Ch 6 Microbial Metabolism: Fueling Cell Growth (I)

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

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 reversibly 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

Match the type of enzyme inhibition on the left with the example of an inhibitor on the right.

Competitive inhibition = Sulfa drugs Non-competitive inhibition by regulatory molecules = Allosteric regulators Non-competitive inhibition by enzyme poisons = Mercury

Photosynthetic organisms 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

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

anaerobic

Although the 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

The energy released by ______ is captured by cells to make ATP; this ATP can then be used for biosynthesis, or ______.

catabolism; anabolism

Enzymes are biological ______ that are typically _______.

catalysts; protein

Some enzymes act with the assistance of a non-protein component. This component is called a _____; if that component is an organic molecule it can be called a ____.

cofactor, coenenzyme

Identify each of the following by the most precise descriptive term as either a cofactor or coenzyme: magnesium: ______ ; NADP+: _____; zinc: _____.

cofactor, coenzyme, cofactor

The diagram shows a type of metabolic pathway known as a(n) ____ pathway.

cyclical

Consider the effect of temperature on enzyme activity. If the temperature is too high, proteins will ____ and no longer function.

denature

This figure shows one half of a redox reaction. Compound X is the electron ____ and Compound Y is the electron _____.

donor, acceptor

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

electrons or hydrogen

The capacity to do work is the definition of _____.

energy

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 or electron, terminal or final

Proteins that function as biological catalysts are called

enzymes

All of the following accurately 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 use it to power _____ reactions of _____."

exergonic, catabolism, endergonic, anabolism

Fill in the blank question. 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 a process called

fermentation

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 or krebs or citric acid or tricarboxylic acid

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 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 all chemical reactions in a cell is called

metabolism

The TCA cycle completes the ______ of glucose.

oxidation

Cells use three key metabolic pathways referred to as the central metabolic pathways. These collectively ______.

oxidize glucose to CO2

During cellular metabolism, three key metabolic pathways together gradually _______. These are collectively referred to as the central metabolic pathways.

oxidize glucose to CO2

Each type of the major electron carriers 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

In oxidation-reduction reactions, or redox reactions, the substance that loses electrons is ____, and the substance that gains those electrons is _____.

oxidized, reduced

In oxidation-reduction reactions, or redox reactions, the substance that loses electrons is _____, and the substance that gains those electrons is ____.

oxidized, reduced

In aerobic respiration, ____ serves as the terminal electron acceptor.

oxygen or O2

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

pentose phosphate

Unlike chemoorganotrophs, photosynthetic organisms generate ATP by ______.

photophosphorylation

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

potenital; kinetic

What are the two main forms of energy?

potential and 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

Photophosphorylation is similar to oxidative phosphorylation except for the fact that the energy of light is used to create the ___ ____ force.

proton motive

The form of energy that results from the electrochemical gradient established by the electron transport chain is the ______.

proton motive force

The figure depicts oxidation-reduction reactions, which are also known as ____ reactions.

redox

During cellular ____, electrons extracted from glucose via the central metabolic pathways are transferred to the electron transport chain, where they are used to generate a proton motive force that can be harvested to make ATP via oxidative phosphorylation.

respiration

Enzymes function as biological catalysts, accelerating the conversion of one substance, the ____, into another, the ____.

substrate or reactant; product

Energy is defined as ______.

the ability to do work

Proton motive force is ______.

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

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.

Metabolism is best defined as ______.

the sum total of all chemical reactions in a cell

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

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

The metabolic pathway that oxidizes a 2-carbon acetyl group to release two molecules of CO2 and generates the most reducing power of all the central metabolic pathways is called the ____ acid cycle.

tricarboxylic or citric

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

The central metabolic pathways together produce ______.

water and carbon dioxide

What are the reduced forms of the electron carriers NAD+ and FAD?

- FADH2 - NADH

The main energy currency of cells is the molecule called ___.

ATP

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

- ATP - reducing power - precursor metabolites

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

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

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.

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

- 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. - Together they generate the most reducing power of all the central metabolic pathways.

Which of the following explain why a cell might undergo fermentation?

- 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.

Which of the following correctly describe respiration?

- 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.

Which of the following are true about glycolysis?

- 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 six precursor metabolites.

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 as part of which of the following?

- fermentation - cellular respiration

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

- photophosphorylation - oxidative phosphorylation

Consider the figure of relative energy (y-axis) versus progress of reaction (x-axis). Which represents the activation energy of the reaction catalyzed by an enzyme?

A

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

It increases their rate

Match the following three phosphorylation processes for ATP production with the correct description.

Substrate-level phosphorylation = Energy released in an exergonic reaction is used to power the addition of Pi to ADP. Oxidative phosphorylation = Energy from exergonic reactions is used to create a proton motive force that drives the addition of Pi to ADP. Photophosphorylation = The sun's radiant energy and an electron transport chain create a proton motive force that drives the addition of Pi to ADP.

Consider the following linear metabolic pathway of a bacterial cell: Starting compound → Intermediate-a → Intermediate-b → End Product. The first two reactions are catalyzed by enzymes A and B, respectively. If a mutant cell arose that was unable to produce enzyme B, what would be the impact on the other components of the pathway?

The cell could still produce intermediate-a but would be unable to produce intermediate-b or the end product.

What is the active site of an enzyme?

The critical site to which a substrate binds by weak forces.

Consider the figure showing the relationship between catabolism and anabolism. Which side shows catabolism, and which side shows anabolism?

The left side shows catabolism, and the right side shows anabolism.

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

Two molecules of pyruvate, each with three carbon atoms.

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

allosteric

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

In the figure, Compound X donates electrons to Compound Y. Which of the following correctly describes this process?

X is oxidized by the reaction, and Y is reduced by the reaction.

The ____ energy is the energy it takes to start a reaction.

activation

In this figure, the relative energy (y-axis) of a reaction is plotted over time (x-axis). One curve represents the reaction in the absence of an enzyme, and the other in the presence of an enzyme. In each case, A and B represent the of the ____ _____ reaction.

activation energy

The critical site of an enzyme to which a substrate binds by weak forces is called the ____ ____.

active site

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

adenosine triphosphate

Atoms that are more electronegative than others ______.

have a higher affinity for electrons