A population of data is known to be normally distributed with a mean of 75 and standard deviation of 12. A random sample of 16 is taken from the population. Which of the following represents the standard deviation of the sample means?

[Q1] Which point represents pKa1?  [Q2] Which point represents a 50/50 mixture of the plus 1 and 0 charged species?  [Q3] At which point does the major molecular species have a net charge of 0?  [Q4] Which point represents the isoelectric point of this amino acid? [Q5] At which point are there as many molecules with a net charge of 0 as have a net charge of -1?  

Upload an image of your drawing. The role of lactate (CH3CH(OH)CO2-) in metabolism was evaluated in a review article on lactate metabolism by L. B. Gladden (full citation: Gladden, L. B. (2004). Lactate metabolism: a new paradigm for the third millennium. The Journal of physiology, 558(Pt 1), 5–30). The paragraph below is from the article. La- is lactate. “La- can no longer be considered the usual suspect for metabolic ‘crime’, but is instead a central player in cellular, regional and whole body metabolism. Overall, the cell-to-cell lactate shuttle has expanded far beyond its initial conception as an explanation for muscle and exercise metabolism to now subsume all of the other shuttles as a grand description of the role(s) of La- in numerous metabolic processes and pathways.” One of the proposed metabolic roles of lactate involves a metabolite shuttle between two types of cells within the brain. Glu is the primary excitatory neurotransmitter in the brain. The proposed shuttle system is shown in an illustration from the abovementioned article and depicts, among other things, the recycling of Glu. Image Description This picture depicts a chain of events that occurs in and between a glutaminergic neuron and an astrocyte, two types of cells within the brain. Two different reaction cycles are shown.   In the first, La (lactate) begins in the astrocyte. It is able to pass out of the astrocyte and into the glutaminergic neuron. There, in the presence of LDH (lactate dehydrogenase), lactate is converted into Pyr (pyruvate). Here the two reaction cycles intersect with each other. In the presence of AAT (alanine amino transferase), pyruvate is converted into Ala. Simultaneously, this allows Glu in the glutaminergic neuron to be converted into 2-oxoglutamate. The Ala is then able to pass out of the glutaminergic neuron and back into the astrocyte. In the astrocyte, the entire process is reversed. Ala is converted back into pyruvate in the presence of AAT, allowing 2-oxoglutamate in the astrocyte to simultaneously be converted into Glu. Pyruvate is then converted back into lactate in the presence of lactate dehydrogenase. At this point, the cycle repeats.  In the second cycle, Glu begins in the glutaminergic neuron. It is able to pass out of the glutaminergic neuron and into the astrocyte. There, in the presence of an unnamed enzyme, NH4- is added to Glu to create Gln. The NH4- was provided by converting the Glu produced in the previous cycle (through conversion of Ala into pyruvate) back into 2-oxoglutamate in the presence of GDH (glutamate dehydrogenase). This creates a new 2-oxoglutamate that can be converted into Glu again the next time the first cycle brings Ala into the astrocyte. Meanwhile, the Gln that was created by the addition of NH4- is able to pass out of the astrocyte and into the glutaminergic neuron. There, the entire process is reversed. Gln is converted back into Glu and a free NH4- in the presence of an unnamed enzyme. This regenerates the Glu in the glutaminergic neuron that began this cycle. Meanwhile, the released NH4- is added back to a 2-oxoglutamate by glutamate dehydrogenase, re-forming the Glu that was transformed into 2-oxoglutamate in the first reaction cycle when pyruvate in the glutaminergic neuron was converted into Ala. The cycle then is able to repeat. La- is lactate, Pyr is pyruvate, AAT is alanine amino transferase, 2-oxoglu (2-oxoglutamate) is another name for a-ketoglutarate, GDH is glutamate dehydrogenase, LDH is lactate dehydrogenase  One of the reactions shown in the diagram is the conversion of Glu to Gln. Draw out this reaction. Include the structures of the substrate and product, as well as the key intermediate structure in the reaction, along with any cofactors or co-reactants required for the reaction. (2 pts.)  Draw out the reaction that takes 2-oxoglu, which is another name for a-ketoglutarate, directly to Glu (the reaction labeled GDH reaction). You may use names of the substrate and product; structures are not necessary. Include any cofactors and give the enzyme name. (2 pts.) 

