Ch 6 micro
In biosynthetic pathways, feedback inhibition refers to
the end product acting as an allosteric inhibitor of the pathway
The central metabolic pathways together produce _
water and carbon dioxide by oxidizing glucose to co2
The transition step occurs twice for every molecule of glucose that enters glycolysis, oxidizing pyruvate to form acetyl-CoA. Together, these generate
2 Nadh 1 precursor( acetyl coa)
Two 3-carbon molecules enter the latter phase of glycolysis for each initial glucose molecule, meaning the steps of this phase occur twice for each glucose. During this second phase of glycolysis, what is the total number of NADH and ATP molecules produced from a single glucose molecule?
2 Nadh 4 atp in second phase of glycolysis
The TCA cycle incorporates an acetyl group from the transition step and releases two different precursor metabolites, two molecules of blank , and two molecules of blank . (Not counting reducing power)
2 of co2 and 2 of atp
In response to changing energy needs, cells can regulate allosteric enzymes of catabolic pathways. High levels of which of the following would most likely inhibit such enzymes, thereby slowing down catabolic processes
ATP
The critical site of an enzyme to which a substrate binds by weak forces is called the
Active site
Enzymes are changed by the reaction as they lower the activation energy
False
Consider the three key central metabolic pathways (glycolysis, pentose phosphate pathway, and the TCA cycle). What three beneficial products of these pathways?
precursor metabolites reducing power ATP
The statement "the substrate fits into the active site of an enzyme like a hand into a glove" refers to what important property of enzymes?
Enzyme specificity
Consider the pathway that converts the amino acid threonine to the amino acid isoleucine. Isoleucine is an allosteric inhibitor of the first enzyme of the pathway. This is an example of the mechanism called
Feedback inhibition
In competitive inhibition such as occurs with sulfa drugs, as the concentration of the blank increases relative to the , blank the more likely the active site of the enzyme will be occupied, thereby blocking the regular function of the enzyme.
Inhibitor substrate
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.
Most coenzymes are derived from organic compounds called
Vitamins
Which of the following describe enzyme specificity?
With few exceptions, a unique enzyme is required to catalyze each reaction in a cell. The substrate must align spatially with the active site. Hydrogen and ionic bonding occur to induce the correct fit between substrate and active site.
Consider the following biosynthetic pathway: W → X → Y → Z. Which compound is most likely to serve as an allosteric inhibitor?
Z
When referring to the chemical pyruvic acid, biologists often ignore the effect of pH on the molecule and call it
Pyruvate
Each enzyme functions best within a narrow range of environmental conditions. Three important environmental conditions that influence enzyme activity are
Temperature ph and salt contraction
Consider a cell converting glucose into CO2 and water with the release of energy. This is an example of what type of metabolism, and the reactions themselves are considered to be what?
catabolism; exergonic
The sole function of glucose for cells growing in a glucose-salts medium is as an energy source.
false: The cells also use the glucose for carbon building blocks to make amino acids, fatty acids, and all other organic cell components.
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
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
Unlike the electrons carried by NADPH, the electrons carried by NADH and FADH2 are ______.
used in the process that produces ATP by oxidative phosphorylation used to generate proton motive force transferred to the electron transport chain
Unlike the electrons carried by NADH and FADH2, the electrons carried by NADPH are ______.
used to reduce compounds during biosynthetic reactions
Proteins that function as biological catalysts are called
Enzymes
Competitive inhibitions
Sulfa drugs
When cells use glucose to make amino acids and other subunits for biosynthesis, certain intermediates of catabolism called blank metabolites exit the "deconstruction line" of the breakdown process.
precursor
Fill in the Blank QuestionYour Answer correct Electron carriers can also be considered hydrogen carriers. This is because, along with electrons, they carry
proton(h+)
What is the active site of an enzyme?
the place on the enzyme where the substrate binds and The critical site to which a substrate binds by weak forces.
Certain intermediates of catabolic pathways, called precursor metabolites, are important because
they serve as carbon skeletons from which subunits of macromolecules can be made
Glycolysis can be viewed as having two phases. Why is the initial phase sometimes referred to as the investment phase or preparatory phase?
Energy is spent to add two high-energy phosphate groups to glucose, which is then split to yield two 3-carbon molecules.
In _______, the inhibitor changes the enzyme shape so that it is no longer functional. Indeed, the inhibitor is said to "poison" the enzyme.
Noncompetitive inhibitions
The TCA cycle completes the ______ of glucose.
