Chapter 6. Microbial Metabolism (LS)

in aerobic respiration, ___ serves as the terminal electron acceptor

O2

the main energy currency of cells is ATP, which stands for ___ ___

adenosine triphosphate

the general group of electron carries synthesized from the vitamin riboflavin is called ___

flavoproteins

the three key metabolic pathways that gradually oxidize ___ to CO2 are collectively referred to as the central metabolic pathways

glucose

in prokaryotes, the electron transport chain is located in the ___ membrane, whereas in eukaryotic cells it is in the ___ membrane of the mitochondria

cytoplasmic, inner

consider how cells obtain energy to make ATP. The chemical that serves as the electron donor is the ___ source, and the one that ultimately accepts those electrons is the ___ electron acceptor

energy, terminal

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

each types of them major electron carries is referred to by two different abbreviations (NAD+/NADH, NADP+/NADPH, and FAD/FADH2.) the first of each pair refers to the ___ form and the second of each pair refers to the ___ form

oxidized, reduced

___ organisms harvest the energy of sunlight, using it to power the synthesis of organic compounds from CO2, whereas ___ obtain energy by degrading organic compounds made by others

photosynthetic, chemoorganotrophs

enzymes function as biological catalysts, accelerating the conversion of one substance, the ___, into another, the ___.

substrate, product

a cell has only a limited number of electron carrier molecules. During glycolysis, if electrons are not removed from NADH, the cell soon runs out of available NAD+, and the breakdown of glucose ends. This presents a problem for cells that lack a suitable terminal electron acceptor for the electron transport chain or that cannot respire. The solution to this problem is called ___

fermentation

cells constantly produce ATP during ___, reactions of ___ and then use it to power ___ reactions of ___

exergonic, catabolism, endergonic, anabolism

in oxidation-reduction reactions, or redox reactions, the substance that loses electrons is ___, and the substance that gains those electrons is ___

oxidized, reduced

consider the three central metabolic pathways that gradually oxidize glucose to CO2. Why are these amphilbotlic pathways. -"amphibolic" is another way for "catabolic," which refers to the set of processes that breaks down molecules and releases energy -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 those central metabolic pathways -the term "amphibolic" reflects that these are metabolic pathways that take place in an aqueous environment

-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 those central metabolic pathways

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 of electrons, is accomplished by which of the following? -the pentose phosphate pathway -glycosis -cellular respiration -the TCA cycle -fermentation

-cellular respiration -fermentation

in contrast to an exergonic reaction, which of the following accurately describe an endergonic reaction? -the reaction requires an input of energy in order to proceed -the reaction releases energy as it proceeds -the products have more free energy than the starting compounds -the starting compounds have more free energy than the products

-the products have more free energy than the starting compounds -the reaction requires an input of energy in order to proceed

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

True

an atom that has a lower affinity (attraction) for electrons than another is described as ___ than the other a.) less electronegative b.) more electronegative

a.) less electronegative

unlike chemoorganotrophs, photosynthetic organisms generate ATP by ___: a.) photophosphorylation b.) oxidative phosphorylation c.) substrate-level phosphorylation

a.) photophosphorylation

proton motive force is ___ a.) the form of energy that results from the electrochemical gradient established by the electron transport chain b.) the positive charge that repels protons from the electrons orbiting round them in atoms c.) the attractive force that makes up hydrogen bonds, for example, those holding together water molecules

a.) the form of energy that results from the electrochemical gradient established by the electron transport chain

all of the following are true statements regarding energy EXCEPT___: a.) energy is the capacity to do work b.) energy is destroyed each time it is changed from one form to another c.) energy cannot be created d.) energy can exist as potential energy e.) energy can exist as kinetic energy

b.) energy is destroyed each time it is changed from one form to another

in the stair analogy of an electron transport chain, the top of the stairs represents what energy level, and the bottom of the stairs represents what energy level? a.) low; high b.) high; low

b.) high; low

when discussing electron carries in the context of biological reactions, why do we often ignore the location of protons? a.) protons, because of their positive charge, are repelled by electron carriers, whose charge distribution only allows them to cary electrons b.) in aqueous solutions, protons do not require carriers c.) in aqueous solutions, electrons do not require carriers d.) electron carriers only carry electrons, not protons, so the protons do not matter

b.) in aqueous solutions, protons do not require carriers

a bacterium that lacks an electron transport chain would be expected to be oxidase ___: a.) positive b.) negative

b.) negative

which of the following best describes the conversion of energy from one form to another? a.) the potential energy in the chemical bonds of the water molecules is converted into electricity b.) the potential energy of water stored behind the dam is converted to kinetic energy of moving water, which is converted to electrical current c.) the kinetic energy of water stored behind the dam is converted to potential energy of moving water, which is converted to electricity d.) the potential energy of the water is directly converted into electrical energy, which can be used to charge a battery

