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Biological techniques

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Dalhousie University
BIOL 2020

Jan 6th (lecture 1) Two major groups of cells Eukaryotes: Cells that contain membrane bound organelles (nucleus, mitochondria, etc.) Prokaryotes: Cells that do not contain any membrane bound organelles Do have some internal membranes but not surrounding organelles Karyote = nucleus Eu = true Acomparison of prokaryotic and eukaryotic cells SEE SLIDE 5 (CELL 1 INTRODUCTION) Know this Every life form has DNAas its genetic material and has a membrane Genetic code is very similar between the 2 cell types The origin and evolution of cells SEE SLIDE 6 (CELL 1 INTRODUCTION) Was a common ancestor (not sure when that happened) think it's 2.5 billion years old - planet earth is 4.6 billion years old Genetic tree - all organisms have been sequenced - based on ribosomal DNAsequence 3 major groups - bacteria (eubacteria), archaea (archeabacteria), eucarya Bacteria had a common ancestor with both other cells - when looked at archaea, their sequences are closer to Eucarya than they were to bacteria Live in unusual environments (hot water), high salt concentration etc. To give them that ability they have different lipids, different membranes Fossil record for bacteria Now very complicated - genetic exchange from these organism - lateral gene transfer - not a tree anymore - now a bush - DNAsequences from in similar groups - was the gene swapped somewhere? Stanley Miller Graduate student Took a chamber and filled it with Methane, ammonia, hydrogen gas … heated up and bombarded it with electricity in a closed glass compartment - liquid turned pink - kept heating it and cooling it - knew this was what was going on in earth (solar energy, heat, lightning) after 2 weeks took liquid - found amino acids - started with non life form molecules Died a few years ago When look with better equipment that we have today they found 20 amino acids Found in great quantity = Glycine Are problems - initially there is no DNAor RNA building blocks (no nucleotides) These amino acids - L (we use L in our proteins) proteins evolved to only have L First molecules on earth were amino acids - formed proteins Major problem = proteins were thought to be first Can't make proteins without having DNA-- what happened? how did we get these proteins getting formed in the correct sequenced without having the DNAsequence -- Chek (name) discovered that RNAcan be an enzyme - can be catalytic - changed the thinking Miller thought first molecules on earth were proteins Another theory: RNAfirst and the RNAwas made out of ribonucleotides joined together on what called clay (clay theory) - clay provided a sub straight --- still don't know --- need RNAto make proteins but you also need proteins to make RNA- hoe did one thing evolved and how did the function change so another thing could evolve -- co-evolution? First cell First organism was a prokaryote then after than was photosynthetic bacteria (especially cyanobacteria - played huge role - 2 major reasons: ONE: gets its energy from sunlight and electrons from water (energies electrons with sunlight and then photosynthesis - produced oxygen on planet earth) had water on planet earth but no oxygen on primitive earth - oxygen built up in atmosphere and allowed other organisms to grow on surface on earth instead of under rocks Without cyanobacteria we would all be dead - ability to survive set up by cyanobacteria Oxygen also provided the terminal electron accepted for the eukaryotes- terminal electron acceptor TWO Nitrogen fixation - Nitrogen is a gas (n2) 3 bonds linking nitrogens - very stable however we have to get it into our organic molecules - our bodies have nitrogen - somehow we have to get it into our bodies - even though we breathe it in daily we cannot incorporate it - only a few organisms that can fix N (cyanobacteria is one of them) Nitrogen fixation breaks triple bond and then we can incorporate N into nitrate etc 2 billion years ago = Eukaryotes Humans = tiny sliver Prokaryotes/eukaryotes SEE SLIDE 9 (CELL 1 INTRODUCTION) Prokaryotes - have outer cell wall (almost of all them) have DNA Eukaryotes that have cell walls - fungi and plants Rich in membranes - huge nucleus (SEE SLIDE 10 - CELL1 INTRODUCTION) First organism was a prokaryote Anaerobic = lived without oxygen Bacteria gone through a lot of evolution Heterotrophic = used reduced organic molecules (like glucose) as its carbon source compared to an autotroph which is an organism that uses CO2 as its carbon source (sunlight as energy source) Humans are heterotrophic Primitive organism had a membrane it ate an aerobic prokaryote that aerobic organism that it ate (2.5 billion years ago - O2 being formed in earth) invaginated and evolved to form mitochondria - every cell that has mitochondria = have piece of bacteria our cells are partially bacteria. When it ate this bacteria this primitive cells said "yummy" and decided to keep it. Why? Mitochondria (9%% of energy that our bodies make is made by the mitochondria) so we ate something that produces energy for us and decided to keep it -- evidence for this - mitochondria has 2 membranes (one for bacteria and one for invagination)ALSO mitochondria has own DNA- circular like bacteria - Ribosomal RNAencoded on it like Bacteria - ribosomes are also smaller and looks like bacteria 3) This pre-eukaryote (Invaginating membrane) -- formed 2 membranes around the DNAmolecule and created the nucleus - DNAaway from the cytoplasm also created ER (SEE SLIDE 11 - CELL1 INTRODUCTION) Took up photosynthetic cyanobacteria and formed chloroplasts - now have plants that have mitochondria and chloroplasts that came from bacteria Chloroplasts like cyanobacteria Protist - single cell organism Synthetic cells? Craig Venter - made an organism - took a machine that synthesized DNA- put in code and built a live organisms Have capability of generating life Why would he want to make an organism? using it to make biofuels, pharmaceutical drugs etc. Units of length SEE SLIDE 15 (CELL 1 INTRODUCTION) paramecium and frog eggs Unit of measure we talk about is microns, nanometers and angstrom Most cells are 10-30 microns - need microscope to see them Don't need to know lengths for exams Discovery of light microscopy - light and glass lenses Dutch scientist Spectacle makers - eye glasses Used compound microscopes - had 2 lenses Antonie can Leeuwenhoek Father of microscopy Used microscope that he made his self - first to see bacteria and protocol Merchant of cloth and linen - not a scientist - used microscope for certain reason wanted microscope for thread count Van leeuwenmoe images Very skeptical at first Saw bacteria move and the first to see sperm cells Robert Hooke Microscopist Images from Hooke Looks at large organisms (fleas, ticks, mites) Took a piece of cork and cut it thinly and then looked at it under the microscope - squares reminded him of a monastery and he called them cells The invention of the light microscope led to the discovery of cells ONE: 1665 Robert Hooke used the term cells to describe units of cork TWO: 1839 Theodor Schwann reported that animal tissues were made up o
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