EFL True or False Rev Ques

Heat and light are both examples of potential energy.

False - Heat and light are both examples of kinetic energy.

The sign of of a chemical reaction indicates how far from its equilibrium a reaction is at any time.

False - The sign of a chemical reaction, which can be positive (+) or negative (-), refers to the direction in which the reaction proceeds under specific conditions.

Positive favours forward reaction and therefore products, negative favours backwards reaction and therefore the reactants.

A system at equilibrium is said to be in 'a dynamic steady state'. *Possible mistake

False (according to the rev test)

*True - Biochemical reactions within cells often reach equilibrium states where the forward and reverse reactions occur at equal rates, resulting in a dynamic steady state.

A system in 'homeostasis' is in a 'dynamic steady state'.

True - homeostasis involves maintaining a stable internal environment despite external changes, which requires dynamic processes within the system to achieve a steady state

A reaction in which energy is released is said to be exothermic.

True - in an exothermic reaction, energy is released to the surroundings, typically in the form of heat, resulting in a decrease in the internal energy of the system

Processes in which complex molecules are converted into simpler ones are, in isolation, endergonic.

False - Processes in which complex molecules are converted into simpler ones are, in isolation, exergonic.

Endergonic reactions absorb energy from their surroundings to proceed, while exergonic reactions release energy to their surroundings as they proceed.

Processes in which simple molecules are converted into more complex ones are, in isolation, endergonic.

True - energy is typically absorbed from the environment for these reactions to occur

A 'catabolic' pathway is one in which complex molecules are broken to simpler ones.

True - catabolic pathways involve the breakdown of complex molecules into simpler ones, releasing energy in the process.

'Anabolism' refers to the building of complex molecules from simpler ones.

True - anabolism involves the synthesis of complex molecules from simpler ones, requiring energy input in the process.

Catabolism is sometimes said to involve 'molecular divergence', and anabolism to involve 'molecular convergence'.

False - catabolism actually involves "molecular convergence," where complex molecules are broken down into simpler ones, while anabolism involves "molecular divergence," where simpler molecules are combined to form more complex ones

Biosynthetic reactions are referred to as amphibolic processes.

False - Amphibolic processes refer to metabolic pathways that have both catabolic and anabolic functions, meaning they can serve in both the breakdown of molecules for energy and the synthesis of molecules for growth and maintenance. Biosynthetic reactions, while involved in the synthesis of biomolecules, are generally considered to be primarily anabolic rather than amphibolic.

In a complex molecule, kinetic energy is stored in the arrangement of atoms of the molecule.

False - In a complex molecule, kinetic energy is primarily associated with the movement of atoms and bonds, rather than being stored in the arrangement of atoms themselves. The arrangement of atoms contributes more to potential energy rather than kinetic energy.

ATP stands for adenine 5'-triphosphate.

False - ATP stands for adenosine 5'-triphosphate

"A" in ATP refers to adenosine, which consists of adenine (a nitrogenous base) and a ribose sugar molecule.

ATP is an example of a nucleotide.

True - It consists of a nitrogenous base (adenine), a pentose sugar (ribose), and three phosphate groups, making it a nucleotide molecule.

Water is released when ATP is converted into ADP and inorganic phosphate (Pi).

False - water is actually consumed (or hydrolyzed) during the conversion of ATP (adenosine triphosphate) into ADP (adenosine diphosphate) and inorganic phosphate (Pi).

When ATP is hydrolyzed to ADP and Pi, a water molecule is split, providing the necessary energy for the reaction to occur.

Hydrolysis of ATP to ADP relieves electrostatic repulsion occurring between negative charges of phosphate groups.

True - In ATP, the three phosphate groups are negatively charged and repel each other due to their like charges. Hydrolysis of ATP removes one phosphate group, reducing the electrostatic repulsion and stabilizing the ADP molecule.

Under 'standard' conditions in which 1 mol/L each of ADP, ATP and Pi are present, the hydrolysis of ATP to ADP is exergonic.

True - because the standard free energy change (ΔG) for the hydrolysis of ATP to ADP and Pi is negative, indicating that the reaction proceeds spontaneously and releases energy under these conditions.

Catabolic processes are often accompanied by ATP synthesis.

True - catabolic processes involve the breakdown of complex molecules into simpler ones, releasing energy. This energy can be used to synthesise ATP through processes like oxidative phosphorylation, which helps replenish cellular energy stores.

