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Biology 1001A
Tom Haffie

Lecture 1: Light; Energy & Info Themes: interaction of light with biology; fundamental to evolution of light -light is used by biological systems for a source of energy and a source of info about the environment -chlamydomonas (single celled organism) is the best model system for looking at biology of light as a source of energy and a source of info Chlamydomonas: (aka chlamy) a sexually active, light-harvesting, carbon- reducing, hydrogen-belching planimal -genome sequence has attributes of an animal and plant; distantly related to plant and more distantly related to animals -as a model system for understanding basic biology, nothing beats the unicellular flagellate chlamydomonas Cartoon depiction of a single chlamydomonas cell -green alga -found in ponds, rivers -lots of attributes at cellular level (1) single nucleus- gene expression, gene transcription; very similar to nucleus of human or animal cell or plant cell; (2)basal body – found at base of any cilium or flagellum in a eukaryotic cell; where microtubules develop to produce two flagellum a number of human diseases that are caused by mutations that make the cilia in humans that doesn’t develop correctly chlamydomonas is a model system for looking at cilia and flagella structure and function bc eukaryote; and flagella is identical in chlamy as it is in humans (3) endoplasmic reticulum, ribosomes (site of protein synthesis), Golgi (packaging and sorting of proteins) very similar to what happens in a human cell human cells are much harder to work with than chlamy; able to grow litres of chlamy cells in the lab (4) mitochondria- ATP factories of the cell; cellular respiration; eukaryote which has more than one mitochondria; animals cells have mitochondria (5) chloroplast- eukaryote has more than one chloroplast; plants have chloroplast however chlamy cells have BOTH mitochondria and chloroplast within the came cell!!—has both major energy transducing factors of the cell- respiration and photosynthesis one single chloroplast which has a region called (6) pyrenoid which is where carbon fixation takes place (7) eyespot- orange in colour bc has pigment called carotenoid; found within chloroplast but has nothing to do with photosynthesis enables the single chlamy to orient itself in relation to light, the light it wants to harvest for photosynthesis; wants to get closer to light, harvest lots of light so eyespot detects the light and swims towards the light to harvest lots of light for photosynthesis relationship between eyespot and chloroplast but eyespot has nothing to do directly with photosynthesis; just moves the algea  link between eyespot and flagella; pathway not totally known -hundreds of people work on chlamy; graduate, postdocs on a huge variety of things bc chlamys a good system for genetics and cell biology -cell biology—fluorescently labeled a protein, see distribution of different colours of them (green, red, blue) -the power of having a model like chlamy enables us to answer questions that you cant in other systems; too complex in other systems -some chlamy cells living in Canada; many in the Antarctica -species called extremophiles (cells can grow under very extreme conditions) -17 metres below sea ice in Antarcitca theres lots of chlamy cells growing and its -2 degrees; adapted to condition -if you take them out of condition and try to grow them in a regular temp room, these chlamy cells will die; adaptation to extreme environments—cold, dark algea Evolution of Complexity -comes from latin ―complexus‖…entwined, twisted together -complex system, to twist something together you need two things -more than one entity that come together -ex protein complex where many proteins must come together to produce a single molecule or receptor binding of a hormone -something that is more complex has more things that come together to produce that system -defining complexity is hard -measuring complexity is easy (1) measuring complexity of cell size; chlamy is a single eukaryoke; electron micrograph—looks like you have more than one chloroplast (see membranes of chloroplast) electron micrograph takes a very thin slice; but it is in fact one chloroplast; lots of membranes; cell is big (10 microns in diameter); much bigger than bacterium **is a bacterium smaller than a eukaryotic cell??? YES for all cases; bacterium is only 1 micron and eukaryotic cell is much larger (10x increased in diameter, volume is 4/3 pi radius cubed = 1000 fold increase in volume) chlamy has 1000 fold more volume than ecoli; WHY?? the rise of the eukaryotic cell (2) genome size and complexity are directly related? Is genome size a good measure of complexity? -can have very similar organisms with very different genome sizes; so in many cases genome size is not a good indicator of complexity -with chlamy it seems to be; humans have 25x the genome size of chlamy and chlamy is much larger than ecoli (3) PCG (protein coding genes): how many proteins does your genome code for? -might be a better measure of complexity? -junk dna; genome size can mislead you; maybe pcg does too…. Evolution of Multicellularity -chlamy is a great system to look at this; looking at all 6 related species of algea which have vastly different le
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