biology unit 1 part 1

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  • Unit 1
    • Monosaccharides
      • Monomer - individual molecule. Polymer - chain of repeating monomers.
      • Monosaccharide- individual sugar unit in carbohydrates. Disaccharide - pair on monosaccharides. polysaccharide - chain of monosaccharides.
      • Test for reducing sugars, Benedicts test. Add 2cm3 of sample and benedicts reagent, heat for 5 minutes, orange/red precipitate indicates presence of reducing sugar.
    • Disaccharides
      • Glucose + Glucose = Maltose. Glucose + Fructose = Sucrose. Glucose + Galactose = Lactose.
      • Condensation reaction - the removal of a water molecule to join molecules.
      • Hyrolysis - adding a molecule of water to break apart molecules.
      • Test for non-reducing sugars Original benedicts test, no colour change. Add 2cm3 of sample and dilute hydrochloric acid, heat for 5 minutes, add sodium hydrocarbonate, orange/red precipitate.
    • Polysaccharides Starch is a polysaccharide found in plants, form of small grains.
      • Test for starch Add 2cm3 of sample, add two drops of iodine solution, shake, blue/black colouration indicates presence of starch.
    • Digestion
      • Physical
      • Chemical
        • Breaking down large insoluble molecules into soluble ones.
        • Carried out by enzymes which function by hydrolysis.
        • Carbohydrase breaks carbohydrates into glucose.
        • Protease breaks proteins into amino acids.
        • Lipase breaks lipids into glycerol and fatty acids.
      • Starch digestion
        • Food is broken down by the teeth giving it a large surface area, saliva containing amylase hyrolyses starch into maltose.
          • Food enters the stomach, the acid denatures the amylase, the food moves to the small intestine, it mixed with pancreatic juices.
            • The pancreatic juices contain amylase which breaks down the rest of the starch into maltose, the epithelial of the intestine produces maltase hydrolysing maltose into glucose.
      • Sucrose digestion
        • Cells broken down by the teeth to release the sucrose, it passes through the stomach to the small intestine, it produces sucrase which hydrolyses sucrose into glucose and fructose.
    • Proteins
      • Amino acids are the basic monomers that make up a polypeptide. Each has a central carbon atom, an amino group (NH2), carboxyll group (COOH), hydrogen group and an R group.
      • Peptide bond - formed during a condensation reaction between amino acids.
      • Primary structure. Polymerisation joins amino acids together creating a polypeptide, the sequence of the amino acids forms its primary structure which determines its shape and function.
      • Test for proteins Biuret test        Add equal amounts of sample and sodium hydroxide solution, add a few drops of dilute copper sulfate solution, mix, purple colouration indicates presence of proteins.
      • Fibrous proteins have structural functions. Globular proteins have metabolic functions.
      • Fibrous protein structure. Primary - unbranched polypeptide chain. Secondary - chain is tightly wound. Tertiary - chain twisted into second helix. Quaternary - a number of chains wound together.
    • Enzymes
      • Enzymes work as catalysts to lower the activation energy.
      • Lock and Key                       Enzymes are specific, they have an active site whose shape fits exactly to one substrate. Limitations                                 The enzyme is considered a rigid structure although other molecules can bind to the enzyme at sites other than the active site, altering the shape.
      • Induced fit model Enzyme changes its shape in the presence of the substrate, the change puts strain on the substrate, this distorts bonds and lowers the activation energy.
      • Factors affecting enzyme action.
        • Temperature. When temperature is raised molecules have more kinetic energy, as a result they move around more rapidly and collide with each other more often, increasing the rate of reaction.
          • On a graph the rise is due to the molecules coliding with each other, as the temperature continues to rise hydrogen and other bonds in the enzyme molecules break, this causes the active site to change shape.
            • First the substrate fits less easily then the enzyme becomes denatured.
        • Substrate conc. When the amount of substrate is increased rate of reaction increases.
          • At low substrate concentrations enzyme molecules only have a limited number of substrate molecules to collide with therefore the active sites are not working at full capacity.
            • As more substrate is added the active sites become filled until all are working at full capacity.
              • The addition of further substrate molecules has no effect as all active sites are already occupied. There is no increase in the rate of reaction.
      • For an enzyme to work it must come in to contact with its substrate and have an active site which fits the substrate.
      • Inhibitors
        • Competitive
          • Has a molecular shape similar to that of the substrate, this competes with the substrate for the active site, inhibitor prevents reactions happening.
          • If substrate concentration is increased the effectiveness of the inhibitor is reduced.
        • Non competitive
          • Binds to a point on the enzyme other than its active site, it alters the active site preventing its substrate fitting therefore can no longer function.
          • An increase in substrate concentration would have no effect on rate of reaction as the inhibitor and substrate are not competing for the active site.
    • Cell fractionation
      • The process by which cells are broken up and their organelles seperated out..
      • Homogenation - cells are broken up by a homogeniser releasing the organelles, the homogenate is filtered to remove debris.
      • Ice cold - prevent enzyme action breaking down organelles Isotonic - prevent organelles shrinking or bursting as a result of osmotic gain of loss Buffered - keep pH constant.
      • Ultracentrifugation - the process by which the organelles in the homogenate are seperated  in an ultracentrifuge. This spins the homogenate at very high speeds.
        • Spin at low speed first, nuclei forms a pellet at the bottom, the supernatant is filtered off, it is spun at a medium speed, mitochondria, then ribosomes.
    • Structure of epithelial cell.
      • Nucleus
        • Most prominent feature of eukaryotic cell.
        • Nuclear envelope - double membrane, continuous with ER, has ribosomes on, controls entry and exit of materials.
        • Nuclear pore - gap, allows passage of large molecules.
        • Nucleoplasm - jelly material, makes up most of the nucleus.
        • Chromatin - DNA found in the nucleoplasm, form chromosomes take when not dividing.
        • Nucleolous - small body inside the nucleus, manufactures ribosomal RNA.
      • Mitochondrion
        • Double membrane - surrounds organelle, outer controls entry and exit of material, inner is folded to form extentions called cristae.
        • Cristae - extentions of the inner membrane, provide large surface area for enzymes involved in respiration to attach to.
        • Matrix - makes up remainder of mitochondria, semi rigid, contains proteins, lipids, enzymes.
        • Site of respiration, production of ATP, greater the number of mitochondria the greater the production of ATP and greater  its metabolic capacity.
      • Endoplasmic reticulum
        • Sheet like membranes, continuous with the outer nuclear membrane,.
        • Smoth ER - no ribosomes on its surface,. Functions - synthesise, store and transport lipids and carbohydrates.
        • Rough ER - ribosomes on its surface,. Functions - provide large surface area for the synthesis of proteins and glycoproteins, provide pathway for transport of material through the cell.
      • Golgi apparatus
        • Similar to SER, stack of membranes that make up cristae with vesicles, proteins packages by ER pass through the golgi, modifies proteins by adding non-protein materials, labels them to be sorted the transports them in vesicles, they release there contents at surface.
        • Functions - add carbohydrates to proteins to make glycoproteins, produce enzymes, secrete carbohydrates, transport, modify and store lipids, form lysosomes.
      • Lysosomes
        • Vesicles produced by the golgi contain enzymes.
        • Functions - break down material ingested by phagocytes, release enzymes to the outside of a cell (exocytosis) to destroy material around it, digest worn out organelles, completely break down dead cells.
      • Ribosomes
        • Small granuals found in cells, occur in the cytoplasm or on RER, 80S found in eukaryotic cells, 70S found in prokaryotic cells.
        • Contain ribosomal DNA and proteins.

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