MTM Week 9
A 10-year-old patient had 3 days of severe diarrhea after developing a viral gastroenteritis. Now, whenever she drinks milk, she experiences nausea, abdominal pain, and flatulence. She never had this happen before after drinking milk. Which one of the following would be the best advice for this patient?
Her ability to drink milk should return in a few days.
A patient has tried many different "fad" diets to lose weight. Which one of the following meals would lead to the lowest level of circulating glucagon shortly after the meal?
High-carbohydrate meal
Freshly isolated, normal human red blood cells were placed in a solution composed of 150 mM NaCl and 75 mM urea. Which of the following statements is TRUE regarding cell volume changes?
If present, Na+K+2Cl- cotransporters would be activated to bring volume back to normal.
The Na+/H+ transporter in the plasma membrane of many cell types is which of the following?
Important for control of intracellular pH
Which of the following statements about ATP is CORRECT?
In most cases, the energy transfer involves group transfer and not simple hydrolysis of phospho-anhydride bonds
During surgery, exposed tissues are moistened with sterile solution to prevent shrinkage or lysis of the cells. Which of the following does the solution have to possess relative to cells in the tissue?
Isotonic
The kinetics of an allosteric enzyme is shown in the graph. An experimental drug X is added, and the results are shown. Which of the following sets of findings best describes the effect of drug X on enzyme activity?
K50 - increases and Vmax - no change
A person was admitted in a coma. Analysis of the arterial blood gave the following values: PCO2= 30 mm Hg, HCO3-= 5 mmol/l and pH 7.2. What is the underlying acid-base disorder?
Metabolic Acidosis
The ΔG0′ values are determined under standard biochemical conditions and reflect the energy either required, or released, as a particular reaction proceeds. Given the ΔG0′ values below, determine the overall ΔG0′ for the following reaction: Creatine + ATP = Creatine phosphate + ADPGiven half reactions:ATP + H2O = ADP + PO4- ΔG0'= −7.3 kcal/molCreatine phosphate + H2O = Creatine + PO4- ΔG0'= −10.3 kcal/mol
+3.0 kcal/mol
What is the Km for the following plot:
0.125 mM.
The activity of an enzyme is measured at several different substrate concentrations and the data are shown in the table below:
0.5 mM
A newly designed drug is a weak acid with a pKa of 3.8. The drug enters cells via free diffusion through the membrane in its uncharged form. This will occur most readily at which of the following pH values?
2.8
A solution of lactic acid (pH of 3.8) is found to contain 0.2 M in the dissociated form and 0.02 M undissociated form. What is the pKa of the acid?
2.8
ECF osmolality is roughly which of the following?
300 mOsm/kg H20
Antidiuretic hormone (ADH) regulates water retention by acting to increase water reabsorption in the kidneys. If the ADH receptors are antagonized, what effect will this have on extracellular fluid osmolarity and extracellular fluid Na+ concentration? - Table
A
Reaction coordinate diagram for uncatalyzed and enzyme-catalyzed conversion of a reactant S to its product P. Which one of the arrows in the diagram represents the activation energy for the uncatalyzed conversion of S àP?
A
Assume that an increase in blood glucose concentration from 5 to 10 mM would result in insulin release by the pancreas. A mutation in pancreatic glucokinase can lead decreased insulin secretion due to which one of the following events within the pancreatic β-cell?
A reduced ability to raise cAMP levels
The majority of calories in the US diet are derived from carbohydrates, which can contain a variety of glycosidic bonds. Which one of the following carbohydrates contains glucosyl units linked through α-1,6 glycosidic bonds?
Amylopectin
The plasma membrane is made up of a lipid bilayer, which determines the ability of substances to move in and out of the cell. Which of the following substances are lipid soluble and water soluble, respectively?
A
Cyanide is a non-competitive inhibitor of cytochrome oxidase. Cyanide alters the line weaver burke plot by which of the following ways:
B
At low concentrations, sodium chloride (NaCl) is a salt that completely dissociates in water. However, at very high concentrations some Na+ and Cl− ions will reassociate into NaCl. If a 1.0M solution of NaCl represents a very high NaCl concentration, what will the osmolarity (in osmoles/L) of this solution be?
Between 1.0 and 2.0
An 82-year-old woman was transported to the emergency department from her nursing home because her complaining of a headache, fatigue and of a change in her mental state over the past few hours. She has a medical history of diabetes and hypertension. On examination, she has decreased skin turgor, depressed reflexes, and disorientation to time, place, and person. Initial laboratory results show:
Brain swelling due to increased fluid in ICF.
