Cells as the basis of life
Examples in context
Support materials only that illustrate some possible contexts for exploring Science as a Human Endeavour concepts in relation to Science Understanding content.
Stem cell research
Embryonic stem cells have the potential to be grown into specialised cells and could enable the repair or replacement of ailing organs and tissues. In the late 1990s, stem cells were successfully removed from available embryos at fertility clinics and the world’s first embryonic stem cell line was established (ACSBL037), prompting excitement in the international scientific community and concern in religious and political circles. Concerns about the potential for unethical human experimentation has prompted some governments to prohibit some types of stem cell research, or to limit government funding for it (ACSBL040). International groups such as the International Society for Stem Cell Research have convened experts in science, ethics and law to develop guidelines for human embryonic stem cell research, with the aim of promoting transparent and uniform practice worldwide (ACSBL037).
Photosynthesis and productivity
Photosynthesis is one of the most important biological processes on Earth but it is quite inefficient; researchers report that natural trade-offs result in very low efficiency in many important food crops. Research is currently underway to engineer or enhance photosynthesis to improve food and fuel production. This includes the development of artificial leaves that convert solar energy to a liquid fuel via a process similar to photosynthesis, and investigation of combining more efficient algal photosynthesis with plant photosynthesis to improve crop productivity (ACSBL041). These advances have the potential to decrease reliance of fossil fuels and improve agricultural sustainability (ACSBL043).
Cell membrane model development
From the nineteenth century it was accepted that some form of semi-permeable barrier must exist around a cell, although there was no evidence to indicate its structure. Various scientists, including Traube, Quincke, Fricke and Gorter and Grendel, contributed to the theory that the cell membrane was composed of a lipid bilayer, and in the 1950s the use of electron microscopy confirmed these results through direct investigation of the membrane (ACSBL039). The first model of the membrane to incorporate the notion of fluidity was proposed by Mueller and Rudin in the 1960s, and it was demonstrated conclusively by Frye and Edidin in 1970. The results of this experiment were used by Singer and Nicolson as evidence for their 1972 proposal of the fluid mosaic model of the cell membrane (ACSBL038). Ongoing research continues to refine this model, such as research into the structure of channel proteins in the membrane (ACSBL038).
Cells require inputs of suitable forms of energy, including light energy or chemical energy in complex molecules, and matter, including gases, simple nutrients, ions, and removal of wastes, to survive
(ACSBL044)
The cell membrane separates the cell from its surroundings and controls the exchange of materials, including gases, nutrients and wastes, between the cell and its environment
(ACSBL045)
Movement of materials across membranes occurs via diffusion, osmosis, active transport and/or endocytosis
(ACSBL046)
Factors that affect exchange of materials across membranes include the surface-area-to-volume ratio of the cell, concentration gradients, and the physical and chemical nature of the materials being exchanged
(ACSBL047)
Prokaryotic and eukaryotic cells have many features in common, which is a reflection of their common evolutionary past, but prokaryotes lack internal membrane bound organelles, do not have a nucleus, are significantly smaller than eukaryotes, usually have a single circular chromosome, and exist as single cells
(ACSBL048)
In eukaryotic cells, specialised organelles facilitate biochemical processes of photosynthesis, cellular respiration, the synthesis of complex molecules (including carbohydrates, proteins, lipids and other biomacromolecules), and the removal of cellular products and wastes
(ACSBL049)
Biochemical processes in the cell are controlled by the nature and arrangement of internal membranes, the presence of specific enzymes, and environmental factors
(ACSBL050)
Enzymes have specific functions, which can be affected by factors including temperature, pH, the presence of inhibitors, and the concentrations of reactants and products
(ACSBL051)
Photosynthesis is a biochemical process that in plant cells occurs in the chloroplast and that uses light energy to synthesise organic compounds; the overall process can be represented as a balanced chemical equation
(ACSBL052)
Cellular respiration is a biochemical process that occurs in different locations in the cytosol and mitochondria and metabolises organic compounds, aerobically or anaerobically, to release useable energy in the form of ATP; the overall process can be represented as a balanced chemical equation
(ACSBL053)
Multicellular organisms
Examples in context
Support materials only that illustrate some possible contexts for exploring Science as a Human Endeavour concepts in relation to Science Understanding content.
Animal ethics
The use of animals in research has played an important role in furthering scientific understanding of the structure and function of multicellular organisms and the mechanisms of medical interventions. Ethical treatment of animals as sentient, feeling beings has been accepted as a global principle in research and the three strategies of replacement, reduction and refinement form the basis of many international guidelines (ACSBL037). Replacement is defined as the substitution for conscious living higher animals of insentient material, such as through use of tissue culture techniques; reduction involves using only the minimum number of animals needed to meet statistical requirements; and refinement involves decreasing the severity of the impact of the procedure on any animals that have to be used. These strategies are based on scientific research and have been devised to inform sustainable ethical use of animals in research (ACSBL043).
Organ and tissue transplantation
Modern surgical techniques have made it possible for diseased or damaged organs to be replaced by healthy ones from a living or dead donor. Improvements in technologies to store and transport living tissue and the development of immunosuppressive drugs to decrease rejection by transplant recipients have led to increasing numbers of people benefiting from organ and tissue transplants (ACSBL039). However the increased demand for transplantation has also led to illegal organ and tissue trafficking, forced donation and ‘transplantation tourism’, where individuals travel to other countries where it is easier or cheaper to obtain a transplant. These situations may involve violation of human rights and exploitation of the poor, and pose many ethical concerns (ACSBL041).
Bioartificial organs
There is a demand for bioartificial tissues and organs as an alternative to donor organs or tissues, which are in short supply and may be rejected by the recipient’s body (ACSBL040). To design bioartificial organs, scientists use knowledge of the structure and function of organs to design a scaffold and populate it with functional tissue. Healthy cells from the patient’s diseased organ are extracted and grown on the scaffold, with cells applied in layers to encourage them to form tissues. If the patient’s own cells are too badly damaged, organs could be grown using cells from a stem cell bank. Developments in this area could lead to a future in which surgeons would order organs to be grown as needed, removing the need to wait for donors whose organs and tissues might not be a perfect match to the recipient (ACSBL042).
Multicellular organisms have a hierarchical structural organisation of cells, tissues, organs and systems
(ACSBL054)
The specialised structure and function of tissues, organs and systems can be related to cell differentiation and cell specialisation
(ACSBL055)
In animals, the exchange of gases between the internal and external environments of the organism is facilitated by the structure and function of the respiratory system at cell and tissue levels
(ACSBL056)
In animals, the exchange of nutrients and wastes between the internal and external environments of the organism is facilitated by the structure and function of the cells and tissues of the digestive system (for example, villi structure and function), and the excretory system (for example, nephron structure and function)
(ACSBL057)
In animals, the transport of materials within the internal environment for exchange with cells is facilitated by the structure and function of the circulatory system at cell and tissue levels (for example, the structure and function of capillaries)
(ACSBL058)
In plants, gases are exchanged via stomata and the plant surface; their movement within the plant by diffusion does not involve the plant transport system
(ACSBL059)
In plants, transport of water and mineral nutrients from the roots occurs via xylem involving root pressure, transpiration and cohesion of water molecules; transport of the products of photosynthesis and some mineral nutrients occurs by translocation in the phloem
(ACSBL060)