Energy Changes Chemistry of Life

Energy-capacity to do work 1st law of Thermodynamics-energy can neither be created nor destroyed but can change from one form to another and be transferred Example: Plants convert light energy from the sun to make glucose, a form of chemical energy 2nd law of Thermodynamics-every energy transfer increases entropy of the universe (disorder). All living systems will not violate the 2nd law of Thermodynamics

Free Energy-energy available in a system to do work; organisms need this free energy in order to maintain organization, to grow, and to reproduce Exergonic reactions-release free energy AB A + B + Energy Catabolic reactions-reactant(s) are broken down to produce product(s) containing less energy. The energy released can be used for reactions that require energy Endergonic reactions-require free energy A + B + Energy AB In anabolic reactions, reactant(s) are joined together to produce product(s) containing more energy. Free energy required by anabolic reactions is often provided by ATP produced in catabolic reactions

Adenosine triphosphate (ATP)-carries energy in its high energy phosphate bond. ATP is formed from adenosine diphosphate (ADP) and inorganic phosphate. ADP + P(i) + Energy ATP Conversely, when ATP is broken down into ADP and P(i) via hydrolysis, energy is released (exergonic) that can be used in endergonic reations In addition, ATP can donate one of its phosphate groups to a molecule, such as a substrate or a protein, to energize it or cause it to change its shape

Living systems require a consistent input of free energy and an ordered system This free energy input allows for a system’s order to be maintained If either order in the system of free energy flow were to occur, death could result. Biological processes are in place to help offset increased disorder and entropy and to help maintain order within a system; therefore, energy input into the system must exceed the loss of free energy in order to maintain order and to power cellular processes.

Living systems require a consistent input of free energy and an ordered system Energy storage and growth can result from excess acquired free energy beyond the required energy necessary for maintenance and order within a system Changes in free energy can affect population size and cause disruptions to an ecosystem

Metabolism-The totality of all chemical reactions that occur within an organism Reproduction and rearing of offspring require free energy beyond what is normally required for the maintenance and growth of the organism. Energy availability can vary and different organisms utilize a variety of reproductive strategies as a consequence. Some examples include seasonal reproduction by animals and plants and life history strategies (biennial plants, reproductive diapause)

Metabolism-The totality of all chemical reactions that occur within an organism Organisms utilize free energy in order to help regulate body temperature and metabolism. Mechanisms through which these are done include: Endothermy-use of internal thermal energy that is generated by metabolism to maintain an organism’s body temperature. Ectothermy-Use of external thermal energy to assist in the regulation of an organism’s body temperature. Some plant species utilize elevated floral temperatures.

Metabolism There is an important relationship between the metabolic rate/unit body mass and the size of multicellular organisms. In other words, smaller organisms generally have higher metabolic rates.

Energy Coupling Coupled reactions-a chemical reaction having a common intermediate in which energy is transferred from one reaction to another. A system can maintain order by utilizing coupling cellular processes that increase entropy (causing negative changes in free energy) with those that decrease entropy (causing positive changes in free energy). The molecule that is essential for coupling reactions and cellular work is ATP.

Energy Coupling Exergonic reactions, like ATP ADP, is an example of an energetically favorable reaction because it allows for a negative change in free energy that will then be used in order to maintain or to increase order within a system that is coupled by reactions that demonstrate changes in positive free energy The process of cellular respiration and photosynthesis are coupled to each other. The products of one reaction end up being the reactants in the other.

Energy Coupling Electron transport and oxidative phosphorylation are examples of coupled reactions

Modes of Energy Capture Organisms can capture and store free energy from nutritional use in their biological systmes. Autotrophs-”self-feeders”, create their own organic molecules or food; they are known as producers Heterotrophs-cannot create their own organic molecules or food; they are known as consumers. Hydrolysis-help them metabolize carbohydrates, proteins, and lipids as sources of free energy.

The following chart shows modes of nutrition Mode of Nutrition Description; Examples (other Nonprokaryote examples) Photoautotrophy Use light as an energy source and gain carbon from CO2; cyanobacteria (also plants and some protists) Chemoautotrophy Use an inorganic energy source and gain carbon from CO2; some archaebacteria Photoheterotrophy Use light as an energy source and gain carbon from organic sources; some prokaryotes Chemoheterotrophy Use an organic energy source and gain carbon from organic sources; most prokaryotes (also animals, fungi, and some protists)

Modes of Energy Capture Biological systems can capture energy at multiple points in their energy related pathways. Some examples of these pathways include the Kreb cycle, glycolysis, the Calvin cycle, and fermentation. Energy capturing processes, such as NADP+ in photosynthesis and oxygen in cellular respiration use different types of electron acceptors