Biological Change Unit miss E. Mac's Class

Quick, free, online unit converter that converts common units of measurement, along with 77 other converters covering an assortment of units. The site also includes a predictive tool that suggests possible conversions based on input, allowing for easier navigation while learning more about various unit systems. In tropical rainforest: Biological productivity. Of all vegetation types, tropical rainforests grow in climatic conditions that are least limiting to plant growth. It is to be expected that the growth and productivity (total amount of organic matter produced per unit area per unit time) of tropical rainforests would Read More; tundras. Biological change over time evolution unit. What happens to dna that causes biological change? Different types of mutations. Biological effects of warming. Interactions between warming and acidification. Universal effects of climate change. Oxygen minimum zones. Trophic downgrading and shifting baselines. Learning outcomes. Unit Learning Outcomes express learning achievement in terms of what a student should know, understand and be able to do on. Biology - Biology - Evolution: In his theory of natural selection, which is discussed in greater detail later, Charles Darwin suggested that “survival of the fittest” was the basis for organic evolution (the change of living things with time). Evolution itself is a biological phenomenon common to all living things, even though it has led to their differences. Evidence to support the theory.

Biological Change Unit Miss E. Mac's Classic
Biological Change Unit Miss E. Mac's Classics
Biological Change Unit Miss E. Mac's Class Of
Biological Change Unit Miss E. Mac's Class C

(Redirected from Biological unit)

Structure of nucleoprotein MA: The 50S ribosomal subunit from H. marismortuiX-ray crystallographic model of 29 of the 33 native components, from the laboratory of Thomas Steitz. Of the 31 component proteins, 27 are shown (blue), along with its 2 RNA strands (orange/yellow).^[1] Scale: assembly is approx. 24 nm across.^[2]

The term macromolecular assembly (MA) refers to massive chemical structures such as viruses and non-biologic nanoparticles, cellular organelles and membranes and ribosomes, etc. that are complex mixtures of polypeptide, polynucleotide, polysaccharide or other polymeric macromolecules. They are generally of more than one of these types, and the mixtures are defined spatially (i.e., with regard to their chemical shape), and with regard to their underlying chemical composition and structure. Macromolecules are found in living and nonliving things, and are composed of many hundreds or thousands of atoms held together by covalent bonds; they are often characterized by repeating units (i.e., they are polymers). Assemblies of these can likewise be biologic or non-biologic, though the MA term is more commonly applied in biology, and the term supramolecular assembly is more often applied in non-biologic contexts (e.g., in supramolecular chemistry and nanotechnology). MAs of macromolecules are held in their defined forms by non-covalentintermolecular interactions (rather than covalent bonds), and can be in either non-repeating structures (e.g., as in the ribosome (image) and cell membrane architectures), or in repeating linear, circular, spiral, or other patterns (e.g., as in actin filaments and the flagellar motor, image). The process by which MAs are formed has been termed molecular self-assembly, a term especially applied in non-biologic contexts. A wide variety of physical/biophysical, chemical/biochemical, and computational methods exist for the study of MA; given the scale (molecular dimensions) of MAs, efforts to elaborate their composition and structure and discern mechanisms underlying their functions are at the forefront of modern structure science.

A eukaryotic ribosome, which catalytically translate the information content contained in mRNA molecules into proteins. The animation presents the elongation and membrane targeting stages of eukaryotic translation, showing the mRNA as a black arc, the ribosome subunits in green and yellow, tRNAs in dark blue, proteins such as elongation and other factors involved in light blue, the growing polypeptide chain as a black thread growing vertically from the curve of the mRNA. At end of the animation, the polypeptide produced is extruded through a light blue SecY pore^[3] into the gray interior of the ER.

Biomolecular complex[edit]

3D printed model of the structure of a bacterialflagellum 'motor' and partial rod structure of a Salmonella species. Bottom to top: dark blue, repeating FliM and FliN, motor/switch proteins; red, FliG motor/switch proteins; yellow, FliF transmembrane coupling proteins; light blue, L and P ring proteins; and (at top), dark blue, the cap, hook-filament junction, hook, and rod proteins.^[4]

A biomolecular complex, also called a biomacromolecular complex, is any biological complex made of more than one biopolymer (protein, RNA, DNA,^[5]carbohydrate) or large non-polymeric biomolecules (lipid). The interactions between these biomolecules are non-covalent.^[6]Examples:

Protein complexes, some of which are multienzyme complexes: proteasome, DNA polymerase III holoenzyme, RNA polymerase II holoenzyme, symmetric viral capsids, chaperonin complex GroEL-GroES, photosystem I, ATP synthase, ferritin.
RNA-protein complexes: ribosome, spliceosome, vault, SnRNP. Such complexes in cell nucleus are called ribonucleoproteins (RNPs).
DNA-protein complexes: nucleosome.
Protein-lipid complexes: lipoprotein.^[7]^[8]

The biomacromolecular complexes are studied structurally by X-ray crystallography, NMR spectroscopy of proteins, cryo-electron microscopy and successive single particle analysis, and electron tomography.^[9]The atomic structure models obtained by X-ray crystallography and biomolecular NMR spectroscopy can be docked into the much larger structures of biomolecular complexes obtained by lower resolution techniques like electron microscopy, electron tomography, and small-angle X-ray scattering.^[10]

Complexes of macromolecules occur ubiquitously in nature, where they are involved in the construction of viruses and all living cells. In addition, they play fundamental roles in all basic life processes (protein translation, cell division, vesicle trafficking, intra- and inter-cellular exchange of material between compartments, etc.). In each of these roles, complex mixtures of become organized in specific structural and spatial ways. While the individual macromolecules are held together by a combination of covalent bonds and intramolecular non-covalent forces (i.e., associations between parts within each molecule, via charge-charge interactions, van der Waals forces, and dipole-dipole interactions such as hydrogen bonds), by definition MAs themselves are held together solely via the noncovalent forces, except now exerted between molecules (i.e., intermolecular interactions).^{[citation needed]}

MA scales and examples[edit]

The images above give an indication of the compositions and scale (dimensions) associated with MAs, though these just begin to touch on the complexity of the structures; in principle, each living cell is composed of MAs, but is itself an MA as well. In the examples and other such complexes and assemblies, MAs are each often millions of daltons in molecular weight (megadaltons, i.e., millions of times the weight of a single, simple atom), though still having measurable component ratios (stoichiometries) at some level of precision. As alluded to in the image legends, when properly prepared, MAs or component subcomplexes of MAs can often be crystallized for study by protein crystallography and related methods, or studied by other physical methods (e.g., spectroscopy, microscopy).^{[citation needed]}

Cross-sections of phospholipid (PLs) relevant to biomembrane MAs. Yellow-orange indicates hydrophobic lipid tails; black and white spheres represent PL polar regions (v.i.). Bilayer/liposome dimensions (obscured in graphic): hydrophobic and polar regions, each ~30 Å (3.0 nm) 'thick'—the polar from ~15 Å (1.5 nm) on each side.^[11]^[12]^[13]^[14]

A graphical representation of the structure of a viral MA, cowpea mosaic virus, with 30 copies of each of its coat proteins, the small coat protein (S, yellow) and the large coat protein (L, green), which, along with 2 molecules of positive-senseRNA (RNA-1 and RNA-2, not visible) constitute the virion. The assembly is highly symmetric, and is ~280 Å (28 nm) across at its widest point.^{[verification needed]}^{[citation needed]}

Virus structures were among the first studied MAs; other biologic examples include ribosomes (partial image above), proteasomes, and translation complexes (with protein and nucleic acid components), procaryotic and eukaryotic transcription complexes, and nuclear and other biological pores that allow material passage between cells and cellular compartments. Biomembranes are also generally considered MAs, though the requirement for structural and spatial definition is modified to accommodate the inherent molecular dynamics of membrane lipids, and of proteins within lipid bilayers.^{[citation needed]}

Research into MAs[edit]

The study of MA structure and function is challenging, in particular because of their megadalton size, but also because of their complex compositions and varying dynamic natures. Most have had standard chemical and biochemical methods applied (methods of protein purification and centrifugation, chemical and electrochemical characterization, etc.). In addition, their methods of study include modern proteomic approaches, computational and atomic-resolution structural methods (e.g., X-ray crystallography), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS), force spectroscopy, and transmission electron microscopy and cryo-electron microscopy. Aaron Klug was recognized with the 1982 Nobel Prize in Chemistry for his work on structural elucidation using electron microscopy, in particular for protein-nucleic acid MAs including the tobacco mosaic virus (a structure containing a 6400 base ssRNA molecule and >2000 coat protein molecules). The crystallization and structure solution for the ribosome, MW ~ 2.5 MDa, an example of part of the protein synthetic 'machinery' of living cells, was object of the 2009 Nobel Prize in Chemistry awarded to Venkatraman Ramakrishnan, Thomas A. Steitz, and Ada E. Yonath.^{[citation needed]}

