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33<script language="JavaScript" type="text/javascript">var compliments=new Array("A really good website explaining everything you need to know in a way everyone can understand","I have been very impressed with your site and have used it to improve my own knowledge to update it in the lastf year while I was doing my PGCE","I have recently found your website - It is very useful and I shall be recommending it to my students - Just wanted to say thanks for your time","I have never come across such a creative, marvellously organized website. It is outstanding","Its really an excellent site for students as well as teachers information . So being as a human being and biology teacher I want to say u thanks for making such a wonderful resourceful site as guide line in general","Would be better if there is MC questions as well - but overall this is a VERY VERY useful site for revision","Thanks for this website: very useful indeed since there are not really many notes on the extension bit!","Having been a professor for many years...as well as a student for many years prior...I really appreciate the dedication and teaching savvy your site demonstrates. My field is ed tech....and I can only hope more professors move beyond their fears of technology and embrace the potential of multimedia instructional tools","I am not a specialist science teacher and have to learn before I teach - found this very useful for GCSE (p.s - also used for my daughters coursework - worked well) Thanks","I would like to thank you for the site that you created. I am a GCSE student and 
33your site provides suberb information for revision and has been a valuable asset","This was the first time I had encountered your website and I was impressed to see how easy it was to find the information relevant to me. Thankyou","I was particularly attracted to your comprehensive but clear designs of cells and easy to understand explanations","So much relevant information. I wish I had found it sooner","I loved the website and spent a lot longer than I really thought on it as I became hooked with all the interesting information","My compliments on an excellent website! It is well designed and easy to follow. It is great to see an interactive site where one has to scroll over the spaces to get the answers","I am writing to you as I am currently studying a part time access course to university, with human biology as my first module. I am enjoying looking at the spinneret site","Thank you so much for taking the time to make the website interactive. The interactivity really aided in my comprehension of the material. There are very few resources of this type for Biology on the World Wide Web. Yours is exceptional!!","Your website is great","I am an A-level student student currently studying Biology, Chemistry and maths. I find your web site very helpful and interesting.Thank you!","I just wanted to tell you that your site has been truly useful for my daughter and for me to help her with her revision. You have done a wonderful job of making the subject not only interesting but extremely easy to understand.","I found this site extremley helpful, especially as I have only just started doing my degree and am struggling with some of the concepts. The question and answer sections are very helpful and I feel I understand each concept a little more than before. Thank you","I think this is a fantastic site for students trying to study for a test or just surfing around to learn something new. I hope that you continue developing this site, with more info, theory, examples, etc. Great job so far!","Thank you very much! The site is great! More mouse overs which give answers would be great. It's a wonderful method to test if I know what I'm doing...","I just want to thank you for taking the time to make this web page... The information will help me ever so much in getting the kids to understand the concepts....A concerned new teacher.","I am a student studying biology at as level, and I found this page very helpful, thank you very much.","I love your website. I was just looking for a diagram or description of a fructose molecule and accidentally stumbled on your pages, which are so clear and well organized","Your website has proven to be a great assistance to me as I prepare my twelth grade students to sit the GCSE biology exam","helpful site here","this site would certainly help clarify some basics concepts very effectively","extremely useful website for biology. very helpful for tests and exams","many thanks for your website: the howlers were absolutely brilliant. I have not laughed so much in ages","This is the best site I've had the pleasure of coming across for biological information delivered in extremely clear concise and to-the-point accuracy."," The untold hours of research and information-gathering that have obviously gone into your site, not to mention the excellent (and intriguing) mouse-overs and animation are much appreciated.","Thank you again for access to this very excellent site!","i would just like to say that your website is really good, its really helped me do my work. thankyou","i am teaching students and i find your website very useful especially the diagrams","may i take time to say how much this website has helped my son","the best interactive online notes for GCSE biology on the web","This is a great site. It's simple and easily understood by students of intermediate knowledge in the Bioprocess fields.","Contains some of the most common, but essentail topics that a student would need to recall/enchance their knowledge learn in the theory lesson. Though further animations can be included, this is overall bravo.","an excellent source of pertinent biology resources.","Thank you for putting in into a simple language for me to understand. Antibodies now make sence to me ","As a teacher of Biology I find your website informative and extremely useful - it is incredibly precise and manages to get exactly the right balance of detail and ease of access","This is a good website to go on to find out info on enzymes","What an excellent website. Love the use of color, the way you scroll to see the answer, photos, etc. DId a really great job. Far and above all others.","All most all the information are very accurate and important and the way you have design your web page is very attractive","This is so informative! It makes my reserach work become easier than ever. I used this 4 my presentation/reporting in school","Your information is vital to us young and willing to learn b
33iologists","A very informative site for teachers teaching I.G.C.S.E.curriculum","Thanks for the comprehensiveness","I find this an excellent website and has everything you need for GCSE and A level Biology as I am studying an Access Course I find it very useful","your notes are laid out in perfect order. I have found it so much easier to revise efficiently!","The entire sylabus is covered in the detail i need. The information provided is excellent","This is exactly what i needed as i have missed over 3 months of school","This infomation is great, well written, and easy to understand.","The site is excellent","my class is using your website as an adiitional place to learn more abot biology as well as having a great time","we hope you continue to improve your fabulous site","Great site. I intend to refer my .. clients to it.","thank you this information has helped me with my course work","This website is kind of ddepenndable . Thannks .","I think this websites is usefull to me and i think i can get a wonderful grade if i continue to use this website as a reference.","It is really difficult to find something that will actually help me with my work, and this did! thanks again","Just discovered this site, it looks very usefull! Thanks.","this site ... has helped me to do a lot of my previous home works","nice website, thanks for making us do loads of work in class. it was fun and es[pecially fun for em beacause i love science!!","this helped us with my daughters homework - thankyou!","This website has really helped me with my coursework. Thanks a lot. It's easy to use