Metabolism - class-XI
Description: metabolism | |
Number of Questions: 34 | |
Created by: Arav Srivastava | |
Tags: biology biomolecules carbohydrate metabolism bio-chemistry molecular biology metabolism, cell respiration, and photosynthesis |
In a reaction, reactants form a transition state, before the formation of products. Which of the following is affected by the action of enzyme?
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Products only
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Reactants only
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Transition state only
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Products and reactants
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Transition state and products
Any chemical reaction includes the formation of transition state between reactant and product. Formation of transition state requires high energy content of reactant molecules for alignment of reacting groups, the formation of transient unstable charges, rearrangements of chemical bonds etc. The energy required for formation of the transition state is termed as activation energy. Enzymes enhance the rate of reaction by lowering down the activation energy of transition state. Thus, the correct answer is option C.
An enzyme increases the rate of a reaction by?
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enzymes speed up reactions by lowering activation energy.
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Increasing the rate of random collisions of molecules
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Removing the product of the reaction so allowing it to continue
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Bringing the reacting molecules into precise orientation with each other
- Enzymes provide activation energy for the reactions they catalyze.
- Catalysts lower the activation energy for reactions.
- The lower the activation energy for a reaction, the faster the rate. Thus enzymes speed up reactions by lowering activation energy.so, option A is correct.
Biochemical reactions are carried out by enzymes
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By decreasing the energy of the reactants
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By increasing the activation energy of the reaction
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By decreasing the activation energy of the reaction
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By increasing the energy of the products of the reaction
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By decreasing the energy of the products of the reaction
Any chemical reaction includes the formation of transition state between reactant and product. The energy required for formation of the transition state is termed as activation energy. Enzymes enhance the rate of reaction by lowering down the activation energy of transition state. Thus, the correct answer is option C.
Energy released from enzyme-substrate interaction is
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Activation energy
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Binding energy
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Constant energy
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Variable energy
The transition state is the state of the activated complex which is highly unstable and readily changes into the product. At the transition state, the enzyme attaches to the substrate to form an enzyme-substrate complex by forming a weak chemical bond. Binding energy is the free energy that is released by the formation of weak interactions between a complementary substrate and enzyme.
Chemical reactions require energy for
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Oxidation
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Entropy
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Activation
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Enthalpy
Chemical reactions take place mainly at a specific temperature in presence of a catalyst. The substrate and product have different energy state. The energy gap between the substrate and the product is known as activation energy which is the minimum energy required to initiate a reaction. In presence of a catalyst, the activation energy lowers and the substrate changes into the product.
Energy required for start of a chemical reaction is
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Activation energy
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Entropy
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Potential energy
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Kinetic energy
Activation energy is required for :
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Bringing reactants together
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Destabilisation of bonds of reactants.
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Both A and B
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None of the above
Enzymes increase the rate of biochemical reaction through
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Changing equilibrium
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Lowering activation energy
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Forming reactant-product complex
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Forming enzyme-product complex.
Enzymes are biological catalysts. A catalyst is a chemical that increases the rate of a chemical reaction without itself being changed by the reaction. Without a catalyst, the amount of energy required for the reaction is large. Enzymes and catalysts both affect the rate of a reaction. The lower the activation energy for a reaction, the faster the rate of chemical reaction. Thus enzymes speed up reactions by lowering activation energy.
Enzymes enhance rate of reaction by
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Combining with product
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Forming reactant-product complex
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Changing equilibrium of reaction
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Lowering activation energy
Enzymes are proteins which accelerate the rate of the reaction. The substrate and product have different energy state. The energy gap between the substrate and the product is known as activation energy which is the minimum energy required to initiate a reaction. The enzymes lower the activation energy and lead to the faster conversion of substrate to the product.
State whether the following statements are true or false.
The totality of metabolism in humans must include both anabolism and catabolism.
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True
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False
Metabolism includes both the synthesis of biomolecules(known as anabolism) and breaking down of substrates to generate energy(known as catabolism).
An example of destructive metabolism (catabolism) is
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Photosynthesis
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Respiration
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Glycogenesis
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Both B and C
Destructive metabolism is the breakdown of more complex substances into simpler ones with release of energy.
Which one of the following is a catabolic process?
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Regulation
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Photosynthesis
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Digestion
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Secretion
Metabolism refers to series of reactions in which product of one reaction becomes reactant for the next one. It includes catabolism (degradative pathways) and anabolism (synthetic pathways). Digestion is the process in which complex compounds are broken down into the simpler form. Hence, option C is the correct answer.
Assertion : Smaller the organism higher is the rate of metabolism per gram weight.
Reason : The heart rate of a six month old baby is much higher than that of an old person.
