MODULE 1: Chapter 2.1 Flashcards
What is the primary function of photosynthetic organisms in biological systems?
They convert solar energy into chemical energy through oxidation-reduction reactions
This chemical energy sustains life and produces carbohydrates from CO2.
What are the three types of work that energy conversion in living systems supports?
- Osmotic work
- Chemical work
- Mechanical work
What is homeostasis in the context of living organisms?
A highly ordered steady state that requires energy to maintain
Organisms must maintain steady states with respect to temperature and concentrations of biomolecules.
What is the ultimate power source for life on Earth?
Solar energy produced by thermonuclear reactions in the Sun
What process do photosynthetic autotrophs use to generate O2 and glucose?
Photosynthesis
What do heterotrophs depend on for energy?
Photosynthetic autotrophs to produce O2 and glucose
Heterotrophs cannot convert solar energy into chemical energy directly.
Define redox reactions.
Linked oxidation-reduction reactions where electrons are transferred between compounds
What happens to chlorophyll during light absorption in photosynthesis?
Photooxidation occurs, transferring an electron from chlorophyll to an acceptor molecule
What is photophosphorylation?
The process that generates ATP from light-induced electron transfer
What are the two main laws of thermodynamics relevant to biological processes?
- First law: Energy cannot be created or destroyed, only transformed
- Second law: Spontaneous processes tend toward increasing entropy
What is the difference between an open and a closed system?
- Open system: Matter and energy are exchanged
- Closed system: Only energy is exchanged
What is enthalpy (H)?
The heat content of a system defined by the equation H = E + PV
What is the formula for energy change (ΔE) in a biological system?
ΔE = Efinal − Einitial = q − w
What is an exothermic reaction?
A reaction that releases heat and has a negative ΔH value
What unit of energy is equivalent to one calorie?
4.184 joules
Fill in the blank: The combustion of glucose is an _______ reaction.
exothermic
True or False: Biological systems are isolated systems.
False
What is the relationship between calories and joules?
1 Calorie = 1 kcal = 4.184 kJ
Strict adherence to capitalization conventions does not always occur.
What is the equation for the complete oxidation of 1 mole of glucose?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Heat
The heat produced is at constant pressure (qP).
What is the change in enthalpy (ΔH) for the complete oxidation of 1 mole of glucose?
ΔH = 2803 kJ/mol
This is the energy released during aerobic respiration.
What does the second law of thermodynamics state?
All spontaneous processes tend toward the dispersal of energy in the absence of energy input.
What is entropy (S) a measure of?
Entropy is a measure of the spreading of energy.
How is the change in entropy of the universe represented mathematically?
ΔSuniverse = ΔSsystem + ΔSsurroundings > 0
What happens to entropy when ice melts at room temperature?
The entropy of the system increases as the solid state (ice) transitions to a liquid state (water).
What is the Boltzmann constant (kB)?
kB = 1.3806 × 10−23 J/K
What is the equation to quantify entropy?
S = kB lnW
What does Gibbs free energy (G) represent?
G = H − TS
What indicates that a reaction is favorable in the forward direction?
ΔG < 0
What does ΔG represent when it equals zero?
The reaction is at equilibrium.
What is the standard free energy change (ΔG°)?
The free energy change at 1 atm and 298 K when all reactants and products are at 1 M concentrations.
What is the relationship between standard free energy change and equilibrium constant?
ΔG°′ = −RT ln Keq
What does it mean if Keq > 1?
The reaction proceeds spontaneously to form products.
What is the mass action ratio (Q)?
Q is the ratio of actual concentrations of products over reactants.
How can an endergonic reaction still occur in living systems?
By coupling it to an exergonic reaction through a common intermediate.
What is the equation for actual free energy change (ΔG)?
ΔG = ΔG°′ + RT ln Q
What indicates that a reaction is spontaneous under cellular conditions?
ΔG < 0
What does the sign of ΔH indicate?
If ΔH is negative, the reaction is enthalpically favorable.
What happens to reaction spontaneity when product concentrations are lower than reactant concentrations?
The actual free energy change ΔG can be negative, making the reaction spontaneous.
What is the relationship between ΔG and reaction rate?
ΔG reveals directionality but not the rate of the reaction.
