CORE CONCEPTS
- Created by: Former Member
- Created on: 30-05-19 15:41
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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
- Phospholipid bilayer
- 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
- DNA helicase breaks H bonds + unzips strand, free DNA nucleotides enter
- 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
- Translation
- 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
- Consists of amylose and amylopectin
- 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
- Monosaccharide
- 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)
- Uses
- 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
- Water
- 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
- Biosensors
- 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
- Competitive
- 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
- Use
- Membranes
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