biochem chapter 15

What material in vertebrate muscle serves as a reservoir for high-energy phosphate groups? Creatine phosphate Muscle glycogen Phosphoenolpyruvate

Creatine phosphate

Which of the following is NOT true regarding energy charge? When the energy charge of a cell is high, catabolic pathways are inhibited. The energy charge of a cell is typically buffered, with values from 0.80 - 0.95. Energy charge = [ATP]/[ADP] + [Pi]

Energy charge = [ATP]/[ADP] + [Pi]

flavin adenine dinucleotide

FAD, can accept two electrons. In doing so, takes up two protons.

The reduced form of flavin adenine dinucleotide is: FADH. FAD. FADH++. FADH2. None of the above.

FADH2.

Metabolism is regulated through control of

(1) the amounts of enzymes (2) their catalytic activities, (3) the accessibility of substrates.

can divide metabolic pathways into two broad classes:

(1) those that convert energy from fuels into biologically useful forms, such as ATP or ion gradients (catabolism) (2) those that require inputs of energy to proceed. (anabolism)

Nicotinamide adenine dinucleotide

(NAD+),In the oxidation of a substrate, the nicotinamide ring accepts a hydrogen ion and two electrons, which are equivalent to a hydride ion (H−). The reduced form of this carrier is NADH. known as redox reaction

What is the standard-state free energy (?G°?) for the hydrolysis of ATP to ADP? +45.6 kJ/mol -45.6 kJ/mol -30.5 kJ/mol -14.6 kJ/mol +30.5 kJ/mol

-30.5 kJ/mol

The electron carrier(s) that include(s) ATP is/are: NAD+. FAD. FMN. A and B. A, B, and C.

A and B.

Pantothenate kinase associated degeneration: is a predominantly neurological disorder. can cause anemia. effects tissues that are dependent on aerobic metabolism. A and C. A, B, and C.

A and C.

What are the major purpose(s) for which organisms require energy? the performance of mechanical work active transport the synthesis of biomolecules A and C A, B, and C

A, B, and C

Which activated carrier(s) contain(s) adenosine phosphate units? NADH FADH2 coenzyme A A and B A, B, and C

A, B, and C

Which of the following molecules has a higher phosphoryl-transfer potential than ATP? phosphoenolpyruvate creatine phosphate 1,3-bisphosphoglycerate A and B A, B, and C

A, B, and C

Metabolic processes are regulated by: transcriptional regulation of the amount of enzyme. allosteric control of enzyme activity. the accessibility of substrates by compartmentalization. A and B. A, B, and C.

A, B, and C.

Some of the mechanisms by which enzyme catalytic activity is controlled are: allosteric control. feedback inhibition. covalent modification. A and C. A, B, and C.

A, B, and C.

What factors account for the high phosphoryl-transfer potential of nucleoside tri-phosphate?

ATP has a higher phosphoryl-tranfer potential due to; Resonance stabilization o ADP and Pi more stabilized by resonance than ATP. Charge repulsion o The negative charges destabilizes the molecule making it higher in energy. Stabilization by hydration o More H2O can surround ADP and Pi than ATP increasing stabilization due to solvation. Entropy o Proton release by inorganic phosphate means there are a greater number of products than reactants and so entropy of the system increases as a result of the reaction.

What makes ATP an efficient energy currency?

ATP has a larger phosphoryl-transfer potential the amount of energy released when the phosphorylated compound transfers the phosphoryl group to water under standard conditions. The energy released is called the standard free energy of hydrolysis. This intermediate position enables ATP to function efficiently as a carrier of phosphoryl groups.

Krebs cycle

Acetyl CoA brings the breakdown prod- ucts of proteins, sugars, and fats into the citric acid cycle where they are completely oxidized to CO2.

graph shows how the delta G for the hydrolysis of ATP varies as a function of the Mg2+ concentration. A) how does the decreasing Mg2+ concentration affect the delta G of hydrolysis for ATP? B) Explain this effect.

