Thermodynamics

Question 1

what is the 2nd law of thermodynamics

Answer 1

all energy transformations lead to more disorder
as usable energy decreases, unusable energy increases Ie, entropy increases

Question 2

do cells defy 2nd law of thermodynamics

Answer 2

cells don’t live in isolation, the chemical reactions the generates the cells orders produces heat which is dispersed into the environment and therefore entropy increases

Question 3

what is Gibbs free energy

Answer 3

can be used to define spontaneity of a reaction

a spontaneous reaction can occur if a system
- gives up energy spontaneously
- becomes more random and increases energy

Question 4

describe the why the change in free energy is important

Answer 4

spontaneous energy changes will have a negative value.

this is because a spontaneous process must decrease enthalpy H and/or increase entropy S

therefore spontaneous reactions occur when change in GFE is -ve
biological processes require more order to generate proteins DNA organs ect and therefore require a GFE +ve

Question 5

describe the energy relationships and metabolic pathways in relation

Answer 5

free energy flows between catabolic and anabolic processes allowing them to occur, food -> makes building blocks for synthesis ->molecules that form cells
this is facilitated by catabolic and anabolic pathways where heat is lost and energy (ATP + NADP) facilitates the catabolic pathway

Question 6

describe the metabolic pathways ( more depth in enzyme lecture )

Answer 6

each step in metabolic pathways is catalysed by enzymes

in these pathways the spontaneous reactions move towards equilibrium but never reach it,

example - glucose

glucose has high potential energy and is used as food for organisms
it can be degraded into heat but a small series of reactions facilitated by enzymes allows this potential energy to be stored or used at different points

Question 7

describe ATP hydrolisis

Answer 7

ATP —> ADP which releases free energy which is used from catabolic processes to drive unfavourable reactions ( Giggs energy +ve )

catabolism is used to break complex molecules into simple molecules
anabolism does the reverse.
ATP allows anabolic ( thermodynamically unfavourable reactions to proceed )

change in Gibbs free energy for ADP to ATP is +30.5kJ/mol

Question 8

describe the PEP –> Pyruvate process

Answer 8

glucose releases its potential energy when degraded, an intermediate step though produces phosphoenolupyruvate ( PEP )

PEP acts in an intermediate for ATP production as PEP is converted to Pyruvate where ATP is released as result

the change in Gibbs energy is -31.3kJ therefore some energy is

• released as its converted into pyruvate
• saved as potential energy in an ATP molecule