Chapter 5 micro
This diagram depicts the production of ethanol from pyruvate via fermentation. What best explains the mechanism?
CO2 removal converts pyruvate to the terminal electron acceptor acetaldehyde, which receives 2 electrons and protons from NADH + H+, making ethanol.
The sum total of all chemical reactions in a cell is called
Metabolism
In aerobic respiration _____ serves as the terminal electron
Oxygen
Enzymes function as biological catalysts, accelerating the conversion of one substance, the_______, into another, the __________.
Substrate and product
The central metabolic pathway that splits glucose and gradually oxidizes it to form two molecules of pyruvate is___________.
glycolysis
Atoms that are more electronegative than others
have a higher affinity for electrons
An atom that has a lower affinity (attraction) for electrons than another is described as________ than the other.
less electronegative
Proton motive force is ______.
the form of energy that results from the electrochemical gradient established by the electron transport chain
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 Terminal
Metabolic pathways can be linear,
branched and cyclical
All of the following accurately describe enzymes EXCEPT
enzymes provide energy to help reactions proceed more rapidly
metabolic pathway
series of chemical reactions that converts a starting compound to an end product
electron transport chain
series of electron carrier proteins that shuttle high-energy electrons during ATP-generating reactions
Enzyme Inhibition
means by which cells regulate enzyme activity; may be competitive or noncompetitive inhibition
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 _______
noncompetitive regulation
Cofactors
nonprotein enzyme helpers
Chemoorganotrophs
obtain energy from organic compounds
Consider three major groups of electron carriers found in electron transport chains. Match each description with the correct name.
oxidation
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
Consider the three key central metabolic pathways (glycolysis, pentose phosphate pathway, and the TCA cycle). What three beneficial products of these pathways?
reducing power precursor metabolites ATP
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
When a molecule other than O2 serves as the terminal electron acceptor for the electron transport chain, the organism is utilizing _______ respiraton.
Anaerobic
Although the pentose phosphate pathway is used by cells to break down glucose, it is particularly important because of its contribution to
Biosynthesis
Anabolism
Biosynthetic processes Assemble subunits of macromolecules Use ATP to drive reactions
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 Coenzyme
Identify each of the following by the most precise descriptive term as either a cofactor or coenzyme: magnesium: ________; NADP+: __________; zinc: ___________.
Cofactor Coenzyme Cofactor
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
Precursor Metabolites
are intermediates of catabolism that can be used in anabolism Serve as carbon skeletons for building macromolecules ex. pyruvate can be converted into amino acids alanine, leucine, or valine
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
Tricarboxylic acid (TCA) cycle
Completes oxidation of glucose Produces 2 CO2 2 ATP 6 NADH 2 FADH2 Precursor metabolites
Which of the following correctly describe cytochromes found in an electron transport chain?
Cytochromes are proteins that contain heme, a molecule that holds an iron atom in its center. Several different cytochromes exist.
In prokaryotes, the electron transport chain is located in the _____ membrane, whereas in eukaryotic cells it is in the _______ membrane of metochondria.
Cytoplasmic, or cell inner or internal
Use the following four words to correctly complete the sentence: endergonic, exergonic, anabolism, catabolism."Cells constantly produce ATP during_________ reactionts of ___________ and then use it to power ___________ reactions of ___________.
Exergonic Catabolism Endergonic Anabolism
Which of the following are important electron carriers for a cell?
FAD/FADH2 NAD+/NADH NADP+/NADPH
True or false: With respect to prokaryotic species such as E. coli, each individual cell will have an electron transport chain made up of the same components.
False
The central metabolic pathway that generates reducing power in the form of NADPH is the ______
Pentose phosphate pathway
Catabolism
Process that degrade compounds to release energy Cells capture to make ATP
Chemolithotrophs
Prokaryotes unique in ability to use reduced inorganic compounds as sources of energy that harvest energy by oxidizing inorganic chemicals
Photophosphorylation is similar to oxidative phosphorylation except for the fact that the energy of light is used to create the____________ Force.
Proton motive
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
Exergonic reaction
Reactants hace more free energy. Energy is released in reaction
The figure depicts oxidation-reduction reactions, which are also known as ______ reactions.