Question 1 (5 points) The titration curve for Histidine is shown here.    Question 1 refers to this titration curve. Answer the following questions with the letter on the curve that signifies the correct position on the curve. (1 pt. each)  Image Description  The graph titled “Histidine Titration” illustrates the titration curve of histidine, depicting the relationship between pH and the equivalents of OH⁻ (hydroxide ions) added. The x-axis represents the equivalents of OH⁻ added, ranging from 0 to 3.0, and the y-axis represents the pH, ranging from 0 to 12. Key points labeled A, B, C, D, E, and F mark significant stages in the titration process. Point A, at approximately pH 2, corresponds to the fully protonated form of histidine. Point B, around 0.5 equivalents OH⁻ and pH 3, represents the first buffering region where the carboxyl group (COOH) is being deprotonated to COO⁻. Point C, at around 1.0 equivalents OH⁻ and pH 6, indicates the first equivalence point where the carboxyl group is fully deprotonated. Point D, around 1.5 equivalents OH⁻ and pH 8, marks the second buffering region where the imidazole side chain begins deprotonation. Point E, at around 2.0 equivalents OH⁻ and pH 9, represents the second equivalence point where the imidazole side chain is fully deprotonated. Finally, Point F, at around 3.0 equivalents OH⁻ and pH 11, indicates the stage where the amino group is deprotonated. 

The multiple-choice part of this exam consists of four diagrams with individual question numbers that are circled or ovaled. From the list of possible responses A–J below, select the letter that corresponds with the correct response for each question. Note: Each letter has more than one response. Only one of the possible responses needs to be correct, not all of them combined.   One of the questions has more than one correct answer option. This question will be graded after the exam so the correct points can be given.

Urea Cycle Questions 32–44 Image Description A diagram of the urea cycle, a critical metabolic pathway in the liver responsible for converting ammonia to urea, which is then excreted from the body. The diagram includes several numbered labels corresponding to various molecules, enzymes, and steps in the urea cycle. Let’s go through the numbers and their associated components in the urea cycle. Molecule 32 is produced by molecule 34 in the presence of the cofactor molecule 33. This reaction occurs simultaneously with the reaction of oxaloacetate into molecule 39. Molecule 33 refers to a cofactor necessary for the reaction that converts molecule 34 to 32. Molecule 34 is the product of glutamine reacting with molecule 36 and releasing a free ammonium. Molecule 35 is required and produced in the reaction where molecule 34 is converted into alpha-ketoglutarate. Molecule 36 is required for the conversion of glutamine into molecule 34 and a free ammonium. Molecule 37 is required and produced in the process of converting HCO3- into CO2-phosphate. Molecule 38 is required and produced in the process of converting amino-CO2 into carbamoyl phosphate (amino-CO2-phosphate).  Molecule 39 is the product of a reaction involving oxaloacetate, in which molecule 34 is converted into molecule 32 in the presence of the cofactor molecule 33. Molecule 39 transfers from the matrix into the cytosol as molecule 41. Molecule 40 is required and produced in the process of citrulline being combined with molecule 41 to produce argininosuccinate.    UTP or UDP or PLP (vitamin B6) ATP/ADP or biotin ATP/AMP or phosphatase or fumarate GTP/GDP or kinase or glutamate NAD+/NADH or dehydrogenase or  α -ketoglutarate NADP+/NADPH or transaminase or carnitine FAD/FADH2 or mutase or CO2 or HCO3- Pi or 2Pi (phosphate) or synthase or citrate H2O or urea or phosphorylase CoASH or Asp or UDP-Glc

Fill in the blank: If the Pearson correlation value (r) is negative then the _______is also negative.

