C. Incorrect! Catalysts themselves are not altered or consumed during the reaction.

Transcription

1 Human Physiology - Problem Drill 04: Enzymes and Energy Question No. 1 of 10 Instructions: (1) Read the problem and answer choices carefully, (2) Work the problems on paper as needed, (3) Pick the answer, and (4) Review the core concept tutorial as needed. 1. Which of the following statements about catalysis is true? (A) Catalysts are molecules or substances that effect the conversion of reactants to reaction products. (B) Catalysts are molecules or substances that effect the conversion of enzymes to reaction products. Question #01 (C) Catalysts themselves are altered or consumed during the reaction. (D) Catalysts themselves are sometimes altered or consumed during the reaction. (E) Gibbs free energy (Δ G) refers to the energy that is required to initiate a reaction. A. Correct! Catalysts are molecules or substances that effect the conversion of reactants to reaction products. Catalysts are molecules or substances that effect the conversion of reactants to reaction products. Catalysts themselves are not altered or consumed during the reaction. Catalysts themselves are not altered or consumed during the reaction. Gibbs free energy (Δ G) refers to the energy that a system has available for work. Catalysts are molecules or substances that effect the conversion of reactants to reaction products. By interacting with one or more of the reactants, catalysts provide an alternative reaction pathway. Catalysts themselves are not altered or consumed during the reaction. Gibbs free energy (Δ G) refers to the energy that a system has available for work. Δ G is the net change in free energy (products reactants), given as kcal/mol or kj/mol. The correct answer is (A).

2 Question No. 2 of 10 Instructions: (1) Read the problem and answer choices carefully, (2) Work the problems on paper as needed, (3) Pick the answer, and (4) Review the core concept tutorial as needed. 2. Which of the following statements about enzymes is true? (A) Enzymes function as catalysts by lowering the Energy of activation (Ea). (B) Enzymes function as catalysts by increasing the Energy of activation (Ea). Question #02 (C) The enzyme class known as Transferases, hydrolyze esters, ethers and amides. (D) Enzymes function as catalysts by lowering the Gibbs free energy (ΔG). (E) Enzymes function as catalysts by increasing the Gibbs free energy (ΔG). A. Correct! Enzymes function as catalysts by lowering the Energy of activation (Ea). Enzymes function as catalysts by lowering the Energy of activation (Ea). The enzyme class known as Transferases, are involved in intra- or inter-molecular functional group transfer. Enzymes do not change the Gibbs free energy (ΔG). Enzymes do not change the Gibbs free energy (ΔG). Most biochemical reactions are catalyzed by enzymes. For reactants to form products, a certain input of energy is necessary to get things going. This energy is called the energy of activation. Enzymes function as catalysts by lowering the Energy of activation (Ea), but they do not change the Gibbs free energy (ΔG). Enzymes lower the activation energy, as compared to the same reaction without one, which helps ensure the reaction will proceed. Enzymes are often named after their substrate, function and/or location within the body. For example, salivary amylase is found in the mouth and breaks down starch. The International Union of Biochemistry and Molecular Biology has developed a nomenclature for enzymes and categorized them into 6 broad classes: I oxidoreductase oxidation-reduction (i.e., electron transfers) II transferase intra- or inter-molecular functional group transfer III hydrolase hydrolysis of esters, ethers, and amides IV lyase elimination or addition V isomerase isomerization VI ligase formation of ester, thiol ester, and amide linkages The correct answer is (A).

3 Question No. 3 of ph. (A) An enzyme has an optimal ph range. (B) Has no effect on enzyme function. Question #03 (C) The optimal ph for most enzymes in human cells is around 8. (D) The optimal ph for most enzymes in human cells is around 8.7. (E) If the ph changes, the enzyme adapts and retains its catalytic function. A. Correct! An enzyme has an optimal ph range. An enzyme has an optimal ph range. The optimal ph for most enzymes in human cells is around 7. The optimal ph for most enzymes in human cells is around 7. If the ph changes enough, the enzyme itself can denature. The loss of tertiary structure in the enzyme can remove its active site and, therefore, render it noncatalytic. Enzymes can perform many reactions in a short amount of time, up to millions per second. Enzyme rates are dependent on the conditions of the solution and the concentration of the substrates. The maximum rate of an enzyme (all enzyme active sites bound to substrate) is known as Vmax. The Vmax of an enzyme has an optimal ph range. If the ph becomes too acidic or basic, the enzyme activity decreases. The optimal ph for most enzymes in human cells is around 7. Each enzyme might have a slightly different optimal ph but, if the ph changes enough, the enzyme itself can denature. The loss of tertiary structure in the enzyme can remove its active site and, therefore, render it non-catalytic. The correct answer is (A).

