Ch 6 SmartBook

Although Pentose phosphate pathway is used by cells to break down glucose, it is particularly important because of its contribution to

Biosynthesis

Metabolic pathways can be linear, _, or _

Branched, cyclical

With respect to their synthesis, how are amino acids typically grouped?

By structurally related families that share common biosynthesis pathways

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

Cellular respiration; fermentation

An organism that uses hydrogen sulfide as an energy source is called a _ and is most likely _

Chemolithotroph; prokaryotic

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

Nucleotide subunits of DNA and RNA are composed of three units: a 5-carbon sugar, and a nucleobase. They are initially synthesized

As ribonucleotides that can be converted to deoxyribonucleotides by replacing the 2' hydroxyl group with a hydrogen atom

When a compound binds to the active site of an enzyme, blocking access of the substrate to that site, the process is called

Competitive

Match up each type of enzyme inhibition with its characteristic.

Competitive Inhibition -> Inhibitor binds to the active site of the enzyme, blocking access of the substrate Non-competitive inhibition by regulatory molecules -> Inhibitor reversible changes the shape of the enzyme so that the substrate can no longer bind to the active site Non-competitive inhibition by enzyme poisons -> Inhibitor permanently changes the shape of the enzyme, making the enzyme non-functional

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

Disaccharides, polysaccharides, lipids, fatty acids, monosaccharides, proteins

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?

Energy source Starting point from which all cell components are made

Consider how cells obtain energy to ATP. The cynical that serves as the electron donor is the _ source, and the one that ultimately accepts those electrons is the _ electron acceptor.

Energy; terminal

All of the following describe enzymes EXCEPT

Enzymes provide energy to help reactions proceed more rapidly

Use the following four words to correctly complete the sentence: endergonic, exergonic, anabolism, catabolism. "Cells constantly produce ATP during _ reactions of _ and then us it to power _ reactions of _."

Exergonic; catabolism; endergonic; anabolism

The sole function of glucose for cells growing in a glucose-salts medium is as an energy source.

False

In order to form lipids, how are fatty acids and glycerol synthesized?

Fatty acid chains are assembled from 2-carbon acetyl groups from the transition step; the precursor to glycerol comes from glycolysis.

The figure depicts oxidation-reduction reactions, which are also know as _ reactions

Redox

The group of obligate anaerobes that use sulfate (SO42-) as a terminal electron acceptor and produce hydrogen sulfide as an end product are called the sulfate-

Reducers

Cellular respiration uses the _ power of NADH and FADH2 generated in glycolysis, teh transition step, and the TCA cycle to synthesize ATP

Reducing or Reductive

Consider the figure showing chemical energy sources and terminal electron acceptors. If Mn2+ were used as an energy source, the two molecules on the chart that could serve as terminal electron acceptors are _ and _

NO3- and O2

Glutamate synthesis is especially important for bacteria, because it provides a mechanism for the incorporation of _ into organic material.

Nitrogen or ammonium

In oxidation-reduction reactions, or redox reactions, the substance that loses electron is _, and the substance that gains those electrons is _

Oxidized; reduced

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 NADPG is the _ _ pathway

Pentose phosphate

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

Consider the three key central metabolic pathways (glycolysis, Penrose phosphate pathway, and TCA cycle). What three beneficial products of these pathways?

Precursor metabolites; ATP; reducing power

Some members of which of the following groups can use inorganic chemicals such shorten sulfide and ammonia for energy?

Prokaryotes only

Photophosphorylation is similar to oxidative phosphorylation except for the fact that the energy of light is used to creat the _ _ force

Proton Motive

The form of energy that result from the electrochemical gradient established by the electron transport chain is the _

Proton motive force

The electron transport chain consists of large protein-complexes embedded in a membrane. These pass electrons from one to the next, while simultaneously pumping _ across the membrane.

