(BQ) Part 2 book Cambridge international AS and A level Biology coursebook has contents: Photosynthesis, homeostasis, inherited change, selection and evolution, genetic technology, amino acid R groups,...and other contents.
Cambridge International A Level Biology 286 Chapter 13: Photosynthesis Learning outcomes You should be able to: ■■ ■■ ■■ describe the absorption of light energy in the light dependent stage of photosynthesis explain the transfer of this energy to the light independent stage of photosynthesis and its use in the production of complex organic molecules describe the role of chloroplast pigments in the absorption of light energy ■■ ■■ ■■ discuss how the structure of a chloroplast fits it for its functions explain how environmental factors influence the rate of photosynthesis describe how C4 plants are adapted for high rates of carbon fixation at high temperatures Chapter 13: Photosynthesis Fuel from algae Despite millions of hours of research, we still have not managed to set up a chemical manufacturing system that can harvest light energy and use it to make complex chemicals, in the way that plants and some protoctists So, why not just let the cells it for us? Figure 13.1 shows a photobioreactor – a series of tubes containing the single-celled photosynthetic organism Chlorella Provide light, carbon dioxide and minerals, and the cells photosynthesise Bioreactors like this are being used around the world to produce biomass for animal feed, and chemicals that can be used as food additives or in the manufacture of cosmetics They can also be used to convert energy from the Sun into ethanol or biodiesel but, so far, the bioreactors cannot produce biomass cheaply enough to compete with the use of fossil fuels Figure 13.1 A photobioreactor An energy transfer process a ribosomes As you have seen at the beginning of Chapter 12, the starch grain process of photosynthesis transfers light energy into chemical potential energy of organic molecules This energy can then be released for work in respiration (Figure 12.2) Almost all the energy transferred to all the ATP molecules in all living organisms is derived from light energy used in photosynthesis by autotrophs Such photoautotrophs include green plants, the granum photosynthetic prokaryotes and both single-celled and many-celled protoctists (including the green, red and brown algae) A few autotrophs not depend on light energy, but use chemical energy sources These b chemoautotrophs include the nitrifying bacteria that are so important in the nitrogen cycle Nitrifying bacteria obtain their energy from oxidising ammonia (NH3) to nitrite (NO2–), or nitrite to nitrate (NO3–) outer membrane inner membrane chloroplast envelope lipid droplet stroma lamella thylakoid light light thylakoid membrane An outline of the process Photosynthesis is the trapping (fixation) of carbon dioxide and its subsequent reduction to carbohydrate, using hydrogen from water It takes place inside chloroplasts (Figure 13.2) photosystem stroma primary pigment reaction centre accessory pigments thylakoid Figure 13.2 a A diagram of a chloroplast b A photosystem: a light-harvesting cluster of photosynthetic pigments in a chloroplast thylakoid membrane Only a few of the pigment molecules are shown 287 Cambridge International A Level Biology An overall equation for photosynthesis in green plants is: n CO2 + n H2O carbon dioxide water light energy in the presence of chlorophyll (CH2O)n + n O2 carbohydrate oxygen Hexose sugars and starch are commonly formed, so the following equation is often used: 6CO2 + 6H2O carbon dioxide 288 water light energy in the presence of chlorophyll C6H12O6 + O2 carbohydrate oxygen Two sets of reactions are involved These are the light dependent reactions, for which light energy is necessary, and the light independent reactions, for which light energy is not needed The light dependent reactions only take place in the presence of suitable pigments that absorb certain wavelengths of light (pages 295–296) Light energy is necessary for the splitting (photolysis) of water into hydrogen and oxygen; oxygen is a waste product Light energy is also needed to provide chemical energy, in the form of ATP, for the reduction of carbon dioxide to carbohydrate in the light independent reactions The photosynthetic pigments involved fall into two categories: primary pigments and accessory pigments The pigments are arranged in light-harvesting clusters called photosystems of which there are two types, I and II In a photosystem, several hundred accessory pigment molecules surround a primary pigment molecule, and the energy of the light absorbed by the different pigments is passed to the primary pigment (Figure 13.2b) The primary pigments are two forms of chlorophyll (pages 295–296) These primary pigments are said to act as reaction centres The light dependent reactions of photosynthesis The light dependent reactions include the splitting of water by photolysis to give hydrogen ions (protons) and the synthesis of ATP in photophosphorylation The hydrogen ions combine with a carrier molecule NADP (page 275), to make reduced NADP ATP and reduced NADP are passed from the light dependent to the light independent reactions Photophosphorylation of ADP to ATP can be cyclic or non-cyclic, depending on the pattern of electron flow in one or both types of photosystem Cyclic photophosphorylation Cyclic photophosphorylation involves only photosystem I Light is absorbed by photosystem I and is passed to the primary pigment An electron in the chlorophyll molecule is excited to a higher energy level and is emitted from the chlorophyll molecule This is called photoactivation Instead of falling back into the photosystem and losing its energy as thermal energy or as fluorescence, the excited electron is captured by an electron acceptor and passed back to a chlorophyll molecule via a chain of electron carriers During this process, enough energy is released to synthesise ATP from ADP and an inorganic phosphate group (Pi) by the process of chemiosmosis (page 270) The ATP then passes to the light independent reactions Non-cyclic photophosphorylation Non-cyclic photophosphorylation involves both photosystems in the so-called ‘Z scheme’ of electron flow (Figure 13.3) Light is absorbed by both photosystems and excited electrons