LEcture 14/ 5 depression expression

sacchardies or sugars and lipids, saccharides.Common mono sacchrides - they havea chemcial. formula of (CH2O)n. The N refers to the number of carbon atoms in that sugar molecule. the vast majority of sugar moelcuesl that youre going to encaounter in your body has three to six carbon atoms. there are sugar molcules with seven, eight, and nine cabons but they are rare. but we are going to stick to sugar molcules that have anywhere between three to six carbon atoms. If u look at the structure of these sugar moelcules they are going to either contain an aldehyde or ketone group for all sugars. all sugars. are aldehydes or ketones.

sugards with aldhyde are aldoses and thsoe that have ketoen groups are called ketoses. So we name sugars with these names except for the small ones, the three carbon sugars.

three carbon sugars. we have special anems fro those two . glyceraldehyde. and dihydroxyacetone. so glyceraldhye is a aldos sugar and dihydroxyaceton is a ketone sugar. as u go higher carbon number sugars, aldoriose and ketotrioins, the keto and trios part, aldotriose because it has three carbon atoms and ketotrios because it contains a keton group but has three carbon atoms. glucose is an aldohexose because it has an aldose sugar but contains six carbon atoms. fructose is a ketohexose and ribsome is a aldopentose. deoxyribsoe is an aldopentose. so the names describe the aldehydye vs keton contect and also carbon number.

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so the msot common monoscarride are the trisose, tetrose, pentrose, and hexose. heptose and beyond are rare.

monosachriddes have asymetric center. this applies to all except hydroxyacetone. so tahts one of the three carbon sugars we looked at. looking at the structure of dihydoxyacetone it does not ahve a achiral carbon atom the other ones do. all ecept dihydroxyaceton the sugar molecules are optically active . the fact that they have a chiral carbon they are an entatiomers of these sugars. for amino acids they had L and D amino acids. im biochem we use the L . mnooscharies coome in enteriomeric forms.

example 3-carbon aldose sugar ant there are nonsuperimpeoble mirror images. so we can have the D and L form. in biochem our body uses D form. opposite of the L amino acids. we dont know why yet. HOw to tell them apart. we are going to draw the fissure projeciton. for gluceralhyde u put the aldehyde group at the top and then draw the sugar molecule verically down. and then dpendong on whether the OH group is on the. left or right it detmeines if its L or D> so here the OH group is on the right so thats’s the D . As u move onto longer sugar mocluesl. there can be more than one chiral carbon. .. .

in that case to determine whether it is an L or D sugar u look at the hydroxyl group that is attached to the carbon atom that is furthest away form the cabryonyl or the cabronyl group whether its alhydye or keont. for ribsose and and arabinose u look at the Oh group that is attached to the last chiral carbon that contain an OH group. so if on the left it is L-Ribsoe and if u look at this sugar its on the right and that is d ribose. if u look at the psotingin of the OH group. on the chrial cabon tahts furthest away fromo the carbonyl group. /

L arisbonse. if u applu the correct rule it will look like thise. if u inccorely look athe other chiral cabon atoom the last one and u might say its OH on the right. just be careful where and chech to see where the one that is furthest away from the carbonyl. . .

most common D alodes in ur boyd. theyre grouped dpeonogn on how many carbon atoms are presentes. and the names that have squres and on them are the ones that are most commonly enocunted in human biochem.

memorize glucose and ribose the chemcial structure and the name . ribose is 5 carbon and glucose is 6 carbon. they are more importnant than the others. this is where we get most of our calories from. all the cells rely on glucose to generate ATP. it can also get atp from protein and fats as well, but it will use glucose if possible. so it is an importnatn sugar molecule. Ribose - its not a main calori source but it is used to synthesize DNA and RNA.

memorise glucose ribose

Ribose is a five carbon sucar, glucosei s ais a six cabron.

most common keptoses. memories ribolose, furctose and xylulose. know the structure and the names. they are imporntant in metabolism.

glucose shows in the gluycolysis pathway. xylulose shows up in the pentose phosphate pathway. these are all metbolic pathway that laeds to ATp generation so its very ciricla so u know these structure is imponrtant not only for this poart o fht eoucse but fo rthe later parot.