4 Question No. 4 of 10 Instructions: (1) Read the problem and answer choices carefully, (2) Work the problems on paper as needed, (3) Pick the answer, and (4) Review the core concept tutorial as needed. 4. Which of the following statements about temperature effects on enzymes is true? (A) As the temperature becomes exceedingly high, the enzyme will denature and this will result in increased catalytic activity, due to increased collisions. (B) As the temperature becomes exceedingly low, the enzyme will denature and this will result in increased catalytic activity, due to increased collisions. Question #04 (C) Enzymes can switch to a different cofactor, than their usual one, depending on the temperature of its surrounding. (D) Enzymes are also affected by temperature; higher temperatures result in more collisions between the enzyme and substrates and, therefore, up to a certain point will increase the maximum activity rate of the enzyme. (E) Because higher temperatures result in more collisions between the enzyme and substrates and, increases in temperature always result in increases in the maximum activity rate of the enzyme. A. Incorrect! As the temperature becomes exceedingly high, the enzyme will denature and lose its active site and its catalytic activity. As the temperature becomes exceedingly high, the enzyme will denature and lose its active site and its catalytic activity. While there are enzymes that can function in higher temperatures, the cofactor used would not changes based on surrounding temperature changes. D. Correct! Enzymes are also affected by temperature; higher temperatures result in more collisions between the enzyme and substrates and, therefore, up to a certain point will increase the maximum activity rate of the enzyme. Enzymes are also affected by temperature; higher temperatures result in more collisions between the enzyme and substrates and, therefore, up to a certain point will increase the maximum activity rate of the enzyme. Enzymes are also affected by temperature; higher temperatures result in more collisions between the enzyme and substrates and, therefore, up to a certain point will increase the maximum activity rate of the enzyme. The point at where enzyme activity begins to decrease is the optimal temperature. As the temperature decreases, a point will be reached where enzymatic activity will stop. Conversely, as the temperature becomes exceedingly high, the enzyme will denature and lose its active site and its catalytic activity. The correct answer is (D).

5 Question No. 5 of 10 Instructions: (1) Read the problem and answer choices carefully, (2) Work the problems on paper as needed, (3) Pick the answer, and (4) Review the core concept tutorial as needed. 5. Which of the following statements about inborn errors of metabolism is true? Question #05 (A) Inborn errors of metabolism are a group of genetic inherited diseases, in which a defective gene produces an enzyme that doesn t perform its intended chemical reaction. (B) Inborn errors of metabolism are a group of genetic inherited diseases, in which a defective gene produces a coenzyme that doesn t perform its intended chemical reaction. (C) Inborn errors of metabolism usually lead to a dramatic decrease of the substrate for that particular enzyme, which can be toxic to the body. (D) Inborn errors of metabolism usually lead to a build-up of the enzyme, which can be toxic to the body. (E) Inborn errors of metabolism can be categorized into broad groups, such as disorders of enzymes, coenzymes and cofactors. A. Correct! Inborn errors of metabolism are a group of genetic inherited diseases, in which a defective gene produces an enzyme that doesn t perform its intended chemical reaction. Inborn errors of metabolism are a group of genetic inherited diseases, in which a defective gene produces an enzyme that doesn t perform its intended chemical reaction. Inborn errors of metabolism usually lead to a build-up of the substrate for that particular enzyme, which can be toxic to the body. Inborn errors of metabolism usually lead to a build-up of the substrate for that particular enzyme, which can be toxic to the body. Inborn errors of metabolism can be categorized into broad groups, such as disorders of carbohydrate metabolism and disorders of amino acid metabolism. Inborn errors of metabolism are a group of genetic inherited diseases, in which a defective gene produces an enzyme that doesn t perform its intended chemical reaction. This usually leads to a build-up of the substrate for that particular enzyme, which can be toxic to the body. Inborn errors of metabolism can be categorized into broad groups, such as disorders of carbohydrate metabolism and disorders of amino acid metabolism. Phenylketonuria is an example of an inborn error of metabolism. Normally, the enzyme, phenylalanine hydroxylase (PAH), metabolizes the amino acid phenylalanine into tyrosine. The excess levels of phenylalanine (substrate for PAH) affect normal brain development and leads to intellectual disabilities. In most cases, when diagnosed at birth, this disease can be controlled by a specific diet. The correct answer is (A).