are emitted from the primary pigments of both reaction centres These electrons are absorbed by electron acceptors and pass along chains of electron carriers, leaving the photosystems positively charged The primary pigment of photosystem I absorbs electrons from photosystem II Its primary pigment receives replacement electrons from the splitting (photolysis) of water As in cyclic photophosphorylation, ATP is synthesised as the electrons lose energy while passing along the carrier chain Photolysis of water Photosystem II includes a water-splitting enzyme that catalyses the breakdown of water: H2O → 2H+ + 2e− + 12 O2 Oxygen is a waste product of this process The hydrogen ions combine with electrons from photosystem I and the carrier molecule NADP to give reduced NADP 2H+ + 2e− + NADP → reduced NADP Reduced NADP passes to the light independent reactions and is used in the synthesis of carbohydrate The photolysis of water can be demonstrated by the Hill reaction The Hill reaction Redox reactions are oxidation–reduction reactions and involve the transfer of electrons from an electron donor (reducing agent) to an electron acceptor (oxidising agent) Sometimes hydrogen atoms are transferred, so that dehydrogenation is equivalent to oxidation Key flow of electrons in non-cyclic photophosphorylation flow of electrons in cyclicChapter 13: Photosynthesis photophosphorylation chains of electron carriers 2e– ADP + Pi 2e– NADP + 2H+ ATP H2O primary pigment photosystem I O2 Key 2H+ flow of electrons in non-cyclic photophosphorylation flow of electrons in cyclic photophosphorylation chains of electron carriers reduced NADP light primary pigment photosystem II increasing energy level Figure 13.3 The ‘Z scheme’ of electron flow in photophosphorylation light In 1939, Robert Hill showed that isolated chloroplasts (dichlorophenolindophenol), can substitute for the – water had ‘reducing power’ and liberated oxygen from plant’s NADP in this system (Figure 13.4) DCPIP becomes 2e in the presence of an oxidising agent The ‘reducing colourless when reduced: power’ was demonstrated by using ADP + Pi a redox agent that chloroplasts in light NADP + 2H+ oxidised DCPIP reduced DCPIP changed colour on reduction This technique can be 2e– ATP used to investigate the effect of light intensity or of light (blue) (colourless) H2O primary pigment reduced wavelength on the rate1 of photosynthesis of a suspension H2O photosystem I 2 O2 NADP O 3+ 2 of chloroplasts Hill used Fe ions as his acceptor, Figure 13.4 shows classroom results of this reaction but various redox agents, such as the blue dye DCPIP 2H+ light primary pigment BOX 13.1: Investigating the Hill reaction photosystem II blue 1.8 placed in light 1.6 Colorimeter reading / arbitrary units increasing can be isolated from a leafy plant, such as Chloroplasts energy lettuce or spinach, by liquidising the leaves in ice-cold bufferlevel and then filteringlight or centrifuging the resulting suspension to remove unwanted debris Working quickly and using chilled glassware, small tubes of buffered chloroplast suspension with added DCPIP solution are placed in different light intensities or in different wavelengths of light and the blue colour assessed at intervals The rate of loss of blue colour (as measured in a colorimeter or by matching the tubes against known concentrations of DCPIP solution) is a measure of the effect of the factor being investigated (light intensity or the wavelength of light) on chloroplast activity 1.4 Key chloroplasts in light chloroplasts in dark for five minutes, then in light 1.2 1.0 0.8 0.6 0.4 0.2 Figure 13.4 The Hill reaction Chloroplasts were extracted from lettuce and placed in buffer solution with DCPIP The colorimeter reading is proportional to the amount of DCPIP remaining unreduced colourless 10 Time / minutes 12 14 16 289 Cambridge International A Level Biology CO2 (1C) QUESTIONS 13.1 Examine the two curves shown in Figure 13.4 and explain: a the downward trend of the two curves b the differences between the two curves 13.2 Explain what contribution the discovery of the Hill reaction made to an understanding of the process of photosynthesis RuBP ribulose bisphosphate (5C) unstable intermediate (6C) Calvin cycle The light independent reactions of photosynthesis 290 The fixation of carbon dioxide is a light independent process in which carbon dioxide combines with a fivecarbon sugar, ribulose bisphosphate (RuBP), to give two molecules of a three-carbon compound, glycerate 3-phosphate (GP) (This compound is also sometimes known as PGA.) GP, in the presence of ATP and reduced NADP from the light dependent stages, is reduced to triose phosphate (TP) (three-carbon sugar) This is the point at which carbohydrate is produced in photosynthesis Most (five-sixths) of the triose phosphates are used to regenerate RuBP, but the remainder (one-sixth) are used to produce other molecules needed by the plant Some of these triose phosphates condense to become hexose phosphates which, in turn, are used to produce starch for storage, sucrose for translocation around the plant, or cellulose for making cell walls Others are converted to glycerol and fatty acids to produce lipids for cellular membranes or to acetyl coenzyme A for use in respiration or in the production of amino acids for protein synthesis This cycle of events was worked out by Calvin, Benson and Bassham between 1946 and 1953, and is usually called the Calvin cycle (Figure 13.5) The enzyme ribulose bisphosphate carboxylase (rubisco), which catalyses the combination of carbon dioxide and RuBP, is the most common enzyme in the world Chloroplast structure and function In eukaryotic organisms, the photosynthetic organelle is the chloroplast In dicotyledons, chloroplasts can be seen with a light microscope and appear as biconvex discs about 3–10 μm in diameter There may be only a few chloroplasts in a cell or as many as 100 in some palisade mesophyll cells GP × glycerate 3-phosphate reduced (3C) NADP NADP ADP ATP TP × triose phosphate (3C) ATP ADP + Pi glucose (6C), amino acids and lipids Figure 13.5 The Calvin cycle The structure of a chloroplast is shown in Figures 13.2a and 13.6 Each chloroplast is surrounded by an envelope of two phospholipid membranes A system of membranes also runs through the ground substance, or stroma The