BMSC 230 Final Exam Questions with
Verified Answers
Enzymes only - ANSWER-Speed up the rate of a chemical reaction, they do NOT
change the equilibrium constant for reactions
• canNOT make a thermodynamically unfavourable reaction proceed
Two thermodynamic properties - ANSWER-The free energy difference (deltaG)
between the products and reactants
• deltaG determines spontaneity
The free energy required to initiate the conversion of reactants to products
• the rate at which the reaction will proceed
• enzyme affects rate
Spontaneous reactions occur when - ANSWER-deltaG is negative
• exergonic - release energy
Non-spontaneous reactions - ANSWER-Have a positive deltaG and require the input
of energy
• often involving ATP cleavage - endergonic
When a system is at equilibrium - ANSWER-There is no net change in the
concentration of reactants and products
• deltaG = 0
deltaG provides No info on - ANSWER-The rate of the reaction
• only spontaneity
deltaG of the forward reaction - ANSWER-deltaG = deltaG• + RT ln ([prod]\[react])
deltaG• = standard free energy change
• at standard conditions (1.0M, 1atm, 298K, pH7)
R = gas constant
T = absolute temp (K)
A simple way to calculate the concentration of the reactants and products when the
reaction has reached equilibrium and deltaG is 0 - ANSWER-deltaG•' = -RT Keq —>
deltaG•' = -2.3RT log Keq
Keq = ([prod]/[react])
Relationship between Keq & deltaG - ANSWER-Keq = 1 —> deltaG•' = 0
• equilibrium
Keq < 1 —> deltaG•' = +
,• favours the reverse reaction
Keq > 1 —> deltaG•' = -
• spontaneous - favours the forward reaction
Two or more reactions - ANSWER-Can be completed together (coupled)
• free energy changes that occur for each one are additive - if overall reaction is neg
the reactions proceed
Couple an unfavourable with a favourable so it will proceed
• provide a new mechanism for the unfavoured process
ATP is the energy currency - ANSWER-Used in mammals and most living organisms
Other nucleoside triphosphates - ANSWER-GTP
UTP
CTP
Are energy rich and are sometimes used as free energy donors
• ATP is the most common
High energy bonds in ATP - ANSWER-Acid Anhydride bonds (2) - bonds between
two acid groups (phosphates) that lose a water molecule upon formation
ATP has high - ANSWER-Phosphoryl transfer potential
• readily transfers a phosphate group to water
The active form of ATP is usually in complex with - ANSWER-Mg2+
Mn2+
The standard free energy of the hydrolysis of ATP - ANSWER-The terminal
phosphate group is cleaved off to yield ADP and inorganic phosphate (Pi)
• very negative -30.5kJ/mol
ATP + H2O <—> ADP + Pi
deltaG = -30.5kJ/mol
Large standard free energy of ATP is due to - ANSWER-1. Electrostatic repulsion -
at pH7 ATP carries 4 neg charges which repel
2. When ATP is hydrolyzed the electrostatic repulsion is reduced
3. Resonance stabilization - Pi has greater resonance stabilization than any of the
phosphates on ATP
4. Increase in Entropy - hydrolysis results in 2 molecules instead of 1, increasing
entropy
5. Stabilization of hydration - water binds ADP & Pi = stabilization, reverse reaction is
less favourable
Sometimes ATP releases - ANSWER-Pyrophosphate - 2 phosphate groups joined
together
• results in AMP as a product
• still releases lots of energy
,ATP + H2O <—> AMP + PPi
deltaG = -45.6kJ/mol
Phosphoryl-transfer potential - ANSWER-Allows ATP to donate and accept a
phosphate
• truly a carrier of phosphate groups
The energy of ATP comes from - ANSWER-The breakdown, or catabolism of the
biomolecules we eat
• the carbon fuels we eat (glucose & fats) - oxidized into CO2, the energy released is
used to regenerate ATP from ADP & Pi
Oxidation reactions - ANSWER-Involve the loss of electrons from the molecule being
oxidized and the gain of electrons by another molecule that is reduced
• oxidation is loss
• reduction is gain
Sometimes redox reactions involve - ANSWER-The loss or gain of one or more
protons
The more reduced carbon is to begin with - ANSWER-The more free energy is
released by its oxidation
• more C-H bonds —> electrons
• less bonds to O
Two major sources of fuels that humans use are - ANSWER-Glucose - C6H12O6
Fatty acids - R-COOH
• fatty acids are far more reduced - they have fewer oxygens then glucose, more CH
(electrons) - it's degradation yeilds more energy
NADH donates its electrons in - ANSWER-A process called oxidative
phosphorylation - results in ATP synthesis
When energy is released from carbon in a redox reaction - ANSWER-The energy of
the oxidation is initially a high phosphoryl-transfer potential compound that is
