Biological Molecules - Topic definitions.

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  • Biological Molecules - definitions
    • Isomers = Compounds that have the same chemical formula but which differ in the arrangement of atoms.
    • Polymers= long chains of repeating monomer units.
    • Polar = molecules that have two ends or poles that interact differently to water and fat. A hydrophilic head is attracted to water but not fat, whereas a hydrophobic tail mixes readily with fat but is repelled by water.
    • Dipeptide = Two linked amino acids.
    • Organic = a molecule consisting of carbon.
    • Inorganic = a molecule not consisting of carbon.
    • Non-polar = An insoluble molecule that doesn't attract H20 molecules.
    • Covalent = Really strong bonds/forces that hold atoms together in definite shapes.
    • Monomer = a single unit in a molecule.
    • Magnesium = Important constituent of chlorophyll, therefore an important part of photosynthesis.
    • Iron = part of haemoglobin, important in carriage of oxygen by red blood cells
    • Phosphate =  Make nucleotides (ATP). Part of phospholipids found in the plasma membrane
    • Calcium = Structural component of bones and teeth.
    • Water = Consists of two hydrogen atoms covalently bonded to one oxygen
    • Hydrogen Bonds = Slightly negative charged oxygen atom makes it attract the slightly positive hydrogen atom of another water molecule.
    • H20 Solvent = a good solvent as positive and negative parts will attract other charged particles e.g. ions/polar molecules. Allows chemical reactions to take place, acts as a transport medium. Non-polar molecules cannot dissolve.
    • Thermal H20 = Large amount of heat energy needed to raise the temperature of water as it has a high specific heat. This prevents large fluctuations of temperature enabling stable aquatic habitats and a stable environment for enzymes to function.
    • Latent heat vaporization = Large amount of heat energy needed to change the liquid into vapor. This allows organisms to cool while sweating.
    • H20 Transfer = Allows light to pass through, enabling plants to photosynthesise.
    • H20 Density = When in its solid form of ice, it's density is lower so water float on the surface and insulates the water under it. This also prevents the water from completely freezing and allows organisms to survive beneath the ice.
    • Cohesion and structure tension = Individually the hydrogen bonds are weak, but because there are many of them,they stick together in a strong lattice framework. The "sticking" together of water molecules is called COHESION. Cohesion between water molecules produce surface tension, allowing insects to be supported by water and move across.
    • Condensation reaction = where water is removed/eliminated from a molecule.
    • Hydrolysis = where water is added to a molecule.
    • Carbohydrates = molecules made up of carbon, hydrogen and oxygen. Include sugars, starch, glycogen and cellulose. Provide a source of energy - plants (starch), animals (glycogen). Structural role = cellulose.
    • Monosaccharides = Source of energy for respiration.
    • Disaccharides = Joining two hexose units = condensation reaction.
    • Polysaccharides = Starch and glycogen = storage. Cellulose + Chitin = Structural.
    • Chitin=Found in insects and forms part of the exoskeleton. Chitin has amino acids instead of a OH group forming a mucopolysaccharide.
    • Proteins = Consist of carbon, hydrogen, oxygen and nitrogen. Some have sulphr and phosphorus. .
    • Lipids = consist of carbon, hydrogen and oxygen elements. Phosphate present in phospholipids. Lipids cotain lessoxygen than carbohydrates.
    • Primary structure = sequence of amino acids in its polypeptide chains linked by bonds.
    • Secondary structure = consists of alpha helix and beta pleated sheets and hydrogen bonds.
    • Tertiary structure = 3D folding of polypeptide, disulphide bonds, ionic hydrogen and hydrophobic bonds - produces globular proteins.
    • Quaternary structure = combination of two or more polypeptides some have non protein groups attached.
    • Fibrous proteins = Consist of polypeptides in parallel chains or sheets with lots of cross-linkages to form long fibers e.g. keratin.
    • Globular proteins = compact and folded as a specific spherical molecule (3D)


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