Unit Two Chapter 6. Microbial Metabolism: Fueling Cell Growth
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
The electron transport chain of mitochondria has ______ different protein complexes.
4
Catabolism vs Anabolism
Catabolism (breakdown) and Anabolism (build up)
terminal electron acceptor
Chemical that is ultimately reduced as a consequence of fermentation or respiration
With respect to prokaryotic species such as E. coli, each individual cell will have an electron transport chain made up of the same components. T or F.
False
enzyme
a molecule, usually a protein, that functions as a catalyst, speeding up a biological reaction
The ___________________ energy is the energy it takes to start a reaction.
activation
Metabolic pathways can be linear, _____________________ or __________________.
branch cycle
Purines and pyrimidines are synthesized
in distinctly different manners
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
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
All of the following accurately describe enzymes EXCEPT
enzymes provide energy to help reactions proceed more rapidly
The enzymes of the tricarboxylic acid cycle are found in the ______________________ matrix in eukaryotes and in the _____________________ in prokaryotes.
mitochondrial cytoplasm
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
pentose phosphate pathway
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
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 three central metabolic pathways that gradually oxidize glucose to CO2 are
glycolysis pentose phosphate pathway tca, krebs, citric acid cycle
Atoms that are more electronegative than others
have a higher affinity for electrons
In terms of their metabolism, prokaryotes are _______ with respect to compounds they use for energy and _______ in their biosynthetic processes.
highly diverse; remarkably similar
This picture of a set of stairs best exemplifies the electron
transport chain
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.
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
The light-independent reactions of photosynthesis occur _______ the light-dependent reactions, and function to _______.
after; synthesize organic compounds from CO2
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
Which subunits make up the structure of all proteins?
amino acids
Enzymes are biological ______ that are typically _______.
catalysts; protein
The diagram shows a type of metabolic pathway known as a(n)
cyclical
Examples of electron carriers are proteins that contain heme, a molecule that holds an iron in its center. These are called
cytochromes
Consider the effect of temperature on enzyme activity. If the temperature is too high, proteins will _________________ and no longer function.
denature
substrate
(1) Substance on which an enzyme acts to form products; (2) surface on which an organism will grow.
Describes a chemical reaction that requires a net input of energy because the products have more free energy than the starting compounds.
endergonic
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
kinetic energy
energy of motion
Proteins that function as biological catalysts are called
enzymes
progress of reaction
enzymes function as biological catalysts: a-a specific enzyme facilitates each step of the metabolic pathway b-an enzyme catalyzes a chemical reaction by lowering the activation energy of the reaction
Describes a chemical reaction that releases energy because the starting compounds have more free energy than the products.
exergonic
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.
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
Lipid synthesis generally requires the components _________________ and __________________ acids.
glycerol fatty
Metabolic pathways can be
linear, branched, cyclical
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
Fermentation
metabolic process that stops short of oxidizing glucose or other organic compounds completely, using an organic intermediate as a terminal electron acceptor
cellular respiration
metabolic process that transfers electrons stripped from a chemical energy source to an ETC, generating a proton motive force that is then used to synthesize ATP
catabolism
metabolic processes that harvest energy released during the breakdown of compounds such as glucose, using it to synthesize ATP
Anabolism
metabolic processes that synthesize and assemble the subunits of macromolecules, using the energy of ATP; biosynthesis
The sum total of all chemical reactions in a cell is called
metabolism
which subunits make up nucleic acids?
one or more phosphate groups, a pentose sugar (five-carbon sugar, either deoxyribose or ribose), and a nitrogen-containing base (either adenine, cytosine, guanine, thymine, or uracil)
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
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
Energy is the ability 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
The form of energy that results 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
The three main types of electron carriers in a typical electron transport chain are
quinones cytochromes flavoproteins
The figure depicts oxidation-reduction reactions, which are also known as __________________ reactions.
redox
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
potential energy
stored energy
The central metabolic pathways together produce
water and carbon dioxide
photosynthetic
Pertaining to photosynthesis, the process of using the energy of light to synthesize organic compounds from CO2.
energy
capacity to do work
metabolism can be separated into two components:
catabolism and anabolism
The energy released by ______ is captured by cells to make ATP; this ATP can then be used for biosynthesis, or ______.
catabolism; anabolism
Competitive inhibition
-Inhibitor binds to the active site of the enzyme, blocking access of the substrate -sulfa drugs
Non-competitive inhibition by enzyme poisons
-Inhibitor permanently changes the shape of the enzyme, making the enzyme non-functional. Enzyme poisons such as mercury are used in certain antimicrobial compounds. -mercury
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 -Allosteric regulators
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.
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
Louis Pasteur
A French chemist, this man discovered that heat could kill bacteria that otherwise spoiled liquids including milk, wine, and beer.
endergonic
A chemical reaction that requires the input of energy in order to proceed.
All of the following are essential for an electron transport chain to function EXCEPT
ATP
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
Electron Transport Chain (ETC)
Group of membrane-embedded electron carriers that pass electrons from one to another, and, in the process, create a proton motive force.
precursor metabolites
Metabolic intermediates that link catabolic and anabolic pathways because they can either be broken down to generate ATP or used to make subunits of macromolecules
Which of the following are important electron carriers for a cell?
NAD+/NADH NADP+/NADPH FAD/FADH2
What are the reduced forms of the electron carriers NAD+ and FAD?
NADH FADH2
Which of the following combinations of molecules is produced during the light-dependent reactions of photosynthesis and used in the light-independent reactions?
NADPH and ATP
Photophosphorylation
Synthesis of ATP using the energy of a proton motive force created by harvesting radiant energy.
substrate-level phosphorylation
Synthesis of ATP using the energy released in an exergonic (energy-releasing) chemical reaction during the breakdown of the energy source.
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.
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.
Proton motive force is
The potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions (H+) across a biological membrane during chemiosmosis.
Why does anaerobic respiration yield less energy than aerobic respiration?
The terminal electron acceptors used in anaerobic respiration have lower electron affinities than O2.
In photosynthesis, what do the light reactions, or light-dependent reactions, accomplish?
They capture radiant energy and convert it to chemical energy in the form of ATP.
With respect to the location of the electron transport chain, the inner membrane of mitochondria is analogous to the cytoplasmic membrane of bacterial cells. T or F.
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.
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?
cellular respiration fermentation
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
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
What are the two main forms of energy?
kinetic and potential
An atom that has a lower affinity (attraction) for electrons than another is described as
less electronegative
Enzymes function as biological catalysts, accelerating the conversion of one substance, the ___________________ into another, the _______________.
substrate product
Metabolism is best defined as
sum total of all chemical reactions in a cell
oxidative phosphorylation
synthesis of ATP using the energy of a proton motive force created by harvesting chemical energy; the enzyme ATP synthase catalyzes the reaction
ATP
the energy currency of cells. Hydrolysis of the bonds between its phosphate groups can be used to power endergonic (energy-consuming) reactions
proton motive force
Form of energy generated as an electron transport chain moves protons across a membrane to create a chemiosmotic gradient.
activation energy
Initial energy required to break a chemical bond.
adenosine diphosphate (ADP)
Molecule that accepts an inorganic phosphate (Pi ) generating ATP.
chemoorganotrophs
Organisms that harvest energy by oxidizing organic chemicals.
What is the active site of an enzyme?
The critical site to which a substrate binds by weak forces.
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.
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.
The main energy currency of cells is the molecule called
atp
Although the pentose phosphate pathway is used by cells to break down glucose, it is particularly important because of its contribution to
biosynthesis
In the case of plants, algae, and cyanobacteria, the two major products of photosynthesis are
glucose and oxygen
