Introduction to Biochemical Kinetics and Thermodynamics

Question 1

state what it is meant by the key term - metabolism

Answer 1

metabolism is the net co-ordinated enzyme catalysed chemical reactions within an organism

Question 2

state 3 additional introductory facts about - ‘Energetics and Metabolism’

Answer 2

1. chemical reactions involve the breaking and making of bonds
2. energetics dictates the dates and equilibrium positions of reactions
3. therefore, energetics is a key to understanding metabolism

Question 3

state what it is meant by the key term - chemical energy

Answer 3

chemical energy is the energy ‘locked up’ in molecules as heat energy (translation, vibration and rotation) in chemical bonds (electron sharing)

Question 4

1. does forming chemical bonds use or release energy?

2. does breaking chemical bonds use or release energy?

Answer 4

1. forming chemical bonds releases energy

2. breaking chemical bonds uses energy

Question 5

state 3 facts about organisms and their system type

Answer 5

1. biological organisms are open systems
2. energy is exchanged between them and their surroundings as they consume energy-storing molecules and release energy to the environment by doing work
3. single cells are also biological systems

Question 6

state what it is meant by the key term - Entropy (S)

Answer 6

Entropy (S) is the measure of disorder within a system

Question 7

state 4 additional facts about Entropy (S)

Answer 7

1. systems are thought of having a certain amount of disorder
2. it takes energy to make a system more ordered
3. the more ordered a system is, the lower its Entropy (S)
4. as a system becomes more disordered, the lower its energy and the higher its Entropy (S) becomes

Question 8

state what it is meant by the key term - Enthalpy (H)

Answer 8

Enthalpy (H) is the measure of heat content within a system

Question 9

state 3 additional facts about Enthalpy (H)

Answer 9

1. the Enthalpy (H) of a reaction (ΔH) is the heat change during the reaction
2. energy can be added to a closed system by head (Q) and work (w)
3. adding heat or work increases the total Enthalpy (H) or energy of the system

Question 10

state a fact about measuring Enthalpy (H)

Answer 10

measuring Enthalpy (H) is inaccessible, but measuring ΔH is much more easy

Question 11

what is the difference between exothermic and endothermic reactions ?

Answer 11

exothermic - gives out heat, -ΔH (releases energy)

endothermic - takes in heat, +ΔH (takes in energy)

Question 12

state what it is meant by the key term - Hess’s Law

Answer 12

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)

Question 13

state 2 facts about ‘Equilibrium and Steady States’ with regard to open vs closed systems

Answer 13

1. closed system reactions eventually reach an equilibrium

2. open system reactions can reach a steady state of reaction

Question 14

state what it is meant by the - 2nd Law of Thermodynamics

Answer 14

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)

Question 15

explain, using 3 points, the 2nd Law of Thermodynamics

Answer 15

1. this means that entropy (or chaos) is always increasing
2. the universe tends towards chaos
3. the ultimate end product of metabolism is dispersed heat

Question 16

state what it is meant by the key term - Gibbs Free Energy (G)

Answer 16

G is a thermodynamic quantity equal to the Enthalpy (of a system or process) minus the product of the Entropy and the absolute Temperature

Question 17

ΔG = what ?

Answer 17

ΔG = Gproducts - Greactants

Question 18

what is the calculation for G ?

Answer 18

ΔG = ΔH - TΔS

where temp is measured in Kelvin

Question 19

state what it is meant by the key term - free energy

Answer 19

free energy is the energy released to the surroundings in a process

Question 20

what has the biggest influence on whether or not a reaction proceeds, and why ?

