AQA A Level Biology Paper 1

AQA A Level Biology Paper 1 Water removed from the reactants Condensation The addition of water to the reactants Hydrolysis Add 2cm³ of food sample (in solution). Add 2cm³ of benedict's Reagent. Heat the solution in a water bath for 3 minutes. Change from blue to brick red. CuO formed Test for Reducing Sugars Add 2cm³ of food sample.Add 2cm³ of dilute HCL then heat.Add 2cm³ of NaHCO3.Then do test for reducing sugars. Non-Reducing Sugars Add drops of iodine to starch solution. Colour change to blue-black Test for Starch Mix Test solution with ethanol. Shake for 1 minute. Add water. Cloudy white emulsion Test for Lipids Equal volumes of Test solution and NaOH. Add a few drops of biuret solution (dilute copper (II) sulphate solution). Colour change to mauve/purple Test for Proteins 1. Inhibitor is similar in shape to substrate so it impermanently binds to the active site. 2. Prevents ESC from forming, slowing rate Competitive inhibition (2) 1. Molecule will bind to allosteric site. 2. Binding causes a change in active site. 3. Permanently preventing further ESC. Non-competitive inhibition (3) 1. DNA helicase breaks the hydrogen bonds between the base pairs 2. 2 single strands formed as the double helix "unzips". 3. Free nucleotides in the nucleoplasm bond to the complementary bases on the strand. 4. DNA polymerase joins the new strands together by creating phosphodiester bonds. DNA Replication: Semiconservative (4) Adenosine triphosphate is a molecule that releases a small amount of energy when hydrolysed ATP Prevents the cell from drying out. Allows bacteria to stick to each other Slime capsule (2) Used for attachment of a cell to a surface Fimbria Involved in bacterial conjugation Pilli Invagination of cell membrane. Site of cell respiration (prokaryotes) Mesosome The ability to distinguish two points apart Resolution 1. Very high resolution. 2. Needs thin specimen. 3. Artefacts can occur (remnant left on object during prep, such as air bubbles) Transmission Electron Microscope (3) Lower resolution. 3D image Scanning Electron Microscope Cold. Low temperature slows enzyme activity, minimising self digestion by reducing metabolic rate. Isotonic. Salt and sugar concentration kept the same, minimising organelle size change due to osmosis. Buffered. Minimum changes in pH, so prevents enzymes in organelles denaturing. Solution Required for cell fractionation (6 Marks) 1. Homogenisation. Breaking up cells by blending the sample to create a homogenate. 2. Filtering. Filtering the large, unwanted sil, producing the filtrate. 3. Ultracentrifugation. Spin in a centrifuge so components separate out by weight. Heavier near the bottom of the tube. 4. Supernatant is removed and spun again at higher speed. Separation of Organelles From The Cells (4) The solution not including the pellet at the bottom of the test tube after centrifugation. Supernatant The mass of organelles at the bottom of the test tube after centrifugation. Pellet Nuclei, Chloroplasts, Mitochondria, Lysosomes, Endoplasmic Reticulum, Ribosomes Order of Organelles (Pass me a taco chief) Mitosis acronym Cell grows and carrys out its normal function Interphase Cells grow to normal size. Organelles replicate and genes are expressed to make proteins needed. Interphase G1 DNA and histones replicate