The catalytic mechanism of an enzyme found in the mitochondrial matrix (pH = 7.8) depends on an active site Lys residue (pKa = 9.5) that acts as a general acid. Mutation of a neighboring residue alters the microenvironment of the Lys side chain so that its pKa shifts from 9.5 to 7.2. Would the mutation cause the reaction rate to increase or decrease? Explain your answer.

The catalytic mechanism of an enzyme found in the mitochondrial matrix (pH = 7.8) depends on an active site Lys residue (pKa = 9.5) that acts as a general acid. Mutation of a neighboring residue alters the microenvironment of the Lys side chain so that its pKa shifts from 9.5 to 7.2. Would the mutation cause the reaction rate to increase or decrease? Explain your answer.

Biology 2e

2nd Edition

ISBN:9781947172517

Author:Matthew Douglas, Jung Choi, Mary Ann Clark

Publisher:Matthew Douglas, Jung Choi, Mary Ann Clark

Chapter7: Cellular Respiration

Section: Chapter Questions

Problem 1VCQ: Figure 7.11 Dinitrophenol (DNP) is an "uncoupler" that makes the inner mitochondrial membrane...

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The catalytic mechanism of an enzyme found in the mitochondrial matrix (pH = 7.8) depends on an active site Lys residue (pKa = 9.5) that acts as a general acid. Mutation of a neighboring residue alters the microenvironment of the Lys side chain so that its pKa shifts from 9.5 to 7.4. (a) Calculate the ratio of protonated to deprotonated Lys at pH 7.8 for the normal and mutant enzyme. (b) Would you expect the mutation to increase or decrease the reaction rate? Explain your answer.(c) Lys is a classified as a basic amino acid, but it commonly acts as an acid catalyst in biochemical reactions. Explain this paradox.
Assuming that the pH of the IMS is 1.4 units lower than the pH of the matrix, the free energy yield associated with the transport of a proton from the mitochondrial intermembrane space (IMS) to the mitochondrial matrix is △ G of the reaction is 8.310 KJmol-1 What is the minimum number of protons that must enter the mitochondrial membrane from the IMS in order to synthesize one molecule of ATP?
For the mitochondrial membrane described in pic, how many protons must be transported to provide enough free energy for the synthesis of 1 mol of ATP (assuming standard biochemical conditions)?
An important function of the inner mitochondrial membrane is to provide a selectively permeable barrier to the movement of water soluble molecules and thus to generate different chemical environments on either side of the mem- brane. However, many of the substrates and products of oxidative phosphorylation are water soluble and must cross the inner membrane. How does this transport occur?
Considering that 22.4 kJ/mole is required to transport 1 H+ across the mitochondrial membrane,how much energy is available for proton translocation from the oxidation of FADH2 at Complex II? Answer: 134 kJ/mol Can you please explain why the answer would be 134 kJ/mol?
The fatty acid side chains of the phospholipids in the inner mitochondrial membrane exhibit a large proportion of multiple unsaturations. As a result, will the membrane be hydrophobic or hydrophilic? Also will it be more fluid or more rigid? How do these characteristics help explain the observation that the inner membrane is impermeable to ions such as Mg2+ and Cl–? Hint: what moves these ions through the membrane?
Mitochondrial oxidation of fatty acids is a major source of ATP, yet fatty acids can be oxidized elsewhere. What organelle, besides the mitochondrion, can oxidize fatty acids? What is the fundamental difference between oxidation oc- curring in this organelle and mitochondrial oxidation?
The enzyme dihydrofolate reductase (DHFR) normally resides in the cytosol, and it can be imported into mitochondria by appending a mitochondrial signal sequence. However, when this modified DHFR is incubated with methotrexate, which is a substrate analog that binds tightly to the active site, the modified DHFR is no longer imported. Propose an explanation for this finding.
Hexokinase is an important enzyme in the metabolism of glucose. If theconcentration of hexokinase in our eukaryotic cell is 20 μM, how many glucose molecules are present per hexokinase molecule?
Long term use of high-dosage tetracycline causes cellular damage that mimics mitochondrial disease becauseChoose one :A. mitochondrial proteins are easily denatured by drugs like tetracycline. B. mitochondrial ribosomes are susceptible to inhibition by tetracycline. C. mitochondrial lipid bilayers become leaky due to drugs like tetracycline. D. the mitochondrial inner membrane is solubilized by tetracycline. E. mitochondrial DNA is alkylated by drugs like tetracycline..
The electron-transport chain consists of a number of multi protein complexes, which work in conjunction to pass electrons from an electron carrier, such as NADH, to O2. What is the role of these complexes in ATP synthesis? It has been demonstrated that respiration supercomplexes contain all the protein components necessary for respiration. Why is this beneficial for ATP synthesis, and what is one way that the existence of super complexes has been demonstrated experimentally? Coenzyme Q (CoQ) is not a protein, but a small, hydrophobic molecule. Why is it important for the functioning of the electron transport chain that CoQ is a hydrophobic molecule?
Fill in the bold using the table. Because the inner mitochondrial membrane is impermeable to L, when there is an excess of mitochondrial L, it converts to M using a TCA condensation reaction, M crosses to the cytosol using a designated transport system. In the cytosol, M reconverts to L and oxaloacetate. Oxaloacetate is subsequently converted to malate with simultaneous production of N, a prerequisite cofactor for the glycolysis pathway. This reaction is then followed by conversion of N to pyruvate which produces O, a prerequisite cofactor for the fatty acid synthesis pathway. L M N O A. ATP pyruvate malate NADPH B. ATP citrate ATP NAD+ C. acetyl CoA pyruvate NAD+ NADH D. acetyl CoA citrate NAD+ NADPH E. glucose pyruvate malate NADP+