life at the cellular level (4) - energy (thermodynamics) Flashcards
Give examples of types of energy
Heat
Light
Mechanical
Electrical
What is the first law of thermodynamics
Energy can be converted from one form to another but the total energy of the universe remains constant
What is the second law of thermodynamics
All energy transformations ultimately lead to more disorder in the universe, i.e. increase the entropy
What is entropy
The degree of disorder As usable energy decreases unusable energy increases, entropy increases Entropy is also a gauge of randomness or chaos within a closed system. As usable energy is irretrievably lost, disorganization, randomness and chaos increase.
How do cells maintain order
By performing lots of chemical reactions which require energy
What do cells use energy for
To grow and form complex molecules and systems
Do cells live in isolation
No, they are open systems, taking energy from the sun and food molecules to generate the order required for life
How do cells apply the 2nd law of thermodynamics
The chemical reactions that generate the cell’s order produce heat, which is discharged into the surrounding environment and disorders it, so the total entropy increases
What is Gibbs free energy
“useful”, or Free energy in a closed system can be defined by 3 quantities:
– Enthalpy, H – heat released to surroundings (reflects number/kind of bonds formed/broken)
– Entropy, S – randomness/disorder – Absolute temperature, T
G = H - TS
What can free energy change be used to define
The spontaneity of a reaction
When can spontaneous reactions occur
If a system:
– Gives up energy (water runs downhill spontaneously, giving up potential energy as it goes)
And/or
– Becomes more random and increases in entropy (complex structures decay spontaneously giving up potential energy)
What must a spontaneous process do to enthalpy and entropy
Decrease enthalpy (H) and/or increase entropy (S)
spontaneous reactions only occur if ΔG is
negative
what is the free energy change equation
ΔG = ΔH - TΔS
what does it mean if ΔG is -ve
the reaction releases energy
how much order do biological processes require
more rather than less, so reactions to generate proteins, DNA, cells, organs, etc, etc require reactions that have +ve ΔG
why do cells use a process called “energy coupling”
to carry out thermodynamically unfavourable reactions
what does ΔG = 0 mean
it is incompatible with life
do reactions reach equilibreium
no, as energy passes from the environment to the organism and back to the environment
This works because organisms use pathways of reactions: e.g. food molecules to excretory products
spontaneous reactions move towards equilibrium but do not reach equilibrium
what does life do to maintain a steady state
utilises series of reactions
what does free energy flow between
catabolic processes and anabolic processes allowing them to occur
what is each step in metabolic pathways catalysed by
enzymes
what do enzymes do
function to selectively alter the rate of particular parts of metabolic pathways
what are intermediate metabolites
tend to be compartments of several pathways
there aren’t many of them compared to the number of reactions that exist in the cells of our bodies