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If both the assertion and the reason are true and the reason is a correct explanation of the assertion
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If both the assertion and reason are true but the reason is not a correct explanation of the assertion
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If the assertion is true but the reason is false
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If both the assertion and reason are false
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If the assertion is false but reason is true
Given below is a list of different steps (i-vi) involved in respiration.
(i) Utilisation of $O _{2}$ by the cells for catabolic reactions.
(ii) Transport of gases by the blood.
(iii) Pulmonary ventilation by which atmospheric air is drawn in and $CO _{2}$ is released out.
(iv) Released resultant $CO _{2}$.
(v) Diffusion of $O _{2}$ and $CO _{2}$ between blood and tissues.
(vi) Diffusion of gases ($O _{2}$ and $CO _{2}$) across alveolar tissues.
Select an option which has correct sequence of all the steps.
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(iii), (vii), (ii), (v), (i), (iv)
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(iii), (vi), (i), (v), (ii), (iv)
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(iv), (ii), (v), (iii), (i), (v)
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(iv), (vi), (ii), (v), (i), (iii)
In the given question, the correct sequence of steps of respiration is:
(iii) Pulmonary ventilation by which atmospheric air is drawn in and CO2 is released out.
(vi) Diffusion of gases (O2 and CO2) across alveolar tissues.
(ii) Transport of gases by the blood.
(v) Diffusion of O2 and CO2 between blood and tissues.
(i) The utilisation of O2 by the cells for catabolic reactions.
(iv) Released resultant CO2.
Dark reaction is a
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Anabolic
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Catabolic
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Both A and B
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None of the above
The anabolic processes are the reactions in which the smaller organic molecules are used for the production of the large complex molecules. The carbon dioxide molecule is fixed in the dark reactions for the formation of the glucose molecule. Six molecules of CO$ _2$ are fixed to form one molecule of glucose in which the energy is stored.
What are biochemical reactions in the body known as?
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Anabolic reactions
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Metabolic reactions
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Catabolic reactions
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Vital reactions
Which reactions usually release energy that is used to drive chemical reactions.
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Anabolic
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Catabolic
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Photosynthesis
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None of the above
Metabolism refers to series of reactions wherein product of one reaction becomes reactant for the next one. It includes catabolism (degradative pathways) and anabolism (synthetic pathways). Catabolic reactions are the reactions in which complex molecules are broken down into smaller simpler molecules. The catabolic reactions are exergonic reactions( energy releasing reactions). While photosynthesis is an anabolic reaction which requires energy for the formation of complex molecules. Hence option B is the correct answer.
The term metabolism indicates a variety reactions carried out at
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atomic level
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molecular level
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cellular level
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tissue level
The metabolism is a chemical processes that occur within a living organism in order to maintain life and basic unit of life is cell, hence all metabolic reactions occur in cell. So, the correct option is 'Cellular level'
The enzymes ribulose biphosphate carboxylase-oxygenase and phosphoenol pyruvate carboxylase are activated by
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Mg
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Zn
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Mo
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Mn
Both RUBISCO and PEP carboxylase are important enzymes of dark reaction of photosynthesis. RUBISCO catalyzes carboxylation in C3 plants. In the presence of magnesium activated RUBISCO, carbon dioxide combines with ribulose bis phosphate to form phosphoglyceric acid. In C4 plants, mesophyll cells fix carbon dioxide with the help of phospho enol pyruvate in the presence of magnesium activated phospho-enol pyruvate carboxylase.
Haemoglobin is composed of four subunits. When one subunit binds to oxygen, it increases the chances that the other three subunits will also bind to oxygen. What is this type of activity called?
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Inhibition
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Cooperativity
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Enzyme substrate complex
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Catalysis
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Activation
Cyanide causes irreversible inhibition of cytochrome oxidase. This is because it
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Combines with iron.
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Destroys tertiary structure.
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Attaches to copper.
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All the above.
Which statement regarding enzyme inhibition is correct?
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Competitive inhibition occurs when a substrate competes with enzyme for binding to inhibitor protein
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Competitive inhibition occurs when the substrate and the inhibitor compete for active site on the enzyme
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Non-competitive inhibition of an enzyme can be overcome by adding large amount of substrate
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Non-competitive inhibitors often bind to the enzyme irreversibly
An enzyme brings about
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Decrease in reaction time
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Increase in reaction time
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Increase in activation energy
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Reduction in activation energy
Enzymes are proteins which accelerate the rate of the reaction. The substrate and product have different energy state. The energy gap between the substrate and the product is known as activation energy which is the minimum energy required to initiate a reaction. The enzymes lower the activation energy and lead to the faster conversion of substrate to the product.
Nerve gas (DFP) inhibits neurotransmission as it reacts with
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Serine of acetylcholine-esterase.
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Choline of acetylcholine-esterase.
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Acetylcholine.
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Noradrenaline.
An enzyme promotes a chemical reaction by
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lowering the energy of activation
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changing the free energy difference between substrate and product
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increasing molecular motion
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all of these.
