Introduction to Biochemical Kinetics and Thermodynamics Flashcards
state what it is meant by the key term - metabolism
metabolism is the net co-ordinated enzyme catalysed chemical reactions within an organism
state 3 additional introductory facts about - ‘Energetics and Metabolism’
- chemical reactions involve the breaking and making of bonds
- energetics dictates the dates and equilibrium positions of reactions
- therefore, energetics is a key to understanding metabolism
state what it is meant by the key term - chemical energy
chemical energy is the energy ‘locked up’ in molecules as heat energy (translation, vibration and rotation) in chemical bonds (electron sharing)
- does forming chemical bonds use or release energy?
2. does breaking chemical bonds use or release energy?
- forming chemical bonds releases energy
2. breaking chemical bonds uses energy
state 3 facts about organisms and their system type
- biological organisms are open systems
- energy is exchanged between them and their surroundings as they consume energy-storing molecules and release energy to the environment by doing work
- single cells are also biological systems
state what it is meant by the key term - Entropy (S)
Entropy (S) is the measure of disorder within a system
state 4 additional facts about Entropy (S)
- systems are thought of having a certain amount of disorder
- it takes energy to make a system more ordered
- the more ordered a system is, the lower its Entropy (S)
- as a system becomes more disordered, the lower its energy and the higher its Entropy (S) becomes
state what it is meant by the key term - Enthalpy (H)
Enthalpy (H) is the measure of heat content within a system
state 3 additional facts about Enthalpy (H)
- the Enthalpy (H) of a reaction (ΔH) is the heat change during the reaction
- energy can be added to a closed system by head (Q) and work (w)
- adding heat or work increases the total Enthalpy (H) or energy of the system
state a fact about measuring Enthalpy (H)
measuring Enthalpy (H) is inaccessible, but measuring ΔH is much more easy
what is the difference between exothermic and endothermic reactions ?
exothermic - gives out heat, -ΔH (releases energy)
endothermic - takes in heat, +ΔH (takes in energy)
state what it is meant by the key term - Hess’s Law
Hess’s Law states that the total change in Enthalpy (ΔH) to go from the initial to the final state is independent of the path taken
ΔH(A) = ΔH(B) - ΔH(C)
state 2 facts about ‘Equilibrium and Steady States’ with regard to open vs closed systems
- closed system reactions eventually reach an equilibrium
2. open system reactions can reach a steady state of reaction
state what it is meant by the - 2nd Law of Thermodynamics
when energy is converted from one form to another, some of the energy becomes unavailable to do work
Δ(total energy) = Δ(usable energy) - Δ(unusable energy)
explain, using 3 points, the 2nd Law of Thermodynamics
- this means that entropy (or chaos) is always increasing
- the universe tends towards chaos
- the ultimate end product of metabolism is dispersed heat
state what it is meant by the key term - Gibbs Free Energy (G)
G is a thermodynamic quantity equal to the Enthalpy (of a system or process) minus the product of the Entropy and the absolute Temperature
ΔG = what ?
ΔG = Gproducts - Greactants
what is the calculation for G ?
ΔG = ΔH - TΔS
where temp is measured in Kelvin
state what it is meant by the key term - free energy
free energy is the energy released to the surroundings in a process
what has the biggest influence on whether or not a reaction proceeds, and why ?
- Entropy (S) has a very big influence on whether or not a reaction proceeds
- ΔS is most significant as it is multiplied by the Temperature (in Kelvin)
state 4 points to explain what happens when ΔG is negative
- the reaction releases energy when it proceeds
- it can occur spontaneously
- exergonic (releases energy)
- eg - the breakdown of molecules into smaller units (catabolism)
state 4 points to explain what happens when ΔG is positive
- the reaction requires free energy to proceed
- if that energy is not provided, then the reaction does not occur
- endergonic (takes in energy)
- eg - synthesis of complex molecules from its basic constituents (anabolism)
what is the ΔG for forming glucose ?
- 910 KJ/mol
what is the ΔG for forming CO2 ?
- 337.1 KJ/mol
what is the ΔG for forming H2O ?
- 394.4 KJ/mol
what is the formula for Hess’s Law ?
- ΔH’ = total (ΔHn)
- ΔH’ is the heat absorbed or evolved
- total (ΔHn) is the sum of the heat absorbed or evolved in the individual n steps in the reaction
state what it is meant by the key term - energetics
energetics is the branch of science which deals with the properties of energy and the way in which it is redistributed in physical, chemical or biological processes
state what it is meant by the key term - Δg0’
Δg0’ is the free energy change of a reaction under standard biological conditions
what are the 4 parameters for standard biological conditions ?
- all products and reactants have an initial concentration of 1.0 M
- pressure is at 1atm
- temperature is at 25 degrees Celsius
- pH is at 7
what does it mean by equilibrium of a reaction ?
equilibrium means that, for example, the rate at which A is converted to B occurs at the same rate that B is converted to A
what must you consider with products and reactants in an equation ?
always put the products on the top and the reactants on the bottom and multiply their concentrations together
( [P1] x [P2] / [R1] x [R2] )
ensuring the reaction proceeds as we want, knowing that reactions go in the direction which releases energy (-ΔG), what 2 ways can we ensure the reaction goes in the direction we want it to ?
- alter the concentrations so that the ΔG becomes negative
2. couple the reaction with a positive ΔG value to one that has a negative ΔG value, so that the overall ΔG is negative
explain how the 1st reaction of glycolysis has been manipulated to ensure the reaction goes in the desired direction
- Glucose + Phosphate —-> G6P
- under general biological conditions, ΔG is positive
- but the coupled reaction…
- Glucose = ATP —-> G6P + ADP
- under general biological conditions, ΔG is negative
what can released G be used for ?
the free energy (ΔG) released from an exergonic reaction (i.e. - one that has a driving force) can be used to drive a reaction that requires input of free energy
what is ATP ?
ATP is a NUCLEOSIDE - a nucleotide, sugar and a phosphate
state 4 types of Nucleosides, and their functions
- Cytidine - lipid biosynthesis
- Uridine - carbohydrate biosynthesis
- Adenosine - energy carrier
- Guanosine - transmembrane signalling (G proteins), some energetics
what is the total quantity of ATP in the human body ?
approx. 0.2 Moles
- what is the energy used by the human body every day ?
2. each ATP is recycled how many times per day ?
- the energy of the human body requires the hydrolysis of 100-150 M of ATP daily (50 - 75 Kg)
- each equivalent of ATP is recycled 500 - 750 times a single day
state 4 cellular functions of ATP
- ion pumping (membrane potential)
- protein synthesis
- cell replication
- muscle contraction
free energy varies between what 3 places ?
- from one cell type to another
- within the cell when conditions vary
- from compartment to compartment within a cell
what is the free energy of ATP hydrolysis equation ?
ATP^4- + H2O —-> ADP^3- +Pi^2- + H+
why is ATP such a great energy currency ? (4 points)
- large enough to drive many biological reactions important for biosynthesis pathways
- small enough that ATP can be synthesised readily from available nutrients
- relatively stable compound in aqueous solution (won’t spontaneously hydrolyse)
- adenine and ribosyl groups of ATP allow binding to enzymes to regulate enzymatic energy
what represents the energy status of the cell ?
ratios of ATP, ADP and AMP represent the energy status of the cell