membrane system is the site of the light dependent reactions of photosynthesis It consists of a series of flattened fluid-filled sacs, or thylakoids, which in places form stacks, called grana, that are joined to one another by membranes The membranes of the grana provide a large surface area, which holds the pigments, enzymes and electron carriers needed for the light dependent reactions The membranes make it possible for a large number of pigment molecules to be arranged so that they can absorb as much light as necessary The pigment molecules are also arranged in particular light-harvesting clusters for efficient light absorption In each photosystem, the different pigments are arranged in the thylakoid in funnel-like structures (Figure 13.2, page 287) Each pigment passes energy to the next member of the cluster, finally ‘feeding’ it to the chlorophyll a reaction centre (primary pigment) The membranes of the grana hold ATP synthase and are the site of ATP synthesis by chemiosmosis (page 270) The stroma is the site of the light independent reactions. It contains the enzymes of the Calvin cycle, sugars and organic acids It bathes the membranes of the grana and so can receive the products of the light dependent reactions Also within the stroma are small (70 S) ribosomes, a loop of DNA, lipid droplets and Chapter 13: Photosynthesis Rate of photosynthesis photosynthesis varies with the light intensity, initially increasing as the light intensity increases (Figure 13.7) However, at higher light intensities, this relationship no longer holds and the rate of photosynthesis reaches a plateau starch grains The loop of DNA codes for some of the chloroplast proteins, which are made by the chloroplast’s ribosomes However, other chloroplast proteins are coded for by the DNA in the plant cell nucleus QUESTION 13.3 List the features of a chloroplast that aid photosynthesis Factors necessary for photosynthesis You can see from the equation on page 288 that certain factors are necessary for photosynthesis to occur, namely the presence of a suitable photosynthetic pigment, a supply of carbon dioxide, water and light energy Light intensity Figure 13.7 The rate of photosynthesis at different light intensities and constant temperature The effect on the rate of photosynthesis of varying the temperature at constant light intensities can be seen in Figure 13.8 At high light intensity the rate of photosynthesis increases as the temperature is increased over a limited range At low light intensity, increasing the temperature has little effect on the rate of photosynthesis Rate of photosynthesis Figure 13.6 Transmission electron micrograph of a chloroplast from Potamogeton leaf (× 27 000) See also Figure 1.29 high light intensity Factors affecting the rate of photosynthesis The main external factors affecting the rate of photosynthesis are light intensity and wavelength, temperature and carbon dioxide concentration In the early 1900s, F F Blackman investigated the effects of light intensity and temperature on the rate of photosynthesis At constant temperature, the rate of 291 low light intensity 10 15 Temperature / °C 20 Figure 13.8 The rate of photosynthesis at different temperatures and constant light intensities 25 Cambridge International A Level Biology These two experiments illustrate two important points Firstly, from other research we know that photochemical reactions are not generally affected by temperature However, these experiments clearly show that temperature affects the rate of photosynthesis, so there must be two sets of reactions in the full process of photosynthesis These are a light dependent photochemical stage and a light independent, temperature dependent stage Secondly, Blackman’s experiments illustrate the concept of limiting factors Limiting factors experiment 25 °C; 0.4% CO2 Rate of photosynthesis 292 The rate of any process which depends on a series of reactions is limited by the slowest reaction in the series In biochemistry, if a process is affected by more than one factor, the rate will be limited by the factor which is nearest its lowest value Look at Figure 13.9 At low light intensities, the limiting factor governing the rate of photosynthesis is the light intensity; as the intensities increase so does the rate But at high light intensity, one or more other factors must be limiting, such as temperature or carbon dioxide supply As you will see in the next section of this chapter, not all wavelengths of light can be used in photosynthesis This means that the wavelengths of light that reach a plant’s leaves may limit its rate of photosynthesis (Figure 13.16b, page 295) experiment 25 °C; 0.04% CO2 experiment 15 °C; 0.04% CO2 Light intensity Figure 13.9 The rate of photosynthesis at different temperatures and different carbon dioxide concentrations (0.04% CO2 is about atmospheric concentration.) QUESTION 13.4 Examine Figure 13.9, which shows the effect of various factors on the rate of photosynthesis, and explain the differences between the results of: a experiments and b experiments and At constant light intensity and temperature, the rate of photosynthesis initially increases with an increasing concentration of carbon dioxide, but again reaches a plateau at higher concentrations A graph of the rate of photosynthesis at different concentrations of carbon dioxide has the same shape as that for different light intensities (Figure 13.9) At low concentrations of carbon dioxide, the supply of carbon dioxide is the rate-limiting factor At higher concentrations of carbon dioxide, other factors are rate-limiting, such as light intensity or temperature The effects of these limiting factors on the rate of photosynthesis are easily investigated by using an aquatic plant such as Elodea or Cabomba in a simple apparatus as shown in Figure 13.10 The number of bubbles of gas (mostly oxygen) produced in unit time from a cut stem of the plant can be counted in different conditions Alternatively, the gas can be collected and the volume produced in unit time can be measured This procedure depends on the fact that the rate of production of oxygen is a measure of the rate of photosynthesis Growing plants in protected environments An understanding of the effect of environmental factors on the rate of photosynthesis allows their management when crops