photochemistry

Question 1

light processes important for ____ and _____

Answer 1

photosynthesis and vision

Question 2

Uv (290-400nm) and visible (400-700nm) radiation drive photoactive processes because

Answer 2

they cause electronic transitions in moleecules

Question 3

infared (800+nm) causes _____ transitions

Answer 3

vibrational
(heat)

Question 4

energy formula?

Answer 4

E = hv = hc/(wavelength)

Question 5

in formula E =

Answer 5

photon energy (joules)

Question 6

in formula h is the

Answer 6

planck constant

Question 7

in formula v is

Answer 7

photon frequency (nm)

Question 8

in formula c is

Answer 8

speed of light

Question 9

energy is _____ to wavelength

Answer 9

inversly proportional

Question 10

for organic molecule to absorb light it must have

Answer 10

conjugated double bonds or a conjugated pi-orbital system

Question 11

photohcemical process starts with

Answer 11

absorption of photon

Question 12

absorbance of photon results in

Answer 12

elevation of an electron from a ground state to excited state

Question 13

the photons energy must match the difference in ______ between the ____ and ____ states of the molecule

Answer 13

energy
ground
excited

Question 14

because most organic molecules have all electrons in _____ bonds, all electrons are _____ with opposite _____. this is the ____ _____ principle

Answer 14

covalent
paired
spin
pauli exclusion principle

Question 15

net electron spin in organic molecules is ___ and they exist as ____ ____ molecules

Answer 15

O
singlet state molecules

Question 16

when the molecule absorbs a photon, ___ is conserved, therefore excitation is always from…

Answer 16

spin
the ground singlet state to the excited singlet state

Question 17

hydroxyl radicals can attack what biomolecules?

Answer 17

any

Question 18

phototoxic compounds can have ______-icidal properties

Answer 18

insect-icidal

Question 19

Psoralen:
inhibits _____ and sterilizes _____

Answer 19

cell division, blood

Question 20

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 ____

Answer 20

psoralen-DNA
Diels-Alder

thymines, covalently crosslinked
light

Question 21

beer products formed during ___ and ____

Answer 21

malting and fermentation

Question 22

composition of beer from

Answer 22

barley and hops

Question 23

there are 4 catagories of Malt volatiles

Answer 23

lipid oxidation products
maillard reaction products
alipathic sulfur compounds
phenols

Question 24

lipid oxidation products of malt are
short chain _____ and ______ enols. present at ____ conc

Answer 24

short chain aldehydes and shortchain enols (low conc)

Question 25

maillard products of malt are
important for ___ and ____.
they are from sugar ____ and _____
the pigments (___ and ___) are from _____
____ in food from heating

Answer 25

flavour and colour
sugar oxidation and modifications
yellow & brown, melanoidins
caramelization

Question 26

sulfur volatiles of malt
_____ sulfide
from degradation of _____ and _____
must be controlled for ___ ___

Answer 26

dimethyl sulfide
methionine and cysteine
flavour quality

Question 27

phenols of malt are
from ____ and _____ acid during malting
consumed by ___ during fermentation
in ___ content

Answer 27

ferulic and coumaric
yeast
low

Question 28

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)

Answer 28

bitter
skunky
humulus luipulus
egypt
maple
preservative
allelopathic (kills fungi but not yeast)

Question 29

hops flavour from ___ oil.
the thioesters give ____ flavour.
the_______ give hoppy smell.
the ______ give flavour

Answer 29

hop
cheesy
terpenes
hop acids

Question 30

hop acid examples

Answer 30

terpenoid alcohols, ketones and esters

Question 31

hop acids do what to the foam?

Answer 31

stabilize the foam

Question 32

hop acids interconverted by ___ and ___

Answer 32

heat and light

Question 33

iso-alpha-acids
present at ___-___ ppm
flavour threshold at ___ ppm
skunky flavour at ___ppm

Answer 33

10-25
5.6
1

Question 34

light struck reaction of iso-alpha-acids:
makes ___
occurs in ___ light
is visible with _____ (abs at ___nm)
forms ___ volatiles

Answer 34

beer
UV or visible
riboflavin
450
sulfur

Question 35

uv radiation at what range

Answer 35

290-400nm

Question 36

visible light at what range

Answer 36

400-700nm

Question 37

infared radiation at what range

Answer 37

800+

Question 38

_____ transitions required for photochemistry

Answer 38

electronic

Question 39

electrons can only jump to excited state when there is

Answer 39

photon absorbance

Question 40

type 1 vs 2 photosensitizers

Answer 40

type 1 does NOT need light
type 2 needs light

Question 41

cellular defenses against ROS x2
what do they make

Answer 41

catalase, GHS peroxidase
they make water and other nontoxic compounds

Question 42

NaBH4 prevents

Answer 42

proper breakdown of iso-alpha-acids (can’t go light struck bc already reduced - can’t make reg beer)