Oxidation
.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 blank phosphorylation
Oxidative
The central metabolic pathway that generates reducing power in the form of NADPH is the pathway.
Pentose phosphate
Blank organisms harvest the energy of sunlight, using it to power the synthesis of organic compounds from CO2, whereas blank obtain energy by degrading organic compounds made by others.
Photosynthetic;chemoorganotrophs
The pentose phosphate pathway generates which of the following from each molecule of glucose?
Nadh and 2 precursor metabolites
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 Blank regulation
Allosteric
non-competitive inhibitor by regulatory molecules
Allosteric
Although the pentose phosphate pathway is used by cells to break down glucose, it is particularly important because of its contribution to _
Biosynthesis
An organic cofactor that functions as a loosely bound carrier of molecules or electrons to assist an enzyme is called a
Coenzymes
Magnesium, zinc, and copper often function as _______ for enzymes.
Cofactors
Some enzymes act with the assistance of a non-protein component. This component is called a blank; if that component is an organic molecule it can be called a coenzymeblank
Cofactors coenzyme
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
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 amino acid isoleucine is an allosteric inhibitor of the first enzyme of the pathway that converts threonine to isoleucine. Given this, the pathway is likely shut down then the level of isoleucine is ______, and active when the level of isoleucine is
High low
Sulfa drugs inhibit an enzyme in the pathway bacteria use to synthesize folate, making them an effective antimicrobial medication. Why are these medications generally safe for humans?
Humans cannot synthesize folate
When discussing electron carriers in the context of biological reactions, why do we often ignore the location of protons?
In aqueous solutions, protons do not require carriers.
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.
When a reduced electron carrier (reducing power) transfers its electrons to another molecule, what occurs?
The recipient molecule is reduced. The electron carrier is oxidized. The energy level of the recipient molecule is raised.
An organism that uses hydrogen sulfide as an energy source is called a _______ and is most likely _______.
chemolithotroph; prokaryotic
All of the following are true statements regarding coenzymes EXCEPT
each coenzyme is specific to a single enzyme
non-competitive inhibitor by enzyme poisons
Mercury
Consider the effect of temperature on enzyme activity. If the temperature is too high, proteins will and no longer function.
Denature
The enzymes of the tricarboxylic acid cycle are found in the Blank matrix in eukaryotes and in the blank in prokaryotes
Mitochondrial cytoplasm or cytosol
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.
Why do reduced electron carriers such as NADH, NADHP, and FADH2 represent reducing power?
They can easily transfer their electrons to another chemical that has a higher affinity for electrons.
Coenzymes are typically derived from vitamins. All of the following are true statements about these vitamins EXCEPT
humans and other animals can synthesize these vitamins and convert them to the necessary coenzymes
The function of NAD+/NADH, NADP+/NADPH, and FAD/FADH2 in a cell is to carry
hydrogen
The mutual interaction of substrate and enzyme is best described as a(n) ______. Multiple choice question. dynamic mutualism allosteric cooperation induced fit lock and key arrangement
induced fit
An atom that has a lower affinity (attraction) for electrons than another is described as ______ than the other. Multiple choice question. more electronegative less electronegative
less electronegative
Identify each of the following by the most precise descriptive term as either a cofactor or coenzyme: magnesium nadp+, zinc
magnesium=cofactor nadp+=coenzyme zinc=cofactor
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 blank form and the second of each pair refers to the blank form
oxidized ; reduced
In oxidation-reduction reactions, or redox reactions, the substance that loses electrons is blank , and the substance that gains those electrons is blank.
oxidized; reduced
Suppose you are investigating a metabolic pathway in a bacterial species, and you hypothesize that it is regulated by feedback inhibition. The pathway involves the steps: A → B → C → D → E. To evaluate this hypothesis, you could test whether _______ inhibits the enzyme catalyzing the reaction of _
E; A → B
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
Multiple Select Question Select all that apply Which of the following accurately describe fermentation? Multiple select question. NAD+ is regenerated from NADH by the transfer of electrons to pyruvate or a derivative. Glucose is broken down via glycolysis. Fermentation does not involve the tricarboxylic acid (TCA) cycle. It generates more ATP than either glycolysis or respiration. All cells are able to ferment certain substances.
NAD+ is regenerated from NADH by the transfer of electrons to pyruvate or a derivative. Glucose is broken down via glycolysis. Fermentation does not involve the tricarboxylic acid (TCA) cycle.