are grown in protected environments, such as glasshouses The aim is to increase the yield of the crop concerned For example, many hectares of tomato plants are grown in glasshouses In the most sophisticated of these, sensors monitor the light intensity, the humidity of the atmosphere and the concentration of carbon dioxide around the plants The plants grow hydroponically – that is, with their roots in a nutrient solution whose nutrient content can be varied at different stages of the plants’ growth All of these factors are managed by a computer to maximise the yield of the crop Such glasshouse-grown crops have the added advantage that insect pests and fungal diseases are more easily controlled than is possible with field-grown crops, further improving yield Chapter 13: Photosynthesis BOX 13.2: Investigating the rate of photosynthesis using an aquatic plant Elodea, or other similar aquatic plants, can be used to investigate the effect on the rate of photosynthesis of altering the: ■■ ■■ ■■ ■■ light intensity – by altering the distance, d, of a small light source from the plants (light intensity is proportional to ) d wavelength of light – by using different colour filters, making sure that they each transmit the same light intensity concentration of carbon dioxide – by adding different quantities of sodium hydrogencarbonate (NaHCO3) to the water surrounding the plant temperature of the water surrounding the plant – using a large container, such as a beaker, to help maintain the chosen temperatures The aquatic plant needs to be well illuminated before use and the chosen stem needs to be cut cleanly just before putting it into a test tube (Figure 13.10) The bubbles given off are mostly oxygen, but contain some nitrogen To prevent these gases from dissolving in the water, rather than forming bubbles, the water needs to be well aerated (by bubbling air through it) before use 293 Figure 13.10 Investigating the rate of photosynthesis using an aquatic plant C4 plants In the light independent stage of photosynthesis, you may remember that carbon dioxide combines with RuBP to form a six-carbon compound, which immediately splits to form two three-carbon molecules (page 290) Plants that this are called C3 plants However, maize and sorghum plants – and most other tropical grasses – something different The first compound that is produced in the light independent reaction contains four carbon atoms They are therefore called C4 plants Avoiding photorespiration Why tropical grasses need to something different from other plants in the light independent stage of photosynthesis? The reason is a problem with the enzyme rubisco This enzyme catalyses the reaction of carbon dioxide with RuBP But, unfortunately, it can also catalyse the reaction of oxygen with RuBP When this happens, less photosynthesis takes place, because some of the RuBP is being ‘wasted’ and less is available to combine with carbon dioxide This unwanted reaction is known as photorespiration It happens most readily in high temperatures and high light intensity – that is, conditions that are found at low altitudes in tropical parts of the world Tropical grasses such as maize, sorghum and sugar cane have evolved a method of avoiding photorespiration They keep RuBP and rubisco well away from high oxygen concentrations The cells that contain RuBP and rubisco are arranged around the vascular bundles, and are called bundle sheath cells (Figures 13.11, 13.12 and 13.13) They have no direct contact with the air inside the leaf Carbon dioxide is absorbed by another group of cells, the mesophyll cells, which are in contact with air (Figure 13.13) The mesophyll cells contain an enzyme called PEP carboxylase, which catalyses the combination of carbon dioxide from the air with a three-carbon substance called phosphoenolpyruvate, or PEP The compound formed from this reaction is oxaloacetate (Figure 13.14) Cambridge International A Level Biology Still inside the mesophyll cells, the oxaloacetate is converted to malate, and this is passed on to the bundle sheath cells Now the carbon dioxide is removed from the malate molecules and delivered to RuBP by rubisco in the normal way The light independent reaction then proceeds as usual Enzymes in C4 plants generally have higher optimum temperatures than those in C3 plants This is an adaptation to growing in hot climates For example, in one study it was found that in amaranth, which is a C4 plant, the optimum temperature for the activity of PEP carboxylase is around 45 °C If the temperature drops to 15 °C, the enzyme loses around 70% of its activity By contrast, the same enzyme in peas, which are C3 plants, was found to have an optimum temperature of around 30 °C and could continue to work at much lower temperatures than in amaranth light Figure 13.11 Photomicrograph of a section through a leaf of maize (× 125) carbon dioxide photosynthesis in ring of mesophyll cells PEP C3 oxaloacetate light C4 dependent reactions malate C4 pyruvate C3 carbon dioxide 294 photosynthesis in bundle sheath cells Calvin cycle sugars Figure 13.12 Photomicrograph of a section through a leaf of sugar cane (× 120) Figure 13.14 C4 photosynthesis upper epidermis mesophyll lower epidermis Figure 13.13 Tissues surrounding a vascular bundle of a C4 leaf ring of mesophyll cells This tight ring of specialised mesophyll cells excludes air from the cells inside the ring The cytoplasm fixes carbon dioxide The chloroplasts capture light and carry out the light dependent reactions but not the Calvin cycle bundle sheath cells The bundle sheath cells carry out the Calvin cycle but not the light dependent reactions No air gets to these cells, and they get carbon dioxide from the mesophyll cells Chapter 13: Photosynthesis Trapping light energy Chloroplasts contain several different pigments, and these different pigments absorb different wavelengths of light The photosynthetic pigments of higher plants form two groups: the chlorophylls (primary pigments) and the carotenoids (accessory pigments) (Table 13.1) Group Pigment Colour chlorophylls chlorophyll a chlorophyll b yellow-green blue-green carotenoids β carotene xanthophyll orange yellow Table 13.1 The colours of the commonly occurring photosynthetic pigments Chlorophylls absorb mainly in the red and blueviolet regions of the light spectrum