Redox
Endorgonic Reactions
Requires Input of energy - Uphill Reaction - Products have more energy than reactants - + DeltaG - Requires Energy Payment (ATP)
anaerobic respiration
Respiration that does not require oxygen Molecule other than O2 as terminal electron acceptor Also use modified version of TCA cycle
aerobic respiration
Respiration that requires oxygen O2 is terminal electron acceptor
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
This figure shows one half of a redox reaction. Compound X is the electron _________ and Compound Y is the electron ______.
Donor Acceptor
Role of electron carriers
Energy harvested in stepwise process Electrons transferred to electron carriers, which represent reducing power (easily transfer electrons to molecules) Raise energy level of recipient molecule NAD+/NADH, NADP+/NADPH, and FAD/FADH2
The mechanism by which cellular respiration uses reducing power generated in glycolysis, the transition step, and the TCA cycle to synthesize ATP is ________
Oxidative phosphorylation
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
Oxidized Reduced
Unlike chemoorganotrophs, photosynthetic organisms generate ATP by
Photophosphorylation
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
The form of energy that results from the electrochemical gradient established by the electron transport chain is the ______.
Proton motive force
The central metabolic pathways together produce
water and carbon dioxide
Although the actual procedure is much more involved, the basic metabolism of wine-making involves inoculating grape juice with a special strain of the yeast Saccharomyces cerevisiae. S. cerevisiae will preferentially perform aerobic respiration on sugars in the juice but can also ferment those sugars to yield CO2 and alcohol, an 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.
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 ______.
serves as a source of vitamin K, providing much of the host's requirement via absorption in the intestinal tract
Environmental factors Influencing Enzyme Activity
Enzymes have narrow range of optimal conditions Temperature, pH, salt concentration 10°C increase doubles speed of enzymatic reaction up until maximum Proteins denature at higher temperatures Low salt, neutral pH usually optimal
allosteric regulation of enzymes
Enzyme activity controlled by binding yo allosteric site Distorts enzyme shape, prevents or enhances binding Regulatory molecule is usually end product Allow feedback
photosynthetic
Describes bacteria that make their own food using light energy
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
As part of cellular respiration, a membrane-bound enzyme called ________ uses energy from a proton-motive force to add a phosphate
APT synthase
Kinetic Energy
Energy of movement Energy in universe cannot be created or destroyed, but it can be converted between forms
Proteins that function as biological catalysts are called
Enzymes
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.
Respiration
Transfers electrons from glucose to electron transport chain Electron transport chai generate proton motive force
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
Tricarboxylic acid cycle
role of enzymes
speed up chemical reactions that take place in cells Speed up conversion of substrate into product by lowering Activation energy
Potential Energy
stored energy (chemical bonds, rocks on hill, water behind dam)
This picture of a set of stairs best exemplifies the electron
transport chain
ATP
(adenosine triphosphate) main energy source that cells use for most of their work Composed od ribose, adenine, three phosphate groups Adenosine diphospate ADP acceptor of gree energy
Consider the theoretical maximum ATP yield from the complete oxidation of glucose via aerobic respiration in prokaryotes. Match the relative contribution in terms of ATP (substrate-level phosphorylation plus oxidative phosphorylation) with the correct metabolic component.
8 ATP-----> Glycolysis 6 ATP -----> Transition step 24 ATP -----> TCA cycle 38 ATP ------> Total yield of aerobic respiration
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 main energy currency of cells is the molecule called
ATP or adenosinetriphosphate
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?
ATP synthase uses the energy of the proton motive force to drive the synthesis of ATP. The electron transport chain generates a proton motive force.
The _________ energy is the energy it takes to start a reaction.
Activation
The critical site of an enzyme to which a substrate binds by weak forces is called the
Active site
Which of the following are true statements about what happens to glucose inside a cell?
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. Some glucose might enter glycolysis, only to be siphoned off as a precursor metabolite for biosynthesis.
The primary pathway used by many organisms to convert glucose to pyruvate is
Glycolysis
In an electron transport chain, electron carriers are found in what two general locations?
Grouped into large protein complexes that function as proton pumps. Freely moving in the membrane where they can shuttle electrons between protein complexes.
Fermentation
If cells cannot respire, will run out of carriers available to accept electrons Glycolysis will stop
How does the oxidase test help in bacterial identification?
It detects the activity of cytochrome c oxidase, a component of the electron transport chain of some but not all bacteria.
Until the optimal temperature is reached, raising the temperature has what effect on the speed of enzymatic reactions?
It increases their rate.
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.