Modulators
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Inhibit enzyme activity
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Stimulate enzyme activity
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Function as coenzymes
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Both A and B
A modulator is a type of molecule which either stimulates or inhibits enzyme activity. Those which stimulate enzyme activity are known as inducers while those which inhibit enzyme activity are known as inhibitors. The inhibitors can be competitive, non-competitive or allosteric inhibitors.
Which of the following inactivates the enzyme by changing its shape?
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Competitive inhibitor
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Allosteric inhibitor
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Coenzyme
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All of the above
Allosteric means in a different steric conformation or occurrence of more than one shapes. Allosteric modulators bind to a site different from the active site and bring changes in the shape or conformation of the enzyme molecule. The change in shape can activate the enzyme or inhibit the activity of enzyme. An allosteric inhibitor will bind to allosteric site and bring in the conformational changes to reduce the enzyme activity.
Identify the correct statement regarding enzyme inhibition.
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Non-competitive inhibition of an enzyme can be overcomed by adding large amount of substrate.
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Competitive inhibition is seen when a substrate competes with an enzyme for binding to an inhibitor protein.
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Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme.
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Non-competitive inhibitors often bind to the enzyme irreversibly.
Competitive inhibition is the inhibition of an enzyme by an inhibitor which has structural similarity to the active site and thus competes with the substrate for binding with the active site. Competitive inhibition is a reversible inhibition and depends on the relative concentration of substrate and inhibitor.
All of the following statement about feedback inhibition of enzyme is true, with an exception of
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It is exerted through allosteric effects.
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It is directed at the enzyme that catalyzes the first committed step in a branch of a pathway.
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It affects the rate of reaction, not the concentration of enzyme.
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It acts very slowly.
Feedback inhibition is the inhibition mechanism in metabolic pathways where the end product of one reaction are the substrates for next reaction. Such feedback inhibition is usually directed at the first or first few reactions in the pathway to help conserve precious cellular resources, thus in case the end product is not required the metabolic pathway is blocked at the initial stages itself. The feed back regulation is mostly brought about by the allosteric modulators. Usually the first steps in metabolic pathways are catalysed by allosteric enzymes whose catalysis rate can be increased with the help of positive modulators and decreased with the help of negative modulators.
Which of the following is true?
Non-competitive inhibitor differs from a competitive inhibitor in that it
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Reduces the affinity of substrate for enzymes
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Does not alter K$ _m$
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May attach it self to the enzyme at a site other than the active site
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Both B and C
A non-competitive inhibitor is one that binds to a site distinct from the site which binds the substrate; inhibitor binding does not block substrate binding or vice versa. The enzyme is inactivated when inhibitor is bound, whether or not substrate is also present. The inhibitor effectively lowers the concentration of active enzyme and hence, lowers the apparent V$ _{max}$. There is often little or no effect on K$ _m$.
Which of the following statements regarding enzyme inhibition is correct?
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Non-competitive inhibition of an enzyme can be overcome by adding large amount of substrate.
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Competitive inhibition is seen, when a substrate competes with an enzyme for binding to an inhibitor protein.
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Competitive inhibition is seen, when the substrate and the inhibitor compete for the active site on the enzyme.
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Non-competitive inhibitors often bind to the enzyme irreversibly.
A competitive inhibitor is a reversible inhibition where the inhibitor competes with the substrate for the active site of an enzyme. While the inhibitor occupies the active site it prevents binding of the substrate to the enzyme. Many competitive inhibitors are compounds that resemble the substrate and combine with the enzyme to form an enzyme inhibitor complex, but without leading to catalysis. Even fleeting combinations of this type will reduce the efficiency of the enzyme. By taking into account the molecular geometry of inhibitors that resemble the substrate, we can reach conclusions about which parts of the normal substrate bind to the enzyme. Competitive inhibition can be analyzed quantitatively by steady-state kinetics.
Which of the following is an allosteric enzyme?
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Hexokinase
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Phosphofructokinase
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Succinic dehydrogenase
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Cytochrome oxidase
Competitive inhibitors of enzymes compete with the active sites of enzyme.
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True
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False
Competitive inhibitors of enzymes compete with the active site of enzyme making them unavailable for the originally desired substrate.
An inhibitor is added to a cell culture so that succinate accumulates. The enzyme catalysing the formation of which substance has been blocked?
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Citrate
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Oxaloacetate
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$\alpha$-ketoglutarate
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Fumarate
Succinate was placed in one of the most important cyclic pathways in metabolism, a collecting pool of catabolic and a starting point of many anabolic processes. Succinate is a product of substrate-level phosphorylation materialized in the citric acid cycle. It is involved in a macrophage-specific metabolic pathway generating and is also a downstream product of the α-ketoglutarate dehydrogenase complex, a heavily regulated multi-subunit complex.