They reflect green light, which is why plants look green The structure of chlorophyll a is shown in Figure 13.15 The carotenoids absorb mainly in the blue-violet region of the spectrum CH2 H3C chlorophyll a N CH2 N carotenoids 400 450 b 500 550 600 Wavelength of light / nm 650 700 295 CH3 400 450 Mg N CH3 (CH2)2 C OC O O CH2 CH3 O O CH C CH3 (CH2)3 CH CH3 (CH2)3 CH CH3 (CH2)3 CH 500 550 600 Wavelength of light / nm 650 700 N H3C tail chlorophyll b CH3 CH head a Absorbance 13.5 Some of the most productive crop plants in the world are C4 plants However, rice grows in tropical regions and is a C3 plant Research is taking place into the possibility of producing genetically modified rice that uses the C4 pathway in photosynthesis Explain how this could increase yields from rice An absorption spectrum is a graph of the absorbance of different wavelengths of light by a pigment (Figure 13.16a) An action spectrum is a graph of the rate of photosynthesis at different wavelengths of light (Figure 13.16b) This shows the effectiveness of the different wavelengths, which is, of course, related to their absorption and to their energy content The shorter the wavelength, the greater the energy it contains Rate of photosynthesis QUESTION CH3 CH3 Figure 13.15 Structure of chlorophyll a You not need to learn this molecular structure Figure 13.16 a Absorption spectra of chlorophylls a and b, and carotenoid pigments b Photosynthetic action spectrum QUESTION 13.6 Compare the absorption spectra shown in Figure 13.16a with the action spectrum shown in Figure 13.16b a Identify and explain any similarities in the absorption and action spectra b Identify and explain any differences between the absorption and action spectra Cambridge International AS Level Biology Recommended resources Chapter Further reading Prior, R (2013) Circulatory System (Kindle edition) Prior Educational Resources This is a Kindle edition It’s an interactive book, describing the structure and function of the human cardiovascular system, including questions (Note that the content only partially matches the content in the Cambridge syllabus.) Online and interactive resources www.nhlbi.nih.gov/health/health-topics/topics/hhw/ Clear descriptions and diagrams of structure and function of the human heart http://library.med.utah.edu/WebPath/CVHTML/CVIDX.html Photographs and micrographs of the heart, and heart diseases www.fi.edu/learn/heart/vessels/vessels.html Information about blood vessels www.fi.edu/learn/heart/blood/blood.html Information about blood www.histologyguide.org/About_Us/About_Us.html Histology Guide is an interactive site for histology www.histologyguide.org/EM_Atlas/09_Cardiovascular_System.html For the structure of blood vessels http://news.nationalgeographic.co.uk/news/2004/02/0224_040225_evolution.html Information on adaptations to high altitude www.abpischools.org.uk This website from the Association of British Pharmaceutical Societies (ABPI) is good for notes on heart and circulation It includes a glossary, questions and animations Video www.youtube.com/watch?v=H04d3rJCLCE A clear (though fairly basic) overview of heart structure and function, including the roles of the SAN and AVN www.youtube.com/watch?v=kcWNjt77uHc A description of the cardiac cycle Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International AS Level Biology Recommended resources Chapter Further reading www.ash.org.uk Action on Smoking and Health (ASH), based in the UK, has several fact sheets on the effects of smoking For example: fact sheets on Smoking and respiratory disease, and Smoking and cancer Online and interactive resources There are many websites devoted to histology Simply search for ‘Lung histology’ and look through some images www.ash.org.uk/information/resources/visual-resources Visual resources from ASH www.lung.org The American Lung Foundation website Look at the two areas of the website headed Your lungs and Lung disease www.courseweb.uottawa.ca/medicine-histology/english/respiratory This site explains what is visible in sections of trachea, bronchi and lungs www.gwc.maricopa.edu/class/bio202/Respiratory/NormalA.htm www.histologyguide.org/About_Us/About_Us.html www.histologyguide.org/Slide_Box/17_Respiratory_System.html Histology Guide is an interactive site for histology, with a page on the respiratory system www.who.int/mediacentre/factsheets/fs339/en www.who.int/tobacco/en/index.html www.who.int/tobacco/research/youth/health_effects/en A sample of World Health Organization (WHO) publications on smoking www.cdc.gov/tobacco/data_statistics/fact_sheets/fast_facts/ Centers for Disease Control and Prevention (CDC) web pages on smoking Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International AS Level Biology Recommended resources Chapter 10 Online and interactive resources www.rcsb.org/pdb/education_discussion/educational_resources This website has an informative downloadable poster on The structural biology of HIV, showing a painting of the HIV virus surrounded by the structures of its constituent molecules taken from the Protein Data Bank There is also a poster entitled How drugs work? which includes information about antibiotics and antiviral drugs www.abpischools.org.uk Resources for schools produced by the Association of British Pharmaceutical Industries (ABPI) Resources include material on Infectious diseases, covering immunity, medicines and pathogens www.who.int/topics/tuberculosis/en/ www.who.int/topics/cholera/en/ www.who.int/topics/malaria/en/ www.who.int/hiv/en/ www.who.int/topics/measles/en/ www.who.int/csr/disease/smallpox/en/ Information from the World Health Organization (WHO) on each of the diseases covered in Chapter 10 In each case, look at the Fact sheet on the disease first before exploring other resources from the WHO www.healthmap.org/en/ An interactive online resource that provides lots of information about the geographical spread of diseases www.map.ox.ac.uk The Malaria Atlas Project has lots of online resources based on the geographical spread of malaria www.hpa.org.uk/webw/HPAweb&HPAwebStandard/HPAweb_C/1317136987072 Top ten facts about antibiotics and antibiotic resistance www.avert.org/ www.avert.org/about-avert.htm AVERT is an international HIV and AIDS charity, based in the UK, working to avert HIV and AIDS worldwide, through