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chem of life > 2a > Flashcards

2a Flashcards

1
Q

whats a pyranose

A

a 6 membered ring

5 carbons
1 oxygen

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2
Q

whats a furanose

A

5 membered ring

4 carbons
1 oxygen

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3
Q

is glucose a pyranose or a furanose

A

a pyranose bc its a 6 membered ring bc we can draw a cyclohexane chair for it

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4
Q

glucose is mostly open chain or or aliphatic

A

ngl most of the time,, glucose is in a chain!!!

only rlly present in its pyranose form!!!

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5
Q

bc glucose is mostly in its pyranose form,, cyclic form,, what does that mean

A

it means that amines cannot attack its C on the aldehyde for it is an OH now,, so they cant attack it or alter it.

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6
Q

what are conformers

A

structures that differ due to bond rotation

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7
Q

what compounds are seen in a potential energy graph minima

A

the most stable ones,, in this case its the chair conformation

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8
Q

why is the chair conformation the most stable conformer

A

bc all interactions are gauche

60* apart!!

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9
Q

the other local energy minima is slightly above the lowest one,, which conformer is this one

A

this is the boat twist conformer

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10
Q

1-3 diaxial interactions can be strong // weaker due to what

A

the bond length,, lowkey a longer bond reduces the 1-3 diaxial interactions bc the substituents are futher away

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11
Q

what is the best glucose conformer

A

the 4C1 conformer

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12
Q

describe the most stable glucose, 4C1 conformer

A

the primary alcohol

aka CH2 OH is equitorial bc its a big group!

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13
Q

whats an anomeric centre

A

the stereogenic centre we made by making the glucose cyclic,, aka when the lone pair on the oxygen attacks the C of the carbonyl

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14
Q

when the anomeric OH is axial,, we say the conformer is the

A

alpha conformer

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15
Q

when the anomeric OH is equitorial,, we say the conformer is

A

beta conformer

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16
Q

the alpha and beta conformers relationship issss that theyreee

A

theyre diastereoisomers!!!!!

u cant chair flip them bc then all the other substituents would change orientation,, but in alpha and beta all of them have the same config apart from the anomeric OH being either axial or equitorial