Non-biologic counterparts[edit]

Finally, biology is not the sole domain of MAs. The fields of supramolecular chemistry and nanotechnology each have areas that have developed to elaborate and extend the principles first demonstrated in biologic MAs. Of particular interest in these areas has been elaborating the fundamental processes of molecular machines, and extending known machine designs to new types and processes.^{[citation needed]}

References[edit]

^Ban N, Nissen P, Hansen J, Moore P, Steitz T (2000). 'The Complete Atomic Structure of the Large Ribosomal Subunit at 2.4 ångström Resolution'. Science. 289 (5481): 905–20. Bibcode:2000Sci...289..905B. CiteSeerX10.1.1.58.2271. doi:10.1126/science.289.5481.905. PMID10937989.
^William McClure. '50S Ribosome Subunit'. Archived from the original on 2005-11-24. Retrieved 2019-10-09.
^Osborne AR, Rapoport TA, van den Berg B (2005). 'Protein translocation by the Sec61/SecY channel'. Annual Review of Cell and Developmental Biology. 21: 529–50. doi:10.1146/annurev.cellbio.21.012704.133214. PMID16212506.
^Legend, cover art, J. Bacteriol., October 2006.^{[full citation needed]}
^Kleinjung, Jens; Franca Fraternali (2005-07-01). 'POPSCOMP: an automated interaction analysis of biomolecular complexes'. Nucleic Acids Research. 33 (suppl 2): W342–W346. doi:10.1093/nar/gki369. ISSN0305-1048. PMC1160130. PMID15980485. Retrieved 2013-11-14.
^Moore, Peter B. (2012). 'How Should We Think About the Ribosome?'. Annual Review of Biophysics. 41 (1): 1–19. doi:10.1146/annurev-biophys-050511-102314. PMID22577819.
^Neuman, Nicole (January 2016). 'The Complex Macromolecular Complex: Trends in Biochemical Sciences'. Trends in Biochemical Sciences. 41 (1): 1–3. doi:10.1016/j.tibs.2015.11.006. PMID26699226. Retrieved 2018-07-11.
^Dutta, Shuchismita; Berman, Helen M. (2005-03-01). 'Large Macromolecular Complexes in the Protein Data Bank: A Status Report'. Structure. 13 (3): 381–388. doi:10.1016/j.str.2005.01.008. ISSN0969-2126. PMID15766539.
^Russell, Robert B; Frank Alber; Patrick Aloy; Fred P Davis; Dmitry Korkin; Matthieu Pichaud; Maya Topf; Andrej Sali (June 2004). 'A structural perspective on protein–protein interactions'. Current Opinion in Structural Biology. 14 (3): 313–324. doi:10.1016/j.sbi.2004.04.006. ISSN0959-440X. PMID15193311.
^van Dijk, Aalt D. J.; Rolf Boelens; Alexandre M. J. J. Bonvin (2005). 'Data-driven docking for the study of biomolecular complexes'. FEBS Journal. 272 (2): 293–312. doi:10.1111/j.1742-4658.2004.04473.x. hdl:1874/336958. ISSN1742-4658. PMID15654870.
^'Structure of Fluid Lipid Bilayers'. Blanco.biomol.uci.edu. 2009-11-10. Retrieved 2019-10-09.
^Experimental system, dioleoylphosphatidylcholine bilayers. The hydrophobic hydrocarbon region of the lipid is ~30 Å (3.0 nm) as determined by a combination of neutron and X-ray scattering methods; likewise, the polar/interface region (glyceryl, phosphate, and headgroup moieties, with their combined hydration) is ~15 Å (1.5 nm) on each side, for a total thickness about equal to the hydrocarbon region. See S.H. White references, preceding and following.
^Wiener MC & White SH (1992). 'Structure of a fluid dioleoylphosphatidylcholine bilayer determined by joint refinement of x-ray and neutron diffraction data. III. Complete structure'. Biophys. J. 61 (2): 434–447. Bibcode:1992BpJ....61..434W. doi:10.1016/S0006-3495(92)81849-0. PMC1260259. PMID1547331.^{[non-primary source needed]}
^Hydrocarbon dimensions vary with temperature, mechanical stress, PL structure and coformulants, etc. by single- to low double-digit percentages of these values.^{[citation needed]}

