fundamental processes of microbial metabolism, including catabolism and anabolism. This quiz covers key pathways such as aerobic and anaerobic respiration, fermentation, and factors affecting microbial growth. Test your understanding of how these processes contribute to life at the cellular level.

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