CORE CONCEPTS

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  • Core concepts
    • Membranes
      • Phospholipid bilayer
        • Phosphate head - hydrophilic
        • Fatty acid tail -hydrophobic
      • Glycoprotein
        • Carb. chain attached to extrinsic protein, for cell recognition
      • Cholesterol: stability
      • Glycolipid
      • Proteins
        • Extrinsic: cell signalling + cell recognition
        • Intrinsic: passage of polar molecules
      • Permeability
        • Higher temp = increase
        • More cholesterol = less fluid = decrease
        • Short unsaturated chains pack looser = increase
    • Transport
      • Active transport: requires ATP to transport against gradient
      • Diffusion: transport down concentration gradient
      • Facilitated diffusion: transport of polar molecules down a concentration gradient
        • Uses intrinsic/ channel  proteins
      • Osmosis: transport of water down ? gradient
      • Cytosis
        • Endocytosis: transport of large quantities into cell
        • Exocytosis: transport of large quantities out of cell
    • Cell structure
      • Golgi body: modifies some proteins/lipids forms vesicles + lysosomes
      • Nucleus: codes for protein synthesis, nucleolus = sit of rRNA synthesis
      • RER:  transports proteins to Golgi in vesicles
      • SER: synthesises + transports lipids to Golgi
      • Lysosomes: hydrolytic enzymes for autolysis/ phagocytosis
      • Ribosome: protein synthesis, 70S in prokaryotes
      • Mitochondria: site of aerobic respiration, ATP production
      • Cell wall: mechanical strength + support, prevents cell lysis
    • DNA replication
      • DNA helicase breaks H bonds + unzips strand, free DNA nucleotides enter
        • Leading strand: DNA polymeraseforms phosphodiester bond 5'?3'
        • Lagging strand: DNA polymerase forms phosphodiester bond 5' to 3' in segments DNA ligase joins sections
    • Protein synthesis
      • Translation
        • 2nd stage occurs in ribosome
        • 2x codon in ribosome then 2x tRNA line up anticodon then peptide form between a.a repeats until stop codon reached
          • tRNA reused
        • Amino acid attaches to correct tRNA
      • Transcription
        • 1st stage occurs in nucleus
        • DNA helicase  then free RNA nucleotides then RNA polymerase then splicing and joining by DNA ligase
          • RNA polymeraseforms pho-sphodiester bond
    • Biological compounds
      • Water
        • Cohesive, allows for transpiration stream
        • Polar
        • High latent heat of vaporisation, acts as coolant (eg. sweat)
        • Low viscosity, important for lubrication of joints
        • High SHC, stable temp for aquatic life
      • Carbohydrate
        • Monosaccharide
          • a-glucose,   B-glucose, fructose, galactose
        • Disaccharide
          • Sucrose, maltose, lactose
        • Glycogen
          • Branched, compact, main glucose storage in body
        • Starch
          • Consists of amylose and amylopectin
            • Amylose = 1,4 glycosidic bond
            • Amylopectin= 1,4 glycosidic bond + 1,6  between branches
          • Branched, compact
        • Cellulose
          • a-glucose, straight chain (180? rotation)
          • Hydrogen bonds between chains
          • Structure in plants (cell wall)
        • Chitin
          • B-glcuose, straight chain, contains N
          • Insect exoskeleton
      • Lipids
        • Uses
          • Insulation
          • Buoyancy
          • High energy store
          • Metabolic water
          • Waterproof
        • Glycerol + fatty acid
          • Complex = plus extra molecule
        • Triglycerides: 3x fatter acid + 1 x glycol (ester bond)
      • Proteins
        • 1, 2, 3 and 4 structures
        • Globular and fibrous proteins
        • Enzymes, hormones, immunology
      • Food tests
        • Protein: add Biuret solution. Turn purple
        • Reducing sugar: addition of Benedict's solution + heat. Blue to red
        • Non-reducing sugar: addition of HCl + NaOH then Benedict's solution + heat. Blue to red
        • Starch: addition of iodine. Brown to blue/black
        • Lipids: add ethanol. Emulsion forms
    • Enzymes
      • Use
        • Lowers activation energy by providing an alternative pathway
        • Increases rate of reaction
      • Immobilised enzymes
        • Biosensors
          • Instantly measure metabolite concentration
          • Digital (quantitative) and simple (qualitative) types
        • Advantages
          • Increased surface area
          • Easily removable + reusable
          • Works at higher temperature and wider pH
        • Disadvantages
          • Can reduce rate as rely on movement of substrate
          • Successful development is expensive
      • Inhibition
        • Competitive
          • Increase inhibitor decreases chance of substrate binding
          • Similar shape to substrate
          • Inhibitor binds to active site
        • Non-competitive
          • Binds to allosteric site and changes active site shape
          • Substrate can no longer bind
        • End product
          • Increase end product inhibits reaction as product binds as a non-competitive inhibitor
          • Decrease end product reverses inhibition so reaction starts again
      • Factors + graphs
        • pH: Highest ROR at optimum pH, extreme change stops reaction
        • Increase temperature Increase ROR up to a point, then denatures
        • Increase substrate concentration Increase ROR until enzyme is the limiting factor
        • Increase enzyme concentration Increase ROR until substrate is limiting factor
      • Key points
        • Globular protein
        • Specific to substrate
        • Polar
      • Theories

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