Brock Biology Chapter 3: Microbial Metabolism

What is metabolism?

All biochemical reactions needed for life, including catabolism and anabolism.

What are the two main types of metabolic processes?

Catabolism (to obtain energy) and anabolism (to make cellular material).

What does the law of conservation of energy state?

Energy is neither created nor destroyed; it is converted into a usable form.

What is the primary energy currency of the cell?

Adenosine triphosphate (ATP).

What are the fundamental metabolic requirements for all cells?

Water, carbon and other nutrients, free energy, and reducing power.

What is free energy?

Energy available to do work; some reactions release energy while others require it.

What is the symbol for change in free energy?

ΔG' (delta G prime).

What type of reactions are exergonic?

Reactions with a negative ΔG' that release free energy.

What type of reactions are endergonic?

Reactions with a positive ΔG' that require energy.

What are catabolic pathways?

Exergonic cellular processes that generate free energy.

What are anabolic pathways?

Endergonic cellular processes that require energy for synthesis.

What is reducing power?

The ability to donate electrons during electron transfer reactions (redox reactions).

What are redox reactions?

Reactions that involve the transfer of electrons between an electron donor and an electron acceptor.

What are phototrophs?

Organisms that obtain energy from light.

What are chemotrophs?

Organisms that obtain energy from chemical reactions.

What are chemoorganotrophs?

Organisms that obtain energy and reducing power from organic compounds.

What are chemolithotrophs?

Organisms that obtain energy and reducing power from inorganic compounds.

What are heterotrophs?

Organisms that obtain carbon from organic sources.

What are autotrophs?

Organisms that obtain carbon from carbon dioxide (CO2).

What is the redox tower?

A representation of the range of possible reduction potentials in redox reactions.

What is the relationship between reduction potential and energy release?

The further electrons drop in the redox tower, the greater the amount of energy released.

What is the significance of NADH in metabolism?

NADH is a key electron carrier that donates electrons in metabolic reactions.

What does ATP stand for?

Adenosine triphosphate.

How many high-energy phosphate bonds does ATP contain?

Two high-energy phosphate bonds.

What is the role of ATP in cellular metabolism?

ATP stores energy and fuels various cellular processes.

What is the typical yield of ATP from the aerobic respiration of one mole of glucose?

Up to 38 moles of ATP, although some energy is lost as heat.

What is the process of hydrolysis of ATP?

The process that releases energy for anabolic reactions.

What is the difference between aerobic and anaerobic reactions?

Aerobic reactions use oxygen as the electron acceptor, while anaerobic reactions use other substances.

What are energy-rich compounds in cells?

Compounds that have energy-rich phosphate or sulfur bonds, necessary for ATP synthesis.

What type of bonds do Coenzyme A derivatives have?

Energy-rich thioester bonds.

What are the three mechanisms of ATP generation?

Substrate-level phosphorylation, oxidative phosphorylation, and photophosphorylation.

What is substrate-level phosphorylation?

A process where energy-rich bonds in substrates are hydrolyzed to directly drive ATP formation.

What is oxidative phosphorylation?

A process where the movement of electrons generates a proton motive force used to synthesize ATP.

What is photophosphorylation?

A process where light energy is used to form a proton motive force for ATP synthesis.

What is activation energy?

The minimum energy required for a chemical reaction to begin.

What role do catalysts play in chemical reactions?

They facilitate reactions without being consumed and lower the activation energy barrier.

What are enzymes?

Major cellular catalysts that lower activation energy and increase reaction rates, typically proteins.

What is an enzyme-substrate complex?

A temporary complex formed when an enzyme binds to its substrate.

What is the active site of an enzyme?

The region of the enzyme that binds to the substrate.

What are prosthetic groups in enzymes?

Small nonprotein molecules that are tightly bound to enzymes and participate in catalysis.

What are coenzymes?

Loosely and transiently bound nonprotein molecules that assist enzymes, often derived from vitamins.

What is glycolysis?

A nearly universal pathway for glucose catabolism that oxidizes glucose to pyruvate.

What are the two stages of glycolysis?

Preparatory stage (forming key intermediates) and redox stage (energy conservation and formation of pyruvate).

What is the citric acid cycle?

A series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA.

What are the precursors of several amino acids in the citric acid cycle?

α-Ketoglutarate and oxaloacetate.

What is the main purpose of fermentation?

To conserve energy and maintain redox balance through substrate-level phosphorylation.