Catabolic processes generally involve a net dephosphorylation of ATP.

False - catabolic processes typically involve a net production or regeneration of ATP, not dephosphorylation

Anabolic processes frequently involve redox reactions in which co-reactants are oxidised.

True - Redox reactions, where one molecule is oxidized (loses electrons) and another is reduced (gains electrons), are a common way to provide this energy. In anabolic pathways, co-reactants are often oxidized, meaning they lose electrons, while other molecules are reduced to facilitate the synthesis of larger molecules.

"Co-reactants" refer to the molecules or compounds that participate in a chemical reaction alongside the primary reactants.

Energy flow between catabolic and anabolic pathways is confined to reactions in which ATP and ADP participate.

False - While ATP and ADP play crucial roles in cellular energy transfer, other molecules such as NADH/NADPH (nicotinamide adenine dinucleotide), FADH2 (flavin adenine dinucleotide), and various coenzymes also participate in energy transfer between pathways.

FADH is the reduced form of FAD.

False - When FAD (flavin adenine dinucleotide) accepts two electrons and two protons, it becomes reduced to FADH2. Therefore, FADH2 is the reduced form of FAD, not FADH.

During photosynthesis, kinetic energy is transformed into potential energy.

True - because during photosynthesis, light energy (a form of kinetic energy) is converted into chemical energy stored in the bonds of glucose molecules (a form of potential energy)

'NADP' stands for nicotinamide adenine dinucleotide phosphate.

True

FAD is composed of two, joined nucleotides.

True - FAD (flavin adenine dinucleotide) consists of two nucleotides, namely adenine and riboflavin, joined together.

ATP, NAD, NADP and FAD all contain adenine.

True

'Electropositive' means attractive to electrons.

False - "electropositive" refers to the ability to donate electrons, not attract them

Substrate-level phosphorylation is defined as ATP synthesis that occurs as a consequence of oxidation of a co-reactant.

False - because substrate-level phosphorylation refers to ATP synthesis that occurs directly through the transfer of a phosphate group from a substrate molecule to ADP, without involvement of an electron transport chain or oxidative phosphorylation.

Substrate-level phosphorylation takes place in the mitochondrion.

False - substrate-level phosphorylation primarily occurs in the cytoplasm or the matrix of the mitochondria, not specifically within the mitochondrion.

Prokaryotes can carry out substrate-level phosphorylation, but not oxidative phosphorylation.

False - prokaryotes can carry out both substrate-level phosphorylation and oxidative phosphorylation.

Oxidative phosphorylation occurs in the cell membrane of prokaryotes, where electron transport chains and ATP synthase complexes are located.

More ATP is synthesised during anaerobic than during aerobic catabolism of glucose.

False - more ATP is synthesized during aerobic catabolism (such as cellular respiration) of glucose compared to anaerobic catabolism (such as fermentation).

Aerobic catabolism produces a maximum of 36-38 ATP molecules per glucose molecule, while anaerobic catabolism produces a maximum of 2 ATP molecules per glucose molecule.

A human mature red blood cell cannot catabolise glucose to carbon dioxide and water.

True - because mature human red blood cells lack mitochondria, which are essential for aerobic cellular respiration, the process that catabolizes glucose to carbon dioxide and water.

As a result, mature red blood cells primarily rely on anaerobic glycolysis to produce ATP, which converts glucose into lactate rather than carbon dioxide and water.

Fatty acids cannot be catabolised to yield ATP by substrate-level phosphorylation.

False - fatty acids can indeed be catabolized to yield ATP through substrate-level phosphorylation.

During fatty acid oxidation, fatty acids are broken down into acetyl-CoA molecules, which enter the citric acid cycle (Krebs cycle) to generate reducing equivalents (NADH and FADH2) and ATP through substrate-level phosphorylation

An increase in entropy means an increase in randomness.

True

Substrate-level phosphorylation is a more primitive process than oxidative phosphorylation.

True - substrate-level phosphorylation is a simpler and more direct mechanism of ATP synthesis compared to oxidative phosphorylation.

Substrate-level phosphorylation occurs through the transfer of a phosphate group from a substrate molecule directly to ADP, whereas oxidative phosphorylation involves a complex series of electron transport chain reactions coupled with ATP synthase activity.

In both substrate-level phosphorylation and oxidative phosphorylation, the entity being 'phosphorylated' is ADP.

