Author Archives: rlmiesfeld

Glucose and fructose are both C6H12O6. What is the structural difference between them?

After food enters the stomach, gastrin triggers the release of __________ and secretion of __________.

What is the most important biochemical deficiency in the muscle cells of a patient with a mutation in the lactate dehydrogenase gene?

Glucagon-like peptide-1 (GLP-1) is a hormone peptide secreted by intestinal L cells. It is secreted in response to the nutrient detection in the small intestine. The resulting physiological response is the lowering of blood glucose levels. Which of the following is a potential mechanism for how GLP-1 causes this physiological response?

A volunteer with Flying Samaritans brings a small boy to the local physician for treatment. Based on the background information listed below, what is the most likely biochemical basis for the boy’s symptoms? • The boy’s body is hunched over and he is barely able to walk on his own • The physician noticed his wrists andContinue reading “MCAT Style Quiz Question 5.2”

An experiment is performed in which the kinetics of an enzyme-catalyzed reaction at different pH values is monitored. It is found that the Km does not change under these various pH conditions, but that the kcat increases as the pH goes above 7. Which of the following statements is true under these conditions?

Binding of the negatively charge allosteric effector 2,3-bisphosphoglycerate (2,3-BPG) stabilizes the T state of hemoglobin.  A lysine residue in the central cavity of hemoglobin interacts with 2,3-BPG.  In a hemoglobin variant, there is a substitution of this lysine by an asparagine.  Relative to the wild-type hemoglobin, this variant would be expected to have _____________________. 

The sarcomere length of isolated heart myoblasts can be measured over time in the laboratory. The myoblasts are maintained in a buffer during the experiment. In a control experiment, Ca2+ and ATP are added to the buffer and the change in sarcomere length is analyzed. If EDTA, a chelating agent that sequesters Ca2+, was includedContinue reading “MCAT Style Quiz Question 6.2”

Why does it make sense that under conditions of low ATP levels in the cell the pyruvate carboxylase reaction is activated by acetyl-Coenzyme A, whereas the pyruvate dehydrogenase reaction is activated by Coenzyme A under these same conditions?