This a collection of Scientific posters completed by A Level Students at South Bromsgrove High School in 2006. They have used the templates and layout advice from http://www.swarthmore.edu/NatSci/cpurrin1/posteradvice.htm

1. Biological Molecules Carbohydrates Carbohydrates include sugars, starch, glycogen and cellulose. There are Monosaccharides disaccharides and polysaccharides. Monosaccharides consist of 3 separate groups trioses pentoses and hexose's. These are all types of soluble reducing sugars with the exception of sucrose. Disaccharides are carbohydrates whose molecules are made of two monosaccharides linked together. E.g., glucose + glucose = maltose. An example of a hexose (6carbons) molecule, (Glucose) in alpha (right) and beta (left) form. These ring forms are produced when a bond forms between the oxygen attached to carbon 5 and carbon 1. An example of a disaccharide below in a condensation reaction Aldehydes and ketones Aldehydes are reducing agents. This means that aldose sugars are reducing agents, and are called reducing sugars. When a reducing agent reduces anotehr compound, the reducing agent is oxidised. Ketose sugars are not reducing agents but they react to form reducing agents in alkaline conditions used to test for reducing sugars. This means that Ketoses such as fructose are not as strong reducing agents as aldoses such as glucose. All monosaccharides as shown above are either aldoses or ketoses, this also applies to most disaccharides. Sucrose is the only exception. Proteins Proteins are polymers who's molecules are made from many amino acid molecules linked together. Examples of proteins can be seen in the form of enzymes, antibodies and haemoglobin. 3 groups Amino group – NH2 Carboxyl group – COOH R group – always different determining the amino acid. Protein Structure Primary Structure - Sequence of amino acids in a polypeptide chain. Secondary Structure - Repeating three dimensional structure of the polypeptide backbone. The two common structures are alpha helix and beta strand. Tertiary structure - the chain. The three dimensional shape of the polypeptide chain. Quaternary structure - Many proteins or more polypeptide chains are bonded to make a complete molecules. Disulphide links and hydrogen bonds hold the chains together. Phospholipids have a similar structure to triglycerides, but with a phosphate group in place of one fatty acid chain. There may also be other groups attached to the phosphate. Phospholipids have a polar hydrophilic "head" (the negatively-charged phosphate group) and two non-polar hydrophobic "tails" (the fatty acid chains). As shown below Triglycerides Triglyceride molecules are made from one molecule of glycerol linked to three fatty acids, glycerol is an alcohol. Fatty acids are organic acids also called carboxylic acids and always have a COOH group. By condensation this group combines with the - OH group of a glycerol molecule forming an Ester bond. Triglycerides functions are storage molecules, long chains of fat can be broken down for energy. Bonds Proteins – Hydrogen form between groups with dipoles (unevenly charged molecules). Ionic bonds forms between groups with opposite charges, disulphide links form between cysteine side chains. Peptide bonds join 2 peptides to make a dipeptide or more to make a poly peptide Carbohydrates – Glycosidic bonds covalent and formed between c1 and c4, (1 – 4) bond. Phospholipids and triglycerides are joined by ester bonds. A saturated fatty acid contains only single bonds between carbons. Unsaturated contain one or more double bonds between carbon atoms.