True

When 1 mol of glucose is completely catabolised, 6 mol of CO2 and 6 mol of H2O are formed.

True - because during complete aerobic catabolism of glucose through cellular respiration, one molecule of glucose is oxidized to produce 6 molecules of carbon dioxide (CO2) and 6 molecules of water (H2O) as byproducts.

This process occurs in the presence of oxygen and involves the sequential breakdown of glucose through glycolysis, the citric acid cycle, and oxidative phosphorylation.

In aerobic respiration, electrons of highly reduced food molecules (together with protons) finally attach to oxygen, and water is formed.

True - in aerobic respiration, electrons from highly reduced food molecules (such as glucose) are transferred through the electron transport chain to molecular oxygen (O2), along with protons (H+).

These electrons and protons combine with oxygen to form water (H2O) as the final electron acceptor, completing the process of oxidative phosphorylation

Fatty acids, but not glucose, can be broken partially to yield ATP in the absence of oxygen.

False - Both fatty acids and glucose can be partially broken down to yield ATP in the absence of oxygen through anaerobic processes such as glycolysis.

Glycolysis occurs in the cytoplasm and can convert both glucose and some fatty acids into pyruvate, producing a small amount of ATP.

Vigorously exercising muscle is temporarily anaerobic.

True - because during vigorous exercise, muscle cells may consume oxygen faster than it can be supplied by the cardiovascular system.

As a result, muscle cells switch to anaerobic metabolism to meet their energy demands.

Glucose and fats are energy providers in our food by virtue of their highly reduced nature.

True - glucose and fats are energy-rich molecules due to their highly reduced nature. This means they contain a high number of carbon-hydrogen bonds, which store a large amount of potential energy

If the free energies of hydrolysis of glucose 6-phosphate and of ATP under standard conditions are -13.8 and -30.5 kJ/mol respectively, the free energy change occurring under standard conditions when glucose and ATP interact to produce glucose 6-phosphate and ADP is -44.3 kJ/mol.

False - the free energy change occurring under standard conditions when glucose and ATP interact to produce glucose 6-phosphate and ADP cannot be determined simply by adding the individual free energy changes of hydrolysis. The actual free energy change of the reaction depends on the specific conditions and the concentrations of reactants and products. The correct determination of the free energy change requires consideration of the overall reaction and the standard free energy changes of the individual reactions involved.

If the free energy of hydrolysis of 1,3−bisphosphoglycerate to 3−phosphoglycerate is -49.3 kJ/mol and that of ATP to ADP and inorganic phosphate is -30.5 kJ/mol, then the free energy change occurring when 1,3−bisphosphoglycerate and ADP react under standard conditions to give 3−phosphoglycerate and ATP is -18.8 kJ/mol.

True -

If the uncatalysed reactions in which glutamate reacts with +NH4 to produce glutamine and H2O and in which ATP is hydrolysed to ADP and Pi occur under standard conditions with free energies of hydrolysis of +14.2 and -30.5 kJ/mol respectively, then the free energy change occurring under standard conditions when glutamate, +NH4 and ATP react to give glutamine, ADP and Pi is -44.7 kJ/mol.

False -

All energy transformations ultimately result in a decrease in entropy.

False -

If the uncatalysed reactions in which phosphoenolpyruvate is hydrolysed to pyruvate and Pi and in which ATP is hydrolysed to ADP and Pi occur under standard conditions with free energies of hydrolysis of -61.9 and -30.5 kJ/mol respectively, then the free energy change occurring under standard conditions when phosphoenolpyruvate and ADP react to give pyruvate and ATP is -31.4 kJ/mol.

True -

Life occurs with a decrease of entropy of the organism plus its surrounding environment.

False -

Heat is sometimes regarded by biologists as 'the highest form of energy'.

False -

All spontaneous processes occur with an increase in free energy.

False -

The size of of a chemical reaction indicates on which side of the equilibrium the reactant concentrations lie.

False -

Interaction between enzyme and transition state is likely to be stronger than interaction between enzyme and substrate.

True -

Glucokinase has a higher affinity for glucose than has hexokinase.

False -

The initial rate of a reaction (vo) is the rate measured when the substrate concentration is much higher than the enzyme concentration.

True -

Changes in enzyme activity are used in cells to alter flow rates through metabolic pathways.

True -

Allosterically affected enzymes produce a sigmoidal plot of vo against [S].