One of the proposed metabolic roles of lactate involves a metabolite shuttle between two types of cells within the brain. Glu is the primary excitatory neurotransmitter in the brain. The proposed shuttle system is shown in an illustration from the above-mentioned article and depicts, among other things, the recycling of Glu.  Image Description This picture depicts a chain of events that occurs in and between a glutaminergic neuron and an astrocyte, two types of cells within the brain. Two different reaction cycles are shown.   In the first, La (lactate) begins in the astrocyte. It is able to pass out of the astrocyte and into the glutaminergic neuron. There, in the presence of LDH (lactate dehydrogenase), lactate is converted into Pyr (pyruvate). Here the two reaction cycles intersect with each other. In the presence of AAT (alanine amino transferase), pyruvate is converted into Ala. Simultaneously, this allows Glu in the glutaminergic neuron to be converted into 2-oxoglutamate. The Ala is then able to pass out of the glutaminergic neuron and back into the astrocyte. In the astrocyte, the entire process is reversed. Ala is converted back into pyruvate in the presence of AAT, allowing 2-oxoglutamate in the astrocyte to simultaneously be converted into Glu. Pyruvate is then converted back into lactate in the presence of lactate dehydrogenase. At this point, the cycle repeats.   In the second cycle, Glu begins in the glutaminergic neuron. It is able to pass out of the glutaminergic neuron and into the astrocyte. There, in the presence of an unnamed enzyme, NH4- is added to Glu to create Gln. The NH4- was provided by converting the Glu produced in the previous cycle (through conversion of Ala into pyruvate) back into 2-oxoglutamate in the presence of GDH (glutamate dehydrogenase). This creates a new 2-oxoglutamate that can be converted into Glu again the next time the first cycle brings Ala into the astrocyte. Meanwhile, the Gln that was created by the addition of NH4- is able to pass out of the astrocyte and into the glutaminergic neuron. There, the entire process is reversed. Gln is converted back into Glu and a free NH4- in the presence of an unnamed enzyme. This regenerates the Glu in the glutaminergic neuron that began this cycle. Meanwhile, the released NH4- is added back to a 2-oxoglutamate by glutamate dehydrogenase, re-forming the Glu that was transformed into 2-oxoglutamate in the first reaction cycle when pyruvate in the glutaminergic neuron was converted into Ala. The cycle then is able to repeat.   What is the advantage gained by the glutamatergic cell in shuttling lactate when it appears that a pyruvate shuttle would be more direct? (1 pt.)  What role does Ala play in the shuttle system? Again it appears that shuttling pyruvate would be more direct. (1 pt.)  Gln is the amino acid with the highest circulating concentration in the blood. What major role does it play in nitrogen metabolism? (1 pt.)  The article by Gladden cited in the previous question talks about ATP control of glycolysis. Give the name of one enzyme in the citric acid cycle that is controlled by ATP or ADP/AMP levels. (1 pt.)  “Increased nervous system activity requires increased energy metabolism in neurons. The conventional view is that neuronal energy metabolism is fuelled by glucose oxidation (Chih et al. 2001). The action potentials of neuron activity result in Na+ entry and K+ efflux which activates Na+-K+ -ATPase in the neuronal plasma membrane; this ATPase pump activity, in turn, leads to decreased ATP, increased ADP, increased Pi, and increased AMP, standard activators of glycolysis, the TCA cycle and mitochondrial oxidative phosphorylation. ATP synthesis will increase via these energetic pathways with a concomitant utilization of intracellular glucose that lowers glucose, leading to…”  Acetyl CoA and Glu can react to form N-acetyl Glu, which is a potent activator of the enzyme glutamate dehydrogenase. Briefly explain why this compound is well-suited to regulate the activity of this enzyme. (2 pts.)   

A stressor is defined as an expected experience in the family life-cycle that causes a minor disturbance.

The accumulation of stressor affects all families in much the same way.