5. Introduction Organisms are made of a huge variety of compounds. The main organic compounds are carbohydrates, proteins, lipids, and nucleic acids. I will write about these first three groups. The molecules of these groups are mainly made of Carbon, Oxygen and Hydrogen. There are many different lipids, proteins and carbohydrates, they are all made of a small number of simpler molecules joined together. The joining of these smaller molecules happens in a condensation reaction. In which H 2 O is produced. And the opposite can happen by adding water, this is called hydrolysis and is used to break large molecules into smaller ones. E.g. a disaccharide into two monosaccharides. But the first subject topic is lipids. Lipids Lipids are fats, oils and waxes. They are insoluble in water, this is because they have no dipoles and so no charges to attract water molecules. Lipids are made of Carbon oxygen and hydrogen. Most lipids are composed of compounds called triglycerides . Triglycerides are a glycerol bonded to three fatty acid chains. (see fig. 1) They are made from a special type of condensation reaction, called esterfication. Which forms ester bonds between the glycerol and fatty acid. (see fig. 2) Fig. 1 Carbohydrates Carbohydrates are separated into three categories. Monosaccharides - one, single sugar Disaccharides - two, double sugar Polysaccharides - many, multiple sugars. And sugars are separated into reducing sugars, and non-reducing sugars. Reducing sugars can donate electrons to other molecules, all monosaccharides, and some disaccharides are reducing sugars. The Most common monosaccharide is glucose. There are two types of glucose, alpha (  and beta (  .  Glucose is a hexose sugar, because it has a structure like a hexagon (see fig.3). The difference between Alpha and Beta glucose is the 1 st and 4 th carbons. Fig. 3 Chromatography Chromatography is used to separate, then identify the individual chemicals in a mixture. It works by drawing a line on a piece of chromatography paper (in pencil, because ink would run) called the origin. Then dropping a very small amount of liquid onto the origin. You then allow this spot to dry, then repeat the process about 4times, until you have a concentrated spot on the origin line. (see fig. 7) You then put the piece of paper into a solvent, but ensure the line of origin is above the solvent line. Fig. 7 Biological Molecules Holly Stockham Biochemical tests There are tests that you can do to find out what a substance contains. These tests are below: Starch. Adding Iodine to the solution, if it turns blue/black it contains starch. Protein. By adding biurets solution and heating up the solution gently you can see if it contains protein. A positive result would turn the solution lilac. Lipids. You do the emulsion test, which is adding ethanol, shaking, then adding the solution to water. It is called the emulsion test because if the solution contains lipids a white emulsion will be formed. Reducing sugars. Add Benedicts solution, then heat up to near boiling pt. the colour will go from Blue to green to yellow to orange to red . Depending how much reducing sugar it contains. (red containing the most reducing sugar.) Non-reducing sugars. First you must add it to dilute HCL, which hydrolyses the non-reducing sugars to reducing sugars. Then it must be neutralised with NaHCO 3 , then there should be a positive result from the benedicts test (as above) References Advanced Biology by Jones and Jones. CGP AS-level Biology Collins AQA AS Biology Biology toolbox CD Proteins Proteins are made from long chains of amino acids. (see fig. 5) And like lipids and carbohydrates, they are formed by condensation reactions, and broken down by hydrolysis. But the bonds between the amino acids, making the proteins are called peptide bonds (see Fig. 6). Fig.5 An amino acid Fig. 6 Solvent front origin Spot of pigment The chemicals can then be identified comparing Rf values to a table of already known Rf values. The Rf value is calculated by this formula: Rf value = Distance from origin to top of spot Distance from origin to solvent front (Note: The Rf Value will be between 0 and 1.) But sometime the solvent doesn’t completely separate out all the chemicals properly, so you need to do two way chromatography . Where you turn the paper 90 o and place it into another solvent. Which should completely separate out the chemicals. glycerol Fatty acid chain Fig. 2 Ester bonds triglyceride Fatty acids can be saturated or unsaturated. The difference is that saturated fatty acids are completely “covered” in hydrogen, and they have no double bonds. Whereas unsaturated fatty acids have double bonds, and the capability to bond with more hydrogen. If an unsaturated lipid has more than one double bond it is called polyunsaturated. Saturated lipids are normally found in animals, and unsaturated, in plants. There is another type of lipid, a phospholipid . Phospholipids are used in cell membranes because they have a hydrophobic tail and hydrophilic head. So they control what can come in and out. The structure of a phospholipid varies from that of a triglyceride, but not by much. A phospholipid still has the same glycerol backbone as a triglyceride, only instead of having three fatty acid chains, it has two, and a phosphate group, which is ionised to attract water (that’s why the head is hydrophilic). To break up a lipid you need to add water, hydrolysis. Which is normally done by adding a dilute acid, and heating it up. Then you get glycerol and chains of fatty acids again. The main use of triglycerides in the body is as an energy source. They contain much more energy per gram than either carbohydrates or proteins. Triglycerides can be broken down and oxidised in respiration and the energy from them is used to make ATP. Alpha glucose Beta Glucose To form a Disaccharide you must join two monosaccharides together in a condensation reaction (see fig.4) . The monosaccharides bond at carbon 1 and 4, creating a 1-4 glycosidic bond. And produce water. That creates a disaccharide, some key examples of disaccharides are maltose, sucrose, and lactose. Maltose is formed from two alpha glucose molecules, and is the sugar produced when starch is broken down. To break a disaccharide into a monosaccharide/ break down a polysaccharide to a disaccharide you use hydrolysis, it basically means adding water. It reverses the condensation reaction, and is usually done by adding a warm dilute acid. Polysaccharides are formed when 2 or more disaccharides join together. The three main polysaccharides are: Starch (amylose and amylopectin) Amylose is a long unbranched chain, it’s compact, and is therefore good for storage. Amylopectin is branched, which means it is easy to break down the side branches to get at the glucose. Glycogen It’s similar to amylopectin, only with a lot more side branches, so it looks a bit like a brush. This is good for quick energy release, as glycogen is stored in animals. Cellulose Is a straight chain, (a bit like a brick wall) with hydrogen bonds linking the chains together. This is good because it makes the structure strong, as it is used for cell wall. Also enzymes can’t break it, because they can’t reach the glycosidic bonds. Fig. 4 Amine group Functional group Carboxyl group The formation of a protein. Showing the peptide bond The functional group is shown as “R” because it changes in different amino acids. For instance: The Primary structure of a protein is the order of the amino acids. The Secondary structure is the shape e.g. beta pleated sheet or a helix. The Tertiary structure is a globular protein. It’s made up of lots of helixes and beta pleated sheets. It's 3D, enzymes are globular proteins. Globular proteins are therefore affected by all the things you associate with enzymes, like temperature and pH. It is held together by many different bonds, like disulphide, hydrogen bonds, van der waals forces, and ionic bonds. The Quaternary structure is 2 or more polypeptides, so a big group of globular proteins. Beta pleated sheet helix C 4 H 9 leucine C 4 H 9 isoleucine C 3 H 7 valine CH 3 alanine H glycine Functional Group Amino Acid

6. Introduction- A cell is the basic unit from which all living organisms are made. Some cells are big enough to be seen with the naked eye, however most cells are microscopic and can only be seen with microscopes. Bacteria tend to have the smallest cells, around 0.5um across, whereas human cells are between 10um and 30um in diameter. Despite the variations in size, cells have certain features in common. For further information References – www.biologymad.com http://library.thinkquest.org Collins AQA AS Biology Module 1: Molecules, cells and systems Mary Jones and Geoff Jones Advanced Biology Letts Biology Revision guide Organelles Organelles are small structures within cells that perform dedicated functions. As the name implies, you can think of organelles as small organs. Organelles were historically identified through the use of microscopy, and were also identified through the use of cell fractionation. There are many different types of organelles: Eukaryotic cells contain: Cell wall – A layer of tough cellulose fibrils (made of a variety of polysaccharides) that surrounds plant cells to give support and protection. The cell wall allows the cell to become turgid without bursting and maintains the shape of the cell. Cell membrane – A thin boundary around all cells and most organelles that controls what passes in and out of the cell. Proteins are embedded in the cell membrane and are also involved in cell recognition in the immune system. Nucleus – Large, usually round, bounded by double membrane with many pores. The most important part of the cell, controls growth, contains DNA, responsible for cell division, regulates metabolism and protein synthesis. Quite simply, the total control of the cell. Nucleolus – The darkly stained region in the nucleus that is involved with the synthesis of ribosomes. Mitochondrion – Usually round and elongated with a smooth outer membrane and a folded inner membrane. The mitochondria are contained in the cytoplasm of cells and are the site of aerobic respiration and where most of the cells ATP is produced. Chloroplast – A biconcave disc (the perfect compromise between a sphere and a disc) with many internal membranes. Chloroplasts are the site of photosynthesis as they contain the green pigment chlorophyll. Vacuole – A large central organelle in most plant cells, surrounded by a membrane called the tonoplast, full of fluid. Vacuoles store compounds such as sucrose and the difference in water potential compared to the surrounding fluids enables the cell to produce turgor pressure. Rough endoplasmic reticulum (rough ER) – The extensive membrane system that has many cavities and tubes with ribosomes attached. Rough ER is found throughout the cytoplasm connected to nuclear membrane and acts as the transport system in the cytoplasm, collecting, storing, packaging and transporting the proteins made in the ribosomes. Smooth endoplasmic reticulum (smooth ER) – The membrane system with small cavities and no ribosomes, found in small patches in the cytoplasm. The smooth ER is involved in the synthesis of lipids and some steroids. Golgi body – A stack of flattened membrane discs found free in the cytoplasm near to the rough endoplasmic reticulum. The golgi body receives packages (vesicules) of protein from the rough endoplasmic reticulum and is involved in the synthesis and modifying of chemicals before their secretion from the cell. Ribosome – A small and dense structure that acts as an enzyme. The ribosome is attached to the rough endoplasmic reticulum or free in the cytoplasm and is where the genetic code is used to build protein (translation). Prokaryotic cells only contain a cell membrane, cell wall, ribosomes, DNA and a cilia or a flagella (as shown previously). Cell fractionation – Cell fractionation is a process which allows scientists to extract pure samples of a particular organelle. Cell fractionation is a combination of various methods used to separate a cell’s organelles and components. There are two phases of cell fractionation: homogenization and centrifugation. Homogenization is the process of breaking open the cells. Cells are broken apart by chemicals, enzymes, or sound waves. Some scientists even force the cells through small spaces at high pressure to break them apart. Centrifugation is the isolation of the cell organelles. The tissue is chopped up and when the cells are broken apart substances that would normally be kept separate by membranes mix together and can begin to react, so a fluid is added to prevent this which is ice cold, contains a buffer and isotonic. The mixture is then put in a homogeniser (blender) to break up the cells. The resulting mixture is then centrifuged at high speed. The spinning greatly increases the gravitational field, and the organelles separate out according to density and shape. The first most heaviest organelle to sediment out is the nuclei. The remaining fluid, the supernatant, is poured off the centrifuged again to collect other organelles. The order that organelles sediment is: nuclei, mitochondria, chloroplasts (if using plant preparations), rough endoplasmic reticulum, plasma membranes, smooth endoplasmic reticulum and finally ribosomes. Prokaryotic and eukaryotic cells, organelles and microscopy. Sarah Townsend South Bromsgrove High School Microscopy There are two main concepts in microscopy and these are resolution and magnification. Resolution is the ability to distinguish between two clear dots. Magnification is how much bigger a sample appears to be than it is in real life. Light microscope - This microscope uses light to see and magnify objects. The light rays are focused on to a transparent specimen by condenser rays. The rays pass through the specimen and are focused Prokaryotic Cell – (From the Greek meaning ‘before nuclei’ – the DNA is not enclosed by a membrane). All bacteria and cyanobacteria (blue –green algae) are prokaryotes as they lack a membrane – bound nucleus. They are usually smaller than eukaryotic cells and are similar in size to a mitochondrion or a chloroplast. In fact, they probably were prokaryotic cells which came to live inside the larger eukaryotic cells millions of years ago. They have few internal organs that are distinguishable. All prokaryotic cells are surrounded by a cell wall. However this is different from Figure 1 . A prokaryotic cell taken from an electron micrograph a plant cell wall because it contains different polysaccharides. Instead they contain peptidoglycans which are made up of molecules in which peptides and sugars are combined. The cell walls are very strong and important because they prevent the cell from bursting when the cell absorbs water and help to protect against invasion by viruses. Many prokaryotic cells have a thick layer of jelly surrounding them called a capsule which is made of polysaccharides and protects from viruses and antibodies. Beneath the cell wall is a cell surface membrane that is made up of a phospholipid bilayer and the cytoplasm that contains ribosomes that are approximately 20 nm in diameter. The DNA is not chromosomal but in a circular loop called a plasmid. Some contain a flagellum which is used for movement. They divide by binary fission and have three major shapes: rod, spherical and spiral. Figure 2. A eukaryotic cell taken from an electron micrograph. Eukaryotic cell – (From the Greek meaning ‘truly nuclear’ – the larger nucleus contains the DNA inside a membrane). Organisms with complex cells are eukaryotes and are found in plants, animals and fungi. They can be easily distinguished through a membrane bound nucleus (nuclear envelope) and contain membrane bound structures (organelles). The organelles such as the mitrochondrion or chloroplast are there to perform metabollic functions and energy conversion. Other organelles provide structural support and cellular motility. They are generally much larger than prokaryotic cells. Not all eukaryotic cells contain cell walls, only plant cells, not animals cells. The plant cell wall contains pectin, hemicellulose and cellulose (different from a prokaryotic cell). The DNA is linear (chromosomal), complex, organised into chromosomes and combined with histone proteins. They divide by replication (making copies of themselves). The eukaryotic cell is clearly developed from a prokaryotic cell. This is because eukaryotes formed through the merger of prokaryotes, which predate them in the fossil record by some 2 billion years. again by two more lenses – the objective lens and the eyepiece lens. These two lenses produce a magnified image. As many specimens are colourless and nearly transparent, stains are used to make different parts of the specimen show up clearly. Some stains can be added to living cells, but others must be ‘fixed’ by adding a chemical known as a fixative. These chemicals react with substances such as proteins in the cell, making them insoluble and so anchoring them in position. The cells are killed when the fixative is added. Stains may be added either before or after the fixing process. So long as the specimen is thin enough to allow light to pass through, Figure 3. A light microscope they can be used to see major organelles such as the nucleus or mitochondrion. The fluorescent light microscope is the most common and widely used light microscope. This microscope is used to visualise stained cells with fluorescent dyes. However, limitations occur as the microscope can not see beyond 200 nm resolution and x1500 magnification due to the long wavelength of light dissipating if the light is refracted too far. They are relatively cheap. Electron microscope - This microscope uses electrons to see instead of light. They are focused using electromagnets rather than glass lenses. As electrons are easily stopped by air molecules, the space inside must be a vacuum. As our eyes do not respond to electrons, the electrons are allowed to hit a fluorescent screen which emits visible light where the electrons hit. Electrons cannot penetrate materials as well as light, so specimens must be much thinner. This places great limitations on what can be viewed, in particular it is not possible to look at living material, all specimens musty be dead. Specimens are stained using heavy metal ions such as lead or osmium and are taken up by particular parts of the cells. Atoms of these ions have large, positively charged nuclei which scatter electrons rather than letting them pass straight through. These Figure 4. An electron microscope electrons therefore do not arrive on the screen, so leaving a dark area in the image. The structures in a cell which have taken up these heavy metal stains therefore appear dark. Scanning electron microscopes work in a very different way. The electrons do not pass through the specimen but are reflected off its surface. Scanning electron microscopes are used to provide three dimensional images of surfaces. Because the wavelength of electrons are shorter than light, they have a resolution of 1nm and a magnification of x500000. However, they are very expensive. Figure 5. cell fractionation

7. Introduction There are two main types of cells, Eukaryotic and Prokaryotic. They are very different and contain different organelles which help them to do their specific jobs. An Organelle is a discrete structure of a cell with specialized functions. They are similar to the organs in a body because they are vital in the survival of the cell. There are many ways to identify organelles such as microscopy which can be done using different microscopes to give different resolutions and better images. Cell fractionation can also be used as it is a method of splitting up the cell so that all the different organelles are separate. There are two different types of microscopes, light and electron with there being two more different types of electron microscopes. Transition and Scanning which both do different jobs and see different things along with the light microscope. Microscopy There are two different types of Microscopes, Light and Electron microscopes they or both very different with there also being two different types of electron microscopes. Light Microscopes are is a very simple microscope with not a very high resolution or magnification. Resolution being the ability to distinguish between two points on an image and Magnification being how much bigger a sample appears to under the microscope. The resolving power of a microscope is limited by the wavelength of light which is 400 to 600 mm for visible light. To improve the resolving power of a light microscope a shorter wavelength of light is need that is why some microscopes have blue filters as blue has the shortest wavelength of visible light. Light microscopes cost between £100 and £500 compared to the cost of an electron microscope which is over £1,000,000. They are cheep to operate as well as being small and portable. The samples are simple and easy to prepare with little damage done to the samples during this process. A vacuum is not required unlike in the electron microscopes meaning that the specimen has to be dead. The natural colour is maintained in a light microscope even though stains are often needed to make the cells visible but the maximum magnification is only up to 2000 times. Electron microscopes are much more advanced as they have a magnification of over 500,000 times. They use an electron beam which is very expensive and can damage the specimens which also must be stained with an electron dense chemical. Electron microscopes can also be split into Scanning electron microscopes and Transmission electron microscopes. Scanning electron microscopes pas the scanning beam over the surface of the specimen and electrons reflect of it as it has been coated in heavy metals. The reflected electron beams are focused on a florescent screen to make up the image which is linked to a computer to make the image clearer. It is similar to echo location. Transmission electro microscopes pas a beam of electrons through the thin specimen and focusing the image on a screen or film. The TEM is very big, expensive and not very clear. Cells and Microscopy By Abby Pask Organelles There are many different Organelles with many different functions Eukaryotic cells Nucleus- Where DNA is kept and where RNA is transcribed Ribosome's- The site of protein synthesis, where RNA is translated into proteins Mitochondria- The site or aerobic respiration Chloroplasts- the site of photosynthesis Endoplasmic reticulum- There are two types the rough ER and the smooth ER. The ER is the transport network for molecules targeted for certain modifications and specific final destinations. Golgi Apparatus - The ‘post box’ of the cell as it modifies molecules and packages them into small membrane bound sacs called vesicles. Prokaryotic Cells Vacuole- transport and storing nutrients, metabolites, and waste products. Cytoplasm- contains all the enzymes needed for metabolic reactions Nucleoid- The region of the cytoplasm that contains DNA Meosome- A tightly folded region of the cell membrane containing proteins required for respiration and photosynthesis. Capsule- A thick polysaccharide layer outside of the cell wall used for protection and a food reserve. Flagellum- A rigid rotating helical shaped tail used for propulsion. Both types of Cells Cell Membrane- Made of phospholipids and proteins which is used for protection and transport. Cell Wall- Keeps a cell rigid and gives protection. Eukaryotic Cells Eukaryotic cells are the larger of the two types of cell and can be more than 10µm in diameter. They have a true nucleus and contain many organelles that can either be double or single. This makes them very complex cells which have a number or different jobs. The genetics of a Eukaryotic cell is made up of linear DNA and is associated with proteins to form chromatin. It has a true nucleus which means it has a nuclear envelope and is one of the main difference between a eukaryotic cell and a Prokaryotic cell. Another main difference is the number of ribosome's in the cell with the eukaryotic cell having a large number (80S) The cells walls are made up of either chitin in fungi or cellulose in plants but animal cells do not have a cell wall Figure 1. This is a basic diagram of a eukaryotic cell with all the main organelles that it contains including the nucleus and the endoplasmic reticulum Figure 2 . These two photos are different eukaryotic cells that have been magnified using a microscope. The main recognisable organelles have been labels Prokaryotic Cells Prokaryotic cells are much smaller than Eukaryotic cells being less than 5 µm in diameter. They have smaller ribosome's (70s) and less organelles which are all not membrane bound. The genetics of a prokaryotic are also very different as there is circular DNA and no proteins. There is no true nucleus which means that the DNA is free to move within the cytoplasm. The cell walls are made from Glycoprotein's or other polysaccharides, but not cellulose or chitin as these are found in Eukaryotic cells. Prokaryotic cells include bacteria and blue-green algae as they are very small and not very complex Figure 3. This is a basic diagram of a Prokaryotic cell with all the main organelles that it contains including the ribosome's and the Nucleoid Figure 4. This is a prokaryotic cell seen through a microscope it shows the cell wall and cell membrane which outline the cell.

