Concept explainers
The Need for Enzymes. You should now be in a position to appreciate the difference between the
(a) Many reactions that are thermodynamically possible do not occur at an appreciable rate because of the activation energy required for the reactants to achieve the transition state. In molecular terms, what does this mean?
(b) One way to meet this requirement is by an input of heat, which in some cases need only be an initial, transient input. Give an example, and explain what this accomplishes in molecular terms.
(c) An alternative solution is to lower the activation energy barrier. What does it mean in molecular terms to say that a catalyst lowers the activation energy barrier of a reaction?
(d) Organic chemists often use inorganic catalysts such as nickel, platinum, or cations in their reactions, whereas cells use proteins called enzymes. What advantages can you see to the use of enzymes? Can you think of any disadvantages?
(e) Some enzymes can transfer a hydrogen atom without lowering the activation energy barrier. How is this possible?
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Becker's World of the Cell (9th Edition)
- Modified TRUE or FALSE. Write the word TRUE if the statement is correct. If the statement is false, write the incorrect underlined word/s and indicate the correct word/s to make the statement true. The Michaelis-Menten Constant (Km) of an enzyme is equal to the enzyme concentration at which the initial velocity of the reaction is one half of maximum velocity (Vmax).arrow_forwardan inorganic ion. Such as metal ion, that improves the fit of an enzyme with its substrate is a(n)?arrow_forwardSelect all that apply. What is true about the conformational aspects of coupling? O The proton gradient is involved in the release of bound ATP from the synthase as a result of conformational change. O The conformational states interconvert as a result of proton flux through the synthase. There are two sites for substrate on the synthase and two possible conformational states: open (0) and tight-binding (T). Dinitrophenol binds to and inhibits ATP synthase conformational changes, thus inhibiting ATP synthesis. The Fo portion of ATP synthase acts as a rotary motor.arrow_forward
- Please ASA. Thanku. In the reaction Na + Cl à Na+ + Cl-, which component is said to become ‘oxidized’ and which is considered reduced? Na, Cl Cl, Cl Na, Na Cl, Naarrow_forwardRequired partner. Aminotransferases require which of the following cofactors: a. NAD+/NADP+NAD+/NADP+ b. Pyridoxal phosphate c. Thiamine pyrophosphate d. Biopterinarrow_forwardPlease choose the correct letter . and explain a bit why you choose it According to the second law of thermodynamics, a. energy will not be destroyed b. energy will not be created c. potential energy will always increase d. entropy will always increase e. both a and b are correct 2. In one of the reactions of the citric acid cycle, malate is oxidized to oxaloacetate. When this reaction is considered in isolation, a small amount of malate remains and is not oxidized. The best term to explain this is a. enthalpy b. entropy c. equilibrium d. free energy e. loss of energyarrow_forward
- entation . During the process of glycolysis, some hydrogen atoms are removed from glucose in the formation of pyruvate. This is an example of which (4.1) KU process (a) hydrolysis (b) dehydration (c) dehydration synthesis (condensation) (d) reduction If y think the statarrow_forwardHigh potential. What is the equilibrium ratio of phosphoenolpyruvate to pyruvate under standard conditions when [ATP ]/[ ADP ]=10? [ATP]/[ADP] = 10?arrow_forwardEnzymes catalyze chemical reactions. What constitutes the active site of an enzyme? What are the turnover number (kcat), the Michaelis constant (Km), and the maximal velocity (Vmax) of an enzyme? The kcat (catalytic rate constant) for carbonic anhydrase is 5 × 105 molecules per second. This is a “rate constant,” but not a “rate.” What is the difference? By what oncentration would you multiply this rate constant in order to determine an actual rate of prod- uct formation (V)? Under what circumstances would this rate become equal to the maximal velocity (Vmax) of the enzyme?arrow_forward
- your answer. What do you understand by the term Metabolism? In a page, no more than a page write to give even examples of metabolism in your answer. Maximum numl aractors (including HTMI tags addod by toxt oditor): 22.000arrow_forwardLife requires energy. In a short essay (100–150 words), describe the basic principles of bioenergetics in an animal cell. How is the flow and transformation of energy different in a photosynthesizing cell? Include the role of ATP and enzymes in your discussion.arrow_forward. Recall your study of equilibria and kinetics from general chemistry. You used equations with upper case Kand lower case k during the study of equilibria and kinetics respectively. What do the upper and lower case letters refer to?arrow_forward
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