Entropy and biological systems: experimentally-investigated entropy-driven stacking of plant photosynthetic membranes

According to the Second Law of thermodynamics, an overall increase of entropy contributes to the driving force for any physicochemical process, but entropy has seldom been investigated in biological systems. Here, for the first time, we apply Isothermal Titration Calorimetry (ITC) to investigate the Mg21-induced spontaneous stacking of photosynthetic membranes isolated from spinach leaves. After subtracting a large endothermic interaction of MgCl2 with membranes, unrelated to stacking, we demonstrate that the enthalpy change (heat change at constant pressure) is zero or marginally positive or negative. This first direct experimental evidence strongly suggests that an entropy increase significantly drives membrane stacking in this ordered biological structure. Possible mechanisms for the entropy increase include: (i) the attraction between discrete oppositely-charged areas, releasing counterions; (ii) the release of loosely-bound water molecules from the inter-membrane gap; (iii) the increased orientational freedom of previously-aligned water dipoles; and (iv) the lateral rearrangement of membrane components.This work was supported consecutively by Australian Research Council grants (DP0664719 and DP 1093927)

Pediatric Obesity in Primary Care

The purpose of this evidence-based quantitative quasi-experimental research was to compare if providing the parents with information on the health risk associated with childhood obesity would cause the parents to make healthier food choices and encourage their children to be involved in a full hour of physical activity a day. Participants included parents and pediatric and adolescent children 5 to 18 years of age at a solo practice primary care office in a large city in Southern, California, which specializes in treating pediatric and adolescent patients. A pre- and postquantitative intervention design were used and analyzed using the paired t test. The educational intervention on childhood obesity had a significant effect on the pre- and postintervention mean scores for the General Nutrition Knowledge Questionnaire. The preintervention mean score was 45.40, and the postintervention mean score was 51.20, which showed clinical significance with a (p = \u3c .001). The participants’ demographics, age, weight, height, ethnicity, body mass index (BMI), and BMI percentage were analyzed using descriptive statistics. The sample size included participants (N = 54), females (n = 28), and males (n = 26). Considerations for future research may include providing parents with more resources to obtain healthier food choices to prevent childhood obesity, such as a social worker for families who lack financial resources for healthy food choices, a dietician to assist families with meal planning, and community resources for daily physical activity