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| Question | Answer |
| Test for Reducing sugars | food sample dissolved in water equal vol of benadicts heat in water bath if reducing sugar present solution turns orange-brown |
| What is a reducing sugar? | A sugar that can donate electrons to or (Reduce) another chemical |
| name the disaccharides | glucose + glucose = maltose glucose + galactose = lactose glucose + fructose = sucrose |
| how do monosaccharides form | in a condensation reaction where water is removed creating a glycosidic bond |
| what happens when water is added to a disaccharide | it breaks the glycosidic bond releasing the constituent monosaccharides know as hydrolysis |
| how are polysaccharides formed and what are they good for | formed by combing many monosaccharide molecules, joined together by glycosidic bonds. as they are vary large they are insoluble making them usefull for storage |
| What is Starch and where is it found | starch is a polysaccharide that is found in plants in small grains. major energy source. made of chains of A-glucose |
| How is starch suitable for energy storage | Insoluble so does not effect water potential of cell. (osmosis) large and insoluble, does not diffuse compact so easily stored when hydrolysed forms A- glucose which can easily be transported branched ends acted on quickly by enzymes so A-glucose reased rapidly. |
| Test for starch | 2 drops of iodine into test solution if starch is present it turns iodine a blue-black colour |
| What is Glycogen and where is it found | Glycogen is found in animals and bacteria only. it has a similar stucture to starch but has shorter more highly branch chains found in small granules in the muscles and liver. |
| Why is glycogen a good storage molecule in animals | insoluble so does not draw in water by osmosis or diffuse out of cells. compact so can be stored in small spaces. more highly branched than starch so has more ends that can be acted on at the same time by enzymes, so can be broken down into A-glucose more rapidly for respiration. good for animals as higher metabolic rate |
| how does cellulose differ from starch and glycogen | made from monomers of B- glucose. producing differences in structure and function |
| describe the structure of cellulose. | forms strait unbranched chains running parallel to eachother. this alows hydrogen bonds to form cross linking bridges. the over number of H-bonds ads alot of strength. the cellulose molecules are clumped together to form microfibrils. |
| where is cellulose found and what is it good for. | major component in plant cell walls and provides rigidity to the plant cell. the cellulose cell wall also prevents the cell from bursting as water enters. it does this by excerting inward pressure that stops anymore influx of water. (makes them turgid) |
| how is the structure of cellulose suited for its function | made of B-glucose so form long strait unbranched chains. chains run parallel and are cross linked my H-bonds creating collective strength. molecules are grouped to form microfibrils which in turn are grouped to form fibers adding to overall strength. |
| what are lipids | lipids contain H, C and O. the proportion of O to C and H is smaller than that of carbohydrates. they are insoluble in water but soluble in organic solvents. eg alcohols and acetone. |
| what are the roles of lipids | SOURCE OF ENERGY- when oxidised provide more than 2X that of carbs and water WATERPROOFING- insoluble in water eg plants and insects have waxy layer. INSULATION- slow conductors of heat + electrical insulators myelin sheath nerve cells PROTECTION- delicate organs eg kidneys |
| what is a trglyceride | they have 3 fatty acids combined with glycerol. each fatty acid forms a ester bond with glycerol in a condensation reaction |
| state the differences in triglycerides | differences come from variations in fatty acids. if Saturated there are no double bonds between carbon. If mono-unsaturated there is one double bond between carbon atoms. if polyunsaturated there is more than one double bond. double bonds cause the molecules to bend so cannot stick together. eg liquid (oils) |
| structure of triglycerides related to there properties | Good sources of energy due to high ratio of energy storing H-C bonds Low mass to energy ratio. good for storage as lots in small volume large and non polar so insoluble in water. does not effect water potential High ratio of H-O release water when oxidised, important in deserts |
| what is a phospholipid | similar to lipids but one of the fatty acid chains is replaced with a phosphate molecule. |
| what two parts is a phosphlipid made up off | A hydrophilic head( Phosphate) attracted to water. A Hydrophobic tail ( fatty acid ) repels water |
| the structure of phospholipids and there properties | as they are polar they form a bilayer in cell surface membranes. so a hydrophobic barrier is formed between in and out. hydrophilic phosphate heads hold cell surface membrane together ability to form glycolipids with carbohydrates |
| Test for lipids ( emulsion test) | 1) dry grease free test tube 2) add 2cm of sample and 5cm of ethanol 3) shake to dissolve any lipid in sample 4) add 5cm of water and gently shake 5)cloudy white indicates lipid 6) as control repeat using water instead of sample. sample should remain clear |
| describe and draw the structure of a amino acid | basic monomers that make up polypeptides. central carbon with a amino group, carboxyl group, hydrogen and the residual R group. |
| describe the formation of a peptide bond | amino acid monomers combine to form a dipeptide by the removal of water in a condensation reaction. the 2 amino acids then become linked by a new peptide bond between the carbon atom and one of the amino acids and nitrogen of the other |
| describe the secondary stucture of proteins | polypeptide posses both -NH and C=O groups the H has possotive and 0 is slightly negative, these therefore create a weak hydrogen bond causing the polypeptide to be twisted into a 3-D shape or A-helix |
| describe the tertiary structure | A-helices can be twisted and folded even more to give a 3d shape know as tertiary structure. this is maintained by a number of different bonds. disulfide bridges- fairly strong ionic bonds- carboxl and amino weaker(ph) Hydrogen-numbers but weak |
| explain why the 3d shape is important | allows protein to be distinctive and to be recognised by other molecules. |
| describe the Quaternary structure of proteins | arises from the combination of different polypeptide chains and associated non-protein groups into larger more complex protein eg heamoglobin |
| describe the test for proteins (biuret test) | 1)place a sample of solution to be tested into test tube and add equal amount of sodium hydroxide (25 degrees) 2) add few drops of dilute copper sulfate 3) purple colour indicates presence of peptide bonds so protein is present. if no protein solution remains blue |
| what are enzymes | enzymes are globular proteins that act as catalysts so lower the activation energy of a reaction. (without undergoing permant change) |
| describe the structure of a enzyme | specific 3d shape that is a result of the sequence of amino acids. enzymes have a specific region called the active site which is made up of a small number of amino acids. |
| describe the induced fit theory | enzyme is flexible and can move itself around can mould itself around the shape of the substrate forming a enzyme substrate complex. |
| effects of temperature on enzyme action | increase in temperature also increase KE so molecules more around faster and collide more often with more force. this means the enzyme and substrate molecules will come together more frequently so are more effective collisions. increasing rate of reaction. however at too high temperatures the H bonds and other bonds start to break causing its active site to change shape gratdually until a point where the substrate will no longer fit. it is said to be denatured |
| Effect of pH on enzymes | A change in pH alters the shape of the of the active site as a result the substrate can no longer become attached to enzyme. depending on how much the pH changes in may cause the bonds break therefore changing shape of active site |
| effect of enzyme concentration | as long as there is a excess of substrate a increase in enzymes leads to a proportional increase in rate of reaction. |
| effect of substrate concentration | if the enzyme conc is fixed then increase the conc of substrate will be proportional. as more active sites will become filled at any one time until a point of Vmax where all acctive sites are occupied |
| describe competitive inhibiters | they have similar shape to substrate so can occupy active site so compete with substrate for availability. not permanent |
| non competitive inhibiters | fit onto site other than the active site. upon attachment they alter the shape of the enzyme and its active site meaning that substrate molecules can no longer for a ES complex. |
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