Chapter 15: Metabolism Basic Concepts and Design Flashcards
The third state of digestion involves:
acetyl CoA
The reaction pathways that transform fuels into cellular energy are:
catabolic
The metabolic pathways that require energy and are often biosynthetic processes are:
anabolic
What is the standard-state free energy (ΔG°′) for the hydrolysis of ATP to ADP?
−30.5 kJ/mol
Which energy source is used to regenerate ATP from ADP and Pi?
oxidation of carbon to CO2
Which is the correct coenzyme–carrier pair?
coenzyme A: acyl.
Which of the following molecules has a higher phosphoryl-transfer potential than ATP?
phosphoenolpyruvate, creatine phosphate, and 1,3-bisphosphoglycerate
Metabolic processes are regulated by:
transcriptional regulation of the amount of enzyme, allosteric control of enzyme activity, and the accessibility of substrates by compartmentalization.
Some of the mechanisms by which enzyme catalytic activity is controlled are:
allosteric control, feedback inhibition, and covalent modification.
What is meant by intermediary metabolism?
The highly integrated biochemical reactions that take place inside the cell.
Differentiate between anabolism and catabolism.
Anabolism is the set of biochemical reactions that use energy to build new molecules and, ultimately, new cells.
Catabolism is the set of biochemical reactions that extract energy from fuel sources or breakdown molecules.
What are the three primary uses for cellular energy?
- Cellular Movements and the performance of mechanical work
- Active transport
- Biosynthetic reactions
Define: Cellular Energy Currency
ATP
Define: Anabolic Electron Carrier
NADP+
Define: Phototroph
Converts light energy into chemical energy
Define: Catabolic Electron Carrier
NAD+
Define: Oxidation-Reduction Reaction
Transfers electrons
Define: Activated carrier of two-carbon fragments
Coenzyme A
Define: Vitamin
Precursor to coenzymes
Define: Anabolism
Requires energy
Define: Amphibolic Reaction
Used in anabolism and catabolism
Define: Catabolism
Yields energy
What factors account for the high phosphoryl-transfer potential of nucleoside triphosphates?
Charge repulsion, resonance stabilization, increase in entropy, and stabilization by hydration.
Why does it make good sense to have a single nucleotide, ATP, function as the cellular energy currency?
Having only one nucleotide function as the energy currency of the cell enables the cell to monitor its energy status.
Why is ATP usually associated with magnesium or manganese ions?
These divalent ions bind to the negatively charged oxygen atoms found on the phosphoryl groups and help stabilize the charges on ATP.
What is the direction of each of the following reactions when the reactants are initially present in equimolar amounts?
ATP + H2O ADP + Pi
To the left
What is the direction of each of the following reactions when the reactants are initially present in equimolar amounts?
ATP + glycerol glycerol 3-phosphate + ADP
To the right
What is the direction of each of the following reactions when the reactants are initially present in equimolar amounts?
ATP + pyruvate phosphoenolpyruvate +ADP
To the left
What is the direction of each of the following reactions when the reactants are initially present in equimolar amounts?
ATP + glucose glucose-6-phosphate + ADP
To the right
Metabolic pathways frequently contain reactions with positive standard free-energy values, yet the reactions still take place. How is it possible?
The free-energy changes of the individual steps in a pathway are summed to determine the overall free-energy change of the entire pathway. Consequently, a reaction with a positive free-energy value can be powered to take place if coupled to a sufficiently exergonic reaction.
What is the structural feature common to ATP, FAD, NAD+, and CoA?
An ADP unit
Thioesters, common in biochemistry, are more unstable (energy rich) than oxygen esters. Explain.
The electrons of the C=O bond cannot form resonance structures with the C-S bond that are as stable as those that they can form with the C-O bond. Thus, the thioester is not stabilized by resonance to the same degree as is an oxygen ester.
What are the three principle means of controlling metabolic reactions?
- Control of the amount of enzymes
- Control of enzyme activity
- Control of the availability of substrates
The muscles of some invertebrates are rich in arginine phosphate (phosphoarginine). Propose a function for this amino acid derivative.
Arginine phosphate in invertebrate muscle, like creatine phosphate in vertebrate muscle, serves as a reservoir of high potential phosphoryl groups. Arginine phosphate maintains a high level of ATP in muscular exertion.
Creatine is a popular, but untested, dietary supplement.
What is the biochemical rationale for the use of creatine?
The rationale behind creatine supplementation is that it would be converted into creatine phosphate and thus serve as a rapid means of replenishing ATP after muscle contraction.
Creatine is a popular, but untested, dietary supplement.
What type of exercise would most benefit from creatine supplementation?
If creatine supplementation were beneficial, it would affect acitivities that depend on short bursts of activity; any sustained activity would require ATP generation by fuel metabolism, which requires more time.
