Question 1

The direction of a biological reaction is driven by

Accepted Answer

A)  the concentration of the reactants. 
B)  the concentration of the products. 
C)  the energy of the products compared to the energy of the reactants. 
D)  the free energy released by the reaction. 
E)  All of these factors affect the direction of a biological reaction. 
A)  the concentration of the reactants. 
B)  the concentration of the products. 
C)  the energy of the products compared to the energy of the reactants. 
D)  the free energy released by the reaction. 
E)  All of these factors affect the direction of a biological reaction. E

Question 2

An enzyme catalyses the breakdown of a dipeptide into two amino acids. There is a release of energy. Terms that could be used to describe the reaction are

Accepted Answer

A)  hydrolysis and exergonic. 
B)  oxidation and exergonic. 
C)  hydrolysis and endergonic. 
D)  condensation and exergonic. 
E)  condensation and endergonic. 
A)  hydrolysis and exergonic. 
B)  oxidation and exergonic. 
C)  hydrolysis and endergonic. 
D)  condensation and exergonic. 
E)  condensation and endergonic. A

Question 3

The reaction NAD+ + Pi ====> NADH is likely to be catalysed by

Accepted Answer

A)  a ligase. 
B)  a transferase. 
C)  an isomerase. 
D)  an oxidoreductase. 
E)  a hydrolyase. 
A)  a ligase. 
B)  a transferase. 
C)  an isomerase. 
D)  an oxidoreductase. 
E)  a hydrolyase. D

Question 4

The complete oxidation of glucose in a cell is represented by the equation
C6H12O6 + 6O2 ====> 6CO2 + 6H2O, DG = -2879 kJ/mol
The value 2879 kJ/mol is the amount of energy

Accepted Answer

A)  converted into ATP. 
B)  available to convert ADP to ATP. 
C)  provided to the enzymes involved to lower the activation energy. 
D)  required to activate the reaction. 
E)  released as heat. 
A)  converted into ATP. 
B)  available to convert ADP to ATP. 
C)  provided to the enzymes involved to lower the activation energy. 
D)  required to activate the reaction. 
E)  released as heat.

Question 5

Which of the following is the best energy fuel for a cell?

Accepted Answer

A)  Glucose, because it has the highest proportion of C-O bonds. 
B)  Protein, because it has energy-rich C-N bonds. 
C)  Lipids, because they have the highest proportion of C-H bonds. 
D)  ADP, because it forms ATP. 
E)  Cytochromes, because they are involved in electron transport. 
A)  Glucose, because it has the highest proportion of C-O bonds. 
B)  Protein, because it has energy-rich C-N bonds. 
C)  Lipids, because they have the highest proportion of C-H bonds. 
D)  ADP, because it forms ATP. 
E)  Cytochromes, because they are involved in electron transport.

Question 6

Which of the following statements about glucose is CORRECT?

Accepted Answer

A)  It is a metastable compound. 
B)  It has the chemical formula of C6H11O6. 
C)  It is not a monomer. 
D)  It consists of a sucrose and a fructose molecule. 
E)  In a biological sense, energy is extracted from the C-C, C-H and C-O covalent bonds. 
A)  It is a metastable compound. 
B)  It has the chemical formula of C6H11O6. 
C)  It is not a monomer. 
D)  It consists of a sucrose and a fructose molecule. 
E)  In a biological sense, energy is extracted from the C-C, C-H and C-O covalent bonds.

Question 7

The specificity of an enzyme is due to

Accepted Answer

A)  the unique amino acid structure of the binding surface at the active site. 
B)  the fixed shape of the amino acids at the active site. 
C)  the specific covalent bonding between the substrate and the amino acids at the active site. 
D)  the ability of amino acids distal from the active site to react with the substrate and correctly align the substrate. 
E)  All of these answers are correct. 
A)  the unique amino acid structure of the binding surface at the active site. 
B)  the fixed shape of the amino acids at the active site. 
C)  the specific covalent bonding between the substrate and the amino acids at the active site. 
D)  the ability of amino acids distal from the active site to react with the substrate and correctly align the substrate. 
E)  All of these answers are correct.

Question 8

Biological systems contribute to the increase in entropy in the universe by transforming

Accepted Answer

A)  potential energy into chemical energy. 
B)  radiant energy into chemical energy. 
C)  potential energy into kinetic energy. 
D)  kinetic energy into potential energy. 
E)  chemical energy into potential energy. 
A)  potential energy into chemical energy. 
B)  radiant energy into chemical energy. 
C)  potential energy into kinetic energy. 
D)  kinetic energy into potential energy. 
E)  chemical energy into potential energy.

Question 9

An electron transport chain consists of three cytochromes with the following standard redox potentials:
Cytochrome a (Fe3+)/Cytochrome a (Fe2+) +290
Cytochrome b (Fe3+)/Cytochrome b (Fe2+) +120
Cytochrome c (Fe3+)/Cytochrome c (Fe2+) +220
Which cytochrome in the chain is most likely to donate electrons to the final electron acceptor (e.g. O2)?

