option b enzyme kinetics, pigment and anthrocyanin electron conjugation
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Prepared by Lawrence Kok
Option B, Enzyme Kinetics, Pigment and Anthrocyanins electron conjugation.
Evaluate specificity of enzyme for substrateLow Km – High affinityHigh Km – Low affinity
SKSV
vm
][max
Enzyme kinetics
Michaelis Menten eqn
Enzyme Enzyme/substrate complex Product
Rate
Sub conc
Max rate velocity
2maxV
Km
Km = [S] when rate is half Vmax
Rate
Sub conc
High [S] conc – enzyme saturated – all active sites not available (zero order)
Low [S] conc - rate proportional to [S] - all active sites available (1st order)
Saturation occurs in formation of complex
Rate
Sub conc
Enzyme A
Enzyme B
Km – LowRate HIGHERHigh affinity at low [S] conc
Km - HighRate LOWERLow affinity
KmKm
mK
SKSV
vm
][max
Low [S]Km >[S]
High [S]Km <[S]
][
][
max
max
SKV
v
KSV
v
m
m
(1st order) rate prop to [S] All active site available
max
max
max
][
][
Vv
SSV
v
SKSV
vm
(zero order) to [S] All active site saturated
constant
Evaluate specificity of enzyme for substrateLow Km – High affinityHigh Km – Low affinity
SKSV
vm
][max
Enzyme kinetics
Michaelis Menten eqn
Enzyme Enzyme/substrate complex Product
Rate
Sub conc
Max rate velocity
2maxV
Km
Km = [S] when rate is half Vmax
Rate
Sub conc
High [S] conc – enzyme saturated – all active sites not available (zero order)
Low [S] conc - rate proportional to [S] - all active sites available (1st order)
Saturation occurs in formation of complex
Rate
Sub conc
Enzyme A
Enzyme B
Km – LowRate HIGHERHigh affinity at low [S] conc
Km - HighRate LOWERLow affinity
KmKm
mK
m
cat
KK
efficiencycatalytic .
mcat KK
Kcat = turnover number- max sub convert to product per second (Enzyme saturated)
Click here view KM Click here Michaelis Menten
Competitive Inhibitor
Rate
Sub conc
Max rate velocity
Km = [S] when rate is half Vmax
Rate
SKSV
vm
][max
Low [S]Km > [S]
High [S]Km < [S]
][
][
max
max
SKV
v
KSV
v
m
m
(1st order) rate prop to [S] All active site available
max
max
max
][
][
Vv
SSV
v
SKSV
vm
(zero order) to [S] All active site saturated
Compete same active site
Structurally similar
Enzyme kinetics
No Inhibitors
Sub conc Sub conc
Non Competitive Inhibitor
enzyme
substrate inhibitorsubstrate
enzyme
Competitiveinhibition
Non-competitive inhibition
Active site Bind active site
Bind allosteric site
Effect Vmax No change Decrease
Effect Km Increase No change
Bind diff site (allosteric site)
Structurally different
inhibitor substrate
enzyme
Km ↑ - Enzyme affinity ↓
V max - No change High [S] to achieve
Vmax
V max – Lower ↓ Changed Enzyme unavailable
Km - No changeEnzyme affinity
unchanged
allosteric site
Sub Conc
Rate, v
0.02 10.8
0.04 18.5
0.07 26.7
0.1 32.5
0.15 39.2
0.2 43.3
0.3 48.7
0.5 54.4
Enzyme activity measured against substrate conc. Find Vmax and Km
Vmax
Sub conc
Rate
= 60
Km = 0.1
0.1 0.2 0.3 0.4
V max – Lower ↓ - Enzyme unavailableDon’t alter active site – no effect on Km
Alter conformational change enzyme NOT substrate binding (affinity)Km - Unchange- Enzyme affinity unchanged
V max – Unchanged – High [S} will reduced inhibitionCompete for same active site - substrate binding (affinity) lower ↓Km - Change- Enzyme affinity lower ↓
Vmax
Vmax
Km Low Km High
Sucrose conc
RateNo
inhibitor
RateInhibitor
0.029 0.181 0.095
0.058 0.266 0.140
0.088 0.311 0.165
0.117 0.338 0.180
0.175 0.369 0.197
Vmax
Vmax
0.4
0.2 V max – Lower ↓ - Enzyme
unavailableDon’t alter active site – no effect
on Km
Km - Unchange- Enz affinity unchanged
Km same
2maxV
Km
Rate
Sub conc
Sub Conc
Rate, v
0.02 10.80.04 18.5
0.07 26.7
0.1 32.5
0.15 39.2
0.2 43.3
0.3 48.7
0.5 54.4
Enzyme activity measured against substrate concFind Vmax and Km
Vmax
Sub conc
Rate
= 60
Km = 0.1
0.1 0.2 0.3 0.4
At low sub conc, all active site free, rxn directly proportional to sub conc
State /explain how rate enzyme catalyzed rxn related to substrate
conc
Compare enzymes and inorganic catalyst
Enzyme Catalyst
Similarity Both increase rate
Both lower activation energy
No effect on yield
Differences Protein Not protein
Show saturation kinetic (hyperbolic curve)
Do not (linear relationship)
Regulated by inhibitor Less likely
Sensitive to Temp/pressure Not affected
Rate
concRate – 1st order
Rate zero order
At high sub conc, all active site saturated, rate reach its max
2maxV
Km
C C
Absorption of UV by organic molecules and chromophores
Absorption UV radiation by C = C, C = O, N = N, N =O gps
C = C /N = N (π bond)C = O: (lone pair
electron)NO2 (lone pair
electron)
Chromophores gps
Ground
