Energetics of metabolism

Metabolism

Metabolism = all the chemical reactions that occur in the body.

photosynthetic

autotrophs

organic products

O2

heterotrophs

CO2, H2O

Sun sugar everything

degradation

synthesis

The complexity of metabolism

Energy has to abide by the laws of thermodynamics

First law of thermodynamics: energy may change form or be transported but

can not be created or destroyed. This is also know as the principle of

conservation of energy.

Second law of thermodynamics: in all natural processes, the entropy of

universe increases.

Transfer or transformation of energy in a cell releases heat.

Increase in entropy

What is ordered and what is disordered?

Increase

stability

Greater

entropy

All these pathways are go to one direction to increase disorder of universe.

Free energy (∆G)

Free energy: energy, that is released in a system.

∆G = ∆H - T ∆S

∆G= Gibb’s free energy

∆H= change in enthalphy, heat content of the reaction

∆S= change in entropy

T= absolute temperature, in Kelvin

∆G<0 (exergonic) reaction proceeds forward, energy is released or transformed

∆G>0 (endergonic) energy is needed for reaction to occur

It can tell us something

how a reaction proceeds

Free energy (∆G)

Decrease in Gibbs free energy (-G)

Increase in stability

Downhill (toward center of gravity

well, e.g., of Earth)

Movement towards equilibrium

Coupled to ATP production (ADP

phosphorylation)

Catabolism

Exergonic Reaction (Spontaneous)

Endergonic reaction (Non-Spontaneous)

Increase in Gibbs free energy (+G)

Decrease in stability

Not Spontaneous

Uphill Movement away from equilibrium

Coupled to ATP utilization

Anabolism

Energy changes in exergonic and energonic reactions.

(b) An opened hydrolectric system

Metabolism and equilibrium

No work can be performed!

water intake

outflow

Single-step system

Energy can be generated and utilized in the body.

Metabolism and equilibrium

Cellular respiration: glucose is broken down in a series of reactions that

power the work of cell.

The product of each reaction becomes the reactant for the next, no recation reaches equilibrium.

Cellular respiration

Cells convert biochemical energy from nutrients into adenosine

triphosphate (ATP), and then release waste products (CO2 and water).

Steps of cellular respiration:

1. Glycolysis

2. Citric acid cycle

3. Oxidative phosphorylation

Cellular respiration

Cellular work

Coupling of exergonic and endergonic reactions

Energy reuired for:

chemical work

transport work

mechanikal work

Exergonic and endergonic reactions can be coupled to overcome endergonic

reactions.

e.g.

Structure and hydrolysis of ATP

ATP hydrolysis coupled reactions

Endergonic

reaction

Exergonic

reaction

Exergonic

reaction Endergonic

reaction

Exergonic processes drive endergonic processes.

Summery of metabolic coupling

Thank you for your attention!