Accepted Answer

A)  Cytochrome a (Fe3+) 
B)  Cytochrome a (Fe2+) 
C)  Cytochrome b (Fe2+) 
D)  Cytochrome c (Fe3+) 
E)  Cytochrome b (Fe 3+) 
A)  Cytochrome a (Fe3+) 
B)  Cytochrome a (Fe2+) 
C)  Cytochrome b (Fe2+) 
D)  Cytochrome c (Fe3+) 
E)  Cytochrome b (Fe 3+)

Question 10

Which of the following statements about enzyme catalysis is CORRECT?

Accepted Answer

A)  The specificity of an enzyme is determined by the amino acids at the active site. 
B)  All enzymes operate optimally at pH 7.0. 
C)  During substrate binding to the active site, formation of covalent bonds ensures the correct reaction occurs. 
D)  Enzymes require a metal ion or a cofactor for activity. 
E)  All of these answers are correct. 
A)  The specificity of an enzyme is determined by the amino acids at the active site. 
B)  All enzymes operate optimally at pH 7.0. 
C)  During substrate binding to the active site, formation of covalent bonds ensures the correct reaction occurs. 
D)  Enzymes require a metal ion or a cofactor for activity. 
E)  All of these answers are correct.

Question 11

The reduction of a compound involves

Accepted Answer

A)  addition of oxygen. 
B)  gain of electrons. 
C)  loss of protons. 
D)  the conversion of Fe2+ to Fe3+. 
E)  removal of hydrogen. 
A)  addition of oxygen. 
B)  gain of electrons. 
C)  loss of protons. 
D)  the conversion of Fe2+ to Fe3+. 
E)  removal of hydrogen.

Question 12

Which statement about enzymes is NOT true?

Accepted Answer

A)  The active site of most enzymes is specific for a range of substrates. 
B)  Most chemical reactions in a cell require a specific enzyme. 
C)  The reactants that are altered by enzymes are called substrates. 
D)  Enzymes reduce the activation energy required for a reaction. 
E)  Only a small part of the enzyme molecule is involved in the reaction. 
A)  The active site of most enzymes is specific for a range of substrates. 
B)  Most chemical reactions in a cell require a specific enzyme. 
C)  The reactants that are altered by enzymes are called substrates. 
D)  Enzymes reduce the activation energy required for a reaction. 
E)  Only a small part of the enzyme molecule is involved in the reaction.

Question 13

ATP is synthesised using

Accepted Answer

A)  gluconeognesis. 
B)  an irreversible reaction driven by free electrons. 
C)  the addition of a phosphate group to AMP. 
D)  protons donated via the electron transport chain. 
E)  the energy of electrons removed from fuel molecules. 
A)  gluconeognesis. 
B)  an irreversible reaction driven by free electrons. 
C)  the addition of a phosphate group to AMP. 
D)  protons donated via the electron transport chain. 
E)  the energy of electrons removed from fuel molecules.

Question 14

When a biochemical reaction is at equilibrium

Accepted Answer

A)  the rate of the forward reaction is equal to the rate of the reverse reaction. 
B)  there is no net change in the ratio of the concentration of reactants to products. 
C)  the concentration of the reactants is equal to the concentration of the products. 
D)  the rate of the forward reaction is equal to the rate of the reverse reaction and there is no net change in the ratio of the concentration of reactants to products. 
E)  the rate of the forward reaction is equal to the rate of the reverse reaction and the concentration of the reactants is equal to the concentration of the products. 
A)  the rate of the forward reaction is equal to the rate of the reverse reaction. 
B)  there is no net change in the ratio of the concentration of reactants to products. 
C)  the concentration of the reactants is equal to the concentration of the products. 
D)  the rate of the forward reaction is equal to the rate of the reverse reaction and there is no net change in the ratio of the concentration of reactants to products. 
E)  the rate of the forward reaction is equal to the rate of the reverse reaction and the concentration of the reactants is equal to the concentration of the products.

Question 15

Each step in the biochemical reaction A > B > C > D is catalysed by a specific enzyme. Product D binds to the enzyme that converts B to C at a specific site that is not part of its active site. The binding of D to the enzyme decreases the activity of the enzyme. In this biochemical reaction, substance B functions as

Accepted Answer

A)  an enzyme-substrate complex. 
B)  an allosteric inhibitor. 
C)  a substrate. 
D)  an enzyme. 
E)  a cofactor. 
A)  an enzyme-substrate complex. 
B)  an allosteric inhibitor. 
C)  a substrate. 
D)  an enzyme. 
E)  a cofactor.

Question 16

A cofactor

Accepted Answer

A)  provides energy for enzyme activity by adding phosphate residues to particular amino acids (phosphorylation). 
B)  competes with the substrate to bind to the active site of an enzyme. 
C)  controls enzyme activity by regulating expression of the DNA coding for the enzyme. 
D)  is an additional molecule or ion that enables the enzyme to function. 
E)  is covalently linked to the active site of an enzyme to increase activity. 
A)  provides energy for enzyme activity by adding phosphate residues to particular amino acids (phosphorylation). 
B)  competes with the substrate to bind to the active site of an enzyme. 
C)  controls enzyme activity by regulating expression of the DNA coding for the enzyme. 
D)  is an additional molecule or ion that enables the enzyme to function. 
E)  is covalently linked to the active site of an enzyme to increase activity.