Escherichia coli and Pseudomonas aeruginosa both have an electron transport chain that uses O2 as a terminal electron acceptor, yet E. coli is oxidase negative. Based on this information, it is logical to assume that E. coli ______.
Lacks cytochrome c
The series of sequential chemical reactions in a cell that converts a starting compound to an end product is called a
Metabolic pathway
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 FADH2
What are the reduced forms of the electron carriers NAD+ and FAD?
NADH FADH2
The lactic acid fermentation pathway is shown here. What statement best explains what is happening in the diagram?
NADH + H+ are donating 2 electrons and 2 protons to pyruvate, an organic terminal electron acceptor, reducing it to lactate.
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 P to ADP. Oxidative phosphorylation--------->Energy from exergonic reactions is used to create a proton motive force that drives the addition of P 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.
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.
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. https://i.pinimg.com/originals/3e/fb/fa/3efbfa78398affd114da8c6fc21b9e28.png
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.
Other than generating some ATP via the substrate-level phosphorylation steps of glycolysis, what critical role do the 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.
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 correctly describe the transition step and the tricarboxylic acid (TCA) cycle?
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. Together they generate the most reducing power of all the central metabolic pathways.
thermal energy
Thermal energy (also called heat energy) is produced when a rise in temperature causes atoms and molecules to move faster and collide with each other.
True or false: With respect to the location of the electron transport chain, the inner membrane of mitochondria is analogous to the cytoplasmic membrane of bacterial cells.
True
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.
Respiration
Uses reducing power NADH FADH2 generated by glycolysis, transition step, and TCA cycle to synthesize ATP Electron transport chain generates proton motive force Drive synthesis of ATP by ATP synthase
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.
oxidation-reduction reaction or redox reaction
a reaction in which electrons are transferred from one reactant to another. Substance that loses electrons is oxidized substance that gains electrons is reduced Dehydrogenation = oxidation Hydrogenation = reduction
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
E. coli will preferentially use _____ respiration in the presence of O2, but when O2 is not available, it can switch to ______ respiration if a suitable electron acceptor such as nitrate is present.
aerobic anaerobic
In addition to four protein complexes, the mitochondrial electron transport chain has two freely-moving ______, ubiquinone and cytochrome c, that serve to ______.
electron carriers; shuttle electrons between the complexes
A general group of electron carriers found in electron transport chains is quinones, that ______.
exist as several types, including ubiquinone and menaquinone are lipid-soluble organic molecules that move freely in the membrane, transferring electrons between different protein complexes
The three central metabolic pathways that gradually oxidize glucose to CO2 are ________, the _______ _______ pathway, and the __________ cycle.
glycolysis pentose phosphate Krebs or citric acid pr TCA, or tricarboxylic acid
Three central metabolic pathways
glycolysis - splits glucose 6C to two pryruvate 3C Generate modest ATP reducing power precursors pentose phosphate pathway - Primary role is production precursor metabolites, NADPH tricarboxylic acid cycle - Oxidizes pryruvates from glycolysis Generates reducing power, precursor metabolites ATP
The ATP generated by fermentation comes from ______.
substrate-level phosphorylation during glycolysis
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
Glucose
is energy source starting point for all cellular components (includes proteins, lipids. carbohydrates, nucleic acids) some glucose molecules completely oxidized for energy; others used in biosynthesis
Cells use ATP as the ready and immediate donor of free energy. ATP stands for
Adenosine Triphosphate
The TCA cycle completes the ____ of glucose
Oxidation
Pentose Phosphate Pathway
Also breaks down glucose Important in biosynthesis of precursor metabolites A metabolic process that produces NADPH and ribose 5-phosphate for nucleotide synthesis.
The energy released by ______ is captured by cells to make ATP; this ATP can then be used for biosynthesis, or ______.
Catabolism and anabolism
The TCA cycle completes the ______ of glucose.
Oxidation
Consider three major groups of electron carriers found in electron transport chains. Match each description with the correct name.
Quinones ----> 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 Cytochromes ----> Proteins that contain heme, a molecule that holds an iron atom in its center Flavoproteins -----> Proteins that are synthesized from the vitamin riboflavin
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.
Which of the following forms of phosphorylation require an electron transport chain for ATP production?
oxidative phosphorylation photophosphorylation
During cellular metabolism, three key metabolic pathways together gradually _______. These are collectively referred to as the central metabolic pathways.
oxidize glucose to CO2