Higher empty orbital
π electron
Absorb UV to excite π/lone pair e to higher empty orbital
C O lone pair electron :
Chromophores – organic molecule with conjugated double bond
Absorb radiation to excite delocalized e to empty orbital
alternating double/single bond
Filled orbital Bonding orbital
empty orbital antibonding orbital
Biological Pigments (Anthocyanins)Coloured – extensive conjugation of electrons alternating single and double bond
Porphyrin Chlorophyll Heme (hemoglobin)
Anthocyanin
Carotene
absorb absorb absorb absorb
C C
Absorption UV radiation by C = C, C = O, N = N, N =O gps
C = C /N = N (π bond)C = O: (lone pair
electron)NO2 (lone pair
electron)
Ground π electron
Absorpb UV to excite π/lone pair e to higher empty orbital
C O lone pair electron :
Absorb radiation to excite delocalized e to empty orbital
alternating double/single bond
Filled orbital Bonding orbital
empty orbital antibonding orbital
Carotene
Diff bet UV and Visible absorption
Colourless - Absorption in UV rangeElectronic transition from bonding to antibonding
orbital (involve pi / lone pair e)
UV visible
Organic molecules/chromophores
Biological Pigments (Anthocyanins)Coloured – extensive conjugation of electron
Alternating single and double bond Electron in pi orbital delocalized through single and
double bond. π elec excited by absorbing long wavelength in visible
region
Anthocyanin
Chlorophyll
absorb absorb absorb absorbHigher empty orbital
Absorb radiation to excite delocalized e to empty orbital
Filled orbital
empty orbital
Carotene
Colourless – Absorption in UV range Electronic transition from bonding to antibonding
orbital (involve pi / lone pair e)
UV visible
Anthocyanin
Absorption of UV/vis by organic molecule and pigments
Less conjugated system↓
Less alternating single/double bond↓
Absorb shorter wavelength (UV)↓
Colourless compound
More conjugated system↓
More alternating single/double bond↓
Absorb longer wavelength (visible)↓
Colour compound
alternating double/single bond
More conjugation → More delocalization → Absorption in visible rangeExtensive conjugation of double bond allow more delocalization of π elecMore conjugation → More delocalization → Less energy to excite electron → ↓ E lower ( absorb at visible region (colour )
How number of conjugation leads to colour formation from UV to visible?
Biological Pigments (Anthocyanins)Coloured – extensive conjugation of electron
Alternating single and double bond Electron in pi orbital delocalized through single and
double bond. π elec excited by absorbing long wavelength in visible
region
UV visible
Absorption of UV/vis by organic molecule and pigments
More conjugation → More delocalization → Absorption in visible rangeExtensive conjugation of double bond allow more delocalization of π electronMore conjugation → More delocalization → Less energy to excite electron → ↓ E lower ( absorb visible region (colour )
How number of conjugation leads to colour formation from UV to visible?
More conjugation – splitting energy less ∆E ↓ – wavelength increase (visible range)
Filled orbital
empty orbital
100 200 300 400 700nm Wavelength λ
C – C C = C C = C – C = C C = C – C = C – C = C
∆E ↓with more conjugationabsorb from UV to visible
∆E ↓with more conjugationAbsorb at ↓ lower energy (↑ longer λ)
Absorb UV – sunblock Absorb visible region – food dye (Azo dye)Acid/base indicator
alternating double/single bond
CaroteneAnthocyanin Chlorophyll Heme (hemoglobin)
Wavelength - absorbed
Visible light
Colour seen RED – RED reflect to eyes - Blue absorb (complementary colour)
absorbed
REDtransmitted
Carotenoids absorb λ at 460 nm
Biological Pigments (Anthocyanins)
Colour – extensive conjugation of elec. Alternating single/double bond
π elec delocalized through single/ double bond. π elec excited by absorbing long wavelength in visible
region
700 600 500 400
alternating double/single bond
CaroteneAnthocyanin Chlorophyll Heme (hemoglobin)
Wavelength - absorbed
Visible light
Colour seen GREEN– GREEN reflect to eyes - Red/Blue absorb (complementary colour)
absorbed
Greentransmitted
Chlorophyll absorb λ at 400 and 700nm
Biological Pigments (Anthocyanins)
Colour – extensive conjugation of elec. Alternating single/double bond
π elec delocalized through single/ double bond. π elec excited by absorbing long wavelength in visible
region
700 600 500 400
CaroteneAnthocyanin Chlorophyll Heme (hemoglobin)
Wavelength - absorbed
Colour seen RED – RED reflect to eye - Blue absorb
Anthrocyanin – acid base indicator - absorb λ 550nm at pH 1 (acid)