What are common products of fermentation?

Ethanol, lactic acid, and various organic acids.

How does yeast ferment glucose?

Yeast ferments glucose to produce 2 ethanol and 2 CO2, regenerating NAD+ from NADH.

What is the role of NADH in fermentation?

NADH donates electrons to an electron acceptor, such as pyruvate, to regenerate NAD+.

What is the electron transport chain?

A series of protein complexes that transfer electrons from reduced electron donors to external electron acceptors.

What is the result of electron transport in respiration?

Formation of an electrochemical gradient that conserves energy for ATP synthesis.

What is the significance of redox balance in cellular metabolism?

It ensures that electron carriers like NADH are reoxidized to maintain metabolic processes.

What is the role of coenzyme A in metabolism?

Coenzyme A is essential for the synthesis and oxidation of fatty acids and the citric acid cycle.

What is the role of NADH in cellular respiration?

NADH acts as an electron donor in the electron transport chain.

What is the function of ATP synthase?

ATP synthase uses energy from the proton motive force to synthesize ATP.

How many protons are required to produce one ATP in E. coli?

Approximately 3 protons (H+) are needed to make 1 ATP.

What is the difference between aerobic and anaerobic respiration?

Aerobic respiration uses oxygen as the terminal electron acceptor, while anaerobic respiration uses other acceptors.

What is the maximum ATP yield from one glucose molecule during aerobic respiration?

38 ATP can be produced from one glucose molecule during aerobic respiration.

What is fermentation?

Fermentation is a metabolic process that generates ATP without the use of an external electron acceptor.

What is chemolithotrophy?

Chemolithotrophy is a process that uses inorganic chemicals as electron donors.

What is phototrophy?

Phototrophy uses light energy to generate a proton motive force for ATP synthesis.

What is the Calvin Cycle?

The Calvin Cycle is a metabolic pathway used by autotrophs to fix carbon dioxide into organic compounds.

What is nitrogen fixation?

Nitrogen fixation is the process of converting atmospheric nitrogen (N2) into ammonia (NH3) for biological use.

What is the role of RubisCO in the Calvin Cycle?

RubisCO catalyzes the first step of the Calvin Cycle, converting ribulose bisphosphate into 3-phosphoglyceric acid.

What is the significance of proton motive force (pmf)?

The pmf is essential for ATP synthesis and drives the rotation of ATP synthase.

What is the difference between substrate-level phosphorylation and oxidative phosphorylation?

Substrate-level phosphorylation generates ATP directly from a substrate, while oxidative phosphorylation uses the electron transport chain.

What are terminal electron acceptors in anaerobic respiration?

Terminal electron acceptors can include nitrate, sulfate, or carbon dioxide.

What is the primary electron donor in chemolithotrophy?

In chemolithotrophy, inorganic compounds like hydrogen sulfide or ferrous iron serve as electron donors.

What is the main difference between chemoorganotrophs and chemolithotrophs?

Chemoorganotrophs use organic compounds for carbon, while chemolithotrophs typically use inorganic sources.

What is the function of cytochrome in the electron transport chain?

Cytochromes are proteins that transfer electrons and help create the proton gradient.

How does anaerobic respiration conserve energy compared to aerobic respiration?

Anaerobic respiration conserves less energy than aerobic respiration because it uses less electropositive electron acceptors.

What is the role of photopigments in phototrophy?

Photopigments absorb light energy and transfer it to the photosynthetic reaction center.

What is the outcome of glycolysis?

Glycolysis converts glucose into two molecules of pyruvate, producing a net gain of 2 ATP and 2 NADH.

What is the significance of the c ring in ATP synthase?

The c ring rotates to facilitate the synthesis of ATP from ADP and inorganic phosphate.

What is the energy yield from one molecule of FADH2 during oxidative phosphorylation?

One molecule of FADH2 yields approximately 2 ATP during oxidative phosphorylation.

What are the products of the Calvin Cycle?

The Calvin Cycle produces glucose and other carbohydrates from carbon dioxide.

What is the significance of the electron transport chain in respiration?

The electron transport chain generates a proton gradient that drives ATP synthesis.

What is the role of ammonia in nitrogen fixation?

Ammonia is the product of nitrogen fixation and is used to synthesize amino acids and nucleotides.

What is the importance of reducing power in biosynthesis?

Reducing power, provided by NADPH, is essential for the reduction of carbon compounds during biosynthesis.