As the Mg2+ concentration decreases the hydrolysis of ATP increases. b) Mg 2+ binds to the phosphoryl groups of ATP and helps to mitigate charge repulsion. As the Mg 2+ concentration decrease there is less charge stabilizing of ATP and leading to a greater repulsion and an increases the delta G on hydrolysis.

During catabolic processes, the oxidation of energy-rich molecules often results in the reduction of NAD+ to NADH. What comparable molecule is the most commonly used reductant for reductive steps in anabolic processes? Coenzyme A NADPH FAD

NADPH

Which of the following is the electron donor used for reductive biosynthesis? NADH NADPH FADH2 CoA-SH ATP

NADPH

Which of the following vitamins participates as an activated carrier? Retinol Ascorbic acid Nicotinic acid

Nicotinic acid

What are the activated electron carriers for catabolism? For anabolism?

The activated electron carriers for catabolism are NADH and FADH2. For anabolism, the electron carrier is only NADPH (this is used almost exclusively for reductive biosynthesis as an electron donor).

Which of the following does NOT contribute to the high phosphoryl transfer potential of ATP? The adenine ring structure Electrostatic charge repulsion A resonance stabilization

The adenine ring structure

Why are molecules kinetically stable in the face of a large thermodynamic driving force for reaction with O2(in regard to the electron carriers) and H2O (for ATP and acetyl CoA).

The kinetic stability of these molecules in the absence of specific catalysts is essential for their biological function because it enables enzymes to control the flow of free energy and reducing power.

The reaction of NADH with Oxygen to produce NAD+ and H2O is very exergonic yet the reaction of NADH and oxygen takes place very slowly. Why does a thermodynamic favorable reaction not take place rapidly?

The reactants are kinetically stable because of a large activation energy, enzymes are used to lower the activation energy so that the reaction takes place when the cells need the reaction to take place.

In a metabolic pathway: a reaction with a positive ΔG can occur if coupled to a reaction with a greater negative ΔG. it is ΔG°, not ΔG, which determines whether a reaction can occur. a reaction with a positive ΔG cannot occur.

a reaction with a positive ΔG can occur if coupled to a reaction with a greater negative ΔG.

Controlling the catalytic activity of enzymes is important in regulation of metabolic pathways. Two ways in which this may be accomplished are: allosteric regulation and decreasing the intracellular enzyme concentration through secretory processes. allosteric regulation and irreversible covalent modification. allosteric regulation and reversible covalent modification.

allosteric regulation and reversible covalent modification.

The metabolic pathways that require energy and are often biosynthetic processes are: anabolic catabolic. ametabolic. All of the above. None of the above.

anabolic

The reaction pathways that transform fuels into cellular energy are: anabolic. catabolic. ametabolic. All of the above. None of the above.

catabolic

Metabolic reactions and processes that break down material and transform fuels into cellular energy are referred to as ________________ and those performing energy requiring biosynthetic processes are known as __________________. intermediary metabolism; metabolism catabolic; anabolic anabolic; catabolic

catabolic; anabolic

Acyl groups generated during the metabolism of carbohydrates and fatty acids are activated by attachment to: pyruvate. glyceraldehyde-3-phosphate. coenzyme A.

coenzyme A.

Which is the correct coenzyme-carrier pair? NADH: acyl tetrahydrofolate: electrons coenzyme A: acyl lipoamide: aldehyde thiamine pyrophosphate: glucose

coenzyme A: acyl

why have a single nucleotide, ATP, function as the cellular energy currency?

having a single currency allows the cells to monitor its energy status.

ATP is an energy-rich molecule because

its triphosphate unit contains two phosphoanhydride linkages. A large amount of free energy is liberated when ATP is hydrolyzed to adenosine diphosphate (ADP) and orthophos- phate (Pi) deltaG=-30.5kJ/mol

Which energy source is used to regenerate ATP from ADP and Pi? oxidation of carbon to CO2 electrochemical potential of stored glycogen reduction of pyruvate to lactate All of the above. None of the above.

oxidation of carbon to CO2

The hydrolysis of ATP drives metabolism by: shifting the equilibrium of the reaction. providing energy in the form of heat. providing a part of the activation energy for a key reaction.

shifting the equilibrium of the reaction.