Insulin is synthesized in the β-cells of the pancreas as a proinsulin molecule. In order for proinsulin to be biologically active, which of the following posttranslational modifications of the hormone is required?
Cleavage of peptide bonds
The enzyme reaction scheme below most closely depicts:
Competitive inhibition
A patient is diagnosed with an insulinoma, a rare neuroendocrine tumor, the cells of which are derived primarily from pancreatic β cells. Which of the following would logically be characteristic of an insulinoma?
Decreased glucose in the blood
Five drugs are listed in the following table (A-E). If these drug molecules are all equally lipophilic, which of the following conditions would produce the highest rate of transport of the drug molecule into a cell by simple diffusion?
Drug C
If a poison such as cyanide stops the cellular production of ATP, which of the following processes will cease?
Exit of Na+ from the cell
Which of the following most accurately summarizes the effects of hyperventilation on arterial pCO2, serum pH, and serum bicarbonate concentration - Table
F
The rate of absorption of a drug taken orally is found to increase as the dose ingested is increased up to a point where further increases in dose result in no further increases in the rate of absorption. Absorption does not appear to result in the splitting of ATP. Which of the following processes best describes the drug absorption?
Facilitated diffusion
For the reaction A → B, ΔG0′ = −60 kJ/mol. The reaction is started with 10 mmol of A and no B is initially present. After 24 hours, analysis reveals the presence of 2 mmol of B and 8 mmol of A. Which of the following is the most likely explanation?
Formation is kinetically slow; equilibrium has not been reached by 24 hours
Which of the following GLUT transporters has the highest km value or lowest affinity for glucose?
GLUT 2
After digestion of a piece of cake that contains flour, milk, and sucrose as its primary ingredients, the major carbohydrate products that enter the blood are which of the following?
Glucose, Galactose, and Fructose
A 78-year-old male is gardening outside on a hot day. After a while, the man is thirsty, fatigued, profusely sweating and dizzy. He manages to go inside his home and call his daughter who reaches her father's house right before he faints. What has likely happened to this individual?
Heat exhaustion
ΔG0' is defined as the standard free energy change when:
The reactants are present in concentrations of 1.0 Mol/L at pH 7.0
Which of the following statements is true regarding enzymes:
They decrease the activation energy so that the reaction attains transition state faster
During regulatory volume increase, many cells will decrease which of the following?
efflux of K+
The first physiological change that occurs upon infusing a hypertonic solution intravenously into an experimental rat will be which of the following?
increase in the extracellular osmolality
Which one of the factors would need to be lower to contribute to the greater net flux of Solute A compared to Solute B shown in the graph assuming the solutes are of identical size and charge?
membrane thickness
A 62-year-old woman eats a high-carbohydrate meal. Her plasma glucose concentration rises, and this results in increased secretion from the pancreatic islet cells. The insulin response is an example of which of the following?
negative feedback
Which of the following parameters indicate whether the reaction, A → B, is thermodynamically favourable under standard state conditions at neutral pH?
ΔG0′
Given that the standard free energy change (∆G0') for the hydrolysis of ATP is −7.3 kcal/mol and that for the hydrolysis of glucose-6-phosphate is −3.3 kcal/mol. what is the ∆G0' for the phosphorylation of glucose?Glucose + ATP → Glucose-6-phosphate + ADP
−4.0 kcal/mol
Glucagon release does not alter muscle metabolism because of which one of the following?
Muscle cells lack the glucagon receptor.
A buffer pair (HA/A-) has a pK of 6.4. At a blood pH of 7.4, the concentration of HA is:
One tenth of A-
Certain tumor cells are known to have a plasma membrane Na+ channel that is activated by acidic extracellular ph. In these cells, if acid is added to the extracellular medium, which of the following would occur?
Rate of ATP utilization will increase
In an intact cell, the actual free energy change (ΔG) associated with an enzyme catalyzed reaction is frequently different from the standard free energy change (ΔG0') of the same reaction because in the intact cell
Reactants and products are not at 1M conc
A patient with alcoholism developed pancreatitis that affected his exocrine pancreatic function. He exhibited discomfort after eating a high-carbohydrate meal. The patient most likely had a reduced ability to digest which one of the following?
Starch
