Concept explainers
To review:
Five mechanisms that the cell could use to reduce the activity of Xase in the absence of sugar X.
Introduction:
The prokaryotes synthesize the proteins only when their need arises. This is carried out by shutting off the mechanisms, through which the proteins are synthesized. The prokaryotes do this to save energy as well as
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- D-glucose is added to cells and the rate of glucose transport is plotted against D- glucose concentration. In the presence of the D-galactose derivative 6-0-benzyl-D- galactose, the curve is shifted to the right, indicating that D-glucose and the D- galactose derivative both compete for a place in the binding site. External factors such as the addition of ATP or ion gradients doesn't change the rate of absorption into cells. Which of the following is true, select all that apply: O the enzyme is a uniport O mediated transport is occurring O non-mediated transport occurring O passive transport is occurring O active transport is occurringarrow_forwardKinases catalyze the transfer of a phosphate group from a phosphate donor such as adenosine triphosphate (ATP) to a substrate. A well‑known kinase is hexokinase. Hexokinase catalyzes the first step of the glycolysis cycle, and converts glucose to glucose‑6‑phosphate. The reaction of glucose with ATP is shown. The enzyme‑bound base is abbreviated as :B−, and ATP is abbreviated as a diphosphate bonded to adenosine monophosphate (AMP). The first arrow of the reaction mechanism is drawn for you; draw the remaining curved arrows to show how phosphorylation occurs.arrow_forwardA bacterial lactose transporter, which is highly specific for lactose, contains a Cys residue that is essential to its transport activity. Covalent reaction of N-ethylmaleimide (NEM) with this Cys residue irreversibly inactivates the transporter. A high concentration of lactose in the medium prevents inactivation by NEM, presumably by sterically protecting the Cys residue, which is in or near the lactose-binding site. You know nothing else about the transporter protein. Suggest an experiment that might allow you to determine the Mr of this Cys-containing transporter polypeptide.arrow_forward
- The pathway shown below is used by a fungus to create Fructose-1,6-diphosphate from glucose. A silent mutation occurs in the gene that encodes enzyme 3. This fungus is grown on media that only contains the precursor. Discuss the effects of this mutation on: (i) The function of Enzyme 3 (ií) The production of Fructose-1,6-diphosphate Enzyme 1 Glucose-6- Enzyme 2 fructose-6- Enzyme 3 Fructose-1,6- Glucose phosphate phosphate diphosphatearrow_forwardSydney Brennen isolated Salmonella typhimurium mutants that were implicated in the biosynthesis of tryptophan and would not grow on minimal medium supplemented with intermediates in tryptophan biosynthesis, some mutants were able to grow while others remained unable to grow. Review the data attached to order the biosynthetic pathway by both enzymatic step and by intermediate biomolecule. Label the step impacted by each of the mutant cell lines.arrow_forwardWhat is meant by: “The hierarchy of cell sorting?” b) Discuss this in the context of the thermodynamic model of cell interactions (use examples)arrow_forward
- Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Terms can be used once, more than once, or not at all. Submit dCTP GMP AMP GTP dTTP activation inhibition dGTP My Answers Give Up UTP + Gln + ATP → CTP + Glu+ ADP + P₁. Cofactor: dCMP + H₂O →→→→DUMP + NH3. Cofactor: CDP+ [2H] → dCDP+ H₂O. Cofactor: Effect: Effect: Effect: Reset Helparrow_forwardMany antibiotics, which are molecules that are toxic to bacteria, function as enzyme inhibitors. Imagine that both Antibiotic A and Antibiotic B inhibit the ribosome. Antibiotic B kills the bacteria. In contrast, Antibiotic A only temporarily stops growth, with the bacteria remaining alive and able to resume growth when the antibiotic is removed. Which of the following statements provides a reasonable explanation for the difference between Antibiotic A and Antibiotic B? Antibiotic A is a competitive enzyme inhibitor whereas Antibiotic B is a non- competitive enzyme inhibitor. Antibiotic A is a reversible enzyme inhibitor whereas Antibiotic B is a non- reversible enzyme inhibitor. Antibiotic A is a non-reversible enzyme inhibitor whereas Antibiotic B is a reversible enzyme inhibitor. Antibiotic A is a non-competitive enzyme inhibitor whereas Antibiotic B is a competitive enzyme inhibitor.arrow_forwardWhat if the cell found itself in an environment that contained ampleamounts of both lactose and glucose?arrow_forward
- In a certain bacterial species, the amino acid arginine is synthesized by a particular enzyme so the bacterium does not require arginine in its growth medium. A key enzyme, which we will call arginine synthetase, is necessary for arginine biosynthesis. When these bacteria are given arginine in their growth media, they stop synthesizing arginine intracellularly. Based on this observation alone, propose three different regulatory mechanisms to explain why arginine biosynthesis ceases when arginine is added to the growth medium. To better understand the mechanism of regulation, you measure the amount of intracellular arginine synthetase protein when cells are grown in the presence and absence of arginine. Under both growth conditions, the amount of this protein is identical. Which mechanism of regulation would be consistent with this experimental observation?.arrow_forwardCan you answer all the parts to this question please A. Where does a low barrier hydrogen bond (LBH) form transiently during the serine protease mechanism? B. What part does this LBH play in the serine protease mechanism?arrow_forwardPhosphofructokinase 1 (PFK1) activity is regulated by the concentration of ATP through allostery. Increasing the cellular concentration of ATP decreases the affinity of the enzyme for the substrate fructose-6-phosphate. Given that ATP is also one of the substrates for PFK1, how does this regulation mechanism work so effectively? a) ATP can bind to two places on PFK, when ATP is bound in the other site, PFK changes conformation leading to lower affinity for fructose-6-phosphate b) At high concentrations, ATP binds and reverses the PFK reaction c) ATP decreases the activity of aldolase, leading to product inhibition of PFK d) ATP at high concentration binds in place of fructose-6-phosphatearrow_forward
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