Kamis, 19 November 2015
Energy in living organisme cell
Cells Transform Different Types of Energy
Living organisms require a continual input of free energy for three major purposes: (1) the performance of mechanical work in muscle contraction and other cellular movements, (2) the active transport of molecules and ions, and (3) the synthesis of macromolecules and other biomolecules from simple precursors. The free energy used in these processes, which maintain an organism in a state that is far from equilibrium, is derived from the environment.
The First Law of Thermodynamics states that energy can be neither created nor destroyed. The amount of energy in the universe is constant. Nevertheless, energy can be converted from one form into another. Photosynthetic organisms, or phototrophs, use the energy of sunlight to convert simple energy-poor molecules into morecomplex energy-rich molecules that serve as fuels. In other words, photosynthetic organisms transform light energy into chemical energy. Indeed, this transformation is ultimately the primary source of chemical energy for the vast majority of organisms, human beings included. Chemotrophs, which include animals, obtain chemical energy through the oxidation
of foodstuffs generated by phototrophs. Chemical energy obtained from the oxidation of carbon compounds may be transformed into the unequal distribution of ions across a membrane, resulting in an ion gradient. This gradient, in turn, is an energy source that can be used to move molecules across membranes, that can be converted into yet other types of chemical energy, or that can convey
information in the form of nerve impulses. In addition, chemical energy can be transduced into mechanical energy. We convert the chemical energy of a fuel into structural alterations of contractile proteins that result in muscle contraction and movement. Finally, chemical energy powers the reactions that result in the synthesis of biomolecules.At any given instant in a cell, thousands of energy transformations are taking place. Energy is being extracted from fuels and used to power biosynthetic processes. These transformations are referred to as metabolismor intermediary
metabolism. (P:569)
ATP Is the Universal Currency of Free Energy in Biological Systems
Just as commerce is facilitated by the use of a common currency, the commerce of the cell metabolism is facilitated by the use of a common energy currency, adenosine triphosphate(ATP). Part of the free energy derived from the oxidation of foodstuffs and from light is transformed into this highly accessible molecule, which acts as the free-energy donor in most energy-requiring processes such as motion, active transport, or biosynthesis. ATP is a nucleotide consisting of an adenine, a ribose, and a triphosphate unit (Figure 14.3). The active form of ATP is usually a complex of ATP with Mg2+ or Mn2+. In considering the role of ATP as an energy carrier, we can focus on its triphosphate moiety. ATP is an energy-rich molecule because its triphosphate unit contains two
phosphoanhydride bonds. A large amount of free energy is liberated when ATP is hydrolyzed to adenosine diphosphate (ADP) and orthophosphate (Pi) or when ATP is hydrolyzed to adenosine monophosphate (AMP) and pyrophosphate (PPi).
The precise ∆G°for these reactions depends on the ionic strength of the medium and on the concentrations of Mg2+ and other metal ions. Under typical cellular concentrations, the actual ∆G for these hydrolyses is approximately -12 kcal mol-1 (-50 kJ mol-1).
The free energy liberated in the hydrolysis of ATP is harnessed to drive reactions that require an input of free energy, such as muscle contraction. In turn, ATP is formed from ADP and Pi when fuel molecules are oxidized in chemotrophs or when light is trapped by phototrophs. This ATP ADP cycle is the fundamental mode of energy exchange in biological systems. Some biosynthetic reactions are driven by hydrolysis of nucleoside triphosphates that are analogous to ATP namely, guanosine triphosphate (GTP), uridine triphosphate (UTP), and cytidine triphosphate (CTP). The diphosphate forms of these nucleotides are denoted by GDP, UDP, and CDP, and the monophosphate forms by GMP, UMP, and CMP.
Enzymes can catalyze the transfer of the terminal phosphoryl group from one nucleotide to another. The phosphorylation of nucleoside monophosphates is catalyzed by a family of nucleoside monophosphate kinases. The phosphorylation of nucleoside diphosphates is catalyzed by nucleoside diphosphate kinase, an enzyme with broad specificity. It is intriguing to note that, although all of the nucleotide triphosphates are energetically equivalent, ATP is nonetheless the primary cellular energy carrier. In addition, two important electron carriers, NAD+ and FAD, are derivatives of ATP. The role of ATP in energy metabolism is paramount. (P:572)
Berg, Tymoczko, Stryer.
Biochemistry, fifth edition
© W. H. Freeman and Company and Sumanas, Inc.
from: center library of Syarif Hidayatullah State Islamic University, Jakarta
Living organisms require a continual input of free energy for three major purposes: (1) the performance of mechanical work in muscle contraction and other cellular movements, (2) the active transport of molecules and ions, and (3) the synthesis of macromolecules and other biomolecules from simple precursors. The free energy used in these processes, which maintain an organism in a state that is far from equilibrium, is derived from the environment.
The First Law of Thermodynamics states that energy can be neither created nor destroyed. The amount of energy in the universe is constant. Nevertheless, energy can be converted from one form into another. Photosynthetic organisms, or phototrophs, use the energy of sunlight to convert simple energy-poor molecules into morecomplex energy-rich molecules that serve as fuels. In other words, photosynthetic organisms transform light energy into chemical energy. Indeed, this transformation is ultimately the primary source of chemical energy for the vast majority of organisms, human beings included. Chemotrophs, which include animals, obtain chemical energy through the oxidation
of foodstuffs generated by phototrophs. Chemical energy obtained from the oxidation of carbon compounds may be transformed into the unequal distribution of ions across a membrane, resulting in an ion gradient. This gradient, in turn, is an energy source that can be used to move molecules across membranes, that can be converted into yet other types of chemical energy, or that can convey
information in the form of nerve impulses. In addition, chemical energy can be transduced into mechanical energy. We convert the chemical energy of a fuel into structural alterations of contractile proteins that result in muscle contraction and movement. Finally, chemical energy powers the reactions that result in the synthesis of biomolecules.At any given instant in a cell, thousands of energy transformations are taking place. Energy is being extracted from fuels and used to power biosynthetic processes. These transformations are referred to as metabolismor intermediary
metabolism. (P:569)
ATP Is the Universal Currency of Free Energy in Biological Systems
Just as commerce is facilitated by the use of a common currency, the commerce of the cell metabolism is facilitated by the use of a common energy currency, adenosine triphosphate(ATP). Part of the free energy derived from the oxidation of foodstuffs and from light is transformed into this highly accessible molecule, which acts as the free-energy donor in most energy-requiring processes such as motion, active transport, or biosynthesis. ATP is a nucleotide consisting of an adenine, a ribose, and a triphosphate unit (Figure 14.3). The active form of ATP is usually a complex of ATP with Mg2+ or Mn2+. In considering the role of ATP as an energy carrier, we can focus on its triphosphate moiety. ATP is an energy-rich molecule because its triphosphate unit contains two
phosphoanhydride bonds. A large amount of free energy is liberated when ATP is hydrolyzed to adenosine diphosphate (ADP) and orthophosphate (Pi) or when ATP is hydrolyzed to adenosine monophosphate (AMP) and pyrophosphate (PPi).
The free energy liberated in the hydrolysis of ATP is harnessed to drive reactions that require an input of free energy, such as muscle contraction. In turn, ATP is formed from ADP and Pi when fuel molecules are oxidized in chemotrophs or when light is trapped by phototrophs. This ATP ADP cycle is the fundamental mode of energy exchange in biological systems. Some biosynthetic reactions are driven by hydrolysis of nucleoside triphosphates that are analogous to ATP namely, guanosine triphosphate (GTP), uridine triphosphate (UTP), and cytidine triphosphate (CTP). The diphosphate forms of these nucleotides are denoted by GDP, UDP, and CDP, and the monophosphate forms by GMP, UMP, and CMP.
Enzymes can catalyze the transfer of the terminal phosphoryl group from one nucleotide to another. The phosphorylation of nucleoside monophosphates is catalyzed by a family of nucleoside monophosphate kinases. The phosphorylation of nucleoside diphosphates is catalyzed by nucleoside diphosphate kinase, an enzyme with broad specificity. It is intriguing to note that, although all of the nucleotide triphosphates are energetically equivalent, ATP is nonetheless the primary cellular energy carrier. In addition, two important electron carriers, NAD+ and FAD, are derivatives of ATP. The role of ATP in energy metabolism is paramount. (P:572)
Berg, Tymoczko, Stryer.
Biochemistry, fifth edition
© W. H. Freeman and Company and Sumanas, Inc.
from: center library of Syarif Hidayatullah State Islamic University, Jakarta
Selasa, 23 Desember 2014
Assessment of
laboratory/practical work
Description
The use
of a laboratory situation to assess aspects of a student’s work that may not appropriately
be assessed by regular paper-based tests. A wide variety of testing objectives
are possible and Brown, Bull and Pendlebury (1997) offer a long list of potential
objectives which may need to be included in assessment. As a result of deciding
what exactly it is that needs to be assessed, the teacher must decide whether
any simple paper-and-pencil test method is adequate, or whether the laboratory
needs to be the venue for assessment. Typically, students are required to
perform some experimental procedure, note the results and evaluate their
findings
Variations
Many,
including ‘dry practicals’, where the results of a laboratory experiment are presented
and students are required simply to analyse them and to evaluate and comment on
them. Group work is increasingly a feature of many undergraduate programmes,
reflecting the importance of collaboration skills as a course aim. But the
assessment of group work brings a variety of problems (Wood, 1991).
Marking
systems
These
vary, depending upon the approach. Main problems surround how to balance
assessment of process versus outcome/analysis/evaluation and standardizing this.
The classic science paradigm (methods, results, conclusion) may assist in
producing assessment criteria. Work in the assessment of medical students using
objective, standardized approaches may also be helpful (Harden and Gleeson,
1979).
Advantages
This
method allows assessment of a uniquely important aspect of many subjects,the ‘real
world’ of scientific enquiry.
Drawbacks
There
are practical difficulties towards making assessment equitable for all students:
what happens if a student’s experiment ‘goes wrong’. The cost of this method of
testing may be high. It is also difficult to determine assessment priorities (eg,
process versus outcome) and rewards.
Orals
Oral or viva
voce examinations, though commonly used in
professional and postgraduate assessment, are the subject of great concern to
test developers and psychometricians – especially when loosely described
criteria such as ‘sparkle’ are mentioned. Orals have their attractions, but are
subject to all the well-known biases and problems of selection interviews, and
should only be used in the full knowledge of these problems and how these
effects may be minimized. The new practitioner in higher education is
counselled to beware of and avoid orals, certainly until he or she has read
some of the literature (eg, Wakeford, Southgate and Wass, 1995).
www.kogan-page.co.uk
© Individual contributors, 2003
Contextualised Media for Learning
Tim de Jong, Marcus Specht and Rob Koper Educational Technology Expertise Centre, Open University of the Netherlands, The Netherlands // tim.dejong@ou.nl // marcus.specht@ou.nl // rob.koper@ou.nl
ABSTRACT
In this paper, we analyse how contextualised media can be used to support learning. Additionally, the
advantages of contextualised learning and the types of learning that are fit to be supported are discussed. Our
focus throughout the paper will be on lifelong learning, and the integration of formal and informal learning
therein. However, we think, to this date, most of the research concerning contextualised and mobile learning has been focusing on technological issues. Therefore, as an attempt to shift the discussion to a more educational perspective, a generic technical framework is presented. The technical framework is based on a reference model that came about as the result of a literature analysis in a previous paper. The reference model should provide a foundation that leads to a flexible and generic technical framework that can be used in a range of different learning scenarios. Moreover, a generic technical approach should aim at an easier integration of contextualised learning appliances into current learning.
Keywords
Contextualised learning, Mobile learning, Mobile social software, Technical framework, Ubiquitous computing
read more...
Tim de Jong, Marcus Specht and Rob Koper Educational Technology Expertise Centre, Open University of the Netherlands, The Netherlands // tim.dejong@ou.nl // marcus.specht@ou.nl // rob.koper@ou.nl
ABSTRACT
In this paper, we analyse how contextualised media can be used to support learning. Additionally, the
advantages of contextualised learning and the types of learning that are fit to be supported are discussed. Our
focus throughout the paper will be on lifelong learning, and the integration of formal and informal learning
therein. However, we think, to this date, most of the research concerning contextualised and mobile learning has been focusing on technological issues. Therefore, as an attempt to shift the discussion to a more educational perspective, a generic technical framework is presented. The technical framework is based on a reference model that came about as the result of a literature analysis in a previous paper. The reference model should provide a foundation that leads to a flexible and generic technical framework that can be used in a range of different learning scenarios. Moreover, a generic technical approach should aim at an easier integration of contextualised learning appliances into current learning.
Keywords
Contextualised learning, Mobile learning, Mobile social software, Technical framework, Ubiquitous computing
read more...
ANALISIS KETERAMPILAN PROSES SAINS SISWA SMA PADA
“MODEL PEMBELAJARAN PRAKTIKUM D-E-H”
Oleh:
Susiwi1, Achmad A.Hinduan2, Liliasari2, Sadijah Ahmad3
1Jurusan Pendidikan Kimia FPMIPA UPI
2Sekolah Pascasarjana UPI
3FMIPA ITB
ABSTRAK
Tujuan penelitian ini adalah untuk memperoleh informasi tentang keterampilan proses sains siswa SMA pada Model Pembelajaran Praktikum Diskriptif - Empiris Induktif - Hipotetis Deduktif (MPP D–E–H). Keterampilan berpikir yang tergolong keterampilan proses sains dan merupakan komponen penting dalam suatu penyelidikan meliputi: keterampilan ”merumuskan hipotesis”, keterampilan ”mengendalikan variabel”, dan keterampilan ”merancang percobaan”. Penelitian ini dilakukan dengan studi deskriptif teoretik, dan dilanjutkan dengan studi eksperimental pada implementasi pembelajaran. Penelitian dilaksanakan dengan
melibatkan kelompok SMA-prestasi akademik tinggi, dan SMA-prestasi akademik sedang. Masing-masing kelompok SMA-Sedang maupun kelompok SMA-Tinggi dibagi menjadi kelas eksperimen dan kelas kontrol. Subyek penelitian seluruhnya berjumlah 216 siswa. Dalam penelitian ini digunakan subyek penelitian dari kelas eksperimen sebanyak 130 siswa, yang terdiri dari 43 siswa kelompok SMA-Sedang dan 87 siswa dari kelompok SMA-Tinggi. Adapun kelas kontrol sebanyak 86 siswa yang terdiri dari 43 siswa kelompok SMA-Sedang dan 43 siswa dari kelompok SMA-Tinggi. Untuk mengukur keterampilan proses sains tersebut diatas digunakan Lembar Kerja Siswa (LKS) yang berisi kemampuan-kemampuan yang
dikembangkan dalam praktikum, dan disusun dalam bentuk pertanyaan yang terdiri dari 9 kelompok pertanyaan dengan 15 percobaan. Hasil penelitian menunjukkan bahwa melalui pembelajaran MPP D–E–H: kemampuan “merumuskan hipotesis”, kemampuan “mengendalikan variabel” dan kemampuan “merancang percobaan” dapat dicapai secara tuntas baik pada kelompok SMA dengan prestasi akademik sedang maupun kelompok SMA dengan prestasi akademik tinggi. Untuk itu perlu diadakan diskusi dengan asisten untuk menindak lanjuti hasil rancangan yang dibuat siswa, terutama untuk mengevaluasi perencanaan alat dan bahan, serta cara kerja sehingga percobaan tersebut aman dan efisien untuk dilaksanakan.
Kata Kunci : MPP D-E-H (Model Pembelajaran Praktikum Diskriptif-Empiris Induktif-Hipotetis Deduktif), Keterampilan merumuskan hipotesis,Keterampilan mengendalikan variabel, Keterampilan merancang
percobaan.
SELENGKAPNYA, KLIK...
“MODEL PEMBELAJARAN PRAKTIKUM D-E-H”
Oleh:
Susiwi1, Achmad A.Hinduan2, Liliasari2, Sadijah Ahmad3
1Jurusan Pendidikan Kimia FPMIPA UPI
2Sekolah Pascasarjana UPI
3FMIPA ITB
ABSTRAK
Tujuan penelitian ini adalah untuk memperoleh informasi tentang keterampilan proses sains siswa SMA pada Model Pembelajaran Praktikum Diskriptif - Empiris Induktif - Hipotetis Deduktif (MPP D–E–H). Keterampilan berpikir yang tergolong keterampilan proses sains dan merupakan komponen penting dalam suatu penyelidikan meliputi: keterampilan ”merumuskan hipotesis”, keterampilan ”mengendalikan variabel”, dan keterampilan ”merancang percobaan”. Penelitian ini dilakukan dengan studi deskriptif teoretik, dan dilanjutkan dengan studi eksperimental pada implementasi pembelajaran. Penelitian dilaksanakan dengan
melibatkan kelompok SMA-prestasi akademik tinggi, dan SMA-prestasi akademik sedang. Masing-masing kelompok SMA-Sedang maupun kelompok SMA-Tinggi dibagi menjadi kelas eksperimen dan kelas kontrol. Subyek penelitian seluruhnya berjumlah 216 siswa. Dalam penelitian ini digunakan subyek penelitian dari kelas eksperimen sebanyak 130 siswa, yang terdiri dari 43 siswa kelompok SMA-Sedang dan 87 siswa dari kelompok SMA-Tinggi. Adapun kelas kontrol sebanyak 86 siswa yang terdiri dari 43 siswa kelompok SMA-Sedang dan 43 siswa dari kelompok SMA-Tinggi. Untuk mengukur keterampilan proses sains tersebut diatas digunakan Lembar Kerja Siswa (LKS) yang berisi kemampuan-kemampuan yang
dikembangkan dalam praktikum, dan disusun dalam bentuk pertanyaan yang terdiri dari 9 kelompok pertanyaan dengan 15 percobaan. Hasil penelitian menunjukkan bahwa melalui pembelajaran MPP D–E–H: kemampuan “merumuskan hipotesis”, kemampuan “mengendalikan variabel” dan kemampuan “merancang percobaan” dapat dicapai secara tuntas baik pada kelompok SMA dengan prestasi akademik sedang maupun kelompok SMA dengan prestasi akademik tinggi. Untuk itu perlu diadakan diskusi dengan asisten untuk menindak lanjuti hasil rancangan yang dibuat siswa, terutama untuk mengevaluasi perencanaan alat dan bahan, serta cara kerja sehingga percobaan tersebut aman dan efisien untuk dilaksanakan.
Kata Kunci : MPP D-E-H (Model Pembelajaran Praktikum Diskriptif-Empiris Induktif-Hipotetis Deduktif), Keterampilan merumuskan hipotesis,Keterampilan mengendalikan variabel, Keterampilan merancang
percobaan.
SELENGKAPNYA, KLIK...
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