and appealing. Very good job!","These notes are fantastic and so appreciated! They are helping me through my Biology GCSE.","thanks so much...this is an awesome page to study for my tests. KEEP DOING WHAT U DO","Very good topics covered - worth browsing - easy to understand and well presented. Definitely use it again.","I have recently found your website and for once i can relate to what is being said - in other words plain English","Hello this site is really good. I used it for my projet and i got full marks of it. ","who ever decides to go on this site would surely get the information they need","NO DOUBT ABOUT IT, this the best site of bio i ever seen! :)","I just would like to say that this is the best site I have ever found","I now understand my entire matric syllabus better then i thought was possilbe","Great site and study tool.","Thank you for this information it makes my teaching this subject easier.","These experiments are fantastic. Can I use them for my classes?","Just want to say that your site is really useful! The rollover mouse thing is simple but ingenious and these web pages really help me revise for Bio GCSE.","i would like to say a very big thank u as u guys helped me so much in my IGCSE biology and i'm happy to tell u that i managed A* because of u!!!!"," I absolutely love this site. It is very interesting and informative and as a nursing student it has really helped me. I will definitely pass this page on to my colleagues.","Keep up the good work and dont close this site. EVER","I have enjoyed your notes on various topics. They have good basic knowledge on science topics"," i liked all your information. i got an A+.so thanks for all your help.","Thank you very much for assembling this information!!","It's especially helpful to be able to rotate the molecules for a better look at the structure. I wish these had been around when I was studying biochemistry!","this is a good web site thanks","great clarity and simplicity!","this was reaaaaalllly helpful on my science project. :) and i like the fact that when you hover over the answers they turn red","found the heart info really useful and normally i find it hard to teach myself but i actually understand it more compared to when i did it in college","This site is great, it puts the information down in an easy to follow format but highlights the important details","Animation and the information are really helpful. Thanks for the wonderful website!","This site has been invaluable as a refresher course. Thanks!","I really enjoyed reading your brief introduction to Insulin structure","I am SO grateful I happened upon this site!!!  Absolutely love the format which makes the content easier to navigate","i learnt many thing through your link.. thanks for dedicating such website","oh my god basically it contains in and out regarding to bio technology and also covers microbiology widely","I  am happy to say that this website is an invaluable resource for practicing Biology teachers who live and work in third world countries.","hey this really worked","This gives me enough information to complete the project.It is really great as it gives us some questions to answer and reveal the correct answer when you just pass your mouse(arrow) over it.The information is also the 'professional' type!","Thanks heaps. Your simple description and diagrams helped me a bundle - without over complicating things! :)","I want to send out a large THANK YOU for your work convert
33ing the jmol versions to jsmol","Thanks so much for your work on updating the 3D structures of molecules page to JSMol and HTML5.  I use your pages in my non-science majors courses, and it is very helpful!","Thank you so much for creating this website and putting in so much effort! It is excellent, even as a website it is easy to see the passion you have for your subject. Oct26 ");var complimentsCt=compliments.length;{{randomNum=Math.floor((Math.random()*complimentsCt));var statement=compliments[randomNum];}}</script>
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179	<li><a href="#" class="top_parent" title="Mostly AS and A level" onmouseover="loadXMLDoc('list4','../navlists/list4.txt')">Higher level Topics</a>
180	<div id="list4">			
181	<ul>
182	 <li><a href="conten.html#AandAS" title="Contents page -
183	 Fourth column">A/AS level Section</a></li>		
184	</ul>
185	</div>
186 				
187	</li>
188</ul>
189	
190<ul>			
191	<li><a href="#" title="Interactive movable molecules -
192	New format - no security risk" class="top_parent" onmouseover="loadXMLDoc('list6','../navlists/list6.txt')">3D molecules [Jsmol]</a>
193		<div id="list6">
194		<ul>
195		<li><a href="jsmol/jscontents.html" title="This takes you to a menu that is separate from the main Biological Topics">MOLECULES MENU</a></li>
196		</ul>
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202
203<!-- DROPDOWN MENU END-->
204
205<div class="section group" title="Main sections of the BioTopics website
206Each section leads to a menu of its own" style="background-color: #99FF99; font-weight: bold; text-align: center;">
207<div class="disposable2">
208	<div class="col span_1_of_3">
209	<span title="The main section: BioTopics pages">Biological Facts</span> and <span title="Howlers are Biological misconceptions">Fallacies</span>
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213	
214	Last modification 01/10/2026
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218	Biological Chemicals and Supplies
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222
223
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225	<div class="col span_1_of_3" onclick="window.location ='conten.html'" style="cursor: pointer" title="More than 2 million pages are now being downloaded per year from this website!">
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229<!-- width="190" -->
230
231	
232<br/>
233<font face="Gill Sans MT" size="3"><b>Click here to visit the Biological Topics Contents Page 
234<br><span title="I had not updated this number, but it certainly has crept up over time!"> (currently 259 topics)</span></b></font></a>
235<br/>
236<i title="Some users have misunderstood the format - the gaps are to assist your comprehension in a tutorial style"><b>Interactivity</b> is key to most of this material. Don't forget to run the cursor over any gaps in the text, coloured text, unlabelled diagrams and other links in the text or margin...... <a href="interactiveinnovations3.html" title="Just click ...">
237<br/>More explanation about these features</a> is available.</i>
238<br/>
239
240<script language="JavaScript" type="text/javascript">document.write('<h4><font color="#008000" title="More than 60 unsolicited recommendations ...">What other visitors have said about this material:</font></h4>');document.write('<font face="sans-serif" color="#008000" title=" ... You should see a new comment each time you visit this page - but I have put these comments in the original format including odd spellings etc">'+'&quot;'+statement+'&quot;'+'</font>');</script>
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250	
251<center>	
252<h3 title="All sections of the AS specification are now covered">Most recent material <span title=" I hope you appreciate the division into basic information on the left-hand column, and extension material on the right-hand side"> -  AS and A level topics
253</span></h3>
254
255<b style="background-color:blue;color:white">. Now covers all the AQA specification - 58 sections .</b>
256<br/>
257<a href="Background.html">Background information on these higher level topics</a>
258<br/>
259<b><i title="Mouseover for more detail">Click on the categories below to expand/contract</i> </b>
260<br/>
261
262
263<b>AS</b>
264 <a href="javascript:expandcontract('biolchem')">
265 <span title="These feature mouseover effects for extra detail and some have further spoken explanations"><i><b>Biological Chemicals</b></i></span></a> ...
266
267<span id="biolchem" style="display:none"><a href="A15/Monomers_and_polymers.html" title="Some underlying biochemical principles, condensation and hydrolysis applicable to the next few topics">Monomers and polymers</a> ... 