transferred to ADP to form ATP
ATP synthesis - ANSWER-Results from the transfer of a phosphate group from one
high phosphoryl-transferase potential compound to ADP
• substrate level phosphorylation
A major reoccurring theme in metabolism is - ANSWER-Activated carriers
Activated carriers - ANSWER-Small organic molecules that function as coenzymes
• ATP is an activated carrier of phosphoryl (phosphate) groups transferred from ATP
in an exergonic process
Activated carriers of electrons for fuel oxidation - ANSWER-Fatty acids &
carbohydrates generate electrons - passes to electron acceptor O2
, • electrons released from oxidation are transferred to carriers, the reduced form of
the carriers transfer electrons to O2
• NAD+
The reactive part of NAD+ is - ANSWER-The nicotinamide ring - accepts 2 electrons
& 1 H+
Activated carriers for fuel oxidation - ANSWER-NAD+ (2.5 ATP)
FAD (1.5 ATP)
The reactive sites on FAD - ANSWER-Accept an electron and proton (H+)
• to the N on the centre and right ring
The electrons in FADH2 - ANSWER-Are eventually donated to oxygen, and in the
process ATP will be synthesized
In many biosynthetic reactions - ANSWER-The precursor molecules are more
oxidized then the final product
• need for electrons & ATP
The primary electron donor is NADPH
NADH is used primarily for - ANSWER-The generation of ATP, while NADPH is used
for reductive biosynthesis
• both provide electrons
Coenzyme A (CoA) - ANSWER-A carrier of 2-carbon units - acetyl groups
A carrier of longer carbon units - acyl groups
• fatty acids
CoA contains a pantothenic acid moiety - B vitamin
Acetyl groups are important in both - ANSWER-Catabolism
Anabolism
Acetyl groups are attached to - ANSWER-CoA through the reactive sulfhydryl group
to form acetyl CoA
The hydrolysis of acetyl CoA - ANSWER-Releases the acetyl group - has a very
large negative standard free energy change
• thermodynamically favourable
Transfer of the acetyl group is exergonic
Most activated carriers that act as coenzymes are derived from - ANSWER-Vitamins
- particularly vitamin B
• modify the vitamins
3 primary ways in which metabolic pathways are regulated - ANSWER-1. The
amount of an enzyme that catalyzes a regulated step in the pathway can be
regulated itself
• control amount of enzyme - affecting what/how much it codes for
Verified Answers
Enzymes only - ANSWER-Speed up the rate of a chemical reaction, they do NOT
change the equilibrium constant for reactions
• canNOT make a thermodynamically unfavourable reaction proceed
Two thermodynamic properties - ANSWER-The free energy difference (deltaG)
between the products and reactants
• deltaG determines spontaneity
The free energy required to initiate the conversion of reactants to products
• the rate at which the reaction will proceed
• enzyme affects rate
Spontaneous reactions occur when - ANSWER-deltaG is negative
• exergonic - release energy
Non-spontaneous reactions - ANSWER-Have a positive deltaG and require the input
of energy
• often involving ATP cleavage - endergonic
When a system is at equilibrium - ANSWER-There is no net change in the
concentration of reactants and products
• deltaG = 0
deltaG provides No info on - ANSWER-The rate of the reaction
• only spontaneity
deltaG of the forward reaction - ANSWER-deltaG = deltaG• + RT ln ([prod]\[react])
deltaG• = standard free energy change
• at standard conditions (1.0M, 1atm, 298K, pH7)
R = gas constant
T = absolute temp (K)
A simple way to calculate the concentration of the reactants and products when the
reaction has reached equilibrium and deltaG is 0 - ANSWER-deltaG•' = -RT Keq —>
deltaG•' = -2.3RT log Keq
Keq = ([prod]/[react])
Relationship between Keq & deltaG - ANSWER-Keq = 1 —> deltaG•' = 0
• equilibrium
Keq < 1 —> deltaG•' = +
,• favours the reverse reaction
Keq > 1 —> deltaG•' = -
• spontaneous - favours the forward reaction
Two or more reactions - ANSWER-Can be completed together (coupled)
• free energy changes that occur for each one are additive - if overall reaction is neg
the reactions proceed
Couple an unfavourable with a favourable so it will proceed
• provide a new mechanism for the unfavoured process
ATP is the energy currency - ANSWER-Used in mammals and most living organisms
Other nucleoside triphosphates - ANSWER-GTP
UTP
CTP
Are energy rich and are sometimes used as free energy donors
• ATP is the most common
High energy bonds in ATP - ANSWER-Acid Anhydride bonds (2) - bonds between
two acid groups (phosphates) that lose a water molecule upon formation
ATP has high - ANSWER-Phosphoryl transfer potential