Protons

Cells can quickly alter the activity of certain key enzymes, using other molecules that bind reversible and distort them. This control of enzymes is called _ regulation

allosteric; or non-competitive

The process by which chemolithoautotrophs and photoautotrophs incorporate CO2 into organic compounds is called

carbon fixation

Enzymes are biological _ that are typically _

catalysts; protein

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 the effect of temperature on enzyme activity. if the temperature is too high, proteins will _ and no longer function.

denature

oxidative phosphorylation, quinones, cytochromes, and flavoproteins are all _ carriers.

electron

The function of NAD+/NADH, NADP+/NADPH, and FAD/FADH2 in a cell is to carry

electrons

Hydrogen sulfide is produced as a result of certain types of anaerobic respiration. Some chemolithotrophs can then use this as a/an

energy source

All of the following accurately describe enzymes EXCEPT

enzymes provide energy to help reactions proceed more rapidly

Prokaryotes are remarkably diverse in their metabolism. Many are _ anaerobes which use O2 if it is available, but they can use an alternative if it is not.

facultative

Starch and cellulose are both polymers made up of the monosaccharide _, which means that hydrolysis of the polymers releases subunits that can enter directly into the central metabolic pathway of _ to be oxidized.

glucose, glycolysis

Lipid synthesis generally requires the components _ and _ acids

glycerol, fatty

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

glycolysis

The enzymes of the tricarboxylic acid cycle are found in the ______ matrix in eukaryotes and in the _____ in prokaryotes.

mitochondrial; cytoplasm

The TCA cycle completes the _ of glucose

oxidation

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

Which of the following forms of phosphorylation require an electron transport chain for ATP production?

oxidative phosphorylation and photophosphorylation

Energy is the ability to do work and can exist as _ energy (stored energy) and _ energy (energy of motion).

potential and kinetic

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

precursor metabolites

The three main types of electron carriers in a typical electron transport chain are _, _, and flavoproteins.

quinones and cytochromes

Consider the representation of an electron transport chain. O2 is serving as the terminal electron acceptor. Is it being oxidized or reduced?

reduced

Cellular respiration uses the _ power of NADH and FADH2 generated in glycolysis, the transition step, and the TCA cycle to synthesize ATP

reducing

The ATP generated by fermentation comes from

substrate-level phosphorylation during glycolysis

As part of cellular respiration, a membrane-bound enzyme called ATP _ uses energy from a proton-motive force to add a phosphate group to ADP.

synthase

Proton motive force is

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

Proton motive force is _

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

In competitive inhibition, why is the inhibitor able to bind to the active site, thereby blocking access of the substrate?

the inhibitor has a chemical structure similar to the normal substrate

Oxidative phosphorylation, the mechanism by which cellular respiration uses the NADH and FADH2 generated in glycolysis, the transition step, and the TCA cycle to synthesize ATP, involves what two steps?

The electron transport chain generates a proton motive force. ATP synthase uses the energy of the proton motive force to drive the synthesis of ATP.

Microorganisms can grow on a variety of organic compounds other than glucose, including polysaccharides, proteins, and lipids. How do they accomplish this?

They break these macromolecules down into appropriate precursor metabolites that are then introduced into central metabolism or used in biosynthesis.

Other than generating some ATP via the substrate-level phosphorylation steps of glycolysis, what critical role do th additional steps of fermentation accomplish?

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

Although the actual procedure is much more involved, the basic metabolism of wine-making involves inoculation grape juice with a special strain of yeast Saccharomyces cerevisiae. S. Cerevisiae will preferentially perform aerobic respiration on sugars in the juice but can also ferment those sugar to yield CO2 and alcohol, and important component of wine. Assume you inoculate a completely full container of juice and then close the lid. What will the yeast do?

They will grow aerobically, consume the O2 dissolved in the juice, and then switch to fermenting sugars to yield alcohol.