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

other than generating some ATP via the substrate-level phosphorylation steps of glycolysis, what critical role do the additional steps of fermentation accomplish? a.) they produce end products, such as ethanol or lactic acid, which are used to inhibit the growth of competitors b.) they consume excess reducing power in order to regenerate NAD+ so that it can accept electrons to keep glycolysis going c.) they use up extra ATP so that glycolysis can continue producing additional reducing power d.) they generate end products such as ethanol, which the cell can then use as an energy source

b.) they consume excess reducing power in order to regenerate NAD+ so that it can accept electrons to keep glycolysis going

all of the following are essential form an electron transport chain to function EXCEPT ___: a.) electron carries such as quinones, cytochromes, and flavoproteins b.) protein complexes that function as proton pumps c.) ATP d.) electrons e.) a terminal electron acceptor f.) a membrane

c.) ATP

menaquinone is a quinone used in the electron transport chain of some prokaryotes. It plays an important role for humans and other mammals because it ___ a.) provides a major source of energy and carbon b.) inhibits the growth of pathogens, thereby helping the normal microbiota maintain a good microbial community for the host c.) serves as a source of vitamin K, providing much of the host's requirement via absorption in the intestinal tract d.) limits the growth rate of bacteria, keeping them from overpopulating the small intestine

c.) serves as a source of vitamin K, providing much of the host's requirement via absorption in the intestinal tract

the process that links the electron transport chain to ATP synthesis is called the ___ theory

chemiosmotic

in oder for the 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? a.) this information doesn't tells us anything about the electron affinities of these molecules b.) the energy source has a higher affinity for electrons, and the terminal electron acceptor has a lower affinity for electrons c.) the energy source and the terminal electron acceptor have equal but opposite electron affinities d.) the energy source has a lower affinity for electrons, and the terminal electron acceptor has a higher affinity for electrons

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

fermentation

does not use and electron transport chain; yields the least ATP of the three processes

the series of sequential chemical reaction in a cell that converts a starting compound to an end product is called a ___ pathway

metabolic

catabolism

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

anabolism

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

metabolism

the sum total of chemical reactions in a cell

photophosphorylation

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

anaerobic respiration

uses an electron transport chain; does not yield either the most or the least amount of ATP relative to the other two processes

aerobic respriation

uses an electron transport chain; yields more ATP than the other two processes

which of the following are true about glycolysis? -the pathway provides the cell with a large amount of ATP, reducing power, and a number of precursor metabolites -the pathway splits glucose and reduces it to form two molecules of pyruvate -the pathway splits glucose and oxidizes it to form two molecules of pyruvate -the pathway provides the cell with a small amount of ATP, some reducing power, and 6 precursor metabolites

-the pathway splits glucose and oxidizes it to form two molecules of pyruvate -the pathway provides the cell with a small amount of ATP, some reducing power, and 6 precursor metabolites

free energy is best defined as ___: a.) the leftover energy that is not used by the cell b.) the energy available to do work c.) stored energy present in chemical bonds d.) energy of motion

b.) the energy available to do work

which of the three central metabolic pathways generate a modest amount of ATP via substrate level phosphorylation? -tricarboxylic acid (TCA) cycle -glycolysis -pentose phospate pathway

-tricarboxylic acid (TCA) cycle -glycolysis

the ATP generated by fermentation comes from ___ a.) the reducing power obtained from the oxidation of glucose b.) substrate-level phosphorylation during glycolysis c.) the tricarboxylic (TCA) cycle d.) oxidative phosphorylation driven by NADH

b.) substrate-level phosphorylation during glycolysis

oxidation phosphorylation

energy from exergonic reactions is used to create a proton motive force that drives the addition of Pi, to ADP

in the electron transport chain, electron carries are found in what two general locations? -tightly bound to lipids of the phospholipid bilayer -grouped into large protein complexes that function as proton pumps -attached to ATP synthase -as part of glucose transporter -freely moving in the membrane where they can shuttle electrons between protein complexes

-grouped into large protein complexes that function as proton pumps -freely moving in the membrane where they can shuttle electrons between protein complexes

which of the following correctly describe cytochromes found in an electron transport chain? -several different cytochromes exist -cytochromes are proteins that contain heme, a molecule that holds an iron atom in its center -cytochromes are always found bound to one of the protein complexes that function proton pumps

-several different cytochromes exist -cytochromes are proteins that contain heme, a molecule that holds an iron atom in its center

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

unlike the electrons carried by NADH and FADH2, the electrons carried by NADPH are ___: a.) used to produce ATP by oxidative phosphorylation b.) transferred to the electron transport chain c.) used to generate proton motive force d.) used to reduce compounds during biosynthetic reactions

d.) used to reduce compounds during biosynthetic reactions

which of the following correctly describe the transition step and the tricarboxylic acid (TCA) cycle? -together they generate the most reducing power of all the central metabolic pathways -the TCA cycle generates most of the ATP for the cell -the TCA cycle reduces a 2-carbon acetyl group to release two molecules of CO2 -the transition step converts the pyruvate from glycolysis into acetyl-CoA -the TCA cycle oxidizes a 2-carbon acetyl group to release two molecules of CO2

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

which of the following are reasons an organism might use fermentation? -they lack the ability to perform glycolysis -a suitable inorganic terminal electron acceptor is not available -they lack an electron transport chain -the energy yield is greater from fermentation than from respiration

-they lack an electron transport chain -a suitable inorganic terminal electron acceptor is not available