Energetics Flashcards
What is the first law of thermodynamics
-Energy cannot be created or destroyed, only transformed
What is Enthalpy?
Total heat absorbed by a system assuming constant pressure (only in bio). Change in enthalpy is delta H
What is the enthalpy of a exothermic reaction and why?
Negative, because it releases heat.
What is the enthalpy of an endothermic reaction and why?
Positive, because it absorbs heat
What kinds of ‘work’ are carried out in biological systems?
- Mechanical; by muscles
- Electrical; by nerves
- Chemical; in molecule synthesis
What is the second law of thermodynamics?
-When energy is converted from one form to another, some of it becomes unavailable to do work
What is a formula using enthalpy and entropy used to describe the second law of thermodynamics?
- Enthalpy (delta h) = Free Energy (delta G) + Entropy (Delta S) * Temp
What is entropy?
The measure of unavailable energy in a system
What is free energy?
the energy available to do work at a constant temperature
What formula can be used to derive free energy?
- Delta G = Delta H - Delta S * T
What must be true of delta G for reactions to occur spontaneously?
Delta G must be negative (releases free energy)
What must be true of delta G if a reaction cannot occur spontaneously?
Delta G must be positive
What is an Exergonic reaction?
One which releases energy/has a negative delta G
Are catabolic reactions typicall exergonic or endergonic?
Exergonic
What is an Endergonic reaction?
One which has a positive Delta G, i.e. the total free energy of the products is higher than that of the reactants, so external energy is required
Delta G varies with conditions. Temperature and Pressure are relatively stable in biological systems. What other factor can influence it?
Concentration of the components of a reaction
What is a general formula to describe how delta G varies with concentration of A and B?
Delta G = Delta G0 + RT ln ([C]c * [D]d)/[A]a * [B]b
What are the two strategies to make a reaction proceed in the direction required by an organism?
- Make delta G negative by altering concentrations
- Couple a negative delta G reaction with a positive delta G reaction, so that the overall delta G is negative
What are the functions of all the NTPS?
- CTP; lipid biosynthesis
- UTP; Carb biosyntheis
- ATP; energy carrier
- GTP; transmembrane signalling
What is the free energy of hydrolysis of ATP?
Delta G Naught Prime = -30.5 kJ/mol
What does delta G nought prime mean?
Components and products are 1M, but pH is 7.
What makes ATP effective as a universal energy source for biological reactions?
- High enough delta G to drive many important metabolic processes, but small enough that it can be synthesised from available nutrients
- Has a negative delta G but does not spontaneously hydrolyse.
- Phosphorylation of ADP drives catabolism. Hydrolysis of ATP drives Anabolism, mechanical work, and active transport
- Adenine and Ribosyl make it able to bind to/regulate enzymes