Colour seen Yellow – yellow reflect to eye - Blue absorb
Wavelength - absorbed
Anthrocyanin – acid base indicator - absorb λ 470nm at pH 12 (alkali)
+ H+
+ OH-
Add acid
Add base
Change in number OH gpChange in number conjugationAbsorb at diff wavelength
RED YELLOW
Number conjugation increase ↓
Absorb longer wavelength
Number conjugation decrease ↓
Absorb shorter wavelength
Biological Pigments (Anthocyanins)
Colour – extensive conjugation of elec. Alternating single/double bond
π elec delocalized through single/ double bond. π elec excited by absorbing long wavelength in visible
region
Anthocyanin
Wavelength - absorbed
Colour seen RED – RED reflect to eye - Blue absorb
Anthrocyanin – acid base indicator - absorb λ 550nm at pH 1 (acid)
Colour seen Yellow – yellow reflect to eye - Blue absorb
Wavelength - absorbed
Anthrocyanin – acid base indicator - absorb λ 470nm at pH 12 (alkali)
+ H+
+ OH-
Add acid
Add base
Change in number OH gpChange in number conjugationAbsorb at diff wavelength
RED YELLOW
Number conjugation increase ↓
Absorb longer wavelength
Number conjugation decrease ↓
Absorb shorter wavelength
Biological Pigments (Anthocyanins)
AnthrocyaninsSoluble – OH gpC6C3C6 sys Used as acid/base indicatorChange in number OH gpChange in number conjugationAbsorb diff wavelengthDiff colour at diff pH
Colour – extensive conjugation of elec. Alternating single/double bond
π elec delocalized through single/ double bond. π elec excited by absorbing long wavelength in visible
region
Click here, diff colour diff pH
Click here, anthrocyanin change colour at diff pH
Anthocyanins – used as acid/base indicatorIdentify λ max which correspond to max absorbance at
diff pH and suggest colour in acid/base condition.
pH Max Colour absorb
Colour pigment
1 550 Green Red
12 475 Blue Yellow/orange
wavelength wavelength
Anthocyanins – used as acid/base indicatorIdentify λ max which correspond to max absorbance at
diff pH and suggest colour in acid/base condition.
pH Max Colour absorb
Colour pigment
1 550 Green Red
7 350 None visible Colourless
Explain folowing observationi. Carrot are boiled, little colouration in water, when they are fried colour change to orangeii. Red cabbage is boiled, water turn purple but when vinegar added colour change to redCarotenoid are coloured due to extended π conjugation elec. (Non water soluble long hydrocarbon chain)
In oil, they are soluble – produced a orange colour.
Colour due to anthrocyanin, water soluble contain OH form H2 bond with water. Colour change in diff pH (acid) due to diff number of conjugation as its protonated.
Non water soluble – No colour in waterCarotenoids
ORANGE
AcidRED
BaseYELLOWDegree conjugation increase
↓Absorb longer λ
Degree conjugation decrease ↓
Absorb shorter λ
Tetracene - Greater delocalization elec (Higher conjugation bond) - Absorb longer wavelength – visible light (colour)
Organic compounds shown anthracene and tetracene.Predict with reference to conjugation double bond, which absorb visible light (colour)
Carotene absorb light in blue/green region, so complementary colour (red and orange) are transmitted
Anthracene Tetracene
Absorption spectrum of carotene was shown. Explain why carotene have colour.
Carotene
700 600 500 400
RED
Absorption spectrum of anthrocyanin is shown.Explain what effect, the absorption at 375 and 530 nm have on colour of anthrocyanin
At 375 nm - No effect, lies outside visible spectrum (UV region) At 530 nm - Visible colour, red, complementary to blue-green - Absorb green – Reflect Red
700 600 500 400 300 200
AnthocyaninRED
Absorption of UV by organic molecules and chromophore
How Phenolphthalein indicator changes colour ?
Reason for colour change• change in conjugation• change in delocalization
AcidicColourless
Limited delocalization, only in benzene ring
Carbon sp3 – prevent delocalization on whole sys
Absorb UV region
AlkalinePink
Delocalization on whole sysExtensive delocalization in 3
benzene ringCarbon sp2 – allow delocalization
Absorb at visible region
Acidcolourless
BasePINK
PinkColourless
sp3 – Prevent delocalization whole sysLower degree conjugation
sp2 – Allow delocalization whole sysHigher degree conjugation
∆E energy diff ↑ higher
Less conjugationLess delocalizationAbsorb UV region
∆E ∆E
∆E energy diff ↓ lower
More conjugationMore delocalization
Absorb visible region
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttp://creativecommons.org/licenses/http://4photos.net/en/image:44-225901-Water_droplets_on_blue_backdrop__images
Prepared by Lawrence Kok
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