14 Questions
What is the enzyme responsible for the breakdown of glycogen?
Glycogen phosphorylase
What is the result of the radioactive decay of 228 Ra?
1 alpha particle + 1 beta particle
How is radioactivity typically detected?
Ionisation of gases in a Geiger counter
What is the half-life of the radionuclide given to the patient?
6 hours
What is the product of the citric acid/Krebs'/TCA cycle?
NADH and FADH2
What happens in the initial step of the citric acid/Krebs'/TCA cycle?
Acetyl CoA combines with oxaloacetate to form citrate
What is the main purpose of oxidative phosphorylation?
The oxidation of NADH and FADH2 in small steps for maximum ATP production
What would happen if ATP synthase stopped working during oxidative phosphorylation?
The electron transport chain would show very low activity
What is the rate law for the elementary reaction of an inhibitor I binding to an enzyme E?
d[EI]/dt = k1 [I][E]
How many substrate molecules are turned over by the enzyme alkaline phosphatase per second?
62.5 s-1
What increases glycolysis?
AMP
Which cells benefit from gluconeogenesis?
Brain, red blood cells, anaerobic muscle, and lactating mammary
Which enzyme is responsible for glycogen breakdown?
Glycogen phosphorylase
What is the unit of the maximal initial reaction rate vmax?
μmol L-1 s-1
Study Notes
Thermodynamics
- ΔG = -RT ln K
- R = 8.314 J K-1 mol-1
- If ΔG0’ = -220 J mol-1, K can be calculated
Enzyme Kinetics
- Inhibitor I binds to enzyme E according to the reaction scheme
- Rate law for this elementary reaction: d[EI]/dt = k1 [I][E] – k-1 [EI]
Enzyme Alkaline Phosphatase
- vmax = 12.5 μmol L-1 s-1
- Concentration of active enzyme = 0.2 μmol L-1
- Turnover number = 62.5 s-1
Pyruvic Acid Reaction
- In the forward reaction, pyruvic acid donates a proton to water
- In the backward reaction, pyruvate acts as an acid
- Protonated water is not accurately described by “H3O+“
Glycolysis Regulation
- Glycolysis is upregulated by increased levels of AMP
- Glycolysis is downregulated by increased levels of ATP, citrate, and alanine
Gluconeogenesis
- Provides glucose for cells that need a constant supply (brain, red blood cells, anaerobic muscle, and lactating mammary)
- Clears cells of molecular debris
Glycogen Breakdown
- Glycogen phosphorylase is responsible for glycogen breakdown
Radioactive Decay
- 228Ra decays to 228Th, releasing 2 alpha particles
- Radioactivity can be detected via ionisation of gases in a Geiger counter
Radionuclide Decay
- Half-life of radionuclide = 6 hours
- Amount of radionuclide left after 12 hours = 10mCi
- Initial amount of radionuclide = 40 mCi
Citric Acid/Krebs’/TCA Cycle
- Products of the citric acid/Krebs’/TCA cycle include NADH and FADH2
- Initial step: acetyl CoA combines with oxaloacetate to form citrate
Oxidative Phosphorylation
- Main purpose: ATP production through oxidation of NADH and FADH2
- If ATP synthase stopped working, the electron transport chain would show very low activity
Quiz on chemical reaction thermodynamics and enzyme kinetics, including equilibrium constants and reaction rates.
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