Answer 20

1. Entropy (S) has a very big influence on whether or not a reaction proceeds
2. ΔS is most significant as it is multiplied by the Temperature (in Kelvin)

Question 21

state 4 points to explain what happens when ΔG is negative

Answer 21

1. the reaction releases energy when it proceeds
2. it can occur spontaneously
3. exergonic (releases energy)
4. eg - the breakdown of molecules into smaller units (catabolism)

Question 22

state 4 points to explain what happens when ΔG is positive

Answer 22

1. the reaction requires free energy to proceed
2. if that energy is not provided, then the reaction does not occur
3. endergonic (takes in energy)
4. eg - synthesis of complex molecules from its basic constituents (anabolism)

Question 23

what is the ΔG for forming glucose ?

Answer 23

• 910 KJ/mol

Question 24

what is the ΔG for forming CO2 ?

Answer 24

• 337.1 KJ/mol

Question 25

what is the ΔG for forming H2O ?

Answer 25

• 394.4 KJ/mol

Question 26

what is the formula for Hess’s Law ?

Answer 26

1. ΔH’ = total (ΔHn)
2. ΔH’ is the heat absorbed or evolved
3. total (ΔHn) is the sum of the heat absorbed or evolved in the individual n steps in the reaction

Question 27

state what it is meant by the key term - energetics

Answer 27

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

Question 28

state what it is meant by the key term - Δg0’

Answer 28

Δg0’ is the free energy change of a reaction under standard biological conditions

Question 29

what are the 4 parameters for standard biological conditions ?

Answer 29

1. all products and reactants have an initial concentration of 1.0 M
2. pressure is at 1atm
3. temperature is at 25 degrees Celsius
4. pH is at 7

Question 30

what does it mean by equilibrium of a reaction ?

Answer 30

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

Question 31

what must you consider with products and reactants in an equation ?

Answer 31

always put the products on the top and the reactants on the bottom and multiply their concentrations together

( [P1] x [P2] / [R1] x [R2] )

Question 32

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 ?

Answer 32

1. 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

Question 33

explain how the 1st reaction of glycolysis has been manipulated to ensure the reaction goes in the desired direction

Answer 33

1. Glucose + Phosphate —-> G6P
2. under general biological conditions, ΔG is positive
3. but the coupled reaction…
4. Glucose = ATP —-> G6P + ADP
5. under general biological conditions, ΔG is negative

Question 34

what can released G be used for ?

Answer 34

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

Question 35

what is ATP ?

Answer 35

ATP is a NUCLEOSIDE - a nucleotide, sugar and a phosphate

Question 36

state 4 types of Nucleosides, and their functions

Answer 36

1. Cytidine - lipid biosynthesis
2. Uridine - carbohydrate biosynthesis
3. Adenosine - energy carrier
4. Guanosine - transmembrane signalling (G proteins), some energetics

Question 37

what is the total quantity of ATP in the human body ?

Answer 37

approx. 0.2 Moles

Question 38

1. what is the energy used by the human body every day ?

2. each ATP is recycled how many times per day ?

Answer 38

1. the energy of the human body requires the hydrolysis of 100-150 M of ATP daily (50 - 75 Kg)
2. each equivalent of ATP is recycled 500 - 750 times a single day

Question 39

state 4 cellular functions of ATP

Answer 39

1. ion pumping (membrane potential)
2. protein synthesis
3. cell replication
4. muscle contraction

Question 40

free energy varies between what 3 places ?

Answer 40

1. from one cell type to another
2. within the cell when conditions vary
3. from compartment to compartment within a cell

Question 41

what is the free energy of ATP hydrolysis equation ?

Answer 41

ATP^4- + H2O —-> ADP^3- +Pi^2- + H+

Question 42

why is ATP such a great energy currency ? (4 points)

Answer 42

1. large enough to drive many biological reactions important for biosynthesis pathways
2. small enough that ATP can be synthesised readily from available nutrients
3. relatively stable compound in aqueous solution (won’t spontaneously hydrolyse)
4. adenine and ribosyl groups of ATP allow binding to enzymes to regulate enzymatic energy

Question 43

what represents the energy status of the cell ?

Answer 43

ratios of ATP, ADP and AMP represent the energy status of the cell