268<a href="A15/Carbohydrates.html" title="Monosaccharides, disaccharides, polysaccharides">Carbohydrates</a> ... 
269<a href="A15/Lipids.html" title="Fats and oils, phospholipids">Lipids</a> ... 
270<a href="A15/Proteins.html" title="Amino acids, Similarities and differences, Plant &amp; animal proteins, Levels of protein structure">Proteins</a> ... 
271<a href="A15/water.html" title="The Biological Significance of Water and molecular explanation">Water</a> ... 
272<a href="A15/Enzymes.html">Enzymes</a> ...  
273<a href="A15/pH.html">pH</a> ... 
274<a href="A15/ATP.html" title="Adenosine triphosphate">ATP</a> ... 
275<!-- missing DNA structure! -->
276<a href="A19/Nucleic_acids.html" title="Information-carrying molecules
277(DNA and RNA)
278Nucleic acids are polymers of nucleotides
279Nucleotides join to form longer molecules
280A DNA molecule is composed of two long polynucleotide chains
281An RNA molecule is comparatively short
282Mathematical certainties?
283Getting things in proportion
284Long-term versus short-term
285Ribose and deoxyribose - possible bonding sites
286Why uracil in RNA, but thymine in DNA?
287Nucleotide nomenclature
288Pairings of nucleotides in DNA
289Comprehension test">Nucleic Acids</a> ... 
290
291<a href="A15/DNA_replication.html" title="How DNA is copied">DNA replic<sup>n</sup></a> ...
292<a href="A15/Inorganic_ions.html" title="mineral salts, electrolytes, hydrogen ions, iron ions, sodium ions, phosphates">Inorganic ions</a>
293</span>
294 
295 <a href="javascript:expandcontract('cells')">
296<i title="OK I tweaked that title a bit ... "><b>Cells and cellularity</b></i></a>
297<br/>
298<span id="cells" style="display:none">
299
300<a href="A15/Eukaryotic_cells.html" title="Some nice images">Eukaryotic cells</a> ...
301<a href="A15/Prokaryotic_cells.html" title="Some more nice images">Prokaryotic cells</a> ... 
302<a href="A15/studying_cells.html" title="loads of good images and some mouseover tables for comprehension tests">Studying cells (with the microscope)</a> ...
303<a href="A15/Virus_particles.html" title="I am pleased with these images too">Virus particles</a> ... 
304<a href="A15/Endosymbiont_theory.html" title="Some thought-provoking stuff linking prokaryotes and eukaryotes">Endosymbiosis</a> ...
305<a href="A15/Transport_across_cell_membranes.html" title="Eukaryotic cell membrane structure, phospholipids, proteins, glycoproteins, glycolipids, the fluid mosaic model, simple diffusion, facilitated diffusion, osmosis, active transport, co-transport, adaptations for rapid transport across membranes">Transport across cell membranes</a> ... 
306<a href="A19/cell_cycle.html" title="Interphase, G1,S,G2, Mitosis, Behaviour of chromosomes, kinetochores and the spindle, prophase, prometaphase, metaphase, anaphase, telophase, Cytokinesis, Cancer, chemotherapy, Binary fission in prokaryotic cells, viral replication, ">The cell cycle</a> ... 		
307<a href="A19/Cell_recognition.html" title="Cell recognition, the interaction between antigens and antibodies, the immune response, vaccination, HIV, and monoclonal antibodies">Cell recognition</a>
308</b></span>
309
310<a href="javascript:expandcontract('exchanges')"><i title=""><b>Exchanges with the environment</b></i></a>
311<br/>
312
313<span id="exchanges" style="display:none">
314<a href="A20/Surface_area_to_volume_ratio.html" title="Single-celled organisms vs multicellular organisms
315Surface area to volume ratio
316Cells getting together
317Getting longer
318Staying flat
319Getting specialised
320All systems go
321Metabolic rate
322If only cells were cubes
323Spherical objects, real units
324Bergmann's rule">Surface area to volume ratio</a>
325. . . 
326<a href="A20/Gas_exchange.html" title="Gas exchange surfaces
327Gases must dissolve before they can be exchanged
328The (body?) surface of a single-celled organism
329The tracheal system of an insect
330The gills of fish
331The leaves of dicotyledonous plants
332Specialisation for terrestrial environments
333Terrestrial insects
334Xerophytic plants
335The human gas exchange system
336The bronchial tree and factors affecting flow in the airways
337Structure of an alveolus
338The mechanism of breathing (how we breathe in and out)
339Conditions affecting the functioning of the respiratory system
340Pulmonary ventilation rate (PVR), tidal volume and breathing rate
341Respiratory quotient (RQ) (from the sublime to the ridiculous)
342The use of a simple respirometer to measure volumes of gases involved in gas exchange">Gas exchange</a>
343 . . . 
344<br/>
345<a href="A20/Digestion_and_absorption.html" title="The digestion process
346Digestion of carbohydrates
347Polysaccharides (carbohydrate polymers)
348Oligosaccharides (mostly carbohydrate dimers)
349Digestion of proteins
350Polypeptides
351Dipeptides
352Digestion of lipids
353Absorption of the products of digestion
354Absorption of amino acids and of monosaccharides
355Micelles and chylomicrons in the absorption of lipids">Digestion and absorption</a>
356 . . .  
357
358<a href="A20/Mass_transport_in_animals.html" title="Mass transport: a delivery system for lots of molecules
359Haemoglobin
360The role of haemoglobin and red blood cells in the transport of oxygen
361Inside the lungs, the circulation, the tissues
362Oxyhaemoglobin Dissociation curve
363The cooperative nature of oxygen binding
364Effects of external factors on the dissociation of oxyhaemoglobin
365Carbon dioxide concentration (the Bohr effect)
366Temperature
3672,3 BPG
368Different types of haemoglobin with different oxygen transport properties.