True -

Feed-back inhibition is an example of competitive inhibition in action.

False -

Loss of enzyme activity at extremes of pH is due to denaturation of the enzyme.

True -

Allosterically affected enzymes usually have quaternary structure.

True -

An allosteric effector is a cell metabolite that binds non-covalently to the active site of an enzyme.

False -

The Michaelis constant is equal to half the substrate concentration present when Vmax is reached.

False -

Riboflavin and niacin are vitamin precursors of FAD and NAD respectively.

True -

Competitive inhibitors compete with the enzyme for binding to substrate.

False -

In the presence of a non-competitive inhibitor, Vmax decreases.

True -

The Michaelis-Menten equation was derived in order to explain in molecular terms how enzymes affect activation energies of catalysed reactions.

False -

The decrease in vo of an enzyme-catalysed reaction that is observed when the temperature is increased is due to enzyme denaturation.

True -

Km has units of concentration.

True -

Cyanide is a reversible, non-covalently binding, competitive inhibitor of the terminal respiratory system.

False -

The Michaelis-Menten equation is Vmax = (vo x [S]) / Km + [S].

False -

Some antibodies are catalytic.

True -

Hexokinase has a high Vmax for glucose.

False -

A 'holoenzyme' is the polypeptide part of an enzyme that contains a cofactor.

False -

In competitive inhibition, Km is decreased and Vmax unchanged, while in non-competitive inhibition, Km is unchanged and Vmax increased.

False -

It is not easy to estimate Km from a Michaelis-Menten plot.

True -

A plot of 1/vo against 1/[S] (where vo is the initial rate of an enzyme-catalysed reaction and [S] is the concentration of substrate in contact with a fixed concentration of enzyme) gives a hyperbolic curve.

False -

A 'cofactor' is a particular type of coenzyme that is a complex, organic molecule, the precursor of which is often a vitamin.

False -

In the presence of a competitive inhibitor, the apparent Km of the enzyme-substrate combination decreases.

False -

The increase in vo of an enzyme-catalysed reaction that is observed when the temperature is increased is due to increased kinetic energy of the reactants.

True -

Vmax is an indication of the catalytic efficiency of an enzyme.

True -

The 'transition state' of an enzyme-catalysed reaction is another name for the enzyme-substrate complex.

False -

Vmax occurs when all the substrate has enzyme attached to it.

False -

A transition state of an enzyme-catalysed reaction is also a competitive inhibitor of the reaction.

False -

A 'prosthetic group' is a polypeptide part of an enzyme that contains a cofactor.

False -

The bigger the value of Km, the more stable is the enzyme-substrate complex.

False -

FAD and NAD are both examples of 'coenzymes'.

True -

An enzyme increases the rate of a spontaneous reaction by increasing the activation energy of the reaction.

False -

Derivation of the Michaelis-Menten equation depends on the assumption that the reaction passes through a transition state.

False -

An enzyme increases the rate of a non-spontaneous reaction by lowering the activation energy of the reaction.

False -

Part of the derivation of the Michaelis-Menten equation involves an assumption that ES, the enzyme-substrate complex, is in a dynamic steady-state.

True -

The hyperbolic curve of a Michaelis-Menten plot of vo against [S] levels off at high [S] because the reaction is approaching equilibrium.

False -

Part of the antiviral action of AZT involves competitive inhibition of viral DNA synthesis.

True -

Changes catalysed by one enzyme in amino-acid R groups of a second enzyme can affect the activity of that second enzyme.

True -

Km tells you about the affinity of an enzyme for a substrate (and vice-versa).

True -

Glucokinase and hexokinase are isomerases.

False - (next batch complete up to here)

The 'binding energy' between substrate and enzyme allows the activation energy barrier of a catalysed reaction to be lowered.

True -

The optimum pH of catalysed reactions depends in part on the charge pattern of enzyme amino-acid R groups.

True -

Increasing [S] can relieve the effect of a competitive inhibitor.

True -

Allosteric inhibitors are non-competitive inhibitors.

True -

Quoting a Km value for an enzyme without mentioning the substrate is not useful.

True -

The Michaelis constant (Km) can be defined as the sum of the rate constants for the (part) reactions in which the enzyme-substrate complex decays, divided by the rate constant of the (part) reaction in which enzyme-substrate complex is formed.

True -

Enzyme-catalysed covalent modification of enzyme structure is used by cells to alter activity of enzymes.

True -