8. Phospholipids have a similar structure to triglycerides, but with a phosphate group in place of one fatty acid chain. There may also be other groups attached to the phosphate. Phospholipids have a polar hydrophilic "head" (the negatively-charged phosphate group) and two non-polar hydrophobic "tails" (the fatty acid chains). This mixture of properties is fundamental to biology, for phospholipids are the main components of cell membranes. RECAP OF LIPIDS What's the difference between a phospholipids and triglyceride Molecule? Triglycerides are the familiar fats and oils. The molecules are made from one molecule of glycerol linked to three fatty acids. Glycerol is an alcohol. Fatty acids are organic acids (also called carboxylic acids) and also have a -COOH group. BY condensation, this group combines with the -OH group of a glycerol molecule, forming an ester bond. Because triglycerides are fat, they acts as a storage molecule. Phospholipids have two fatty acids and a phosphate molecule attaches where as a triglyceride molecule only has three fatty acid chains. There function is to form membranes. Biochemical tests These five tests identify the main biologically important chemical compounds. For each test take a small amount of the substance to test, and shake it in water in a test tube. If the sample is a piece of food, then grind it with some water in a pestle and mortar to break up the cells and release the cell contents. Many of these compounds are insoluble, but the tests work just as well on a fine suspension. Starch (iodine test). To approximately 2 cm³ of test solution add two drops of iodine/potassium iodide solution. A blue-black colour indicates the presence of starch as a starch-polyiodide complex is formed. Reducing Sugars (Benedict's test). To approximately 2 cm³ of test solution add an equal quantity of Benedict’s reagent. Shake, and heat for a few minutes at 95°C in a water bath. A precipitate indicates reducing sugar. The colour and density of the precipitate gives an indication of the amount of reducing sugar present, so this test is semi- quantitative. A blue colour means no reducing sugar, a green precipitate means relatively little sugar; a brown or red precipitate means progressively more sugar is present. Non-reducing Sugars (Benedict's test). Using a separate sample, boil the test solution with dilute hydrochloric acid for a few minutes to hydrolyse the glycosidic bond. Neutralise the solution by gently adding small amounts of solid sodium hydrogen carbonate until it stops fizzing, then test as before for reducing sugars. Biological molecules Chris Kelly 12WH South Bromsgrove High School, A Specialist Technology College, Bromsgrove, Worcestershire, B60 3NL . Lipids (emulsion test). Lipids do not dissolve in water, but do dissolve in ethanol. This characteristic is used in the emulsion test. Do not start by dissolving the sample in water, but instead shake some of the test sample with about 4 cm³ of ethanol. Decant the liquid into a test tube of water, leaving any undissolved substances behind. If there are lipids dissolved in the ethanol, they will precipitate in the water, forming a cloudy white emulsion. The test can be improved by adding the dye Sudan III, which stains lipids red. Protein (biuret test). To about 2 cm³ of test solution add an equal volume of biuret solution, down the side of the test tube. A blue ring forms at the surface of the solution, which disappears on shaking, and the solution turns lilac-purple, indicating protein. Conclusion Biochemistry is a particularly difficult area in biology as it is split up into different sections. For example you have to remember the types, function and importance carbohydrates-monosaccharides, disaccharides and polysaccharides and proteins, Lipids and biochemical tests. Fatty acids are long molecules with a polar, hydrophilic end and a non- polar, hydrophobic "tail". The hydrocarbon chain can be from 14 to 22 CH2 units long, but it is always an even number because of the way fatty acids are made. The hydrocarbon chain is sometimes called an R group, so the formula of a fatty acid can be written as R-COO-. Saturated or unsaturated If there are no C=C double bonds in the hydrocarbon chain, then it is a saturated fatty acid (i.e. saturated with hydrogen). These fatty acids form straight chains, and have a high melting point. If there are C=C double bonds in the hydrocarbon chain, then it is an unsaturated fatty acid (i.e. unsaturated with hydrogen). These fatty acids form bent chains, and have a low melting point. Fatty acids with more than one double bond are called poly-unsaturated fatty acids (PUFAs). These fatty acids are joined by a condensation reaction however in this reaction it is known as ESTERIFICATION and an ESTER bond is formed. With three branches three ester bonds can form so three fatty acids can bond so therefore it is called a triglyceride. Is first molecule of a fatty acid Acknowledgments Literature cited For further information