369Fetal and maternal haemoglobin
370Large and small mammals
371High altitude vs low altitude
372The general pattern of blood circulation in a mammal
373Structure of the human heart, and events within the cardiac cycle
374Arteries, arterioles, (venules) and veins
375Structure of capillaries
376Formation of tissue fluid">Mass transport in animals</a>
377<br/>
378
379<a href="A20/Mass_transport_in_plants.html" title="Mass transport: two delivery systems for molecules
380Xylem
381Cells involved
382The main driving force in the uptake of water is a pull from above
383Roots give a small push from below
384Cohesion-tension - not just a theory
385Phloem
386Cells involved
387Translocation of sucrose by mass flow under pressure
388Heat and chemical treatments
389Summary of differences
390Evidence for cohesion-tension
391A classic ringing experiment
392Single leaf labelling with CO2 radioisotope to trace translocation of photosynthate
393">Mass transport in plants</a>
394
395 </span>
396 
397
398 <a href="javascript:expandcontract('geninfo')">
399<i title="also Variation and relationships between organisms"><b> Genetic information</b></i></a>
400 
401<span id="geninfo" style="display:none"> <a href="A20/DNA_genes_and_chromosomes.html" title="DNA - different types in different places
402Prokaryotic cells - no loose ends
403Eukaryotic cells - all wound up
404Mitochondria and chloroplasts - keeping their own information safe
405Viral DNA and RNA - putting it about
406What is a gene?
407The genetic code is not a secret (any more)
408Non-coding DNA
409The genetic codes for each amino acid
410Coding for degeneracy 
411ORFs - another way of defining genes (and finding them)">DNA, genes and chromosomes</a>
412 . . 
413<a href="A20/DNA_and_protein_synthesis.html" title="Transcription
414Similarities with DNA replication
415Exons, introns and splicing
416Translation
417More about ribonucleic acids:mRNA, tRNA
418Connecting each tRNA with its amino acid ">
419DNA and protein synthesis</a>
420 . . 
421<a href="A20/Genetic_diversity.html" title="Genetic diversity and uniformity
422Gene mutations
423Mutagenic agents
424Base deletion
425Consequences of base deletions
426Base substitution
427Not all base substitutions cause a change
428Differences in the number of chromosomes
429Meiosis does more than halve chromosome number
430Meiosis results in genetic variation
431Comparison of meiosis with mitosis
432The genetic code
433Life cycles
434The life cycle of a fern ">
435Genetic diversity</a>
436 . . 
437<a href="A20/Genetic_diversity_and_adaptation.html" title="Genetic diversity in a population
438Natural selection acts upon genetic diversity
439The principles of natural selection in the evolution of populations
440Species are seen to be adapted to their environment
441Changes in allele frequency ">
442Genetic diversity and adaptation</a>
443 . . 
444<a href="A17/Species_and_taxonomy.html" title="24 examples classified! Groups within the standard phylogenetic classification system, The bottom line (or two), Putting names to all the categories, Names behind the naming system, How many domains? How many kingdoms?">Species and taxonomy</a>
445 . . 
446<a href="A15/Biodiversity.html" title="Species richness, Species abundance,  Index of diversity together with some example calculations, and thoughts about reduction of biodiversity as a consequence of certain farming techniques and the balance between farming and conservation, as well as friends and enemies of Biodiversity"> Biodiversity within a community</a>
447 . . 
448<a href="A20/Investigating_diversity.html" title="Comparing diversity
449Reasons for making comparisons
450Encouraging genetic diversity
451Discouraging interbreeding
452Quantitative investigations of variation
453Mean and standard deviation
454Other sampling statistics
455Sorting out your giraffes
456Identifying Scottish Wildcats
457Investigation of genetic diversity in different breeds of dog">
458Investigating diversity</a>
459 </span>
460 
461  ...
462	
463	<br/> <b>A2</b>
464 <a href="javascript:expandcontract('energy')">
465<i title="In and between organisms"><b>Energy transfers</b></i></a>
466 
467 <span id="energy" style="display:none">
468
469
470<a href="A17/Respiration_processes.html" title="Respiration and energy, Acids and bases, Glycolysis, Anaerobic respiration, The link reaction, The Krebs cycle, Electron transfer chain, Balancing the equation, Respiration and oxygen, Glycolysis in more detail, Consequences of anaerobic respiration, Ins and Outs of mitochondria, The link reaction in more detail, One cycle, three names, Et Cetera Et Cetera, Accounting for protons, and energy">Respiration processes</a>  
471 . . . 
472<a href="A17/Photosynthesis_reactions.html" title="The light-dependent reaction, The LDR in more detail, Photosystem II, Photosystem I, Photophosphorylation, Cyclic photophosphorylation, The Hill reaction, The light-independent reaction, The Calvin cycle, The LIR in more detail, Carbon dioxide fixation, Reduction, Regeneration of RuBp, Photorespiration - the downside of RuBisCO, Evolution of photosynthesis, Environmental factors that limit the rate of photosynthesis, Experiments to investigate the effect of environmental variables on the rate of photosynthesis, Chromatography of photosynthetic pigments, Common agricultural and horticultural practices used to overcome the effect of these limiting factors">Photosynthesis reactions</a>
473. . . 
474<a href="A19/Energy_and_ecosystems.html" title="Energy and ecosystems, Plants, photosynthesis, production, planet Earth, Measuring biomass and chemical energy, Dry biomass, Mass of carbon in biomass, Using calorimetry to measure chemical energy, Biomass in power generation, Primary production - by Plants, Gross primary production, (GPP), Net primary production (NPP), NPP = GPP - R, Biomass transfer to consumers, N = I - (F + R), N = I - F - R, secondary production, Farming practices and agricultural production">Energy and ecosystems</a>
475. . .
476<a href="A19/Nutrient_cycles.html" title="Nutrients are recycled within natural ec
476osystems
477Saprobiotic nutrition
478The nitrogen cycle
479Inorganic nitrogen compounds 
480Organic nitrogen compounds in plants
481Organic nitrogen compounds in animals
482Decomposition of organic nitrogen compounds in plant and animal wastes, and dead plants and animals
483The role of bacteria in the nitrogen cycle
484Ammonification
485Nitrification
486Nitrogen fixation
487Non-biological nitrogen fixation 
488Biological nitrogen fixation
489The reduction of nitrogen
490In Biology, not all vegetables are legumes
491The establishment of root nodules
492Other symbiotic associations
493Other nitrogen fixers
494Symbiotic
495Free-living
496Denitrification
497The phosphorus cycle
498Inorganic phosphates - not quite so simple
499Organic phosphates 
500Mycorrhizae
501The answer lies in the soil
502Crop rotation
503Natural fertilisers
504Taking the urine?