What is an endergonic reaction?
A reaction that requires energy input to proceed.
Endergonic reactions are unfavorable (ΔG°′ > 0).
How can an endergonic reaction occur in living systems?
It can be coupled to an exergonic reaction through a common intermediate.
The overall change in free energy must be favorable (exergonic).
What does ΔG°′ represent in coupled reactions?
The standard change in free energy for the reactions.
ΔG°′ value is equal to the sum of the ΔG°′ values for the two separate reactions.
What principle explains the shift in equilibrium when C is continually consumed?
Le Châtelier’s principle.
The equilibrium of reaction 1 shifts toward more product formation.
What is ATP and its role in living systems?
ATP is a carrier of chemical energy due to its two phosphoanhydride bonds.
Each bond contains approximately 30 kJ/mol of potential energy.
What is the ΔG°′ for the cleavage of the phosphoanhydride bond between the β and γ phosphates of ATP?
-30.5 kJ/mol.
The cleavage of the phosphoanhydride bond releases energy that can drive coupled reactions.
What is the phosphorylation potential (ΔGp) of ATP in actual cellular conditions?
Closer to ∼50 kJ/mol.
This value accounts for the concentrations of reactants and products in living cells.
What is the significance of the enzyme active site in ATP-coupled reactions?
It decreases the energy barrier for hydrolysis, allowing ATP to participate in reactions.
Enzyme active sites provide an ideal chemical environment for product formation.
What is an example of an ATP-coupled reaction?
The conversion of glutamate to glutamine by glutamine synthetase.
This reaction involves the transfer of a phosphoryl group from ATP to glutamate.
What are the two steps involved in the glutamine synthetase reaction?
- Transfer of the γ-phosphoryl group of ATP to glutamate.
- Replacement of the phosphoryl group by an amine group from NH4⁺ to form glutamine.
ADP is released in the first step, and Pi is released in the second step.
What cellular functions utilize ATP hydrolysis?
Muscle contraction and ion transport across cell membranes.
ATP hydrolysis induces conformational changes in proteins like myosin and Na⁺–K⁺ ATPase.
What are the three chemical properties of ATP that account for its large ΔG°′ upon hydrolysis?
- Electrostatic repulsion between charged groups.
- Greater resonance forms of released phosphate.
- Increased solvation of phosphate ion and ADP.
These factors favor the hydrolysis reaction.
What is the adenylate system?
A system that manages short-term energy needs by interconverting ATP, ADP, and AMP.
It prevents metabolic catastrophe by maintaining ATP levels.
What is the most common reaction for re-forming ATP?
ADP + Pi → ATP by ATP synthase.
This occurs during oxidative phosphorylation and photophosphorylation.
What is the role of adenylate kinase?
It converts AMP to ADP by transferring the γ-phosphoryl group from ATP.
This enzyme is crucial for maintaining ATP levels.
What does energy charge (EC) measure?
The ratio of ATP to ADP and AMP concentrations in the cell.
EC indicates the energy state of the cell, with normal values ranging from 0.7 to 0.9.
What is the calculated EC value in rat hepatocytes under steady-state conditions?
0.81.
Based on adenine nucleotide concentrations: [ATP] = 3.4 mM, [ADP] = 1.3 mM, [AMP] = 0.3 mM.
What is the role of catabolic pathways?
To extract energy from metabolic fuels and generate ATP.
Catabolic pathways convert high potential energy compounds into low potential energy compounds.
What happens when EC levels decrease due to sustained flux through anabolic pathways?
Enzymes responsible for ATP synthesis become activated, increasing flux through catabolic pathways.
This typically involves degrading stored metabolic fuel.
What do photosynthetic autotrophs use to produce ATP?
Sunlight.
Heterotrophs use nutrients from their diet for ATP synthesis.
What is homeostasis?
The use of energy to maintain a dynamic steady state of an organism that can adjust to changing environmental conditions.
Homeostasis is crucial for organisms to survive in varying environments.
What happens to enzymes when energy charge (EC) levels decrease?
Enzymes responsible for ATP synthesis become activated, and the flux through catabolic pathways increases.
This occurs as metabolic fuel stored in carbohydrates or lipids is degraded.
