Plant & Soil Sciences eLibrary^PRO

Lesson Outline

Lesson Media Objects

Jablonski Diagrams

(Take Passel Quiz)

The Interaction of Light with Biological Molecules

Rate Me

Equilibrium

Equilibrium is the natural ratio of the molecules involved in a chemical reaction. Consider this example

A + B C + D

Molecules A and B on the left of the arrows are called substrates, whereas molecules C and D on the right of the arrow are termed products. The natural equilibrium is useful for determining whether a reaction will proceed strongly to either the left (more substrates) or to the right (forming more products). We could use a specific example of a generalized biochemical reaction found in most organisms

Carbohydrate + O₂ CO₂ + H₂O

Equilibrium is often difficult to understand. Most students have no difficulty identifying the above equilibrium must lie to the right, because this is the respiration that provides us with energy from food. However, this is also the same equation that is the basis for photosynthesis; that reaction clearly involves movement of water and carbon dioxide to the left to make carbohydrate. It is important to realize that living systems are not at equilibrium. The biosphere provides life because it is a disequilibrium powered by sunlight. Individually, we only reach equilibrium after we die.

Biochemists view living biological systems as in a transient, semi-stable state consisting of many reactions at disequilibrium.

Maintaining a living complex biological system, a constant input of energy is required. This constant input of life-sustaining energy is sunlight.

Comments

Be the first to write a comment...

Add Comment

Control Panel

Community Blogs Community Media

My Joined Communities

more Register for another course

Class Blogs Class Media

This project was supported in part by the National Research Initiative Competitive Grants CAP project 2011-68002-30029 from the USDA National Institute of Food and Agriculture, adminstered by the University of California-Davis and by the National Science Foundation (NSF), Division of Undergraduate Education, National SMETE Digital Library Program, Award #0938034, administered by the University of Nebraska. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the USDA or NSF.