505Urea - a compound that changed our thinking about the chemistry of life
506Artificial fertilisers
507Weapons take priority
508Hydroponic growing
509Environmental issues arising from the use of fertilisers
510Leaching
511Washday problems
512Eutrophication">Nutrient cycles</a>
513</span> 
514  . . 
515 <a href="javascript:expandcontract('response')" title="Nerve and muscle cells and regulation of body conditions">
516<i><b>Response... </b></i></a>
517
518<span id="response" style="display:none">
519<a href="A19/Survival_and_response.html" title=" Survival tactics, Flowering plants and tropisms, Nice or nasty?, Background, experimentation on planr growth responses, Indoleacetic acid (IAA), Other phytohormones, Shoots, Auxin movement - sideways and down in shoots, Roots, The fall and rise of auxin in roots, Taxes, Fine-tuning the response, Kineses, Choice chambers, Animal antics, Bacteria too, The simple reflex, Other reflex actions">Survival and response</a>, 
520
521
522<a href="A17/Receptors.html" title="The structure of a Pacinian corpuscle, The human retina, photochemistry, Layers of cells in the retina, With sensory neurones, an ending is just the beginning, Finger pinching, with wires attached, All in the back of the eye, colour blindness ">Receptors</a>, 
523<a href="A17/Control_of_heart_rate.html" title="Receptors in the circulatory system, Within the heart, Hearts don't just beat faster ... , ECG starting with P">Control of heart rate</a>, 
524
525<a href="A17/Nerve_impulses.html" title="Structure of the neurone, The nature of nervous impulses along the axon, resting potential, Action potential, factors affecting the speed of nervous conduction, Myelination, Axon diameter, Temperature, Types of neurones, How a Schwann cell myelinates (part of) an axon, Stimulation of an axon, The sodium/potassium ion pump">Nerve cells, impulses</a> , 
526<a href="A17/Synaptic_transmission.html" title="Types of synapse, acetylcholine, acetylcholine esterase,  neurotransmitter substances, acetylcholine esterase inhibitors, organophosphate insecticides, nerve gases, nerve agents, synaptic interactions between neurones, progress of nervous impulses, Unidirectionality, Temporal summation, spatial summation, inhibitory synapses, Effects of specific drugs on synapses, neuromuscular junction, effects of specific drugs ">Synaptic transmission</a> , 
527<a href="A17/Skeletal_muscle.html" title="Muscles work by shortening, Muscles work in pairs - and take it in turns, Structure of skeletal muscle, Gross structure, Finer structure, Microscopic structure, Ultrastructure of a myofibril, Getting the process started, Myofibril contraction, Actin-Myosin cycle, The processes behind muscle power, ATP and phosphocreatine in muscle contraction, Slow and fast skeletal muscle fibres, The arm as a lever, Other types of muscle, More illuminating names for the different areas of a sarcomere, Working in from the outside, Proteins on the pull, Actin, Myosin, Accessory proteins, An M word, G words, Not to be confused with .., Creatine as a supplement">Skeletal muscle</a>, 
528<a href="A19/Homeostasis.html" title="Maintenance of a stable internal environment, physiological control systems, pH control,  acid-base homeostasis, Temperature control, Thermoregulation, stable blood glucose concentration,  Osmoregulation, Negative feedback restores systems to their original state, Inputs and outputs, Keeping things in proportion, Positive feedback">Homeostasis</a>, 
529
530<a href="A19/blood_glucose_control.html" title="Glucose is fuel - so it must not run out
531Storage of surplus glucose
532Getting more glucose back into the bloodstream
533Summary of activity of insulin and glucagon
534The second messenger model
535Diabetes mellitus
536Type 1 diabetes
537Type 2 diabetes
538Hypogycaemia, hyperglycaemia
539Measuring the concentration of glucose in blood
540and more">Control of blood glucose concentration</a>
541
542<br/> 
543 <a href="A19/blood_water_potential_control.html" title="
544Balancing the aqueous inputs and outputs
545ADH production and release
546Formation of glomerular filtrate
547Reabsorption of glucose and amino acids 
548(with sodium ions and water) from the proximal convoluted tubule
549It all gets concentrated outside of the loop of Henle 
550The last movement of ions in the distal convoluted tubule
551Fine-tuning the reabsorption of water under the control of ADH
552Blood sweat and tears . . .
