July 22nd

Question 1

electrophoresis

Answer 1

separates DNA and proteins based on size

Question 2

UV spectroscopy

Answer 2

passing UV light through a chemical species and plotting wavelength vs absorbance - useful for studying double bonds or atoms wiht lone pairs bc need electrons that are free to interact

Question 3

H-NMR

Answer 3

type of nuclear magnetic resonance

• type of proton= how many peaks
• desheilded proton = to the left ( means that there are lots of electron withdrawing groups)
• splitting = hydrogens on adjacents carbons will split a peak into n + 1 subpeaks, n = # of hydrogens on adjacent carbon

Question 4

H-NMR

Answer 4

type of nuclear magnetic resonance

• type of proton= how many peaks
• desheilded proton = to the left ( means that there are lots of electron withdrawing groups)
• splitting = hydrogens on adjacents carbons will split a peak into n + 1 subpeaks, n = # of hydrogens on adjacent carbon

Question 5

Electrophoresis

Answer 5

separate proteins - charge and size

electrolysis cell so anode is positive ( neg proteins travel here)

polyacrylamide gel (PAGE) is standard gel used ( acts like a sieve- allowing smaller ones to pass faster)

Question 6

PAGE limitations

Answer 6

mass and charge ( so it’s good if say proteins have similar size)

Question 7

SDS-PAGE

Answer 7

separates proteins based on their size only - they all get same negative charge

Question 8

isoelectric focusing

Answer 8

separate proteins based on PI point

• acidic gel at positive anode
• electrolytic cell as well so anode is positively charged (acidic amino acids will be attracted to the positive side- this is also where low pH is) they will eventually stop when they reach their PI

Question 9

what pH is at the anode in isoelectric focusing

Answer 9

low pH and positive anode

Question 10

thin-layer chromatography

Answer 10

spots on the stationary phase, mobile phase runs through it

pare is highly polar

paper = polar (silica paper) and the mobile phase is polar

Question 11

thin-layer chromatography

Answer 11

spots on the stationary phase, mobile phase runs through it

Question 12

is silica polar

Answer 12

very

Question 13

column chromatography

Answer 13

column filled with silica or alumina beads as absorbent (stationary phase) and solvent passed through

• first eluted = less polar

Question 14

what travels highest in TLC

Answer 14

nonpolar substances ( bc paper is silica)

Question 15

RP-chromatography

Answer 15

-N-M-N, so if RP than the mobile phase is polar

Question 16

size -exclusion

Answer 16

beads contain tiny holes, so the biggest ones get eluted first

Question 17

HPLC

Answer 17

N-M-N, the mobile phase is non-polar

Question 18

Hills coefficent

Answer 18

numerical value for cooperativity in enzyme kinetics

• the value of hills constant indicates the nature of binding by the molecule
• if hills is greater than 1 = positive cooperative binding
• if hills less than 1 = negative cooperativity - ligand binds, the affinity for further ligans decreases
• hills= 1 = no cooperativity

Question 19

cooperativity in enzymes

Answer 19

• show a sigmondal (S-shaped) graph- due to cooperativity amoung substrate binding sites
• 2 states; high affinity (R) relaxed state, or (T) low-affinity tight state
• binding of substrate, encourages other enzymes to go to R states
• hills coeficient tells us about cooperativity ( if >1 = positive, if <1 = negative

Question 20

catalytic effecicency

Answer 20

kcat/km ( high efficentcy if large kcat or small km= high affinity)

Question 21

kcat

Answer 21

measures the number of substrates turned ober/ enzyme/second

Question 22

extractions

Answer 22

2 immiscible solvents - form 2 layers

• seperatory funnel –> denser one on bottom ( commonly the aqueous layer is more dense)

Question 23

are dipole-dipole interactions in molecules going to put them in the aquous layer

Answer 23

not commonly no

Question 24

simple distillation

Answer 24

• differences in BP - lower will vaporate first

- below 150 and have atleast 25 C difference between them

Question 25

vaccum distillation

Answer 25

if BP is over 150 - using a vacuum lowers the ambient pressure and thereby decreasing the heat needed to boil a liquid

Question 26

fractional distillation

Answer 26

to separate 2 with simular BP (less than 25 degrees)

• fractional column ( squiggly) - surface area is increased, as vapor rises it condenses on this surfaces and refluxes down untill it vaporizes again

Question 27

is cellulose polar or nonpolar

Answer 27

polar (used as stationary phase on TLC) - hella OH

Question 28

gas chromatography

Answer 28

same principle as column chromatography but the elutent is the gas, how well do they adhere to the absorbant

• and on the edges of column is crushed metal or polymer in a coil which is heated - particles that adhere to the sides - eluted last
• smaller ones travel faster
• injected compound must be volatile

Question 29

just plain old simple column chromatography

Answer 29

N-M-N

mobile phase is the solvent and the column is filled with silica or alumina beads

Question 30

mass spectrometry

Answer 30

ionization and fragmentation of compounds, fragments run through magnetic feild, which seperates mass-to-charge ration

• can determine total mass or relative concentrations of different fragments

Question 31

MRI

Answer 31

magnetic resonance imaging - most actually measure H-NMR spectra of water molecules in different environments in the body

Question 32

spectroscopy

Answer 32

measures energy differences by determining the frequencies of electromagnetic radiation absorbed by the molecules

The basic principle shared by all spectroscopic techniques is to shine a beam of electromagnetic radiation onto a sample, and observe how it responds to such a stimulus. The response is usually recorded as a function of radiation wavelength

spectroscopy is the study of the interaction between matter and electromagnetic radiation (via electron spectroscopy, atomic spectroscopy, etc). Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, by a prism.

Question 33

IR vs UV spectroscopy

Answer 33

• the wavelength of infrared light is longer than uv/vis. -
• Infrared absorption by molecules corresponds to differences in vibration energy. Infrared spectroscopy can therefore be used to identify molecular vibrations and uniquely recognize compounds and functional groups
• Uv/vis absorption by molecules correspond to differences in the (covalent) bonding of atoms.
• used for studying lone pairs or molecules with pi bonds such as transition metal ions, highly conjugated organic compounds, and biological macromolecules.

Question 34

UV spec

Answer 34

• wavelength of max absorbance can be determined
• record absorbance and plot against wavelength
• absorbance caused by electronic transitions between orbitals
• works bc molecules with pi electrons or non-bonded electrons can be excited by UV light to higher antibonding orbitals

Question 35

NMR

Answer 35

certain atoms have atomic nuclei that have magnetic moments

when they are placed in a mag feild, their moments tend to aligh with or against the direction of applied field

Question 36

if nuclei align with applied field…

Answer 36

they are said to be in alpha state= lower energy