Question 17

ATP

Accepted Answer

A)  is the only energy carrier in the cell. 
B)  drives energetically favourable reactions. 
C)  gives up its energy in the form of high energy electrons. 
D)  often transfers energy from degradative to synthetic pathways. 
E)  supplies energy for the diffusion of compounds across cell membranes. 
A)  is the only energy carrier in the cell. 
B)  drives energetically favourable reactions. 
C)  gives up its energy in the form of high energy electrons. 
D)  often transfers energy from degradative to synthetic pathways. 
E)  supplies energy for the diffusion of compounds across cell membranes.

Question 18

The enzyme 'thermolysin' has a zinc ion as part of its active site. This ion destabilises chemical bonds in the substrate by attracting electrons and is called

Accepted Answer

A)  an electron carrier. 
B)  an inhibitor. 
C)  a coenzyme. 
D)  a cofactor. 
E)  a hydrolyase. 
A)  an electron carrier. 
B)  an inhibitor. 
C)  a coenzyme. 
D)  a cofactor. 
E)  a hydrolyase.

Question 19

When cells oxidise molecules such as fatty acids or glucose, which molecule generally operates as the electron carrier?

Accepted Answer

A)  ATP 
B)  NADH 
C)  DNA 
D)  RNA 
E)  FADH 
A)  ATP 
B)  NADH 
C)  DNA 
D)  RNA 
E)  FADH

Question 20

The purpose of the cytochromes in electron transport chains is to

Accepted Answer

A)  release energy in small quantities without a large loss to heat. 
B)  reduce NADH to NAD+. 
C)  reduce Fe3+ to Fe2+. 
D)  convert oxygen to water. 
E)  recycle ADP. 
A)  release energy in small quantities without a large loss to heat. 
B)  reduce NADH to NAD+. 
C)  reduce Fe3+ to Fe2+. 
D)  convert oxygen to water. 
E)  recycle ADP.

Exam 3: The Chemistry of Life

The direction of a biological reaction is driven by

An enzyme catalyses the breakdown of a dipeptide into two amino acids. There is a release of energy. Terms that could be used to describe the reaction are

The reaction NAD+ + Pi ====> NADH is likely to be catalysed by

The complete oxidation of glucose in a cell is represented by the equation C6H12O6 + 6O2 ====> 6CO2 + 6H2O, DG = -2879 kJ/mol The value 2879 kJ/mol is the amount of energy

Which of the following is the best energy fuel for a cell?

Which of the following statements about glucose is CORRECT?

The specificity of an enzyme is due to

Biological systems contribute to the increase in entropy in the universe by transforming

Which of the following statements about enzyme catalysis is CORRECT?

The reduction of a compound involves

Which statement about enzymes is NOT true?

ATP is synthesised using

When a biochemical reaction is at equilibrium

A cofactor

ATP

The enzyme 'thermolysin' has a zinc ion as part of its active site. This ion destabilises chemical bonds in the substrate by attracting electrons and is called

When cells oxidise molecules such as fatty acids or glucose, which molecule generally operates as the electron carrier?

The purpose of the cytochromes in electron transport chains is to

Nature of Molecules

Biomolecules

Functioning Cells

Movement Across Membranes

Harvesting Energy

Cells, Tissues and Signals

Cell Division

Inheritance

Genes, Chromosomes and Dna

The Genetic Code

Gene Expression

Genomes, Mutation and Cancer

Viruses

Genetic Engineering and Biotechnology

Reproduction, Growth and Development of Flowering Plants

Structure of Plants

Plant Nutrition, Transport and Adaptation to Stress

Plant Hormones and Growth Responses

Animal Reproduction

Animal Development

Homeostasis: Water, Solutes and Excretion

Gas Exchange in Animals

Circulation

Metabolism, Temperature Regulation and Environmental Stress

Animal and Human Nutrition

Innate Defences and the Immune System

Hormonal Control in Animals

Nervous Systems

Animal Movement

Animal Behaviour

Evolving Life

Evolving Earth

Mechanisms of Evolution

Bacteria

The Protists

Plants

Fungi

Simple Animals: Sponges to Flatworms

Annelids, Molluscs, Nematodes and Arthropods

Echinoderms and Chordates

Australian Biota

Population Ecology

Living in Communities

Ecosystems

Human Impacts

Filters

The reaction NAD⁺ + P_i ====> NADH is likely to be catalysed by

The complete oxidation of glucose in a cell is represented by the equation C₆H₁₂O₆ + 6O₂ ====> 6CO₂ + 6H₂O, DG = -2879 kJ/mol The value 2879 kJ/mol is the amount of energy