Chapter 6: Microbial Metabolism: Fueling Cell Growth

The process that links the electron transport chain to ATP synthesis is called the ____ theory.

chemiosmotic

All of the following processes commonly rely on microbial metabolism to produce items for human use EXCEPT _____. -production of ethanol from corn stalks, sugar cane, and wood for use as biofuel -conversion of crude oil to gasoline at a coastal refinery -wine production -use of Lactococcus and Lactobacillus species in cheese-making

conversion of crude oil to gasoline at a coastal refinery

In eukaryotic cells, glycolysis and the pentose phosphate pathway take place in the _____; the transition step and TCA cycle take place in the ____.

cytoplasm; mitochondria

The energy released when a chemical bond is broken that is available to do work is called _____.

free energy

The central metabolic pathway that splits glucose and gradually oxidizes it to form two molecules of pyruvate is ____.

glycolysis

The primary pathway used by many organisms to convert glucose to pyruvate is _____.

glycolysis

The three central metabolic pathways that gradually oxidize glucose to CO2 are _____, the _____ _____ pathway, and the _____ cycle.

glycolysis, pentose phosphate, TCA

Unlike human cells, some prokaryotes can use _____ as an energy source.

hydrogen sulfide

An atom that has a lower affinity (attraction) for electrons than another is described as _____ than the other.

less electronegative

The series of sequential chemical reactions in a cell that converts a starting compound to an end product is called a _____ pathway.

metabolic

the sum total of chemical reactions in a cell

metabolism

In addition to glucose, which of the following organic compounds can serve as energy sources for microbes?

monosaccharides, fatty acids, lipids, disaccharides, proteins, polysaccharides

Energy released from electrons passing down the electron transport chain is coupled to ____.

movement of protons across the membrane

In the representation of an electron transport chain (shown), the terminal electron acceptor is ____.

oxygen

The central metabolic pathway that generates reducing power in the form of NADPH is the _____ ______ pathway.

pentose phosphate

Photosynthetic organism can generate ATP by ______, a process that uses the sun's radiant energy and an electron transport chain to create a proton motive force.

photophosphorylation

Energy is the potential to do work and can exist as _____ energy (stored energy) and ______ energy (energy of motion).

potential; kinetic

In addition to yielding energy, catabolic pathways generate carbon intermediates that can be used in anabolic pathways for the biosynthesis of macromolecules. These carbon skeletons are called _____ _____.

precursor metabolites

All of the following represent the two fundamental tasks cells need to accomplish in order to grow EXCEPT: synthesizing cell membranes harvesting energy sexual reproduction converting energy into a form that can power energy-consuming reactions production of ribosomes

sexual reproduction

The ATP generated by fermentation comes from ____.

substrate-level phosphorylation during glycolysis

Proteins that contain heme, a molecule that holds and iron atom in its center.

Cytochromes

When a single molecule of glucose is processed by glycolysis in an E. coli cell, which of the following make up the net gain of this process?

-Six precursor metabolites -2 molecules of ATP -2 molecules of NADH

Recall that E. coli can grow in glucose-salts medium, which contains only glucose and a few inorganic salts. This means the glucose is serving what two purposes in the cell? ~A monosaccharide that the cell can assemble into polysaccharide such a cellulose for its cell wall ~Source of nitrogen ~Starting point from which all cell components are made ~Source of phosphate ~Energy source

-Starting point from which all cell components are made -Energy source

Consider the maximum theoretical ATP yield from oxidative phosphorylation of a single molecule of glucose in prokaryotes. Match the relative contributions of the central metabolic pathways and final yield with their approximate contribution in terms of ATP. Include the following pair, already given: 6 ATP from the transition step. 6 ATP 22 ATP 34 ATP

6 ATP - Glycolysis 22 ATP - TCA cycle 34 ATP - Total maximum yield

Testing for the ability of organisms to produce mixed acids via fermentation can be clinically important because it can differentiate members of the ____ family.