553What not to do after a marathon
554The problem with salt">Control of blood water potential</a>
555</span>
556
557<a href="javascript:expandcontract('evolution')" title="Lots of examples">
558
559<br/>
560 <i><b>Genetics, Evolution &amp; speciation</b></i></a> 
561<br/>
562<span id="evolution" style="display:none">
563<a href="A20/Inheritance.html" title="Genetics
564Genotype and phenotype
565Alleles
566Types of crosses
567Genetic diagrams
568Example crosses using fruit flies
569Monohybrid crosses
570Dihybrid crosses
571Sex linkage
572Autosomal linkage
573Chi-squared test
574Calculation of chi-squared
575Monohybrid cross
576Dihybrid cross
577Dihybrid cross- with linkage
578Examples using plants
579Crossing red with white
580Human blood groups
581The ABO series
582Colour blindness in humans
583Non-mendelian ratios
584Epistasis
585Lethal genes"> Inheritance</a>,
586<a href="A20/Populations.html" title="Populations and genetic dynamics
587Frequencies within a population
588Allele frequency
589Genotype frequency
590Phenotype frequency
591The Hardy-Weinberg principle
592Applying the Hardy-Weinberg equation
593Examples
594Heathland flowers
595Phenylketonuria (PKU)
596Multiple alleles
597Heterozygote Advantage
598Sex-linked genes">Populations</a>
599<!-- also in info - not rewritten/replaced -->
600 , 
601
602<a href="A17/Evolution.html" title="Definition + more to be added"> Evolution processes</a> , 
603 
604<a href="A17/Sympatric_speciation.html" title="Definition + Examples: Spartina cordgrass-  A recent discovery, (Monkeyflowers), Not quite a new species, Christmas cactus and Easter cactus, Palms of Lord Howe Island"> Sympatric Speciation</a>, 
605<a href="A17/Allopatric_speciation.html" title="Definition + Posssible examples: Fauna of the Galapagos Islands: Darwin's finches, Galapagos giant tortoises, Not quite giants (St Kilda Wren + Field Mouse), Californian pupfish, Anolis lizards in the Caribbean and USA, Zebras, Giraffes"> Allopatric Speciation</a>, 
606<a href="A17/Populations_in_ecosystems.html" Title="Ecological terms, Estimating population size using quadrats and transects, Mark-release-recapture method, and Succession with examples from Surtsey and Sand dune succession">Populations in ecosystems</a>
607
608</span>
609
610<a href="javascript:expandcontract('geneexpression')" title="Follows on from some AS topics">
611<i><b>The control of gene expression</b></i></a>
612<br/>
613
614<span id="geneexpression" style="display:none">
615
616<a href="A20/Base_sequence_alteration.html" title="Alteration of the sequence of bases in DNA can alter the structure of proteins
617Gene mutation
618Addition
619Deletion
620Substitution
621Transitions 
622Transversions
623Inversion
624Duplication
625Translocation
626Mutagens and mutation rate
627Not all mutations result in a change 
628Downstream changes">Base sequence alteration</a>
629<br/>
630
631<!-- <a href="" title=""></a> -->
632<a href="A20/Cell_potency.html" title="Most of a cell's DNA is not translated
633(potency varies from cell to cell)
634
635Turning on and turning off genes - for positive and negative outcomes
636Totipotent cells
637Pluripotent, multipotent and unipotent stem cells
638Stem cells for meat products
639Induced pluripotent stem cells (iPS cells) 
640Use of stem cells in treating human disorders
641Ethical issues
642Cells' potential varies
643Triploblasty
644">Cell potency</a>
645<br/>
646<a href="A20/Regulation_of_transcription_and_translation.html" title=" Targetting a gene to be transcribed
647Transcriptional factors
648The role of oestrogen in initiating transcription
649Epigenetic control of gene expression
650Methylation of DNA
651Acetylation of histones
652Epigenetics and the development and treatment of disease, especially cancer
653RNA interference (RNAi)
654
655Post-transcriptional gene silencing">Regulation of transcription and translation</a>
656<br/>
657<a href="A20/Gene_expression_and_cancer.html" title="Benign and malignant tumours
658Tumour suppressor genes
659Oncogenes
660Breast cancer
661The effects of oestrogen on breast cancer
662BRCA1 and BRCA2 genes
663TP53 and CHEK2 genes
664Breast cancer in men">Gene expression and cancer</a>
665<br/>
666
667<a href="A20/Using_genome_projects.html" title="Genome sequencing projects
668Vaccine production
669Sequencing methods
670The Sanger or chain termination procedure
671Automated sequencing">Using genome projects</a>
672<br/>
673<a href="A20/Recombinant_DNA_technology.html" title="Sources of DNA fragments
674DNA amplification
675Polymerase chain reaction (PCR)
676Use of enzymes to transfer sections of DNA
677Cell transformation
678Genetic engineering applied to blood clotting proteins
679Reverse transcriptase-polymerase chain reaction
680(RT-PCR)
681The first approved genetically modified food product ">Recombinant DNA technology</a>
682<br/>
683
684
685
686<a href="A20/identification_and_diagnosis_of_heritable_conditions.html" title="Heritable conditions
687Differences in DNA can be exploited for identification and diagnosis of heritable conditions
688DNA probes and hybridisation
689Fluorescence In Situ Hybridization (FISH)
690Screening patients for heritable conditions
691Carrier screening
692Dominant alleles
693Prenatal diagnostic testing
694Pre implantation screening
695Genetic counselling and personalised medicine
696Pharmacogenomics
697">Identification and diagnosis of heritable conditions</a>
698<br/>
699
700<a href="A20/Genetic_fingerprinting.html" title="Variable number tandem repeats (VNTRs)
701Minisatellites 
702Microsatellites  
703Short tandem repeats (STRs)
704Development of DNA fingerprinting
705Restriction Fragment Length Polymorphisms (RFLPs)
706DNA profiling
707Use of genetic fingerprinting and DNA profiling
708Determining genetic relationships
709Determining genetic variability within a population
710Application in forensic science
711Crime scene analysis
712Identification of body remains
713Exceptions to the rule
714 CAG repeats
715Huntington's disease
716polyQ diseases
717Genetic databases
718Familal searching">Genetic fingerprinting and DNA profiling</a>
719
720</span>
721
722<b>Others</b>
723 <a href="javascript:expandcontract('tables')">
724<i title="These are now compatible with mobiles"><b>Some tabular data updated</b></i></a>
725<br/>
726<span id="tables" style="display:none"><a href="jsmol/jsVitamins_and_Minerals.html" title="I left off completing the last bit for some time">Vitamins and Minerals</a> ... <a href="jsmol/plant_minerals.html" title="Now adrift from the previous, and extended">Plant Minerals</a> ...<a href="g11/viral_diseases.html" title="Just a few - not exactly comprehensive
727- but incoming links data show this has gone viral!">Viral diseases</a> ... </span>
728
729
730
731
732
733
734<a href="javascript:expandcontract('water')">
735<i title="All to show the special properties of the wet stuff"><b>More than just H<sub>2</sub>O - and in 3-D</b></i></a>
736<br/>
737<span id="water" style="display:none"><a href="jsmol/watersingle.html" title="See it in 3D">Water molecule</a> ... <a href="jsmol/waterHbonds.html" title="4 possible positions">H bonds in water</a> ... <a href="jsmol/watermoving.html" title="moving molecules animation">Liquid Water</a> ... <a href="jsmol/ice.html" title="See why it floats">Ice</a></span>
738
739
740and <a href="javascript:expandcontract('molecules')" title="Quite a few more to be added soon">
741<i><b>Most recent 3-D Molecules</b></i></a>
742
743<span id="molecules" style="display:none">
744
745<a href="jsmol/Carotene.html" title="A pigment with connections to Vitamin A"><b>Carotene</b></a><i> vs </i> <a href="jsmol/Keratin.html" title="A protein with lots of uses"><b>Keratin</b></a> - two quite different molecules!
