yr 13 sequences

• ATP


  Releases energy in small amounts, broken down in one step and makes energy more reactive, phosphorylates substances to lower activation energy, can be rapidly re-synthesised, is not lost from cells, made from ADP and phosphate
• Light dependent reactions


  Light excites electrons to move along electron transfer chain releasing energy, photolysis of water, NADP reduced
• Light independent reactions


  CO₂ combines with RuBP to form 2 glycerate phosphate molecules using enzyme Rubisco, GP reduced to triose phosphate using NADPH
• Glycolysis


  Phosphorylation of glucose, oxidation of triose phosphate to pyruvate, net gain of 2 ATP
• Krebs cycle


  2C acetyl coenzyme A combines with 4C molecule, NAD and FAD reduced
• Oxidative phosphorylation


  Reduced NAD and FAD pass along carriers through electron transport chain, energy released used to produce ATP
• Measuring biomass


  Collect and dry plant material in oven below 100°C, repeat until constant mass, then weigh
• Nitrogen cycle


  Protein/amino acids/DNA converted to ammonium by saprobionts, ammonium converted to nitrite then nitrate by nitrifying bacteria, nitrates converted to nitrogen by denitrifying bacteria
• Phosphorus cycle


  Phosphate ions in sedimentary rocks, weathering and erosion releases dissolved ions, ions absorbed by plants, passed to animals, excess ions excreted and broken down by bacteria, ions released back into soil/water, deposited to form sedimentary rocks
• Reflex arc


  Stimulus detected by receptors, action potential sent along sensory neurons to central nervous system, reflex neurone sends impulse to effectors (muscles or glands), response is rapid and protective
• Auxin


  Growth factor produced in uneven distribution in shoot tips, causes elongation of cells in shoots towards light, reduces elongation of cells in roots away from light
• Gravity


  Auxin moves by diffusion, causes elongation of cells in shoots away from gravity, prevents elongation of cells in roots towards gravity
• Resting potential


  Na+/K+ pump uses active transport to maintain negative potential difference across membrane
• Action potential


  Na+ channels open causing depolarisation, K+ channels open causing hyperpolarisation, cycle repeats
• Pacinian corpuscles


  Receptors that detect pressure, become deformed by pressure stimulus, Na+ channels open if threshold reached
• Heart beat


  SAN sends wave of electrical activity across atria, AVN delays impulse, bundle of His sends impulses down to ventricles
• Control of heart rate


  Baroreceptors detect changes in blood pressure, chemoreceptors detect changes in CO₂, medulla sends more/fewer impulses to SAN via sympathetic/parasympathetic nerves
• Neurotransmitter release


  Depolarisation of presynaptic membrane causes Ca2+ channels to open, Ca2+ influx causes synaptic vesicles to fuse and release acetylcholine, acetylcholine binds to receptors on postsynaptic membrane
• Muscle contraction


  Calcium ions bind to troponin, removing blocking action of tropomyosin, exposing myosin binding sites, ATP allows myosin to detach from actin, releasing energy for power stroke
• Calorimetry


  Use Benedict's reagent and heat to measure absorbance, use this to determine glucose concentration in unknown samples
• Serial dilutions


  Add part sample to 9 parts sterile liquid to make 10-fold dilutions
• Ultrafiltration in the kidney

  High blood pressure/hydrostatic pressure causes small molecules to pass through basement membrane, proteins too large to pass through
• Glucose reabsorption in the kidney


  Glucose reabsorbed from kidney tubule into blood by diffusion in proximal convoluted tubule, sodium ions actively transported out in ascending limb, water follows by osmosis in descending limb
• ADH role in urine production

  Low blood volume detected by hypothalamus, pituitary releases ADH which increases permeability and opens water channels in collecting duct, more water reabsorbed
• Natural selection


  Variation present in original population, individuals with advantageous alleles more likely to survive and reproduce, increasing frequency of advantageous alleles
• Speciation


  Reproductively isolated populations, different selection pressures lead to different features being selected for, populations become genetically different and unable to produce fertile offspring
• Random sampling


  Randomly placed quadrats or transects to obtain representative samples, measure variables at each site
• Mark-release-recapture


  Capture sample, mark and release, then recapture to estimate population size
• Ecological succession


  Colonisation by pioneer species, changes environment to be less hostile, new species able to establish, leading to climax community
• Types of mutations


  • No effect, change in amino acid sequence, change in protein structure, new allele with no influence on phenotype, positive effect on protein properties
• Transcription regulation


  Transcription factors bind to promoter region, interact with RNA polymerase to promote or prevent transcription
• RNA interference


  siRNA binds to mRNA, prevents translation of proteins
• Epigenetic control


  Methylation of cytosine suppresses transcription, acetylation of histones relaxes DNA structure and stimulates transcription
• In vivo cloning


  Restriction endonucleases cut plasmid and gene of interest, ligase joins them, bacteria transformed and selected for
• In vitro cloning


  Heat breaks DNA bonds, primers and DNA polymerase used to replicate DNA, repeated cycles
• DNA fingerprinting


  DNA cut using restriction endonucleases, separated by electrophoresis, transferred to membrane, probes used to identify specific sequences