Biology- Cycle 1

• 51. What are the basic steps of an optogenetic experiment?

  Inject chlamy opsin gene into brain, stimulate opsin with light to trigger action potential (fire neuron) this is to map the brain
• 50. What is the point of expressing chlamy opsin in brain cells in optogenetics?

  Trigger an action potential in neurons with light
• 49. How is photochemistry different in a photoreceptor vs a photosystem?

  Photoreceptor: energy required from photon to change shape of the molecule photosystem: excited atom gets electron stolen (electron transport) it is easily oxidised
• what's the similarities between the eyespot and the human eye?

  Both contain the pigment retinal that binds with opsin, both are photoreceptors
• what is the difference in opsin in chlamy and the human eye?

  Channelrhodopsin is in the eyespot, and lies on the plasma membrane, its conformation changes from trans to cis, it is motile, flow of calcium ions. Rhodopsin is in the rods and cones, it is not motile, it picks up a g protein, its conformation changes from cis to trans
• 45. Does the retinal in channelrhodopsin or in rhodopsin for from cis to trans?

  rhodopsin
• 44. How does photoisomerization work to change the conformation of retinal?

  When light hits retinal, the conformation changes from trans to cis (chaanging conformation of opsin, opening channels)
• 43. What does an absorption spectrum tell you? What would it say about electrons?

  The relative energies of light, meaning it also tells you about the relative energies of electrons
• 42. Rhodopsin and channelrhodopsin are analogous or homologous structures

  analogous
• 41. What is the difference between a type 1 and type 2 opsin?

  Type 1 opsin: channelrhodopsin and common with bacteria Type 2 opsin: rhodopsin and common in animals (g-protein coupled receptor)
• 40. How are rhodopsin and channelrhodopsin evolutionarily related?

  They are not evolutionarily related, they are analogous
• 39. What is the pigment and the protein within channelrhodopsin?

  Pigment:retinal protein:opsin
• 38. How does rhodopsin work within a photoreceptor in the eye, and where is it located?

  Cis to trans, to pick up g-protein
• 37. What type of cilium is a rod or cone?

  Non-motile cilia (sensory)
• 36. What are the energy states for chlorophyll?

  Red (lower excited state) and blue (higher excited state)
• 35. Do electrons stay in higher energy states?

  No, because it is too unstable
• 34. What is light (or photon) absorption?

  Energy of light captured by an electron (must have equal energies)
• 33. What are the relative energies of blue, green and red light?

  Red-low, green-middle, blue-highest
• 32. What structural characteristic is key in pigment molecules?

  Conjugating system
• 31. How do the basal body and flagella get information from the eyespot?

  Action potential migrates from the membrane to the flagella, information is interpreted by base of flagella, signals to move toward or away from light
• How does a voltage gated channel repolarize a cell?

  Moves sodium out of the cell
• 29. How does channelrhodopsin depolarize a cell?

  Depolarizes by allowing calcium ions to flow into cell
• 28. What type of channel is channelrhodopsin?

  Light gated channel
• 27. What could be the possible protein coding gene that is mutated to make chlamy not Phototactic?

  channelrhodopsin and dynein
• 26. Why might chlamy display negative phototaxis?

  To slow growth rate
• 25. What is phototaxis?

  Movement toward or away from light source
• 24. What is the structure of an eyespot?

  Pigment granules in the chloroplast and channelrhodopsin in the plasma membrane
• 23. What are the two functions of an eyespot and why are they important?

  Energy (traps photon) and information (information about surroundings)
• for overlap between each of them or between all of them?

  Humans and chlamy (both have proteins coding for flagella), Chlamy and plants (proteins that code for photosynthesis), all (proteins that code for DNA replication, cellular respiration and cell cycle)
• 21. What does it mean to be genetically heterogeneous?

  Mutations in two or more loci but give the same phenotype
• 20. What are ciliopathies?

  Diseases linked to mutations in genes involved in cilia structure/function
• 19. What are the two types of cilia and what do they predominantly do?

  Motile (flow and clearance of fluids along a surface) and non-motile(hold sensory proteins: olfaction, eyes, ears)
• 18. What is the protein that will be found in motile cilia?

  dynein
• What protein makes up the shape of cilia?

  tubulin
• 16. What is the basic structure of a cilia? How is that structure arranged?

  Microtubule, 9 doublet, two in the middle, (hollow tube made up of tubulin dimers)
• 15. Why don't plants have flagella?

  Costly, they don't need them
• 13. What are homologs?

  Similarity due to common ancestor
• What kind of trait is a flagella in humans and chlamy?

  homologous
• How would you categorise the flagella of bacteria and eukaryotes?

  Analogous/ homoplasy
• Why would dividing stop in the stationary phase?

  Depletion of nutrients needed for growth (like Fe)