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17
Q

carbs that can be easily oxidised are called

A

reducing sugars

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18
Q

oxidation occurs byyyyy

A

opening the chain structure

to form an aldehyde

which then forms a carboxylic acidddd

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19
Q

a sugar is only reducing if ehat

A

the ring can be opened to give an aldehyde

if the ring cant be open to form an aldehyde,, its not a reducing sugar

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20
Q

tests for if smt is a reducing sugar and its positive results

A

tollens: silver mirror
fehlings: blue
Benedict’s: red

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21
Q

whats an aldose

A

a sugar with an aldehyde group at its end carbon

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22
Q

is an aldose a reducing sugar

A

yesss

bc it has the aldehyde we need

and it can be reduced into a ketone

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23
Q

are ketoses reducing sugars

A

yes

they can tautomerise via enediol to get an aldehyde

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24
Q

whats a ketose

A

sugar with a ketone group

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25
how can an ketose tautomerise to via enediol to give an aldehyde
ketone,, H is removed,, moved onto the O of the carbonyl to give OH that is part of an enol this is then moved onto the end OH to give an aldehyde.
26
trick to seeing if smt is a reducing sugar or not
if theres a OH on the anomeric C. aka on the LHS of the molecule. if ts an OMe group its not a reducing sugar bc we cant get rid of an Me group
27
whats a glycoside and are they a reducing sugar
a glycoside is a sugar moelcule where one of the OHs is replaced. they cannot be recucible sugars bc u cannot get rif of the group attacked to the O aka OH vs OMe to give a carbonly O. this only works if u have OH present!!! bc u can turn this into an aldehyde.
28
describe a haworth projection and how u would draw an alpha or beta sugar
haworth projection is like an angled cyclohexane,, its basically how we normally see sugars drawn alpha would have the anomeric OH pointing down while a hanworth projection would have the beta anomeric OH pointing up
29
hanworth beta
OH points up
30
handowrth alpha
OH points down
31
okay so to clock if smt is a reducing sygar or not, and how do we do the mechanism to prove it is one
okay so we look on the rhs,, the end part of the molecule and welook for the anomeric C,, normally the one next to the o. then we see if there is an OH bonded to this C or not, however it must be directly bonded to it!!! if there is an OH directly bonded to the anomeric C,, its a reducing sugar, and to form an aldehyde we need to deprotonate this OH and push. the e- onto the O to form a carbonyl, the C would also be bound to a H,, so that would form an aldehyde and prove its a reducing sugar.
32
describe an alpha and beta glucose and which one is most favoured
alpha: oh on anomeric C points axial beta: OH on anomeric C points equatorially. beta is most favouredddd. less 1-3 diaxial interactions
33
how does mutarotation occur
basically u form an aldehyde and the aldehyde can rotate and point in different directions and basically the OH near the aldehyde is gonna use its lone pair to attack the carbonyl C,, however if its alpha or beta will depend on what way the aldehyde is pointing in when the OH attacks it. this is bc single bonds can rotate.
34
whats the anomeric effect
the anomeric effect is the effects that states that in prose,, electroegative substituents prefer to be axial thsn equitorial. alpha stuff are made
35
describe what happens in an anomeric effect
the lone pair on the O thats a member of the pyranose ring is used to kick off a substituent on the C next to it. this forms a double bond in the chair and forms a (+) on the O. its a n --> sigma* bc its from lone pair to the C-X sigma* in order to break that bond.
36
whats an anomer
an anomer is a tyoe of stereoisomer basically its either an alpha or beta anomer but which one it is depends on the configuration at the anomeric carbon. aka axial is alpha. equitorial is beta
37
whats a glycoside and what the process of how u make them called
a glycoside is a sugar where a hydroxyl group is removed and is replaced by smt else the process can be known as glycosylation.
38
two different ways we make glycosides
we can make then with sn1 or sn2
39
describe the sn1 way of making a glycoside
sn1 = 2 steps loss of LG aka Br, F , thiol this gives the anomeric C cc+ character lone pair on o member is used to neutralise the CC+ which makes O (+) the O (+) is planar so a nuc can attack the cc+ from above giving equirotial and beta glycoside or from below to give axial and an alpha glycoside. bc the CC+ and O+ switch to give resonance forms.
40
describe the sn2 way to form a glycoside
sn2 = 1 step so u do nuc attack and loss of lg at the same time so nuc attacks the C with the LG and the LG leaves bc the sn2 occurs with inversion of stereochem,, bc the LG was axial,, the nuc will be equitorial,, and if the LG was to be equitorial,, the nuc would be axial
41
whats an o glycoside
when the subs on the anomeric C is an O
42
what is an N glycoside
where the substituent on the anomeric C is an N
43
whats an s glycoside
where the substituent on the anomeric C is an S
44
a disaccharide is also a form of what
a disaccharide is also a form of glycoside bc the OH has been changed to another glycose molecule.
45
what 2 things are needed when forming a disaccharide
u need a glycosyl donor and a glycosyl acceptor!!!!
46
formation of a disaccharide can also be called
glycosylation!!!!! bc ur making a glycoside bc the OH is being swapped for smt else
47
synthesis of disaccarides: describe the 2 things needed and what each one does
u have the glycosyl acceptor and the glycosyl donor the donor is the one that donates itself: aka its the one with the LG and the one that starts the chain. it 'donates' its freedom bc its gonna be the start of the chain. the glycosyl acceptor is the one that has the OH that attacks the anomeric C with its OH lone pair (the oh is the one closest to the other molecule) IT CAN OCCUR VIA SN1 OR SN2
48
glycosyl acceptor
OH lone pair attacks the other moleculeg
49
glycosyl donor
the one with the leaving group
50
disaccharide // glycoside // glycosylation can occur via
sn1 or sn2 reaction
51
when we name the disaccharide ,, what do we include
if its alphs (axial) or beta (equitorial) the numbers that connect eachother 1-4 ,, one being the anomeric C and 4 being the 4th carbon away from the anomeric C on the glycosyl acceptor.
52
bondbetween sugars is called aaaa
glycosidic bond
53
enzymes that break glycosides // disaccharides =
glycosidases (break glycosidic bonds)
54
enzymes that make glycosidic bonds
glycosyltransferases
55
what LG do enzymes in nature use in glycosylation // formation of glycosides // disaccharides
they use uridine diphosphate chems cant make this but nature can.
56
what do glycosidases do
they break glycosidic bonds
57
how are glycosidic bonds broken
u add H+,, which protonates the O that everything bonds to ,, the member O then uses its lone pair to kick the protonated O away. an OH then appears as a substituent
58
cellulose
abundant compound flucose monomers joined by beta 1-4 glycosidic bonds linear chains insoluble in water chemically inert
59
chitin
forms outer skeleton of insects and shellfish
60
glycogen
most common homopolymer in mammals key role in energy storage alpha 1-4 glycosidic bonds braches forned by alpha 1-6 glycosidic bonds
61
the 2 forms of starch
amylose amylopectin
62
amylose
linear alpha 1-4 glycosidic bonds
63
amylopectin
branches with alpha 1-6 glycosidic bonds
64
what are amylopectin and amylose both hydrolysed by
alpha amylase
65
glycoproteins

chem of life (16 decks)

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