11. Jonathan Stevens Module One: Biological Molecules Lipids, Proteins and Carbohydrates Introduction: In the following poster I will go into detail of many things to do with biological molecules, the main aspects I will go into detail are carbohydrates, lipids and proteins. I will show the structures of the molecules and the types of bonding and how they join and get broken down. I will state the chemical tests for the certain types of molecules and what too look for to see If the substance contains the specific type of molecule. I will the state and explains the functions of proteins and etc. Carbohydrates: There are 3 main types of carbohydrates and they are polysaccharides, monosaccharide and disaccharides. All carbohydrates contain 3 elements these elements are carbon, hydrogen and oxygen . Monosaccharide: A monosaccharide is a single sugar this is a molecule of sugar in its smallest form, an example of this is glucose, glucose is a sugar which our body uses, there are two types of glucose there is alpha and beta, the structures of these molecules differ, they are as follows: Alpha Beta Glucose can join together to form long chains which are polysaccharides, the first stage of the joining is when two glucoses join to become a disaccharide the glucoses can join up in different orders and this makes different disaccharides for example alpha plus alpha. The process of joining is between carbon one and carbon four, they join by a glycosilic bond, reaction gives out water and it is called a condensation reaction. The glycosilic bond can also be broken they are broken, they are broken down by adding it with acid, this reaction adds water to the molecule which rejoins the two glucoses, this reaction is a called hydrolosis. The test for monosaccharide is to add benedict's solution to the substance which is at near boiling, if the substance contains monosaccharide the benedict's solution will change to a green – red solution. Disaccharides: Disaccharides are two monosaccharide joined together, they are joined by condensation reaction. The test for disaccharides is as follows, add hydrochloric acid to the solution which is at near boiling, then add benedict's solution to the solution and if the benedict's solution changes to a green to red colour. Polysaccharides: These are massive chains of monosaccharide and disaccharides an example of this is starch which make up bigger molecules. Lipids: Lipids all contain a glycerol backbone which looks as follows: Lipids contain a fattys acid and this has a carboxyl this is shown below, the zig zaged line represents a long hydrocarbon chain, the chain can be saturated or unsaturated. A fatty acid joins to a glycerol backbone they join by esterfication this is a condensation reaction and releases water. A glycerol backbone can join up to three things on its 3 branches, one example it can make is a triglyceride, this is when a glycerol backbone joins to three fatty acids. Esterfication A fatty acid is hydrophobic this means it doesn’t like to react with water this is because the water will breaks the bonds between the glycerol and the fatty acid because if you add water you are adding back hydrogen's, and why do they share hydrogen's if they could have one each. The glycerol head is hydrophilic which means it is water loving. Proteins: Proteins are a key part of the body they have many functions these functions are: ~for enzymes ~anti-bodies ~actin & myosin which make muscles contract ~used to make tissues ~blood clotting involve many proteins ~gives strength to hair and nails Proteins are made up of amino acids and each amino acid has three groups these groups are amino group, functional group and the carboxyl group, a diagram of this is below: The functional group can join to different molecules these molecules make up different proteins and amino acids which have different jobs, examples of these are below: Proteins and amino acids have many structures and these structures are: Primary structure this is the order of the amino acids Secondary structure: this structure is when the long strand of amino acids either curve into a helix or the create a beta pleated sheets, the helix and sheets are joined together by hydrogen bonds. Tertiary structure: the third structure is when the helix’s and sheets join together to form a globular protein this big structure is also known as a enzyme, the big structure is joined together by many bonds these bonds are: di-sulphide, hydrogen, Ionic, Hydrophobic, Van der Waals Quartary structure: this structure is when gobular proteins join together to make bigger structures this structure can join together to make a well known structure which is a red blood cell.