photochemistry Flashcards
light processes important for ____ and _____
photosynthesis and vision
Uv (290-400nm) and visible (400-700nm) radiation drive photoactive processes because
they cause electronic transitions in moleecules
infared (800+nm) causes _____ transitions
vibrational
(heat)
energy formula?
E = hv = hc/(wavelength)
in formula E =
photon energy (joules)
in formula h is the
planck constant
in formula v is
photon frequency (nm)
in formula c is
speed of light
energy is _____ to wavelength
inversly proportional
for organic molecule to absorb light it must have
conjugated double bonds or a conjugated pi-orbital system
photohcemical process starts with
absorption of photon
absorbance of photon results in
elevation of an electron from a ground state to excited state
the photons energy must match the difference in ______ between the ____ and ____ states of the molecule
energy
ground
excited
because most organic molecules have all electrons in _____ bonds, all electrons are _____ with opposite _____. this is the ____ _____ principle
covalent
paired
spin
pauli exclusion principle
net electron spin in organic molecules is ___ and they exist as ____ ____ molecules
O
singlet state molecules
when the molecule absorbs a photon, ___ is conserved, therefore excitation is always from…
spin
the ground singlet state to the excited singlet state
hydroxyl radicals can attack what biomolecules?
any
phototoxic compounds can have ______-icidal properties
insect-icidal
Psoralen:
inhibits _____ and sterilizes _____
cell division, blood
photodynamic therapy based on photochemical reaction of ______-____ adducts via the ________ reaction
for psoralen + 2 thymines: if two ___ are in opposite strands of DNA, the DNA strands will become _________ ______. this process only occur in the presence of ____
psoralen-DNA
Diels-Alder
thymines, covalently crosslinked
light
beer products formed during ___ and ____
malting and fermentation
composition of beer from
barley and hops
there are 4 catagories of Malt volatiles
lipid oxidation products
maillard reaction products
alipathic sulfur compounds
phenols
lipid oxidation products of malt are
short chain _____ and ______ enols. present at ____ conc
short chain aldehydes and shortchain enols (low conc)
maillard products of malt are
important for ___ and ____.
they are from sugar ____ and _____
the pigments (___ and ___) are from _____
____ in food from heating
flavour and colour
sugar oxidation and modifications
yellow & brown, melanoidins
caramelization
sulfur volatiles of malt
_____ sulfide
from degradation of _____ and _____
must be controlled for ___ ___
dimethyl sulfide
methionine and cysteine
flavour quality
phenols of malt are
from ____ and _____ acid during malting
consumed by ___ during fermentation
in ___ content
ferulic and coumaric
yeast
low
hops are
sources of beer’s _____ taste
source of light beer’s ___ flavour
from the plant _____ _____
used in ancient ___
leafy vine plant, leaves shaped like ____ leaf
originally used in brewing as _____
hop acids are ______ (def)
bitter
skunky
humulus luipulus
egypt
maple
preservative
allelopathic (kills fungi but not yeast)
hops flavour from ___ oil.
the thioesters give ____ flavour.
the_______ give hoppy smell.
the ______ give flavour
hop
cheesy
terpenes
hop acids
hop acid examples
terpenoid alcohols, ketones and esters
hop acids do what to the foam?
stabilize the foam
hop acids interconverted by ___ and ___
heat and light
iso-alpha-acids
present at ___-___ ppm
flavour threshold at ___ ppm
skunky flavour at ___ppm
10-25
5.6
1
light struck reaction of iso-alpha-acids:
makes ___
occurs in ___ light
is visible with _____ (abs at ___nm)
forms ___ volatiles
beer
UV or visible
riboflavin
450
sulfur
uv radiation at what range
290-400nm
visible light at what range
400-700nm
infared radiation at what range
800+
_____ transitions required for photochemistry
electronic
electrons can only jump to excited state when there is
photon absorbance
type 1 vs 2 photosensitizers
type 1 does NOT need light
type 2 needs light
cellular defenses against ROS x2
what do they make
catalase, GHS peroxidase
they make water and other nontoxic compounds
NaBH4 prevents
proper breakdown of iso-alpha-acids (can’t go light struck bc already reduced - can’t make reg beer)