Enterobacteriaceae

Although a modest amount of ATP is generated via substrate-level phosphorylation by the central metabolic pathways, these pathways produce a large amount of reducing power that can be used to generate a much larger quantity of ATP via _____ phosphorylation.

oxidative

The mechanism by which cellular respiration uses reducing power generated in glycolysis, the transition step, and the TCA cycle to synthesize ATP is ____ phosphorylation.

oxidative

When cells use glucose to make amino acids and other subunits for biosynthesis, certain intermediates of catabolism called ______ metabolites exit the "deconstruction line" of the breakdown process.

precursor

Which of the following correctly describe some of the forms of energy represented in this photograph? -Potential energy of the water behind the dam -Kinetic energy of chemical bonds made by the photosynthetic organisms utilizing the energy of sunlight -Electrical energy generated by the hydroelectric dam as is captures the energy from moving water -Kinetic energy of the photons that make up sunlight -Potential energy of the water flowing through the dam

-Potential energy of the water behind the dam -Electrical energy generated by the hydroelectric dam as it captures the energy from moving water -Kinetic energy of the photons that make up sunlight

Consider the figure showing the formation and breakdown of ATP. Fill in the labels of the figure by matching the terms with their correct number.

1 - ATP 2 - Energy released drives anabolic reactions 3 - ADP 4 - Energy used comes from catabolic reactions

Place the following steps in the correct order to show how the spatial arrangement of electron carriers in a bacterial electron transport chain helps explain how protons are shuttled from one side of the membrane to the other.

1. An electron carrier (e.g., NADH + H) donates electrons to a hydrogen carrier, which also picks up protons. 2. The hydrogen carrier passes electrons to a carrier that only accepts electrons. 3. Because the electron carrier only accepts electrons, the protons are released to the outside of the cell. 4. A proton motive force is set up as protons are moved from the inside of the cell to the outside.

T/F: Each individual prokaryote within a species will have an electron transport chain made up of the same components.

False

Consider the three central metabolic pathways that gradually oxidize glucose to CO2. Why are these amphibolic pathways?

-Although they are catabolic, the precursor metabolites and reducing power they generate can be diverted for biosynthesis (anabolism). -"Amphi" means "both kinds," which reflects the dual role of these central metabolic pathways.

Which of the following correctly describe respiration? -Electrons extracted from glucose are transferred to the electron transport chain -The electron transport chain uses the electrons to generate a proton motive force that can be used to generate ATP -It is only present in aerobic organisms -All organisms that grow in the presence of O2 must use respiration for their energy needs

-Electrons extracted from glucose are transferred to the electron transport chain -The electron transport chain uses the electrons to generate a proton motive force that can be used to generate ATP

Which of the following are important electron carriers for a cell?

-FAD/FADH2 -NAD+/NADH -NADP+/NADPH

Rank the following energy-generating processes from greatest energy yield at the top to least energy yield at the bottom: fermentation aerobic respiration anaerobic respiration

1. aerobic respiration 2. anaerobic respiration 3. fermentation

When a cell processes glucose or other organic molecules through its central metabolic pathways, it does so to generate what three critical things?

ATP, reducing power, precursor metabolites

The TCA cycle incorporates an acetyl group from the transition step and releases two precursor metabolites, two molecules of ____, and two molecules of ____.

ATP; CO2

Organic compounds

Chemical energy

Proteins that are synthesized from the vitamin riboflavin

Flavoproteins

When discussing electron carriers in the context of biological reactions, why do we often ignore the location of protons?

In aqueous solutions, protons do not require carriers.

Photons of sunlight

Kinetic energy

Aerobic respiration in the ATP-generating process of prokaryotic chemoorganoheterotrophs

O2

Fermentation in the ATP-generating process of prokaryotic chemoorganoheterotrophs

Organic molecule (pyruvate or a derivative)

Energy from exergonic reactions is used to create a proton motive force that drives the addition of P2 to ADP.

Oxidative phosphorylation

The sun's radiant energy and an electron transport chain create a proton motive force that drives the addition of P2 to ADP.

Photophosphorylation

Lipid-soluble organic molecules that move freely in the membrane; includes one that serves as a source of vitamin K for humans and other mammals.

Quinones

Which of the following is an example of activation energy?

The energy of a small flame used to light the natural gas of a Bunsen burner.

In order for cells to obtain energy, they remove electrons from an energy source and ultimately donate them to the terminal electron acceptor. What does this tell us about the electron affinity of the energy source and the terminal electron acceptor?

The energy source has a lower affinity for electrons, and the terminal electron acceptor has a higher affinity for electrons.

Which of the following best describes the conversion of energy from one form to another illustrated in the picture?

The potential energy of water stored behind the dam is converted to kinetic energy of moving water, which is converted to electrical current.

Why does anaerobic respiration yield less energy than aerobic respiration?

The terminal electron acceptors used in anaerobic respiration have lower electron affinities than O2.

Which of the following best summarizes prokaryotes as a group in terms of their metabolism?

They are highly diverse with respect to compounds they use for energy but remarkably similar in their biosynthetic processes.

