Indicate whether the following compounds are likely to cross a membrane by nonmediated or mediated transport: (a) ethanol, (b) glycine, (c) cholesterol, (d) ATP.

#Question id: 528

#Unit 1. Molecules and their Interaction Relevant to Biology

Once inside a cell, glucose is rapidly phosphorylated to glucose-6-phosphate. What is the main purpose of this phosphorylation?

#Question id: 529

#Unit 1. Molecules and their Interaction Relevant to Biology

When a muscle is stimulated to contract aerobically, less lactic acid is formed than when it contracts anaerobically because:

#Question id: 531

#Unit 1. Molecules and their Interaction Relevant to Biology

Glucose labeled with ¹⁴C in C-1 and C-6 gives rise in glycolysis to pyruvate labeled in:

#Question id: 532

#Unit 1. Molecules and their Interaction Relevant to Biology

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change (DG'°) of 23.8 kJ/mol.  Under what conditions (encountered in a normal cell) will the free-energy change (DG) be negative, enabling the reaction to proceed to the right?

#Question id: 533

#Unit 1. Molecules and their Interaction Relevant to Biology

Glucose, labeled with 14C in different carbon atoms, is added to a crude extract of a tissue rich in the enzymes of the pentose phosphate pathway.  The most rapid production of 14CO2 will occur when the glucose is labeled in:

#Question id: 534

#Unit 1. Molecules and their Interaction Relevant to Biology

If glucose labeled with 14C in C-3 is metabolized to lactate via fermentation, the lactate will contain 14C in: