History of the membrane (pump) theory of the living cell from its beginning in mid-19th century to its disproof 45 years ago--though still taught worldwide today as established truth

The concept that the basic unit of all life, the cell, is a membrane-enclosed soup of (free) water, (free) K+ (and native) proteins is called the membrane theory. A careful examination of past records shows that this theory has no author in the true sense of the word. Rather, it grew mostly out of some mistaken ideas made by Theodor Schwann in his Cell Theory. (This is not to deny that there is a membrane theory with an authentic author but this authored membrane theory came later and is much more narrowly focussed and accordingly can at best be regarded as an offshoot of the broader and older membrane theory without an author.) However, there is no ambiguity on the demise of the membrane theory, which occurred more than 60 years ago, when a flood of converging evidence showed that the asymmetrical distribution of K+ and Na+ observed in virtually all living cells is not the result of the presence of a membrane barrier that permits some solutes like water and K+ to move in and out of the cell, while barring--absolutely and permanently--the passage of other solutes like Na+. To keep the membrane theory afloat, submicroscopic pumps were installed across the cell membrane to maintain, for example, the level of Na+ in the cell low and the level of K+ high by the ceaseless pumping activities at the expense of metabolic energy. Forty-five year ago this version of the membrane theory was also experimentally disproved. In spite of all these overwhelming evidence against the membrane-pump theory, it still is being taught as verified truth in all high-school and biology textbooks known to us today. Meanwhile, almost unnoticed, a new unifying theory of the living cell, called the association-induction hypothesis came into being some 40 years ago. Also little noticed was the fact that it has received extensive confirmation worldwide and has shown an ability to provide self-consistent interpretations of most if not all known experimental observations that are contradicting the membrane-pump theory as well as other observations that seem to support the membrane pump theory.     

Perspective: evolution's struggle for existence in America's public schools

The ongoing creation-evolution controversy in North America thrives on the widespread special creationist beliefs of a significant portion of the public. Creation science supports a literal interpretation of the Judeo-Christian Bible, an earth that is no more than 10.000 years old and created ex nihilo in six days by a monotheistic God, with no new kinds arising since the period of creation, and with a single flood of staggering force shaping layers of rocks and trapping the organisms fossilized within them. Despite decisions in numerous court cases that specifically exclude creationism and creation science from primary and secondary biology classes in America's public schools, creationists now work locally to minimize or remove evolution from science teaching standards. The nationally organized movement to resist the teaching of evolution has proven highly effective, influencing state and district school boards in addition to individual teachers and schools. Thus, if teaching about evolution and the nature of science is to survive in America's primary and secondary schools, scientists must likewise work with teachers and reach out to state and local school boards. In this perspective we outline the typical creationist arguments we encounter from students, teachers, school board members, and neighbors. We explain briefly how knowledge of both microevolution and macroevolution is important in medicine, agriculture, and biotechnology. We describe a science education controversy that arose within our own school district, how we responded, and what we learned from it. Finally, we argue that even modest outreach efforts to science teachers will be richly repaid.     

Make biology relevant again! Pre-service teachers’ views on the relevance of biology education

ABSTRACT

Biology education should be relevant to young students so that they can become interested in biology and understand biological topics in their everyday and vocational lives. We conducted interviews and collected mind maps to examine Finnish pre-service biology teachers’ (N = 16) views on the relevance of biology education. Furthermore, we analysed Finnish secondary school biology curricula, which were compared with the pre-service teachers’ answers. We classified the views on relevance into nine main categories using grounded theory as the methodological frame of reference. Pre-service teachers emphasised the relevance of biology to the student’s own life, whereas scientific practices and the nature of science were expressed in secondary school curricula more often. Novice pre-service teachers put more value on general knowledge, while more experienced pre-service teachers were more likely to mention sustainable futures and societal aspects in their reasoning. Based on the results, we identified two stages in the development of the views. This study suggests that pedagogical studies, teaching experience and teacher training have an impact on the pre-service teachers’ views about the relevance of biology education. Moreover, we could find differences between curricula and pre-service teachers’ views, especially regarding scientific practices and the role of the nature of science in biology education.     

Competencies in premedical and medical education: the AAMC-HHMI report

One hundred years ago, Flexner emphasized the importance of science in medicine and medical education. Over the subsequent years, science education in the premedical and medical curricula has changed little, in spite of the vast changes in the biomedical sciences. The National Research Council, in their report Bio 2010, noted that the premedical curriculum caused many students to lose interest in medicine and in the biological sciences in general. Many medical students and physicians have come to view the premedical curriculum as of limited relevance to medicine and designed more as a screening mechanism for medical school admission. To address this, the Association of American Medical Colleges and the Howard Hughes Medical Institute formed a committee to evaluate the premedical and medical school science curricula. The committee made a number of recommendations that are summarized in this essay. Most important were that competencies replace course requirements and that the physical sciences and mathematics be better integrated with the biological sciences and medicine. The goal is that all physicians possess a strong scientific knowledge base and come to appreciate the importance of this to the practice of medicine. While science education needs to evolve, Flexner's vision is as relevant today as it was 100 years ago.     

In memoriam: Lauri Saxén (1927-2005)

Dr. Lauri "Tupu" Saxen died last October (2005) at the age of 78. He was a physician, a scientist, a photographer, a naturalist, a great story-teller and a man who enjoyed science enormously. His name has become synonymous with the Finnish school of Developmental Biology, a school that focuses on reciprocal inductive interactions during vertebrate organogenesis. But many biologists probably don't know the full extent of his importance to the field. A few years ago, I had the occasion to outline some of his contributions which are so varied and important that it is difficult to believe that they are the work of one person, and I have included them in this brief eulogy. One could divide his scientific contributions into five categories: (1) the threshold hypothesis of amphibian metamorphosis; (2) the double-gradient hypothesis of primary embryonic induction; (3) the analysis of reciprocal induction during kidney development; (4) the integration of developmental biology with epidemiology and (5) the maintenance of a national infrastructure for science.     

The excitability of plant cells: With a special emphasis on characean internodal cells

This review describes the basic principles of electrophysiology using the generation of an action potential in characean internodal cells as a pedagogical tool. Electrophysiology has proven to be a powerful tool in understanding animal physiology and development, yet it has been virtually neglected in the study of plant physiology and development. This review is, in essence, a written account of my personal journey over the past five years to understand the basic principles of electrophysiology so that I can apply them to the study of plant physiology and development. My formal background is in classical botany and cell biology. I have learned electrophysiology by reading many books on physics written for the lay person and by talking informally with many patient biophysicists. I have written this review for the botanist who is unfamiliar with the basics of membrane biology but would like to know that she or he can become familiar with the latest information without much effort. I also wrote it for the neurophysiologist who is proficient in membrane biology but knows little about plant biology (but may want to teach one lecture on “plant action potentials”). And lastly, I wrote this for people interested in the history of science and how the studies of electrical and chemical communication in physiology and development progressed in the botanical and zoological disciplines.     

Scientific perspectivism: A philosopher of science's response to the challenge of big data biology

Big data biology—bioinformatics, computational biology, systems biology (including ‘omics’), and synthetic biology—raises a number of issues for the philosophy of science. This article deals with several such: Is data-intensive biology a new kind of science, presumably post-reductionistic? To what extent is big data biology data-driven? Can data ‘speak for themselves?’ I discuss these issues by way of a reflection on Carl Woese’s worry that “a society that permits biology to become an engineering discipline, that allows that science to slip into the role of changing the living world without trying to understand it, is a danger to itself.” And I argue that scientific perspectivism, a philosophical stance represented prominently by Giere, Van Fraassen, and Wimsatt, according to which science cannot as a matter of principle transcend our human perspective, provides the best resources currently at our disposal to tackle many of the philosophical issues implied in the modeling of complex, multilevel/multiscale phenomena.     

Effects of a story-based strategy to enhance pupils’ ability and motivation to read bio-technical texts

This paper reports the results of a survey of the opinions of UK school teachers on the use of living organisms in secondary school science. A total of 285 respondents completed a questionnaire circulated to all members of the Institute of Biology. It was found that the last few years have seen a variety of constraints on the use of living organisms in schools. These include the pressures of time and finance, other effects of the introduction of the National Curriculum (England and Wales), a shortage of skilled technicians and a shift in pupils' perceptions about the ethics and value of the use of animals in schools. Despite all these, most respondents strongly favoured the appropriate use of living materials as an integral part of genuine biology education.     

Neurotransmitter release at central synapses

Our understanding of synaptic transmission has grown dramatically during the 15 years since the first issue of Neuron was published, a growth rate expected from the rapid progress in modern biology. As in all of biology, new techniques have led to major advances in the cell and molecular biology of synapses, and the subject has evolved in ways (like the production of genetically engineered mice) that could not even be imagined 15 years ago. My plan for this review is to summarize what we knew about neurotransmitter release when Neuron first appeared and what we recognized we did not know, and then to describe how our views have changed in the intervening decade and a half. Some things we knew about synapses--"knew" in the sense that the field had reached a consensus--are no longer accepted, but for the most part, impressive advances have led to a new consensus on many issues. What I find fascinating is that in certain ways nothing has changed--many of the old arguments persist or recur in a different guise--but in other ways the field would be unrecognizable to a neurobiologist time-transported from 1988 to 2003.     

New trends in studying structure and function of biological membranes

Thirty years ago Singer and Nicolson constructed the "fluid mosaic model" of the membrane, which described the structural and functional characteristics of the plasma membrane of non-polarized cells like circulating blood lymphocytes as a fluid lipid phase accommodating proteins with a relatively free mobility. It is a rare phenomenon in biology that such a model could survive 30 years and even today it has a high degree of validity. However, in the light of new data it demands some modifications. In this minireview we present a new concept, which revives the SN model, by shifting the emphasis from fluidity to mosaicism, i.e. to lipid microdomains and rafts. A concise summary of data and key methods is given, proving the existence of non-random co-distribution patterns of different receptor kinds in the microdomain system of the plasma membrane. Furthermore we present evidence that proteins are not only accommodated by the lipid phase, but they are integral structural elements of it. Novel suggestions to the SN model help to develop a modernized version of the old paradigm in the light of new data.     

The Mathematical Basis of Mendelian Genetics

In a climate where increasing numbers of students are encouraged to pursue post-secondary education, the level of preparedness students have for college-level coursework is not far from the minds of all educators, especially high school teachers. Specifically within the biological sciences, introductory biology classes often serve as the gatekeeper or a pre-requisite for subsequent coursework in those fields and pre-professional programmes (eg pre-medicine or pre-veterinarian). Thus, how helpful high school science and mathematics experiences are in preparing students for their introductory biology classes is important and relevant for teachers, science educators and policy makers alike. This quantitative study looked at the association between students' high school science and mathematics experiences with introductory college biology performance. Using a nationally representative sample of US students (n?=?2667) enrolled in 33 introductory college biology courses, a multi-level statistical model was developed to analyse the association between high school educational experiences and the final course grade in introductory biology courses. Advanced high school science and mathematics coursework, an emphasis on a deep conceptual understanding of biology concepts and a prior knowledge of concepts addressed in well-structured laboratory investigations are all positively associated with students' achievement in introductory college biology.     

Butterflies & wild bees: biology teachers’ PCK development through citizen science*

Citizen science is a rapidly growing emerging field in science and it is gaining importance in education. Therefore, this study was conducted to document the pedagogical content knowledge (PCK) of biology teachers who participated in a citizen science project involving observation of wild bees and identification of butterflies. In this paper, knowledge about how these biological methods can be taught to students is presented. After two years in the project, four teachers were interviewed and their PCK was captured in the form of content representations (CoRes) and Pedagogical and Professional-Experience Repertoires (PaP-eRs). These results can help future citizen science projects to link their activities to the school curriculum. But not only success can be reported: although one of the project team’s aims was to make the Nature of Science accessible to the teachers and students in the course of the project, the teachers did not take this aspect into account. This paper discusses the possible reasons and proposes various strategies for improving citizen science in the context of school biology learning.     

Creating opportunities for science PhDs to pursue careers in high school education

The United States is confronting important challenges at both the early and late stages of science education. At the level of K–12 education, a recent National Research Council report (Successful K–12 STEM Education) proposed a bold restructuring of how science is taught, moving away from memorizing facts and emphasizing hands-on, inquiry-based learning and a deeper understanding of the process of science. At higher levels of training, limited funding for science is leading PhDs to seek training and careers in areas other than research. Might science PhDs play a bigger role in the future of K–12 education, particularly at the high school level? We explore this question by discussing the roles that PhDs can play in high school education and the current and rather extensive barriers to PhDs entering the teaching profession and finally suggest ways to ease the entrance of qualified PhDs into high school education.In many K–12 classrooms, science is presented as a series of textbook facts; students are not exposed to scientific methods of inquiry and lose interest in science. At the very opposite end of the science training pipeline, life science PhDs and postdocs in the United States are experiencing difficulties in finding university jobs, a situation that will likely persist in the coming decade if research funding fails to grow; we cannot expect all PhD graduates to become principal investigators (PIs) at academic institutions.Might these two problems add up to a solution (or at least a partial solution)? Is there a place for graduates of PhD training programs in teaching K–12 science, particularly at the high school (HS) level (the focus of this article)? We argue that the answer is “yes” and that more PhDs, even if their numbers are small compared with the entire teaching pool, could have a catalytic effect on reinvigorating precollege science education. This topic is not new; the National Research Council (NRC) issued two thoughtful reports on attracting science and math PhDs to secondary school education more than a decade ago (Committee on Attracting Science and Mathematics Ph.D.s to Secondary School Teaching, National Research Council, 2000 ; Committee on Attracting Science and Mathematics PhDs to K-12 Education: From Analysis to Implementation, Division of Policy and Global Affairs, National Research Council, 2002 ). Their recommendations were not implemented, however, and the reports have largely been forgotten. Little has changed since then; the roadblocks, both in perception and logistics, that discouraged a PhD from becoming a HS teacher in the year 2000 still exist. Since the NRC reports were released, the topic of a HS teaching career option for a PhD has rarely been discussed or debated in our scientific community. We feel that it is time to reopen this discussion. The focus of this article is on PhDs entering the high school system, but much of this discussion also pertains to graduates of science master degree programs and to individuals with scientific training becoming involved in all levels of K–12 education. Our goal is to make students, postdocs, and senior scientists aware of the value of high school teaching for certain individuals as well as for our nation''s educational system. We also consider how changes at the local level (including the perception of K–12 teaching within research universities), as well as at the policy level of teacher accreditation, might facilitate this career path.     

What Conceptions do Greek School Students Form about Biological Evolution?

In Greece, since 2000, the teaching of evolutionary theory is restricted solely to lower (junior) high school and specifically to ninth grade. Even though the theory of evolution is included to the 12th grade biology textbook, it is not taught in Greek upper (senior) high schools. This study presents research conducted on the conceptions of Greek students regarding issues set out in the theory of evolution after the formal completion of the teaching of the theory. The sample comprised 411 10th grade students from 12 different schools. The research results show that the students appear to have a positive view of the idea of evolution, the evolution of man, and the common origin of organisms. However, they have retained many alternative views, or else they are completely in ignorance of basic issues in evolutionary theory regarding: what is considered evolution in biology, the main mechanism of evolutionary changes in what is considered natural selection, what the theory of evolution actually explains, and what the word theory means in science. At least in Greece, these views still prevail because the theory of evolution is marginalized in the teaching of biology in Greek schools, and biology education does not help students formulate overall conceptual structures to enable them to understand the question of biological change.

A simple biological indicator of solar ultraviolet radiation

School science laboratory classes and hands-on public engagement activities share many common aims and objectives in terms of science learning and literacy. This article describes the development and evaluation of a microbiology public engagement activity, ‘The Good, the Bad and the Algae’, from a school laboratory activity. The school activity was developed as part of an educational resource which aimed to promote practical microbiology in the classroom. The public engagement activity was derived locally for National Science and Engineering Week 2011 and was subsequently adapted for a national science and engineering fair (The Big Bang 2012 The Big Bang. 2012. About The Big Bang Fair. http://www.thebigbangfair.co.uk/about_us.cfm. [Google Scholar]). The aim of the session was to raise awareness of the importance of algae and to encourage hands-on laboratory examination in a fun and informal manner. Evaluation of the first event, delivered in a workshop format, helped shape the educational resource before publication. The second event was modified to enable delivery to a larger audience. Both events were successful in terms of enjoyment and engagement. Over 2200 people participated in the Big Bang activity over three days, with evaluation indicating 80% of participants had increased awareness/knowledge of algae after the event. The success of both iterations of the activity demonstrates that it is possible to transform a simple school activity into an exciting and effective public engagement activity.     

A No-Holds-Barred Evolution Curriculum for Elementary and Junior High School Students

Understanding the basic mechanism of evolution by natural selection together with examples of how it works in nature is crucial for explaining and teaching the workings of biology and ecology to young students. Dobzhansky said it best in his advice to educators of biology: “Nothing in biology makes sense except in the light of evolution.” This premise is true at all levels of biology but especially so in the elementary years where foundations of science knowledge are laid. Elementary students are capable of learning cohesive and connected stories of biological principles and learning them within a no-holds-barred arena wherein concepts and processes usually reserved for high school years are taught with special care, appropriate exercises, and patient explanations. This story must include solid introductions to the fundamental principles of evolution by natural selection that are threaded within and alongside those of basic biology and ecology. This paper attempts to make the case for the inclusion of connected stories of biology in the earliest years of education and to include within that education the unifying theme of all biology and ecology studies—evolution.     

Membranes,viruses, detergents,and endosomes

The fluid mosaic model for biological membranes was formulated 40 years ago. Ten years later endosomes were discovered as important prelysosomal organelles. At the outset of my research career, I was fortunate to witness both these turning points in biochemistry and cell biology from close up, and to participate in some of the studies. In this short essay, I will describe how this came about, and also try to provide some background as to the general starting situation in those not so distant pioneering years of membrane biology.     

Immortalized cells and one oncogene in malignant transformation: old insights on new explanation

Background

Nearly thirty years ago, it was first shown that malignant transformation with single oncogene necessarily requires the immortal state of the cell. From that time this thesis for the cells of human origin was not disproved. The basic point which we want to focus on by this short communication is the correct interpretation of the results obtained on the widely used human embryonic kidney 293 (HEK293) cells.

Results

Intensive literature analysis revealed an increasing number of recent studies discovering new oncogenes with non-overlapping functions. Since the 1970s, dozens of oncogenes have been identified in human cancer. Cultured cell lines are often used as model systems in these experiments. In some investigations the results obtained on such cells are interpreted by the authors as a malignant transformation of normal animal or even normal human cells (as for example with HEK293 cells). However, when a cell line gains the ability to undergo continuous cell division, the cells are not normal any more, they are immortalized cells. Nevertheless, the authors consider these cells as normal human ones, what is basically incorrect. Moreover, it was early demonstrated that the widely used human embryonic kidney 293 (HEK293) cells have a relationship to neurons.

Conclusions

Thus, the experiments with established cell lines reinforce the notion that immortality is an essential requirement for malignant transformation that cooperates with other oncogenic changes to program the neoplastic state and substances under such investigation should be interpreted as factors which do not malignantly transform normal cells alone, but possess the ability to enhance the tumorigenic potential of already immortalized cells.