Biological Change Unit Miss E. Mac's Classic

Reviews on particular MAs[edit]

Valle M. Almost lost in translation. Cryo-EM of a dynamic macromolecular complex: the ribosome. Eur Biophys J. 2011 May;40(5):589-97. doi: 10.1007/s00249-011-0683-6. Epub 2011 Feb 19. Review. PubMed PMID: 21336521.
Monie TP. The Canonical Inflammasome: A Macromolecular Complex Driving Inflammation. Subcell Biochem. 2017;83:43-73. doi: 10.1007/978-3-319-46503-6_2. Review. PubMed PMID: 28271472.
Perino A, Ghigo A, Damilano F, Hirsch E. Identification of the macromolecular complex responsible for PI3Kgamma-dependent regulation of cAMP levels. Biochem Soc Trans. 2006 Aug;34(Pt 4):502-3. Review. PubMed PMID: 16856844.

Primary sources[edit]

Lasker, K.; Förster, F.; Walzthoeni, T.; Villa, E.; Unverdorben, P.; Beck, F.; Aebersold, R.; Sali, A.; Baumeister, W. (2012). 'Molecular architecture of the 26S proteasome holocomplex determined by an integrative approach'. Proc Natl Acad Sci USA. 109 (5): 1380–7. Bibcode:2012PNAS..109.1380L. doi:10.1073/pnas.1120559109. PMC3277140. PMID22307589.
Russel, D.; Lasker, K.; Webb, B.; Velázquez-Muriel, J.; Tjioe, E.; Schneidman-Duhovny, D.; Peterson, B.; Sali, A. (2012). 'Putting the pieces together: integrative modeling platform software for structure determination of macromolecular assemblies'. PLOS Biol. 10 (1): e1001244. doi:10.1371/journal.pbio.1001244. PMC3260315. PMID22272186.
Barhoum S, Palit S, Yethiraj A. Diffusion NMR studies of macromolecular complex formation, crowding and confinement in soft materials. Prog Nucl Magn Reson Spectrosc. 2016 May;94-95:1-10. doi: 10.1016/j.pnmrs.2016.01.004. Epub 2016 Feb 4. Review. PubMed PMID: 27247282.

Other sources[edit]

Nobel Prizes in Chemistry (2012), The Nobel Prize in Chemistry 2009, Venkatraman Ramakrishnan, Thomas A. Steitz, Ada E. Yonath, The Nobel Prize in Chemistry 2009, accessed 13 June 2011.
Nobel Prizes in Chemistry (2012), The Nobel Prize in Chemistry 1982, Aaron Klug, The Nobel Prize in Chemistry 1982, accessed 13 June 2011.

External links[edit]

Beck Group (2019), Structure and function of large macromolecular assemblies (Beck group home page), Beck Group - Structure and function of large molecular assemblies - EMBL, accessed 13 June 2011.
DMA Group (2019), Dynamics of macromolecular assembly (DMA Group home page), Dynamics of Macromolecular Assembly Section | National Institute of Biomedical Imaging and Bioengineering, accessed 13 June 2011.

Retrieved from 'https://en.wikipedia.org/w/index.php?title=Macromolecular_assembly&oldid=1002119964'

Biological development

The scope of development
- Types of development
- General systems of development
- Constituent processes of development
  - Morphogenesis
Control and integration of development
Development and evolution
- Effect on life histories

Please select which sections you would like to print:

While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.

Our editors will review what you’ve submitted and determine whether to revise the article.

Join Britannica's Publishing Partner Program

Biological Change Unit Miss E. Mac's Classics

and our community of experts to gain a global audience for your work! Conrad H. Waddington

Buchanan Professor of Genetics, University of Edinburgh, Scotland, 1947–75. Author of Principles of Embryology.

Alternative Title: development

Biological development, the progressive changes in size, shape, and function during the life of an organism by which its genetic potentials (genotype) are translated into functioning mature systems (phenotype). Most modern philosophical outlooks would consider that development of some kind or other characterizes all things, in both the physical and biological worlds. Such points of view go back to the very earliest days of philosophy.

