Biochemistry Chapter 3: Metabolism

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Questions and Answers

What is the primary function of the glyoxylate cycle?

To oxidize pyruvate to CO2

To convert glucose to pyruvate

To synthesize essential precursor molecules from C2 compounds (correct)

To generate ATP from the breakdown of glucose

Which of the following statements accurately describes the role of ATP in cellular processes?

ATP is a high-energy compound that is used to store energy and fuel cellular processes (correct)

ATP is a high-energy compound that is used to directly perform cellular work

ATP is a low-energy compound that is used to store energy and fuel cellular processes

ATP is a low-energy compound that is used to directly perform cellular work

Which of these metabolic pathways is involved in the breakdown of glucose to pyruvate?

Citric Acid Cycle

Electron Transport Chain

Glycolysis (correct)

Glyoxylate Cycle

What is the difference between catabolic and anabolic pathways?

Catabolic pathways break down molecules, while anabolic pathways build up molecules (A), Catabolic pathways are exergonic, while anabolic pathways are endergonic (C) Signup and view all the answers

Which of the following is NOT a characteristic of energy-rich compounds?

They are always involved in electron transport chains (C) Signup and view all the answers

What is the main difference between fermentation and respiration?

Respiration utilizes an external electron acceptor, while fermentation does not. (D) Signup and view all the answers

Which of the following is NOT a component of the electron transport chain?

Pyruvate kinase (C) Signup and view all the answers

What is the role of proton motive force in cellular respiration?

To synthesize ATP (C) Signup and view all the answers

Which of the following processes occurs in the cytoplasm?

Glycolysis (B) Signup and view all the answers

What is the main difference between aerobic and anaerobic respiration?

All of the above. (D) Signup and view all the answers

What is chemolithotrophy?

The ability to obtain energy from inorganic compounds (D) Signup and view all the answers

What is the role of photosynthetic reaction centers in purple bacteria?

All of the above. (D) Signup and view all the answers

Which of the following statements about Escherichia coli is TRUE?

E. coli can grow faster with nitrate respiration than with fermentation. (A) Signup and view all the answers

What is the primary source of nitrogen for most microbes?

Ammonia (NH3) (A), Nitrate (NO3-) (B) Signup and view all the answers

Which of the following is NOT a characteristic of fatty acid biosynthesis?

Fatty acid biosynthesis is identical across all species. (D) Signup and view all the answers

What is the primary function of nitrogen fixation?

To convert gaseous dinitrogen (N2) into ammonia (NH3) (D) Signup and view all the answers

Which of the following pathways is NOT involved in the biosynthesis of amino acids?

Calvin cycle (B) Signup and view all the answers

What is the general relationship between temperature and the saturation of fatty acids in bacteria?

Lower temperatures lead to longer and more unsaturated fatty acids. (B) Signup and view all the answers

Study Notes

Chapter 3: Metabolism

This chapter covers metabolism, which encompasses all biochemical reactions necessary for life.
Energy is conserved by converting it into a usable form.
Cells generate Adenosine Triphosphate (ATP) to store and utilize energy in cellular processes.

3.1 Defining the Requirements for Life

Metabolism is the sum total of all biochemical reactions within a cell.
Metabolism includes catabolic & anabolic pathways.

Anabolism and Catabolism

Catabolic pathways release energy by breaking down larger molecules into smaller ones.
Anabolic pathways use energy to synthesize larger molecules from smaller ones.
Energy released in catabolic pathways fuels anabolic processes.

3.1 Defining the Requirements for Life - Energy Sources

Organisms can obtain energy from chemicals (chemosynthesis) or light (photosynthesis).
Chemoorganotrophs: Use organic molecules as energy sources.
Chemolithotrophs: Use inorganic molecules as energy sources.
Phototrophs: Use light as energy sources.

3.4 Cellular Energy Conservation

Adenosine Triphosphate (ATP) is the principal energy currency in cells.
ATP stores energy in high-energy phosphate bonds.
Several other chemicals also store energy in bonds, but ATP is the primary molecule for energy transfer

3.4 Cellular Energy Conservation - Energy Rich Compounds

Several compounds contain energy in their phosphate or sulfur bonds.
Not all phosphate bonds have high energy content.
Examples discussed: Phosphoenolpyruvate, ATP, Acetyl Phosphate, Glucose 6-phosphate, and Acetyl-CoA.
The chapter discusses specific energy values using AG° values.

II. Catabolism: Chemoorganotrophs

Subsections (3.6-3.9) cover specific catabolic pathways used by chemoorganotrophs for energy production.
These include Glycolysis, Citric Acid Cycle, Glyoxylate Cycle, Fermentation pathways, Respiration pathways, and the role of electron carriers.

3.6 Glycolysis

Glycolysis is a crucial universal pathway for glucose catabolism.
This process oxidizes glucose to pyruvate.
It is a two-stage process.

3.6 The Citric Acid Cycle

Pyruvate is oxidized to CO2 in the Citric Acid Cycle (CAC).
The CAC produces important precursor molecules for biosynthesis.
This pathway can process various carbon substrates.

3.6 The Glyoxylate Cycle

The glyoxylate cycle is an alternative to the CAC, used for oxidizing C₂ compounds (like acetate).

3.7 Principles of Fermentation

Fermentation involves substrate-level phosphorylation for ATP production.
It maintains redox balance by reducing oxidized compounds.
It usually involves excretion of the products.

3.8 Principles of Respiration: Electron Carriers

Respiration breaks down glucose to make ATP.
Electrons move from reduced donors to external acceptors (e.g., oxygen).
Reoxidation of NADH and FADH₂ occurs during electron transport.
Electron transport occurs in the cytoplasmic membrane
Creates a proton motive force for ATP synthesis.

3.8 Principles of Respiration: Electron Carriers - Other Electron carriers

Specific electron carriers like NADH dehydrogenases, flavoproteins, cytochromes, and quinones are involved in electron transport chains.

3.9 Principles of Respiration: Generating a Proton Motive Force

Electron transfer during respiration is exergonic.
It drives proton pumping across membranes.
This creates a proton motive force, which is used by ATP synthase to generate ATP.

Cellular Respiration Summary

Cellular respiration involves glycolysis, pyruvate oxidation/citric acid cycle, and oxidative phosphorylation.
These steps produce ATP.

3.10 Anaerobic Respiration and Metabolic Modularity

Microorganisms can adapt metabolic pathways to utilize various electron donors.
Aerobic respiration is more efficient than anaerobic respiration.
Oxygen availability influences the kinds of metabolic processes.

3.11 Chemolithotrophy and Phototrophy

Phototrophy is energy capture via light.
Phototrophs use light energy to synthesize ATP.

IV. Biosynthesis

This section deals with the synthesis of molecules vital for life.
The sections include Autotrophy,sugars, amino acids, nucleotides, and lipids.

3.12 Autotrophy and Nitrogen Fixation

Microorganisms obtain nitrogen from ammonia, and some fix atmospheric nitrogen gas to produce ammonium.

3.14 Amino Acids and Nucleotides

Amino acid and nucleotide biosynthesis occurs via varied multistep pathways.
Amino acid precursors arise from intermediates in central metabolic pathways.

3.15 Fatty Acids and Lipids

Fatty acids can be saturated or unsaturated.
Varying carbon chain lengths are observed across different bacteria species.

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Description

This quiz focuses on Chapter 3 of Biochemistry, which delves into metabolism and its critical biochemical reactions essential for life. It explores the concepts of anabolism and catabolism and how organisms derive energy through various pathways. Understanding these processes is crucial for comprehending cellular functions and energy utilization.