What are the two primary mechanisms of enzyme regulation in metabolic control?
- Bioavailability (compartmentation within the cell and altered rates of protein synthesis and degradation)
- Control of catalytic efficiency through protein modification (covalent modifications and noncovalent binding of regulatory molecules)
These mechanisms help maintain metabolic homeostasis.
How does solar energy sustain life on Earth?
Solar energy is converted to chemical energy by photosynthesis and carbon fixation, which is then transformed into useful work in living cells.
This process is essential for preventing cells from reaching equilibrium with the environment.
What does the first law of thermodynamics state?
Energy is neither created nor destroyed—it is only converted from one form to another.
This principle is fundamental to understanding energy transformations in biological systems.
What does the second law of thermodynamics imply about energy?
Entropy in the universe is always increasing, meaning that without energy input, ordered structures will fail.
This law explains the necessity of energy for sustaining life.
Define photosynthetic autotroph.
An organism that can use photosynthesis to oxidize water and produce oxygen, generating chemical energy in the form of glucose.
Examples include plants and some types of bacteria.
What is the difference between autotrophs and heterotrophs?
Autotrophs convert solar energy to chemical energy; heterotrophs depend on nutrients from autotrophs and other heterotrophs.
This distinction is crucial for understanding food webs in ecosystems.
What is carbon fixation?
The conversion of carbon dioxide into other organic compounds, particularly glucose.
This process is a key part of photosynthesis.
What are redox reactions?
An oxidation–reduction reaction in which electrons are transferred from a compound of lower reduction potential to one of higher reduction potential.
These reactions are essential for energy transfer in biological systems.
What is photooxidation?
Oxidation caused by light, particularly the oxidation of chlorophyll, resulting in electron transfer.
This process is critical for photosynthesis.
What is photophosphorylation?
The conversion of ADP to ATP coupled to the transfer of electrons in photosynthesis.
This process occurs during the light reactions of photosynthesis.
Define oxidative phosphorylation.
A metabolic pathway that oxidizes nutrients, particularly glucose, to generate ATP from ADP.
This process is a key component of cellular respiration.
What is Gibbs free energy (G)?
A measure of the spontaneity of a reaction, defined as G = H − TS, where H is enthalpy and TS is the product of temperature and entropy.
Understanding Gibbs free energy helps predict whether a reaction will occur spontaneously.
What is the equilibrium constant (Keq)?
A measure of the directionality of a reaction under standard conditions, where all products and reactants start at 1 M and proceed to their equilibrium concentrations.
The value of Keq indicates the extent to which reactants are converted to products.
What is energy charge (EC)?
A measure of the energy state of a cell in terms of ATP, ADP, and AMP ratios.
EC is crucial for understanding cellular energy metabolism.
What is enthalpy (H)?
The heat content of a system.
Enthalpy changes are important for understanding the energy changes in chemical reactions.
Define endothermic reaction.
A reaction that absorbs heat, characterized by ΔH > 0.
Endothermic reactions require an input of energy.
Define exothermic reaction.
A reaction that releases heat, characterized by ΔH < 0.
Exothermic reactions are often associated with combustion processes.
What is the adenylate system?
A group of several phosphoryl transfer reactions that interconvert ATP, ADP, and AMP.
This system is fundamental to cellular energy management.
Define catabolic pathway.
A metabolic pathway that converts energy-rich compounds into energy-depleted compounds, releasing energy for the cell.
Catabolic pathways are essential for breaking down nutrients to generate ATP.
What is an anabolic pathway?
A metabolic pathway for the biosynthesis of biomolecules from smaller precursors.
Anabolic pathways require energy input to synthesize complex molecules.
What is the standard free energy change (ΔG°)?
A reference point for comparing chemical reactions under defined conditions: ΔG° = ΔH° − TΔS°.
This measure is important for predicting reaction spontaneity under standard conditions.
Define biochemical standard free energy change (ΔG°′).
The amount of energy needed to go from biochemical standard conditions to equilibrium concentrations.
This measure is crucial for understanding biological reactions.
What is phosphorylation potential (ΔGp)?
The change in free energy of ATP hydrolysis inside a cell.
This value indicates how readily ATP can be hydrolyzed to release energy.
