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2012-11-11 09:32:49
Biology keywords

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  1. Oesphagus
    Carries food from the mouth to the stomach
  2. Assimilation
    Incorporating absorbed molecules into body tissues
  3. Hydrolysis
    The breaking down of large molecules into smaller ones by the addition of water
  4. Hydrolases
    General term given to enzymes that slip up molecules by hydrolysis
  5. Monomer
    One of many small molecules that combine to form a larger one known as a polymer
  6. Polymer
    Large molecule made up of repeating smaler molecules
  7. General formula of monosaccharides
  8. Test for reducing sugars (Benedicts test e.g. maltose)
    Add equal volume of Benedict's reagent to the food sample and heat in a gently boiling water bathfor 5 minutes and if a red-brown precipitate is formed the sample is a reducing sugar
  9. Condensation reaction
    Chemical process of combining  two molecules to form a more complex one and water is generally lost
  10. What is the bond called when two monosaccharides are combined
    Glycosidic bond
  11. What 2 monosaccharides form maltose
    Alpha glucose and alpha glucose
  12. What 2 monosaccharides form sucrose
    Alpha glucose and fructose
  13. What 2 monosaccharides form lactose
    Alpha glucose and galactose
  14. Test for non-reducing sugars (e.g. sucrose)
    • Do the Benedicts test and if it's negative do the following in a separate test tube:
    • Add dilute hydocholoric acid to the food sample and place in a gently boiling water bath for 5 minutes
    • Slowly add sodium hydrogencarbonate solution to the test tube to neutralise the acid
    • Test with pH paper for an alkaline solution
    • Re-test by adding Benedicts solution and placing in the gently boiling water bath for 5 minutes and if a non-reducing sugar is present an orange-brown colour will show
  15. Test for starch
    Add 2 drops of iodine solution to 2cm3 of the food sample and if starch is present it will turn a blue-black colour
  16. Denaturation
    Permanent change due to the unravelling of the structure of a protein as a result of factors such as temperature and pH
  17. How does lactose cause diarrhoea to people who are lactose intolerant
    • The milk lowers the water potential of the small intestine
    • So the water moves from the epithelial cells to the  lumen of the small intestine due to the concentration gradient by osmosis
    • This then causes the faeces to become overly watery which leads to diarrhoea
  18. Egestion
    Process of removing faeces
  19. What 3 enzmyes are produced by the epithelial cells of the small intestine
    Maltase, sucrase and lactase
  20. Polymerisation
    Process of joining many amino acids to form a polypeptide
  21. What is the bond formed between amino acids
    Peptide bond
  22. What is the components of an amino acid
    Amine group, carboxyl group and the R group
  23. What does the amine group consist of
  24. What does the carboxyl group consist of
  25. What is primary structure
    Sequence and number of amino acids joined by peptide bonds
  26. What is secondary structure
    Folding of chains of amino acids into an alpha helix or beta pleated sheet by the formation of H bonds
  27. What is tertiary structure
    Where the secondary structure is further folded to form a coiled 3D structure. The bonds involved as H bonds, ionic bonds and covalent bonds (disulfide bonds)
  28. What is quaternary structure
    Combination of more than one polypeptide
  29. Activation energy
    The energy required to bring about a reaction
  30. Active site
    A group of amino acids that makes up a region of an enzyme into which a substrate fits in order to catalyse a reaction
  31. Competitive inhibition
    • The inhibitor is similar shape to the substrate so can bind at the active site
    • The higher the substrate concentration the less affect the inhibitor has
  32. Non-competitive inhibition
    • Inhibitor is a completly different shape to the substrate to binds to a different site that isn't the active site
    • When it binds the active site changes shape no the substrate can't fit in so no enzyme substate complex can be formed
  33. What does DAM U stand for
    Drawing, actual, magnification and units
  34. What is resolving power
    The minimum distance apart two objects can be in order for them to appear as separate items
  35. Cell fractionation
    Process where cells are broken up and the different organelles they contain are separated out
  36. Before cell fractionation the tissue is placed in a cold, isotonic, buffered solution why?
    • Cold - to reduce enzyme activity that may break down the organlles
    • Isotonic - to prevent organelles bursting or shrinking due to osmotic gain or loss; as it has the same water potential as the tissue
    • Buffered - to maintain a constant pH
  37. Homogenation (1st stage of cell fractionation)
    When cells are broken up by the homegeniser (blender) to separate out the organelles. The resultant fluid is known as the homogenate and this is then filtered out to remove complete cells and large pieces of debris
  38. Ultracentrifugation (2nd stage of cell fractionation)
    The process by which the fragments of the homegenate are separate in a machine called a ultracentrifuge. The organelles are removed heaviest first: nucleus, mitochondria, lysosomes then ribosomes
  39. Advantages and limitations of the transmission electron microscope
    • Advantages: short wavelength, high resolution
    • Limitations: needs to be in a vacuum so living specimens can't be observed, black and white images, specimen needs to be very thin, needs to be prepared so artefacts may appear
  40. Advantages and limitations of the scanning electron microscope
    • Advantages: short wavelength, 3D images can be produced, specimens don'tneed to be that thin as electrons don't penetrate
    • Limitations: lower resolution than TEM and living specimens can't be used
  41. Example of a eukaryotic cell
    Epithelial cells of the small intestine
  42. Example of a prokaryotic cells
    Bacteria such as vibrio cholerae
  43. Funtion of the nucleus (3)
    • Act as the control centre of the cell
    • Hold genetic material of the cell in the form of DNA or chromosomes
    • Manufacture ribosomal RNA and ribosomes
  44. Length of mitochondria and what's inside
    • 1 - 10 micrometres
    • Double membrane - controls entry and exit of material
    • Cristae - extensions of inner membrane, provide a larger surface area for respiration
    • Matrix - control production of their own proteins, enzymes for respiration found in the matrix
  45. Function of the mitochondria (2)
    • Site for aerobic respiration
    • Production of ATP