6 Question No. 6 of Which is true about the Laws of Thermodynamics? Question #06 (A) Only a small number of biological reactions are subject to the laws of thermodynamics. (B) All biochemical reactions, including enzymatic reactions, are subject to the laws of thermodynamics. (C) The first law states - the total energy of the universe is always changing; energy can be created and destroyed. (D) The first law states - the total energy of the universe is always conserved; but energy can be created and destroyed. (E) The second law - The universe tends towards minimal disorder; all spontaneous processes occur in the direction that decreases the entropy of the system plus its surroundings. A. Incorrect! All biochemical reactions, including enzymatic reactions, are subject to the laws of thermodynamics. B. Correct! All biochemical reactions, including enzymatic reactions, are subject to the laws of thermodynamics. The first law states - the total energy of the universe is always conserved; energy can be neither created nor destroyed. The first law states - the total energy of the universe is always conserved; energy can be neither created nor destroyed. The second law - The universe tends towards maximum disorder; all spontaneous processes occur in the direction that increases the entropy of the system plus its surroundings. All biochemical reactions, including enzymatic reactions, are subject to the laws of thermodynamics. These laws describe the transfer of heat and work in thermodynamic processes. The following are the first two laws: The first law states - the total energy of the universe is always conserved; energy can be neither created nor destroyed. The second law - The universe tends towards maximum disorder; all spontaneous processes occur in the direction that increases the entropy of the system plus its surroundings. Entropy (S) describes the degree of disorder in a system. It increases with increasing disorder. The correct answer is (B).

7 Question No. 7 of Which of the following statements about endergonic and exergonic reactions is true? (A) Endergonic reaction: is characterized by a ΔG less than 0; the reaction is unfavourable and it takes more energy to start the reaction than it yields. Question #07 (B) Exergonic reaction: is characterized by a ΔG greater than 0 - in other words, a favourable, spontaneous reaction. (C) Exergonic reaction: is characterized by a ΔG less than 0 - in other words, a favourable, spontaneous reaction. (D) ΔG = ΔH - T, where ΔH = enthalpy change, and T = temperature (K). (E) ΔG = T- ΔS, where ΔS = entropy change, and T = temperature (K). A. Incorrect! Endergonic reaction: is characterized by a ΔG greater than 0; the reaction is unfavourable and it takes more energy to start the reaction than it yields. Exergonic reaction: is characterized by a ΔG less than 0 - in other words, a favourable, spontaneous reaction. C. Correct! Exergonic reaction: is characterized by a ΔG less than 0 - in other words, a favourable, spontaneous reaction. ΔG = ΔH - T ΔS, where ΔH = enthalpy change, ΔS = entropy change, and T = temperature (K). ΔG = ΔH - T ΔS, where ΔH = enthalpy change, ΔS = entropy change, and T = temperature (K). ΔG refers to the energy a system has available for doing work. Based on the laws of thermodynamics, whether a reaction will be exergonic or endergonic can be calculated as follows: ΔG = ΔH - T ΔS, where ΔH = enthalpy change, ΔS = entropy change, and T = temperature (K). Exergonic reaction: is characterized by a ΔG less than 0 - in other words, a favourable, spontaneous reaction. Endergonic reaction: is characterized by a ΔG greater than 0; the reaction is unfavourable and it takes more energy to start the reaction than it yields. Reaction at Equilibrium: when ΔG is equal to 0, the reaction is at equilibrium. The correct answer is (C).

