lab techniques MCAT Flashcards
what part of the battery do the molecules in gel electrophoresis travel towards?
anode which is positively charged; although it’s an electrolytic cell, doesn’t behave like electrochemical solutions in electrolytic cells where the electrons –> cathode (neg charged)
how does mass spectrometry differ from spectroscopy?what’s the base and parent peak? what does the parent peak tell you?
doesn’t study how matter responds to electromagnetic radiation, but rather the matter is engaging with a magnetic field; parent peak (molecular ion) is the heaviest fragment (maybe didn’t ionize) and base peak is the fragment that shows up in the greatest abundance, compare all the peaks to the base peak to figure out the relative abundance; all the fragments have the same acceleration when moving through the beam; parent peak tells you the molecular weight of the sample
what is DNA recombination?
process of pasting together different DNA fragments; achieved by using endonucleases (restriction enzyme) that recognize the same restriction site (palindromic sequence), because no matter how you cut DNA1 and DNA2, as long as they are cut at the same restriction site, they can be pasted together
Process of cloning DNA; why it’s useful
useful b/c it’s not ideal to only have one piece of DNA that needs to be studied; things can go wrong so better to have many; cut out the gene of interest via restriction enzymes, insert into vector (plasmid or virus), insert within a gene that codes for a certain function (i.e. breaking down lactose), plasmid has antibiotic resistance, insert vector into same vial as bacteria, shock system and bacteria take up plasmid via transformation, bacteria divides and grow on medium that has an antibiotic and sugar, so only those that can break down the antibiotic survive (b/c antibiotics kill bacteria, but if the bacteria has resistance, it won’t die), and bacteria that don’t break down the sugar will look a different color and gene of interest is amplified
NMR, IR, vs UV-vis
NMR is how compounds interact with radio waves; about knowing the location of protons, study nuclei with odd numbered atomic mass or atomic number b/c protons experience nuclear spin, if enough energy is supplied proton will adopt beta state which means it orients in the same direction of the magnetic field, when it releases energy to come back down to ground state, releases electrical impulses which are detected by spectrometer; frequency and thus energy is the same, but protons that experience shielding require a greater magnetic field in order to be excited to beta state
IR
infrared spectroscopy studies molecules that have dipoles, when hit with electromagnetic energy from infrared region, dipole will compress and stretch (centers of the positive and negative ends of the dipole move in opposite directions), looking at intramolecular vibrations and rotations, stronger bonds require greater energy to resonate and thus have a smaller wave number; sp > sp2 > sp3; C=O (1700cm-), saturated CH (2800-3000), OH in COOH (2500-3000), OH (3200-3600)
UV-vis
studying conjugated systems and how they respond to electromagnetic energy from UV region (smaller range than IR region), electron excitation from LUMO –> HUMO, study the intensity of the light after it’s been absorbed by the sample, absorbance proportional to concentration, length, and molar absorptivity (constant), each additional conjugated double bond increases wavelength by 30-40nm; when we have 8+ conjugated bonds, move to the visible light region (explains why more conjugation absorbs lower strength of energy)
mobile and stationary phase of gas chromatography
mobile phase is the gas, stationary phase is the liquid along the inner wall of the tube