    Found in cells that have a high metabolic activity and use a lot of ATP e.g.muscles
  46. Functions of rough ER (2)
    • Provide a large surface area for the synthesis of proteins and glycoproteins
    • Provide a pathway for the transport of materials such a proteins throughout the cell

    e.g. liver and secretory cells such as the epithelial cells of small intestine
  47. Functions of the smooth ER (2)
    • Synthesis, store and transport lipids
    • Synthesis, store and transport carbohydrates
  48. Functions of the golgi body (5)
    • Add carbohydrates to proteins to form glycoproteins
    • Produce secretory enzymes
    • Secrete carbohydrates, such as those used to make the cell walls in plants
    • Transport, modify and store lipids
    • Form lysosomes

    E.g. loads found in secretory cells such as epithelial cells
  49. Functions of the lysosomes (4)
    • Break down of foreign materials brought into the cell (phagocytosis)
    • Release enzymes to the outside of the cell (exocytosis) in order to destory surrounding material
    • Digest worn out organelles (autophagy)
    • Completely break down cells after they have dies (autolysis)
  50. Phagocytosis
    Mechanism by which cells engulf particles particles to form a vesticle or a vacuole
  51. Triglyceride
    An individual lipid molecule made up of a glycerol molecule and three fatty acids
  52. 4 roles of lipids
    • Energy source - lipids provide more than twice the energy as carbohydrates
    • Waterproofing - insoluble in water
    • Insulation - fats are slow conductors of heat and help to retain body hear
    • Protection - stored around delicate organs such as the kidneys
  53. Saturated fatty acid
    • A fatty acid where there are no double bonds between the carbon atoms
  54. Unsaturated fatty acid
    A fatty acid in which there is one double bond between the carbon atoms

  55. Polyunsaturated fatty acid
    • A fatty acid in which there is more than one double bond between carbon atoms
  56. What is the difference between a phosholipd and a triglyceride molecule
    • Phospholipid - glycerold molecule andd 2 fatty acids
    • Triglyceride - glycerol and 3 fatty acids
  57. Test for lipids (emulsion test)
    • Add an alcohol such as ethanol to the sample
    • add water and shake gently
    • A cloudy-white colour indicates the presense of lipids
  58. Functions of the phopholipids in a membrane (3)
    • Allow lipid-soluble substance to enter and leave the cell
    • Prevent water-soluble substances entering and leaving
    • Make the membrane flexible
  59. Extrinsic protein
    Proteins that are on the surface or are only part way through the membrance
  60. Intrinsic proteins
    Completely span the membrance from one side to the other
  61. Functions of the proteins in a membrane (5)
    • Provide structural support
    • Acts as carried for water-soluble substances
    • Allow active transport by forming ion channels
    • Help cells adhere together
    • Act as receptors e.g. for hormones
  62. Why the fluid-mosaic model used
    • Fluid - as the membrane is constantly moving because of the flexible structure
    • Mosaic - proteins are embedded in the phospholipd bilayer and vary in shape and size
  63. Diffusion
    The net movement of molecules or ions from a region of high concentration ot a region of lower concentration
  64. Facilitated diffusion
    Diffusion through a carrier protein from a region of high concentration to low concentration
  65. Ficks Law
    Surface area x concentration difference

                  Diffusion distance
  66. Osmosis
    Passage of water molecules from a region of high water potential to a region of lower water potential through a partiall permeable membrane
  67. Hypertonic
    Strong solution (low water concentration)
  68. Hypotonic
    Weak solution (high water concentration)
  69. What happens to an animal cell in a hypertonic and a hypotonic solution
    • Hypertonic (low wp) - leaves cell so shrinks 
    • Hypotonic (high wp) - enters cell so swells and bursts
  70. What happens to a plant cell in a hypertonic and hypotonic solution
    • Hypertonic (low wp) - leaves cell so becomes plasmolysed/crenated
    • Hypotonic (high wp) - enters cell so becomes turgid
  71. Active transport
    The movement of molecules or ions into or out of a cell from a region of low concentration to a region of high concentration using energy and carrier molecule
  72. What does a eukaryotic cell have that a prokaryotic cell doesn't

    • Nucleus and nucleolus
    • Chromosomes
    • Membrane-bounded organlles (mitochondria etc)
    • Chloroplasts
    • ER, golgi body and lysosomes
    • If it has a cell wall it's made of cellulose
  73. Example of a prokaryotic cell (lacking a nucleus)
    Bacteria such as vibrio cholerae
  74. Example of an eukaryotic cell
    Epithelial cells, plant cells and animals cells
  75. What does ORS have to contain
    • Water - for rehydration
    • Sodium - replace lost ions and make use of sodium-glucose pumps
    • Glucose - Encourage uptake of sodium and provides energy
    • Potassium - replace lost ions and stimulate appetite