Among the pre-Socratic philosophers of Greek Ionia, half a millennium before Christ, some, like Heracleitus, believed that all natural things are constantly changing. In contrast, others, of whom Democritus is perhaps the prime example, suggested that the world is made up by the changing combinations of atoms, which themselves remain unaltered, not subject to change or development. The early period of post-Renaissance European science may be regarded as dominated by this latter atomistic view, which reached its fullest development in the period between Newton’s laws of physics and Dalton’s atomic theory of chemistry in the early 19th century. This outlook was never easily reconciled with the observations of biologists, and in the last hundred years a series of discoveries in the physical sciences have combined to swing opinion back toward the Heracleitan emphasis on the importance of process and development. The atom, which seemed so unalterable to Dalton, has proved to be divisible after all, and to maintain its identity only by processes of interaction between a number of component subatomic particles, which themselves must in certain aspects be regarded as processes rather than matter. Albert Einstein’s theory of relativity showed that time and space are united in continuum, which implies that all things are involved in time; that is to say, in development.

The philosophers who charted the transition from the nondevelopmental view, for which time was an accidental and inessential element, were Henri Bergson and, in particular, Alfred North Whitehead. Karl Marx and Friedrich Engels, with their insistence on the difference between dialectical and mechanical materialism, may be regarded as other important innovators of this trend, although the generality of their philosophy was somewhat compromised by the political context in which it was placed and the rigidity with which their later followers have interpreted it.

Biological Change Unit Miss E. Mac's Class Of

Philosophies of the Heracleitan type, which emphasize process and development, provide much more appropriate frameworks for biology than do philosophies of the atomistic kind. Living organisms confront biologists with changes of various kinds, all of which could be regarded as in some sense developmental; however, biologists have found it convenient to distinguish the changes and to use the word development for only one of them. Biological development can be defined as the series of progressive, nonrepetitive changes that occur during the life history of an organism. The kernel of this definition is to contrast development with, on the one hand, the essentially repetitive chemical changes involved in the maintenance of the body, which constitute “metabolism,” and on the other hand, with the longer term changes, which, while nonrepetitive, involve the sequence of several or many life histories, and which constitute evolution.

Get a Britannica Premium subscription and gain access to exclusive content. Subscribe Now

As with most formal definitions, these distinctions cannot always be applied strictly to the real world. In the viruses, for instance, and even in bacteria, it is difficult to make a distinction between metabolism and development, since the metabolic activity of a virus particle consists of little more than the development of new virus particles. In certain other cases, the distinction between development and evolution becomes blurred: the concept of an individual organism with a definite life history may be very difficult to apply in plants that reproduce by vegetative division, the breaking off of a part that can grow into another complete plant. The possibilities for debate that arise in these special cases, however, do not in any way invalidate the general usefulness of the distinctions as conventionally made in biology.

The scope of development

Biological Change Unit Miss E. Mac's Class C

All organisms, including the very simplest, consist of two components, distinguished by a German biologist, August Weismann, at the end of the 19th century, as the “germ plasm” and the “soma.” The germ plasm consists of the essential elements, or genes, passed on from one generation to the next, and the soma consists of the body that may be produced as the organism develops. In more modern terms, Weismann’s germ plasm is identified with DNA (deoxyribonucleic acid), which carries, encoded in the complex structure of its molecule, the instructions necessary for the synthesis of the other compounds of the organism and their assembly into the appropriate structures. It is this whole collection of other compounds (proteins, fats, carbohydrates, and others) and their arrangement as a metabolically functioning organism that constitutes the soma. Biological development encompasses, therefore, all the processes concerned with implementing the instructions contained in the DNA. Those instructions can only be carried out by an appropriate executive machinery, the first phase of which is provided by the cell that carries the DNA into the next generation: in animals and plants by the fertilized egg cell; in viruses by the cell infected. In life histories that have more than a minimal degree of complexity, the executive machinery itself becomes modified as the genetic instructions are gradually put into operation, and new mechanisms of protein synthesis are brought into functional condition. The fundamental problem of developmental biology is to understand the interplay between the genetic instructions and the mechanisms by which those instructions are carried out.

In the language of genetics the word genotype is used to indicate the hereditary instructions passed on from one generation to another in the genes, while phenotype is the term given to the functioning organisms produced by those instructions. Biological development, therefore, consists of the production of phenotypes. The point made in the last paragraph is that the formation of the phenotype of one generation depends on the functioning of part of the phenotype of the previous generation (e.g., egg cell), as the mechanism that begins the interpretation of the instructions contained in the new organism’s genotype.

key people

related topics