Which of the three central metabolic pathways generates the most reducing power?

Tricarboxylic acid (TCA) cycle

T/F: The change in free energy for a given reaction is the same regardless of the number of steps involved.

True

The main energy currency of cells is ATP, which stands for _____ _____.

adenosine triphosphate

The three central metabolic pathways that gradually oxidize glucose to CO2 are catabolic. However, they also generate precursor metabolites and reducing power that can be diverted for use in anabolic pathways. To reflect this dual role, these pathways are sometimes called _____ pathways.

amphibolic

the set of chemical reactions that synthesize and assemble the subunits of macromolecules

anabolism

When a molecule other than O2 serves as the terminal electron acceptor for the electron transport chain, the organism is utilizing _____ respiration.

anaerobic

You are studying bacteria you isolated from sediments at the bottom of a pond. Your research reveals they are using sulfate (SO42) as a terminal electron acceptor. This tells you they are capable of _____ respiration.

anaerobic

In the figure, Compound X donates electrons to Compound Y. Therefore, Compound X is the electron ______ and Compound Y is the electron _____.

donator; acceptor

Metabolism is best defined as

the sum total of all chemical reactions in a cell

When photosynthetic organisms convert the energy of sunlight to the energy of chemical bonds, and when chemoorganotrophs covert the energy of one type of chemical bond to that of another, they are _____.

transforming energy

The step that links glycolysis to the TCA cycle is called the ______ step.

transition

Oxidative phosphorylation and photophosphorylation are similar in that both processes _____.

use an electron transport chain to set up a proton motive force used to generate ATP.

Glucose, catabolism encompasses two key processes: (1) oxidizing glucose molecules to generate ATP, reducing power, and precursor metabolites; and (2) transferring the electrons carried by NADH and FADH2 to the terminal electron acceptor. The second process, transfer to electrons, is accomplished by which of the following?

-Fermentation -Cellular respiration

Pyruvate and pyruvic acid ____.

-are terms that refer to the ionized and the undissociated forms of the molecule -are terms often used interchangeably by biologists

Which of the following accurately describe the pentose phosphate pathway?

-Its primary role is the production of compounds used in biosynthesis -It breaks down glucose -It yields reducing power in the form of NADPH

Which of the following explain why a cell might undergo fermentation? -The cell might lack the pathways for respiration, so fermentation might be the only option. -The cell can obtain more ATP from this pathway than via respiration. -The cell has a limited number of electron carrier molecules that must be regenerated for glycolysis to continue. -This allows the cell to grow in the presence of O2, which otherwise it would be unable to do. -The cell might not have the appropriate terminal electron acceptor available for respiration.

-The cell might lack the pathways for respiration, so fermentation might be the only option. -The cell has a limited number of electron carrier molecules that must be regenerated for glycolysis to continue. -The cell might not have the appropriate terminal electron acceptor available for respiration

When a reduced electron carrier (reducing power) transfers its electrons to another molecule, what occurs?

-The electron carrier is oxidized -The energy level of the recipient molecule is raised -The recipient molecule is reduced

Which of the following correctly describe the transition step and the tricarboxylic (TCA) cycle?

-Together they generate the most reducing power of all the central metabolic pathways. -The TCA cycle oxidizes a 2-carbon acetyl group to release two molecules of CO2. -The transition step converts the pyruvate from glycolysis into acetyl-CoA.

A general group of electron carriers found in electron transport chains is quinones, that _____.

-are lipid-soluble organic molecules that move freely in the membrane, transferring electrons between different protein complexes -exist as several types, including ubiquinone and menaquinone

the set of chemical reactions that degrade compounds, releasing their energy

catabolism

Consider a cell converting glucose into CO2, and water with the release of energy. This is an example of what type of metabolism, and the reactions themselves are considered to be what?

catabolism; exergonic

What happens to an organism if it lacks one or more enzymes in a given biosynthetic pathway?

It must have the end product provided from an external source.

Consider the illustration of a metabolic pathway. Math the labels with their appropriate locations. Assume a sequential order of letters, i.e., enzyme a would come before enzyme b.

Starting compounds - 1 Enzyme a - 2 Intermediate a - 3 Enzyme b - 4 Intermediate b - 5 Enzyme c - 6 End product - 7

Energy released in an exergonic reaction is used to power the addition of P2 to ADP.

Substrate-level phosphorylation

Anaerobic respiration in the ATP-generating process of prokaryotic chemoorganoheterotrophs

Molecule other than O2 such as nitrate, nitrite, or sulfate