8 Question No. 8 of ATP Production. (A) The potential energy used by ATP Synthase, to generate ATP from the phosphorylation of AMP. (B) The potential energy used by ATP Synthase, to generate ATP from the phosphorylation of ATP. Question #08 (C) During oxidative phosphorylation, electrons are transferred from electron donors to electron acceptors. The energy released from this process is used to transport protons into the nucleus. (D) While there is some ATP production during glycolysis, the majority of the cell s ATP is produced through oxidative phosphorylation and the electron transport chain. (E) While there is some ATP production during oxidative phosphorylation, the majority of the cell s ATP is produced through glycolysis. A. Incorrect! The potential energy used by ATP Synthase, to generate ATP from the phosphorylation of ADP. The potential energy used by ATP Synthase, to generate ATP from the phosphorylation of ADP. During oxidative phosphorylation, electrons are transferred from electron donors to electron acceptors. The energy released from this process is used to transport protons into the transmembrane space, setting up gradient and electrical potential. D. Correct! While there is some ATP production during glycolysis, the majority of the cell s ATP is produced through oxidative phosphorylation and the electron transport chain. While there is some ATP production during glycolysis, the majority of the cell s ATP is produced through oxidative phosphorylation and the electron transport chain. During oxidative phosphorylation, electrons are transferred from electron donors to electron acceptors. The energy released from this process is used to transport protons into the transmembrane space, setting up gradient and electrical potential. This potential energy is used by ATP Synthase, to generate ATP from the phosphorylation of ADP. Protons from the intermembrane space flow down their concentration gradient and through ATP Synthase. This provides the necessary energy for ATP production. This process takes place in the mitochondria, around the inner mitochondrial membrane. During oxidative phosphorylation, electrons are transferred from electron donors to electron acceptors. The energy released from this process is used to transport protons into the transmembrane space, setting up gradient and electrical potential. The correct answer is (D).

9 Question No. 9 of Which of the following statements about oxidation and reduction reactions is true? (A) Oxidation is defined as the loss of electrons/hydrogen. (B) Oxidation is defined as the gain of electrons/hydrogen. Question #09 (C) Oxidation and Kinase enzyme reactions are also known as Redox reactions because of their symbiotic relationship. (D) Reduction is defined as the loss of electrons/hydrogen. Reducing agents have the ability to reduce another molecule. (E) Reduction is defined as the loss of electrons and gain of hydrogen. Reducing agents have the ability to reduce another molecule. A. Correct! Oxidation is defined as the loss of electrons/hydrogen. Oxidation is defined as the loss of electrons/hydrogen. Oxidation and Reduction reactions are also known as Redox reactions because of their symbiotic relationship. Reduction is defined as the gain of electrons/hydrogen. Reducing agents have the ability to reduce another molecule. Reduction is defined as the gain of electrons/hydrogen. Reducing agents have the ability to reduce another molecule. Oxidation and Reduction reactions are also known as Redox reactions because of their symbiotic relationship. Oxidation is defined as the loss of electrons/hydrogen. Molecules or substances that have the ability to oxidize other molecules are called oxidizing agents. In biology, glucose is oxidized during cellular respiration. Reduction is defined as the gain of electrons/hydrogen. Reducing agents have the ability to reduce another molecule. During the oxidation of glucose, oxygen is reduced to water. During metabolic reactions, oxidation and reduction usually occur together. The correct answer is (A).

10 Question No. 10 of Nicotinamide Adenine Dinucleotide (NAD). (A) Is a coenzyme found in cells that are active in gamete production. Question #10 (B) Is a coenzyme found in cells that are active in metabolism and ATP production. (C) Specifically, NAD in all of its forms is utilized only as part of the Krebs cycle. (D) In metabolic reactions, NAD only acts as an oxidizing agent. (E) NAD is converted between these 2 forms: NAD + and NADFH 2. A. Incorrect! Is a coenzyme found in cells that are active in metabolism and ATP production. B. Correct! Specifically, NAD is utilized as part of the Krebs cycle and during ATP production via the electron transport chain. Specifically, NAD is utilized as part of the Krebs cycle and during ATP production via the electron transport chain. In different metabolic reactions, NAD can act as an oxidizing agent and later a reducing agent. NAD is converted between these 2 forms: NAD + and NADH. Nicotinamide Adenine Dinucleotide (NAD) is a coenzyme found in cells that is active in metabolism and ATP production. It is produced by cells to function in enzymatic reactions. Specifically, NAD is utilized as part of the Krebs cycle and during ATP production via the electron transport chain. In different metabolic reactions, NAD can act as an oxidizing agent and later a reducing agent. NAD is converted between these 2 forms: NAD + and NADH. The correct answer is (B).