• readily transfers a phosphate group to water
The active form of ATP is usually in complex with - ANSWER-Mg2+
Mn2+
The standard free energy of the hydrolysis of ATP - ANSWER-The terminal
phosphate group is cleaved off to yield ADP and inorganic phosphate (Pi)
• very negative -30.5kJ/mol
ATP + H2O <—> ADP + Pi
deltaG = -30.5kJ/mol
Large standard free energy of ATP is due to - ANSWER-1. Electrostatic repulsion -
at pH7 ATP carries 4 neg charges which repel
2. When ATP is hydrolyzed the electrostatic repulsion is reduced
3. Resonance stabilization - Pi has greater resonance stabilization than any of the
phosphates on ATP
4. Increase in Entropy - hydrolysis results in 2 molecules instead of 1, increasing
entropy
5. Stabilization of hydration - water binds ADP & Pi = stabilization, reverse reaction is
less favourable
Sometimes ATP releases - ANSWER-Pyrophosphate - 2 phosphate groups joined
together
• results in AMP as a product
• still releases lots of energy
,ATP + H2O <—> AMP + PPi
deltaG = -45.6kJ/mol
Phosphoryl-transfer potential - ANSWER-Allows ATP to donate and accept a
phosphate
• truly a carrier of phosphate groups
The energy of ATP comes from - ANSWER-The breakdown, or catabolism of the
biomolecules we eat
• the carbon fuels we eat (glucose & fats) - oxidized into CO2, the energy released is
used to regenerate ATP from ADP & Pi
Oxidation reactions - ANSWER-Involve the loss of electrons from the molecule being
oxidized and the gain of electrons by another molecule that is reduced
• oxidation is loss
• reduction is gain
Sometimes redox reactions involve - ANSWER-The loss or gain of one or more
protons
The more reduced carbon is to begin with - ANSWER-The more free energy is
released by its oxidation
• more C-H bonds —> electrons
• less bonds to O
Two major sources of fuels that humans use are - ANSWER-Glucose - C6H12O6
Fatty acids - R-COOH
• fatty acids are far more reduced - they have fewer oxygens then glucose, more CH
(electrons) - it's degradation yeilds more energy
NADH donates its electrons in - ANSWER-A process called oxidative
phosphorylation - results in ATP synthesis
When energy is released from carbon in a redox reaction - ANSWER-The energy of
the oxidation is initially a high phosphoryl-transfer potential compound that is
transferred to ADP to form ATP
ATP synthesis - ANSWER-Results from the transfer of a phosphate group from one
high phosphoryl-transferase potential compound to ADP
• substrate level phosphorylation
A major reoccurring theme in metabolism is - ANSWER-Activated carriers
Activated carriers - ANSWER-Small organic molecules that function as coenzymes
• ATP is an activated carrier of phosphoryl (phosphate) groups transferred from ATP
in an exergonic process
Activated carriers of electrons for fuel oxidation - ANSWER-Fatty acids &
carbohydrates generate electrons - passes to electron acceptor O2
, • electrons released from oxidation are transferred to carriers, the reduced form of
the carriers transfer electrons to O2
• NAD+
The reactive part of NAD+ is - ANSWER-The nicotinamide ring - accepts 2 electrons
& 1 H+
Activated carriers for fuel oxidation - ANSWER-NAD+ (2.5 ATP)
FAD (1.5 ATP)
The reactive sites on FAD - ANSWER-Accept an electron and proton (H+)
• to the N on the centre and right ring
The electrons in FADH2 - ANSWER-Are eventually donated to oxygen, and in the
process ATP will be synthesized
In many biosynthetic reactions - ANSWER-The precursor molecules are more
oxidized then the final product
• need for electrons & ATP
The primary electron donor is NADPH
NADH is used primarily for - ANSWER-The generation of ATP, while NADPH is used
for reductive biosynthesis
• both provide electrons
Coenzyme A (CoA) - ANSWER-A carrier of 2-carbon units - acetyl groups
A carrier of longer carbon units - acyl groups
• fatty acids
CoA contains a pantothenic acid moiety - B vitamin
Acetyl groups are important in both - ANSWER-Catabolism
Anabolism
Acetyl groups are attached to - ANSWER-CoA through the reactive sulfhydryl group
to form acetyl CoA
The hydrolysis of acetyl CoA - ANSWER-Releases the acetyl group - has a very
large negative standard free energy change
• thermodynamically favourable
Transfer of the acetyl group is exergonic
Most activated carriers that act as coenzymes are derived from - ANSWER-Vitamins
- particularly vitamin B
• modify the vitamins
3 primary ways in which metabolic pathways are regulated - ANSWER-1. The
amount of an enzyme that catalyzes a regulated step in the pathway can be
regulated itself
• control amount of enzyme - affecting what/how much it codes for