education, treatment and care Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International AS Level Biology Recommended resources Chapter 11 Further reading Playfair, J (2004) Living with Germs: In Sickness and in Health Oxford University Press; Kindle edition, 2007 Online and interactive resources www.who.int/topics/immunization/en/ Information about immunisation from the World Health Organization (WHO) www.who.int/features/2010/smallpox/en/ A WHO article on the smallpox eradication programme www.who.int/topics/poliomyelitis/en/ Information about polio www.unicef.org/india/health_3729.htm Polio eradication in India www.nhs.uk/conditions/Myasthenia-gravis/Pages/Introduction.aspx Information about myasthenia gravis Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International AS Level Biology Recommended resources Chapter P1 Further reading Fosbery, R (2012) OCR AS/A2 Biology Student Unit Guide: Practical Skills in Biology Philip Allan Available as a Kindle edition, or as a paperback book Boyle, M (2014) Science Skills – A Level Biology Collins Educational Available as a Kindle edition, or as a paperback book Cadogan, A and Ingram, M (2002) Maths for Advanced Biology Nelson Thornes Penny, J (2013) Maths Skills for Biology A Level Nelson Thornes Online and interactive resources www.gettingpractical.org.uk/documents/LoMsampleJan2010.pdf The Language of Measurement: terminology used in school science investigations A free pdf available from the link above, or the complete book is available to order from www.ase.org.uk/ bookshop/books-for-practical-work/ www.nuffieldfoundation.org/practical-physics/language-measurements A language for measurements: written for physics students, but equally applicable for biology www.theseashore.org.uk/theseashore/Stats%20for%20twits/Different%20kinds%20of%20data.html Clear advice about collecting and handling data from the Field Studies Council: here is a simple description of the different types of data (interval, ordinal and so on) www.theseashore.org.uk/theseashore/Stats%20for%20twits/Additional%20Material/MeansMedians htm Information from the Field Studies Council on the different kinds of averages www.theseashore.org.uk/theseashore/Stats%20for%20twits/How%20big%20a%20sample.html Advice about sample size from the Field Studies Council Other resources www.heckgrammar.co.uk/index.php?p=10310 Merlin Statistics Software: an add-in for Microsoft Excel developed by an A level biology teacher Merlin adds over 30 new functions and six charts to Excel’s existing capabilities Accompanied by a comprehensive booklet to using descriptive statistics and statistical tests in A level biology Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International A Level Biology Recommended resources Chapter 12 Further reading Alberts, B et al (2013) Essential Cell Biology, 4th edn Garland Science ■■ Chapter 13: ‘How Cells Obtain Energy from Food’ including ‘Glycolysis’ and ‘Citric acid cycle’, step‑by-step accounts of these two processes showing animated details of the chemical reactions ■■ Chapter 14: ‘Energy Generation in Mitochondria and Chloroplasts’ including ‘Electron transport chain’, an animated series of diagrams showing structural features of the electron transport chain ‘ATP Synthase – A Molecular Turbine’ is a stunning realistic animation showing this beautiful minimachine in operation Available at: www.garlandscience.com/ECB4-students Jones, M and Jones, G (1997) Advanced Biology Cambridge University Press Elliot, W.H and Elliot, D (2009) Biochemistry and Molecular Biology, 4th edn Oxford University Press Alberts, B et al (2002) Molecular Biology of the Cell, 5th edn Garland Science These biochemistry textbooks are very accessible Online and interactive resources www.rcsb.org/pdb/education_discussion/educational_resources/citric_acid_cycle.pdf A poster available to download on the citric acid cycle (Krebs cycle) showing three-dimensional models of the molecules involved plus summaries of all the reactions www.johnkyrk.com/glycolysis.html www.johnkyrk.com/krebs.html www.johnkyrk.com/mitochondrion.html These animations of respiration are to be found on John Kyrk’s website Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International A Level Biology Recommended resources Chapter 13 Further reading Alberts, B et al (2013) Essential Cell Biology, 4th edn Garland Science ■■ Chapter 14: ‘Energy Generation in Mitochondria and Chloroplasts’ including the animation ‘Light harvesting’, which deals with the structure and function of chloroplasts; other animations show the effects of light on chlorophyll and the subsequent flow of electrons, including the splitting of water, the role of photosystems and the electron transport chains Available at: www.garlandscience.com/ECB4-students Jones, M and Jones, G (1997) Advanced Biology Cambridge University Press Elliot, W.H and Elliot, D (2009) Biochemistry and Molecular Biology, 4th ed Oxford University Press Lea, P and Leegood, R (1994) Plant Biochemistry and Molecular Biology John Wiley & Sons Online and interactive resources www.mhhe.com/biosci/bio_animations/02_MH_Photosynthesis_Web/index.html This is an animation about photosynthesis The three animations that follow can be accessed from here: highered.mcgraw-hill.com/sites/0073532223/student_view0/chapter8/animations_and_videos.html Look for: ‘Photosynthetic electron transport and ATP synthesis’, ‘Cyclic and non-cyclic photophosphorylation’ and ‘How the Calvin cycle works’ www.johnkyrk.com/photosynthesis.html www.johnkyrk.com/photosynthesisdark.html There are animations of photosynthesis on John Kyrk’s website Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International A Level Biology Recommended resources Chapter 14 Further reading Ashcroft, F (2001) Life at the Extremes Flamingo Online and interactive resources highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter20/ This link has animations on endocrine communication, blood sugar control and negative and positive feedback control of the menstrual cycle Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International A Level Biology Recommended resources Chapter 15 Further reading Alberts, B et al (2013) Essential Cell Biology, 4th edn Garland Science + + ■■ Chapter 12 ‘Transport Across Cell Membranes’ including ‘Na /K pump’ and ‘Action