Biochemistry

• Biochemistry exam.

  <|>When a mixture of 3-phosphoglycerate and 2-phosphoglycerate is incubated at 25°C with phosphoglycerate mutase until equilibrium is reached, the final mixture contains six times as much 2-phosphoglycerate as 3-phosphoglycerate
• In biological oxidation-reduction reactions, ∆G°' is involved

  • Options for the correct statement are:
  • ∆G°' is zero
  • ∆G°' cannot be calculated from the information given
  • ∆G°' is incalculably large and positive
  • ∆G°' is +12.7 kJ/mol
  • ∆G°' is -4.44 kJ/mol
• The compound with the largest negative value for the standard free-energy change (∆G°') upon hydrolysis is to be identified
• Types of chemical reactions NOT typically seen in metabolism are:

  • Cleavage and formation of C–C bonds
  • Addition-Elimination Reactions
  • Grignard reactions
  • Group transfers
• Facilitated diffusion across a membrane:

  • Its rate is limited by the solubility of the transported solute in the nonpolar interior of the lipid bilayer
  • A specific membrane protein lowers the activation energy for movement of the solute through the membrane
• Glucose transport into erythrocytes is an example of facilitated diffusion
• Facilitated diffusion through a biological membrane is:

  • Driven by a difference of solute concentration
• For the transport of glucose into an erythrocyte by facilitated diffusion, the free-energy change for glucose uptake into the cell is to be determined
• For a typical phosphoryl-transfer reaction, the type of chemical reaction involved is to be identified
• In biochemical reactions, heterolytic cleavage of bonds is used more often than homolytic cleavage, resulting in reactive species called free radicals
• Glycogen is converted to monosaccharide units by glycogen phosphorylase
• Galactosemia is a genetic error of metabolism associated with a deficiency of UDP-glucose:galactose-1-phosphate uridylyltransferase
• The enzyme glycogen phosphorylase catalyzes a hydrolytic cleavage of a (1 Æ 4) bonds
• Statements about fructose metabolism, mannose pathway, lactase enzyme, and nucleotide sugars are to be determined as TRUE or FALSE
• One common aspect that fermentation to ethanol, lactic acid, and acetoacetate have in common is to be identified
• Matching attributes or strategies used in enzyme-catalyzed reaction mechanisms with the enzymes listed
• In the conversion of glucose to pyruvate via glycolysis, the following enzymes participate:
• Hexokinase
• Triose phosphate isomerase
• Enolase
• Glyceraldehyde-3-phosphate dehydrogenase
• Pyruvate kinase
• Phosphofructokinase-1
• Phosphohexose isomerase
• Enzymes in glycolysis that produce ATP:
• Phosphoglycerate kinase
• Enzymes in glycolysis that produce NADH:
• At which point in glycolysis do C-3 and C-4 of glucose become chemically equivalent?
• When dihydroxyacetone phosphate is converted into glyceraldehyde-3-phosphate by triose phosphate isomerase, C-3 and C-4 of glucose become equivalent; they are both C-1 of glyceraldehyde-3-phosphate
• Alcohol dehydrogenase catalyzes a reversible reaction:
• Ethanol + NAD+ acetaldehyde + NADH + H+
• Calculate ∆G°' for the reaction as written
• The reaction tends to occur favorably under standard conditions in the reverse direction
• Inorganic phosphate (Pi) is required for attaining energy from glucose and its polymers
• Muscle cells have a Ca2+-ATPase that pumps calcium back into the sarcoplasmic reticulum after muscle contractions:
• The protein can accomplish this by having a pore for the calcium ions inside of which the oxygen atoms re-generate the octahedral geometry of the water shell for this ion, but not as accurately for magnesium ion
• Why don't high energy compounds such as phosphoenolpyruvate and phosphocreatine breakdown quickly under physiological conditions?
• These high-energy compounds have large negative ∆G values for hydrolysis, making their breakdown thermodynamically favorable (exergonic). However, the kinetics of their breakdown depends on the availability and activity of enzymes to catalyze these slow reactions. They are kinetically stable
• The free energy of hydrolysis of phosphoenolpyruvate is about -60 kJ/mol
• The enzyme pyruvate kinase catalyzes the reaction: Phosphoenolpyruvate + ADP pyruvate + ATP