746<br/>
747<a href="jsmol/Paxlovid.html"><b>Paxlovid</b></a> - Another new oral COVID-19 treatment awaiting approval
748<br/>
749
750<a href="jsmol/Molnupiravir.html"><b>Molnupiravir</b></a> <i>- a hopeful oral anti-COVID 19 drug</i>
751<br/>
752<a href="jsmol/remdesivir.html" title="an adenosine monophosphate analogue" target="_blank"> <b>Remdesivir</b> </a> <i>- an earlier possible anti-COVID 19 drug - for intravenous use</i>
753<br/>
754<a href="jsmol/halicin.html"><b>Halicin</b></a> - <i>the most recently announced potential new antibiotic</i>
755<br/>
756<a href="jsmol/lugdunin.html"><b>Lugdunin</b></a> - <i>the previous potential new antibiotic</i>
757<br/>
758<a href="jsmol/oxycodone.html" title="An (addictive) opioid, very similar to codeine"><b>Oxycodone (OxyContin)</b></a> <i>-  A drug in the news</i>
759<br/>
760
761<a href="jsmol/salbutamol.html" title="Several antiasthma drugs
762Also used by cyclists"><b>Salbutamol+</b></a> <i> bronchodilator agents - some similar to adrenaline</i>
763<br/>
764
765<a href="jsmol/cardiolipin.html" title="Found in mitochondrial and some bacterial membranes"><b>Cardiolipin</b></a> <i>
765 phospholipid with 4 fatty acid tails</i>
766<br/>
767<a href="jsmol/NSAIDS.html" title="Ibuprofen, naproxen, diclofenac"> <b>NSAIDs</b> </a>Non Steroidal Anti Inflammatory Drugs
768<br/>
769</span>
770
771<br/> <b> Don't miss these: </b>
772	<br/>
773	  <b><a href="howl/howl34.html" title="Not such a laugh - but they show the improvements which are needed both in comprehension and expression
774		And you can work back through them in chronological order">The most recent howlers</a></b>
775		  
776</center>
777	
778	
779	</div><!-- col span_1_of_3 -->
780	<div class="col span_1_of_3" style="background-color: #ffffcc;   font-family: Sans-Serif; cursor: pointer;" title="Quite a popular feature of the BioTopics site:
781carbohydrates
782amino acids and proteins
783lipids
784nucleic acids
785vitamins
786antibiotics
787other compounds" onclick="window.location ='jsmol/jscontents.html'" title="This takes you to the Molecules Menu"> 
788
789	<!-- RHS TOP BOX -->
790	 
791	<div align="center">   <br>
792	
793	<b>3-D interactive structures of about 200 Biological molecules</b>
794	<br>
795	Being carbon-based, Biological molecules deserve better than a flat sheet of paper.
796	<br>
797	
798	Check out the examples, and the interactive display format.
799	<br clear="all">
800	</div>
801	<center>
802	<br>	
803	<a href="jsmol/glucose.html" title="This takes you to the glucose molecule"><img alt="glucosefromjmol (1K)" src="glucosefromjmol.gif" height="97" width="90"/>
804<span title="The most basic carbohydrate" style="color:green">Glucose</span></a>
805	<br>
806	<!-- <h3><b>MOLECULES IN THE NEWS</b></h3>
807	
808	<a href="jsmol/Molnupiravir.html">
809	<img alt="molnupiravir_from_jsmol (28K)" src="molnupiravir_from_jsmol.png" width="90" title="A new oral treatment reducing the effects of COVID-19"/></a>
810	 . . .  
811	 <a href="jsmol/Paxlovid.html">
812	<img alt="paxlovidpic" src="paxlovidpic.png" width="90" title="Another new oral COVID-19 treatment 
813	<!-- awaiting approval "/></a>-->
814<!-- height="265" width="373"	 -->
815<!-- <br>
816<a href="jsmol/Molnupiravir.html" title="A cytidine analogue" style="color:green">Molnupiravir</a> . . .  <a href="jsmol/Paxlovid.html"><span title="A protease inhibitor" style="color:green">Paxlovid</span></a> -->
817
818
819	</center><br>
820<br>
821<!-- There was a problem with the display of .pdb files (proteins and other large molecules). This has now been fixed.
822I hope you are happy with all the molecules! -->
823	</div><!-- col span_1_of_3 -->
824</div> <!-- "section group" -->
825
826<!-- **SECOND LINE****************************************************************************** -->
827<div class="section group">
828
829	<div class="col span_1_of_3" style="background-color: #FFCCFF; cursor: pointer;" title="Howlers are (laughable) mistakes made by my Biology students!" align="center" onclick="window.location ='howl/index.html'">
830
831	
832<div align="center">	
833<a href="howl/index.html" title="Click to go to the howlers menu page - Loads to choose from"><img src="rwolf.gif" title="Click here to see some more howlers" onmouseover="document.getElementById('wolfhowl').play()" align="right" border="0" height="50" width="50" alt="howlers"/><font face="Comic Sans MS" size="4">Howlers - 35 pages!</font></a><br/>
834 <audio id="wolfhowl">
835<source src="howl/wolf5.mp3"/> 
836</audio>
837
838
839<script language="JavaScript" type="text/javascript">document.write('<h4><font color="#FF00FF" title="I have collected loads of these howlers (29 pages) ..."> This one made me smile :</font></h4>');document.write('<font face="Comic Sans MS" color="#FFOOFF" title ="... but I had to choose a reasonably inoffensive one to put here at random (out of 24)...." >'+'&quot;'+chosenhowl+'&quot;'+'</font>');document.write('<h4><font color="#FF00FF"> Click here to see some others!</font></h4>');</script>
839
840
841
842</div><!-- center -->
843
844	</div><!-- col span_1_of_3" -->
845	
846	
847	<div class="col span_1_of_3">
848	<!-- LOWER CENTRAL -->
849	
850<center>
851
852<hr/>
853<h3>It is easy to get in touch using the contact options below</h3>
854<hr/>
855</center>
856</div> <!-- col span_1_of_3 -->
857
858
859
860
861	
862	
863	<div class="col span_1_of_3" style="background-color: #FFFFFF">
864	<br>
865	<!-- Books -->
866		
867<div align="center">	
868		
869<a href="books/booklist.html" title="Books and other media
870"><b>Biological Books</b>- <i>recently restored</i></a>
871
872</div><!-- center -->
873		<ul>
874			
875			<li><b><a href="books/AAS.html" title="Lots of options for the different boards
876			NOW BACK TO A SEPARATE LIST">LATEST AS and A level books</a> </b></li>
877		<li><a href="books/GCSEbooks.html" title="Now also a separate list"><b>GCSE books</b></a></li>
878		<li><b><a href="books/booklist.html#recommendations" title="From Biotutors">Recommendations for the 6th form</a></b></li>
879		<li><a href="books/booklist.html#interest" title="Richard Dawkins Matt Ridley Alice Roberts Richard Fortey David Attenborough 
880Other stuff">General Interest (popular authors, other stuff)</a></li>
881		
882		<li><a href="books/universaluk.html" title="This should track down and present a list of books - any subject any level">Universal book finder</a></li>
883		 	
884	</ul>
885<hr>
886	<div align="center" title="Could be extended ... "><b>Biological supplies</b></div>
887	 	
888	<div align="left">
889	<ul>
890		
891			<li>
892	<a href="anatomical.html" title="Some useful props - available online
893	Amazon.com seem to have improved the delivery of these links
894	Please let me know if you experience any difficulty">Anatomical models</a>
895	</li>
896	</ul>
897	</div>	<!-- left -->
898	
899
900	</div><!-- col span_1_of_3 -->
901</div><!-- section group -->
902
903<center>
904Advertisers on this site use cookies for analytics, advertising and to personalise adverts served. 