potentials’, which are useful animations giving an understanding of the dynamics of processes that are harder to understand from single diagrams ‘Synaptic signalling’ shows electron micrographs of synapses and very clear animations of the release of neurotransmitters and the consequences at a synapse Available at: www.garlandscience.com/ECB4-students Cole, J (1995) Pride and the Daily Marathon MIT Press This is a book about a man who completely lost proprioception It is written by his doctor, Jonathan Cole, a consultant in clinical neurophysiology Sacks, O (2011) The Man Who Mistook His Wife for a Hat Picador; first published in 1985 Oliver Sacks is probably the most famous neurologist in the world In this book he describes people with various neurological disorders, including ‘The Disembodied Lady’ This is a beautifully written book that never fails to spark an interest in the world where biology meets psychology Online and interactive resources www.abpischools.org.uk This site has notes on the nervous system highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation the_nerve_ impulse.html This site has an animation on nerve impulses highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation chemical_ synapse quiz_1_.html This site has an animation on synapses Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International A Level Biology Recommended resources Chapter 16 Further reading Gregory, J (2000) Applications of Genetics Cambridge University Press Hickey, I et al (eds) (2007) BIOS Instant Notes, Genetics, 3rd edn Taylor and Francis Lewin, B (2007) Genes IX Oxford University Press To be consulted when in doubt! Ridley, M (2000) Genome Fourth Estate Read this book Online and interactive resources www.hhmi.org/biointeractive BioInteractive is a free resource for teachers and students, including animations, short films and apps (HHMI in the web address refers to the Howard Hughes Medical Institute.) www.hhmi.org/biointeractive/regulation-eukaryotic-dna-transcription This has an animation of transcription and its regulation www.hhmi.org/biointeractive/sickle-cell-anemia This animation describes the effects of the disease sickle cell anaemia on red blood cells, the mutation responsible and the consequent change to haemoglobin www.dnai.org Many resources on DNA; see also the recommended resources for Chapter www.johnkyrk.com/meiosis.html There is an animation of meiosis on John Kyrk’s website Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International A Level Biology Recommended resources Chapter 17 Further reading Read The Voyage of the Beagle by Charles Darwin to see how this voyage stimulated thoughts about evolution There is an abridged edition in the Penguin Classics series, published 1989 There are also illustrated editions available, and a Kindle edition: Darwin, C (2012) A Naturalist’s Voyage Round the World: The Voyage of the Beagle Balefire Publishing Or read about Darwin and Wallace: Desmond, A and Moore, J (1991) Darwin Michael Joseph Keynes, R (2001) Creation John Murray Keynes is a great-grandson of Charles Darwin Raby, P (2001) Alfred Russel Wallace a Life Chatto and Windus Or read about natural selection and evolution: Larsen, E (2001) Evolution’s Workshop Basic Books Lane, N (2009) Life Ascending Profile Books Jones, S (2000) Almost like a Whale Black Swan Dawkins, R (1989) The Selfish Gene, 2nd edn Oxford Paperbacks Dawkins, R (2006) The Blind Watchmaker, 2nd edn Penguin Books Bell, M et al (eds) (2010) Evolution since Darwin Sinauer Associates Online and interactive resources darwin-online.org.uk For everything Darwin wrote www.sciberbrain.org www.sciberbrain.org/advanced-level The Biochemical Society has set up a special website for education There is an advanced-level animated presentation on evolution A lower-level presentation (standard level) is also available www.hhmi.org/biointeractive BioInteractive is a free resource for teachers and students, including animations, short films and apps (HHMI in the web address refers to the Howard Hughes Medical Institute.) www.hhmi.org/biointeractive/origin-species This features a series of three short films, total running time 65 min, on evolution The films are downloadable and also available on a DVD The overall title is The Origin of Species and the three subtitles are: ■■ ‘The Making of a Theory’ The epic voyages and revolutionary insights of Charles Darwin and Alfred Russel Wallace ■■ ‘The Beak of the Finch’ An examination of 40 years of research into the Galapagos finches providing clues as to how 13 distinct finch species arose from a single ancestral population ■■ ‘Lizards in an Evolutionary Tree’ Examples of adaptive radiation, reproductive isolation and the formation of new species among the Caribbean islands Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International A Level Biology www.hhmi.org/biointeractive/animated-life-ar-wallace This is an amusingly presented, animated cartoon video telling the story of Alfred Russel Wallace It tracks his life and legacy and is an opportunity to correct his frequent omission from history www.wellcometreeoflife.org/video The Tree of Life is an interactive resource developed by the Wellcome Trust, with texts and images exploring the evolutionary links between living things The accompanying video was shown as part of ‘Charles Darwin and the Tree of Life’ broadcast by the BBC in February 2009 Narrated by Sir David Attenborough, it can be downloaded or a DVD can be purchased from the BBC Shop www.johnkyrk.com/evolution.html John Kyrk has an animated timeline of the history of the Earth on his website Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International A Level Biology Recommended resources Chapter 18 Further reading The End of the Line Charles Clover Ebury Press; 2005 978-0091897819 This excellent book details the threats of fishing to the marine environment Online and interactive resources www.csiro.au This is the website of the Commonwealth Scientific and Industrial Research Organisation in Australia CSIRO provides educational resources, particularly on environmental issues With its unique flora and fauna Australia has a particularly strong interest in conservation issues The website section on ‘Biodiversity and Environment’ includes many videos, for example on climate change