NEED ANALYSIS OF STUDENT WORKSHEET (LKS) OF IONIC EQUILIBRIUM AND pH OF THE SALT SOLUTION BASED ON PROBLEM SOLVING

Problem solving skills are one of the skills needed by students in the era of the industrial revolution 4.0, so it becomes a challenge for a teacher to design creative learning. One of the media that supports students' problem solving skills is to use worksheets. Meanwhile, the worksheets used so far are general in nature. Suitable worksheets are developed that support students in solving problems, namely problem solving-based worksheets. This study aims to analyze the need for problem solving-based student worksheets. This type of research is a qualitative descriptive study. This needs analysis is part of the research and development of the 4D model, specifically the Define stage. The subjects in this study were students of class XII in SMA Negeri 3 Cirebon City and chemistry teachers as informants. The results showed that students needed worksheets that were more attractive and easy to understand. The worksheets available are in accordance with KD, KI and the 2013 curriculum, but not yet according to student needs. Based on data obtained from several analyzes including analysis of student perceptions, teacher perceptions, student characteristics, curriculum, assignments, concepts and analysis of learning objectives. So it is necessary to develop problem solving worksheets, especially in the matter of ionic equilibrium and pH of salt solutions which can train students to solve problems and relate theory to facts in everyday life.

Pengembangan LKPD Berbasis Model ARCS Pada Pokok Bahasan Kesetimbangan Ion dan pH Larutan Penyangga

This study aims to develop student worksheets based on the ARCS model on ionic equilibrium and pH of the buffer solution subject, determining the validity of student worksheets of the aspects of content, ARCS characteristics, language, presentation, graphics and find out user responses through student worksheets based on ARCS models on ionic equilibrium and pH buffer solution subject. This research is a Research and Development (R&D) with a 4-D development model. The object of this research is student worksheets based on the ARCS model. The data collection instruments were in the form of validation sheets given to three validators and user questionnaires given to teachers and students. After two revisions, the validity results obtained in the aspects of content, ARCS characteristics, language, presentation and graphics, respectively, namely 93.75%, 93.75%, 98.33%, 97.92% and 98%. the average score was 96.33% that comes to valid criteria. student worksheets which was valid by the validator tested one by one on 3 students who had studied the ion balance and pH of the buffer solution. Furthermore, asking for response to 3 chemistry teachers and 20 students resulted the teacher’s response and resultied a student response 91.07% and 79.73% that comes to very good criteria. Based on the results of the data analysis, it concluded that student worksheets based on the ARCS model was valid and can be used during high school chemistry lessons on the ion balance and pH of buffer solution subject.

Protolytic Equilibria in Organized Solutions: Ionization and Tautomerism of Fluorescein Dyes and Related Indicators in Cetyltrimethylammonium Chloride Micellar Solutions at High Ionic Strength of the Bulk Phase

Ionic equilibrium of 22 hydroxyxanthenes, including halogen and nitro derivatives of fluorescein, and their thio- and aza analogues, were studied spectrophotometrically in micellar solutions of cetyltrimethylammonium chloride at ionic strength of the bulk phase 4.0 M KCl. This micellar pseudophase is characterized by the electrostatic surface potential of +(15–16) mV and the ETN value of 0.623. In the case of dyes bearing the COOH group, colorless lactone is the predominant tautomer of the molecular form H2R. A new classification of fluoresceins is developed. The dyes were divided into four groups based on the nature of tautomerism of the anions. In the case of the fluorescein type, the monoanions HR− exist predominantly as “carboxylate” tautomers, with ionized carboxylic and non–ionized hydroxylic group. For the dyes of the eosin type, the situation is opposite, while for the intervening type of compounds, the concentrations of the two tautomers are comparable. Dyes capable of forming lactone anions HR− were classified as the fourth type. For some of them, even the dianion R2− exists as a lactone. The relationship between the stepwise ionization constants, Ka1/Ka2, varies from 1.3 to 1.07 × 105 and is determined by the state of tautomeric equilibrium of molecules and ions.