Certain intermediates of catabolic pathways, called precursor metabolites, are important because

they serve as carbon skeletons from which subunits of macromolecules can be made

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

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

ATP, reducing power, precursor metabolites

Cellular respiration involves the mechanism of oxidative phosphorylation, which uses the energy of a proton motive force to produce

ATP

Proteins are composed of various combinations of usually how many different amino acids?

20

If the theoretical maximum ATP yield in prokaryotes from oxidative phosphorylation is 34 ATP for a single glucose molecule, what is the total ATP gain when substrate-level phosphorylation is included?

38 ATP

Which of the following are reasons an organism might use fermentation?

A suitable inorganic terminal electron acceptor is not available. They lack an electron transport chain.

All of the following are essential for an electron transport chain to function EXCEPT

ATP

The figure show three examples of chemoorganotrophic metabolism. Which of these three possibilities will yield the most energy for the organism?

Glucose as the energy source and O2 as the terminal electron acceptor

The figure shows three examples of chemoorganotrophic metabolism. Which of these three possibilities will yield the most energy for the organism?

Glucose as the energy source and O2 as the terminal electron acceptor

Microorganisms that can grow on polysaccharides and disaccharides first break these down to glucose or precursor metabolites that can then enter in to the pathway of _ to be oxidized.

Glycolysis

In terms of their metabolism, prokaryotes are _ with respect to compound they use for energy and _ in their biosynthesis processes.

Highly diverse; remarkably similar

Purines and pyramidines are synthesized _.

In distinctly different manners

Autotrophs use carbon dioxide (CO2) to synthesize organic compounds. Which of the following descriptions of this process are true?

In photosynthetic organisms, the process is called the light-independent reactions. It is called carbon fixation. It often involves the Calvin cycle.

The electron transport chain is a cluster of membrane-embedded electron carriers that accept electrons from the coenzymes _ and _ and then pass these electrons along the chain.

NADH and FADH2

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

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

Until the optimal temperature is reached, raising the temperature has what effect on the speed of enzymatic reactions?

It increases their rate.

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

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

Why is glutamate synthesis especially important for bacteria?

It provides a mechanism for incorporating nitrogen into organic material

In respiring bacteria, how does ATP synthase generate ATP?

It uses the energy released from allowing protons to flow back into the cell to add a phosphate group to ADP.

Consider the figure representing metabolism E. Coli growing in a medium that contains only glucose and a few inorganic salts. The four outputs to the sides represent different anabolic pathways involved in the biosynthesis of the four types of biological macromolecules. These four biological macromolecules are _, _, _ and nucleic acids

Lipids; carbohydrates; proteins

Which of the following are true statements about what happens to glucose inside a cell?

Some glucose might enter glycolysis, only to be siphoned off as a precursor metabolite for biosynthesis. Glucose can be used in catabolism to yield energy, or the precursor metabolites generated from its breakdown can be used in anabolism. Some glucose might be oxidized to CO2, generating the maximum amount of ATP.

Electron carriers of the electron transport chain are able to move Preston's across a membrane. They are able to do so because

Some only accept hydrogen atoms

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.

In prokaryotes, how does the energy yield of aerobic respiration compare to anaerobic respiration?

The energy yield of aerobic respiration is greater than anaerobic respiration.

Why does anaerobic respiration yield less energy than aerobic respiration?

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

This picture o a set of stairs best exemplifies the electron _ _

Transport; chain or system

With respect to location of the electron transport chain, the inner membrane of the mitochondria is analogous tot eh cytoplasmic membrane of bacterial cells.

True

for each six-carbon molecule of glucose that enter glycolysis, how many molecules of private are made, and how many carbon atoms does each pyruvate have?

Two molecules of pyruvate, each with three carbon atoms.

The figure illustrates a type of regulation used by cells to rapidly control certain key enzymes. The arrow labeled "1" points to the _ site, and the arrow labeled "2" points to the _ site.

allosteric; active

Cells use ATP as the ready and immediate donor of free energy. ATP stands for _ _

adenosine triphosphate