science, coral reef ecology and conservation www.mongabay.com Mongabay: for information about environmental issues and conservation This has a lot of information about threats to biodiversity www.wwf.org.uk World Wide Fund for Nature (WWF) www.cites.org Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) www.sandiegozooglobal.org San Diego Zoo Global is an international conservation organization Look at the section on San Diego’s frozen zoo www.kew.org Read about the scientific and conservation work of the Royal Botanic Gardens at Kew www.kew.org/science-conservation/save-seed-prosper/millennium-seed-bank/index.htm The Millennium Seed Bank Video BBC DVD ‘The Truth About Climate Change’ is a classic two-part documentary, released in 2008, narrated by Sir David Attenborough BBC DVD ‘State of The Planet’ is another classic documentary narrated by Sir David Attenborough, released in 2004 Worksheets and practicals www.linnean.org/Education+Resources/Secondary_Resources Worksheets on taxonomy and classification (‘What’s in a name’; ‘Who are you?’; ‘Who’s who?’) There are student and teacher versions, the latter with mark schemes Posters are also available A simple laboratory-based practical, ‘How Rich Is Your Habitat?’, is available It uses a simple and convenient model of the real environment in order to understand the principles of random sampling and how to estimate biodiversity It includes use of Simpson’s Diversity Index Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International A Level Biology Recommended resources Chapter 19 Further reading Alberts, B et al (2013) Essential Cell Biology, 4th edn Garland Science ■■ Chapter 10: ‘Modern Recombinant DNA Technology’ including ‘Polymerase chain reaction’, a clear animation Available at: www.garlandscience.com/ECB4-students Brown, T.A (2007) Genomes Garland Science See the topics in the section ‘Classical Genetics’ Online and interactive resources www.sciberbrain.org www.sciberbrain.org/advanced-level The Biochemical Society has set up a special website for education There is an advanced-level animated presentation on genetic engineering A lower-level presentation (standard level) is also available for a gentler introduction www.hhmi.org/biointeractive BioInteractive is a free resource for teachers and students, including animations, short films and apps (HHMI in the web address refers to the Howard Hughes Medical Institute.) www.hhmi.org/biointeractive/polymerase-chain-reaction This is a step-by-step animation explaining the polymerase chain reaction www.hhmi.org/biointeractive/genetic-engineering An animation showing how a new gene can be inserted into a loop of bacterial DNA (a plasmid) A restriction enzyme is shown cutting the DNA, allowing a new piece of DNA to be inserted www.hhmi.org/biointeractive/human-genome-sequencing An animation outlining the principles adopted when trying to sequence the human genome www.abpischools.org.uk/object/download.cfm?lib=liPoster&id=409 This site contains notes on genetic engineering, including a clear and attractive downloadable poster ‘Genetic Engineering – New Horizons in Medicine’ There is also a poster on the human genome project These posters are part of a useful series entitled ‘New Horizons in Medicine’ www.dnalc.org/resources/animations/index.html The DNA Learning Centre at the Cold Spring Harbor Laboratory has many animations on the topics covered in this chapter www.dnaftb.org/ There are many resources to support topics in this chapter in the section in another website from Cold Spring Harbor: DNA from the Beginning www.dnai.org See the sections on ‘Manipulation’ and ‘Applications’ Cambridge International AS and A Level Biology © Cambridge University Press 2014 Cambridge International A Level Biology Recommended resources Chapter P2 Further reading Fosbery, R (2012) OCR AS/A2 Biology Student Unit Guide: Practical Skills in Biology Philip Allan Available as a Kindle edition, or as a paperback book Boyle, M (2014) Science Skills – A Level Biology Collins Educational Available as a Kindle edition, or as a paperback book Cadogan, A and Ingram, M (2002) Maths for Advanced Biology Nelson Thornes Online and interactive resources www.gettingpractical.org.uk/documents/LoMsampleJan2010.pdf The Language of Measurement: terminology used in school science investigations A free pdf available from the link above, or the complete book is available to order from www.ase.org.uk/ bookshop/books-for-practical-work/ www.nuffieldfoundation.org/practical-physics/language-measurements A language for measurements: written for physics students, but equally applicable for biology www.theseashore.org.uk/theseashore/Stats%20for%20twits/Different%20kinds%20of%20data.html Clear advice about collecting and handling data from the Field Studies Council: here is a simple description of the different types of data (interval, ordinal and so on) www.theseashore.org.uk/theseashore/Stats%20for%20twits/Hyptesting%20stats%20format.html Information from the Field Studies Council on hypotheses and null hypotheses www.theseashore.org.uk/theseashore/Stats%20for%20twits/Additional%20Material/SDeviation htm www.theseashore.org.uk/theseashore/Stats%20for%20twits/Additional%20Material/SError.htm Advice about standard deviation and standard error Other resources www.heckgrammar.co.uk/index.php?p=10310 Merlin Statistics Software: an add-in for Microsoft Excel developed by an A level biology teacher Merlin adds over 30 new functions and six charts to Excel’s existing capabilities Accompanied by a comprehensive booklet to using descriptive statistics and statistical tests in A level biology Cambridge International AS and A Level Biology © Cambridge University Press 2014 ... 13.16b a Identify and explain any similarities in the absorption and action spectra b Identify and explain any differences between the absorption and action spectra Cambridge International A Level. .. storage a R NH2 C R COOH H amino acid –2H + H2O C O NH3 b 2NH3 + CO2 CO(NH2 )2 + H2O urea Figure 14.4 a Deamination and b urea formation Ammonia is a very soluble and highly toxic compound In many aquatic... these capillaries has come directly from the glomerulus, so it has much less plasma in it than usual and has lost much of its water and many of the ions and other small solutes The basal membranes