905<br/>
906By continuing to use this site, you agree to their use of cookies. To find out more, see our Privacy Policy.
907</center>
908
909<!-- ******************************************************************************** -->
910<div class="section group">
911
912<div class="col span_1_of_3" title="">
913
914<!-- 	 -->
915
916<!-- SUSPENDED TO PREVENT PAGE LOADING DELAY 
917NOT SURE ABOUT THAT^-->
918
919	<div align="center">
920	
921	As an Amazon Associate I earn from qualifying purchases.<br/>
922	
923BioTopics is a participant in the Amazon EU Associates Programme, an affiliate advertising programme designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.co.uk and Amazon.com.
924<br>
925
926
927
928<a href="https://amzn.to/4oR8wkq">Back to school offers</a>
929<br>
930
931<!-- 
932<a href="https://www.amazon.com/ref=nav_logo&tag=biotopics-20">Amazon.com</a>-->
933<!-- Needs more? -->
934
935<!-- <a href="https://www.amazon.com&tag=biotopics-20">Amazon.com</a><!-- Needs more? -->
936<br>
937<br>
938<!-- <a href="https://www.amazon.co.uk?&linkCode=ll2&tag=biotopics-21&linkId=fcf18c86076cc67a83bb8fa3b535e51b&language=en_GB&ref_=as_li_ss_tl">Amazon.co.uk</a>
939 -->
940<!-- <a href="https://www.amazon.co.uk&tag=biotopics-21&linkId=fcf18c86076cc67a83bb8fa3b535e51b&language=en_GB&ref_=as_li_ss_tl">Amazon.co.uk</a>
941 -->
942
943
944<br>
945<br>
946
947
948
949
950
951</div>
952	</div><!-- col span_1_of_3 -->
953<!-- ******************************************************************************** -->
954	<div class="col span_1_of_3">
955	<div align="center">
956<img src="SZ5star.gif" border="0" width="120" height="80" align="top" alt="Schoolzone Education 5 star award"/>
957<a href="https://www.topmarks.co.uk" target="_top"><img height="60" alt="Topmarks Excellent Site Award" src="https://www.topmarks.co.uk/award.gif" width="120" align="top" border="0"/></a>
958<img src="rated.gif" border="0" width="120" height="80" alt=""/>
959</div><!-- centre -->
960	</div><!-- col span_1_of_3 -->
961	<!-- ******************************************************************************** -->
962	<div class="col span_1_of_3">
963	<hr>
964<div align="left">
965	<a href="wwwlinks.html"><b>External sites</b></a> which may be of use:
966	
967 <ul title="Other categories also">
968<li><a href="wwwlinks.html#Examination boards">Examination boards</a></li>
969<li><a href="wwwlinks.html#otherbiosites">Other teachers' Biology sites</a></li>
970<li><a href="wwwlinks.html#BBC websites">BBC websites</a></li>
971<li><a href="wwwlinks.html#Other support links">Other support links</a> </li>
972<li><a href="wwwlinks.html#Institutions">Institutions</a> </li>
973<li><a href="Science_based_activities.html">Science-based activities</a> </li>
974
975
976
977
978
979</ul> <br clear="all"/>
980</div><!-- align="left" -->
981<!-- ******************************************************************************** -->
982	</div><!-- col span_1_of_3 -->
983</div> <!-- "section group" -->
984<!-- ******************************************************************************** -->
985<br clear="all"/>
986
987<div align="center" title="General links to other sections of the BioTopics website" style="background-color: #99ccff;">
988		<a href="r15/resptest.htm">Responsiveness test</a>
989		<!-- <a href="soundtest.html">Sound test</a> -->
990		
991	<a href="index.html" title="The BioTopics front page - with links to the main sections of the site">	<img src="BioTopics2010blue.gif" border="0" width="125" height="28" alt="www.BioTopics.co.uk" hspace="6"/>Home</a> <a href="conten.html" title="250+ topics (and counting)!">Contents</a>  <a href="fbform.html" title="Pass on a comment without using email">Contact via form</a> 
992
993<a href="nogo/emailpoints.html" title="Better not to use this if your computer is not set up for email">Contact via email</a> <a href="howl/index.html" title="Howlers are laughable mistakes - 35 pages!
994They actually show what concepts people have problems with">Howlers</a> <a href="books/booklist.html" title="Biological and other books, reviews, and other media you can order on-line">Books</a> <a href="wwwlinks.html" title="Some relevant links">WWWlinks</a> <!-- (podcasts, blogs?) --> <!-- TERMS OF REFERENCE USE --> <a href="thismaterial.html" title="For reference only">Terms of use</a> <a href="privacy.html" title="You can rely on us!">Privacy</a> 
995		</div>
996
997</body>
998</html>

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