Diurnal variation of transitory starch metabolism is regulated by plastid proteins WXR1/WXR3 in Arabidopsis young seedlings

Transitory starch is the portion of starch that is synthesized during the day in the chloroplast and usually used for plant growth overnight. Here, we report altered metabolism of transitory starch in the wxr1/wxr3 (weak auxin response 1/3) mutants of Arabidopsis. WXR1/WXR3 were previously reported to regulate root growth of young seedlings and affect the auxin response mediated by auxin polar transport in Arabidopsis. In this study the wxr1/wxr3 mutants accumulated transitory starch in cotyledon, young leaf, and hypocotyl at the end of night. WXR1/WXR3 expression showed diurnal variation. Grafting experiments indicated that the WXRs in root were necessary for proper starch metabolism and plant growth. We also found that photosynthesis was inhibited and the transcription level of DIN1/DIN6 (Dark-Inducible 1/6) was reduced in wxr1/wxr3. The mutants also showed a defect in the ionic equilibrium of Na+ and K+, consistent with our bioinformatics data that genes related to ionic equilibrium were misregulated in wxr1. Loss of function of WXR1 also resulted in abnormal trafficking of membrane lipids and proteins. This study reveals that the plastid proteins WXR1/WXR3 play important roles in promoting transitory starch degradation for plant growth over night, possibly through regulating ionic equilibrium in the root.

Deeper and Deeper on the Role of BK and Kir4.1 Channels in Glioblastoma Invasiveness: A Novel Summative Mechanism?

In the last decades, increasing evidence has revealed that a large number of channel protein and ion pumps exhibit impaired expression in cancers. This dysregulation is responsible for high proliferative rates as well as migration and invasiveness, reflected in the recently coined term oncochannelopathies. In glioblastoma (GBM), the most invasive and aggressive primary brain tumor, GBM cells modify their ionic equilibrium in order to change their volume as a necessary step prior to migration. This mechanism involves increased expression of BK channels and downregulation of the normally widespread Kir4.1 channels, as noted in GBM biopsies from patients. Despite a large body of work implicating BK channels in migration in response to an artificial intracellular calcium rise, little is known about how this channel acts in GBM cells at resting membrane potential (RMP), as compared to other channels that are constitutively open, such as Kir4.1. In this review we propose that a residual fraction of functionally active Kir4.1 channels mediates a small, but continuous, efflux of potassium at the more depolarized RMP of GBM cells. In addition, coinciding with transient membrane deformation and the intracellular rise in calcium concentration, brief activity of BK channels can induce massive and rapid cytosolic water loss that reduces cell volume (cell shrinkage), a necessary step for migration within the brain parenchyma.

Coordinated homeostasis of essential mineral nutrients: a focus on iron

In plants, iron (Fe) transport and homeostasis are highly regulated processes. Fe deficiency or excess dramatically limits plant and algal productivity. Interestingly, complex and unexpected interconnections between Fe and various macro- and micronutrient homeostatic networks, supposedly maintaining general ionic equilibrium and balanced nutrition, are currently being uncovered. Although these interactions have profound consequences for our understanding of Fe homeostasis and its regulation, their molecular bases and biological significance remain poorly understood. Here, we review recent knowledge gained on how Fe interacts with micronutrient (e.g. zinc, manganese) and macronutrient (e.g. sulfur, phosphate) homeostasis, and on how these interactions affect Fe uptake and trafficking. Finally, we highlight the importance of developing an improved model of how Fe signaling pathways are integrated into functional networks to control plant growth and development in response to fluctuating environments.

Electrolytes in regimes of strong confinement: surface charge modulations, osmotic equilibrium and electroneutrality

In this work, we investigate the interplay between osmotic ionic equilibrium and induced interactions between planar surfaces with nanopatterned charged domains.

Química analítica básica

O ácido acético e a solução aquosa de amônia (também chamada erroneamente de hidróxido de amônio) são os exemplos mais comuns mencionados em classe quando se apresentam aos alunos os conceitos e cálculos envolvendo equilíbrios ácidos-bases em solução aquosa. Isto ocorre porque suas constantes de equilíbrio permitem aproximações que simplificam os cálculos, sem se incorrer em erros grosseiros. Mas estes exemplos são particularidades e não devem ser generalizados. Ainda mais! Como tratar os casos dos ácidos e bases polifuncionais (“polipróticos”)? O que acontece com a diluição da amostra? As respostas a estas e outras perguntas serão apresentadas neste artigo com o equacionamento matemático dos sistemas químicos, baseado nos trabalhos alguns autores que se dedicam a equacionar estes problemas de forma didática [1-7]. Mais especificamente, pretende-se destacar e detalhar os textos apresentado Butler [1] em seu excelente livro “Ionic Equilibrium: a mathematical approach”, usado como principal foco neste artigo.