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nomeclauter, N entionmets are mirro images of one anothyer. epimer s are two sugards that differ eonly in the ocnifugriation around one carbon atom but they ar enot necessarily mirror images of one another. so i f u compare mannose and glucse they are both hexose sugar but looking at the stereo chemistyr of the carbon atoms, they are different at hte carbon 2. all the other chiral carbon atoms, the arreagment is identical between mannose and glucose, but in cabron 2 u see the OH on the left and ont he right. that is th only location where the steroechemi is dfferent. if u comapre glucsoe and galactose these two at carbon 4 they are eptimers art carbon four. that is where they differ. if u comapre manose to galactose they are not epimers because one is different at carbon 2 and the ohter one at carbon 4. so they have to differe at one single carbon psotion for it to be an epimer.

Organic chem. al aldehydes and ketones readily react with water. and the water acts as a nucelophile. aldehyde they react with water to form these products. u have a ketone here and add a water molcule and make up the third molceul in the slide.

Aldehyes and ketones in general will undergo this process. another thing is that these reaction can occur with OH’s. so a keton or aldehy with OH is going to make a hemi acetyl that hemi acetyl can under go another addtion reaction with another Oh moelucle and that is going to make acetal. in OChem when an alhdye and keton react iwth one OH the first product is HEMi and the seocn di acetyal. but in biochem there are sepreates names. .

So an aldehydte plus OH is hemi acetal and the third one is acetal

A ketone plus Oh is hemiketal and the second addtion of OH is ketal.

hemi acetal and hemi ketal are going to readily interconver with carbonyl compounds in water . they ar erealivtly unstable and prone to undrgo that reverse reaction. son once hemiacetyl is formed under physioligtcal conditiosn it is easly going to go back to aldehyde or ketone. ketal and acetals are stable and once they are formed they are going to remain as that and not go bakc to the reactant form. all the examples are addition reactions between two spereate molcuels. aldehyde was A and alcohol was B. so it was A plus B is going to C. the same reactiron can happen when the aldhyee or ketone gourp and the OH are part of the same mocluel. two exampels are shown here. so u have an Aldehyde in one end and an OH at the other end and this can undergo an intramolecular addition reaction. and end up witha. cycloic structure.

this happens frequently n in suagar molcules because they either contain a ketone or alhyde as well as mutliple OH. so the example at the bototm of page 15. this is glucose . first its linear glucose but an OH willa ttac the carbonyl carbon and this is formation of a hemiacetyl but its intramolcuela and the end product is a cyclic glucose molcuel.

glucose can be in linear and cyclic form. thsi si a dynamic equilibrium. once u reach equilibium the concentrions of eahc form will not change however it doesn mean that cyclic clucose is permarnely cyclic it can go back to being linear. at equilibium the net concentraion of each does not change. look at glucose cyclication reaction in more detail. linera glucose moelcuel. glucose can cyclize and from cyclic glucose.

there ar etwo distinct cyclic glucose structure that are possible. this is bc when the oH attachs the carbonyl carbon that attach can occur on either. face of that carbonyl group. and dpeenodng on which face it attcks form u end up with either this structure which we call alpha glucose. and the other one is beta glucoses. so u get two distince structures. so it produces a or b. we call a and B as anomers. they are isomeric forms of monocscharies that differe only in their confitiaon about the hemiacetyl or hemiketal carbon atoms. so the structure is the same except fo rthe carbon atoms which is no a hemiacetl group.

hemiacetals can do the reverse reactions. go back to their reactant form so both of these sugars can go back to beomcing the liinear form. and when that linera form recycles to form the cyclic form tit doesnt mean that what use to be a beta glucsoe will be beta again, next time it can cyclize into the alpha form. so the a and b glycose cyclic sugars can interconvert over time and thats bc its going back to the linear form. once ur there the cyclicaiotn rection which side of the cabryonl group it attchs is stochiasti, it is random.

this happns withe very sugar, so lienra glucose in fisher and the cyclic glucose is drawn with haworth perspective. ti si to emphaisze that cyclic sugars are three 3d/. so the plan of the sugar ring is almsot perpendicular to the plan of the screen. so the thick bonds ar ehte ones that exist in front o fhte plan of the screen and the bonds with the thin lines ar ethe ones at the back of the screen. so its a way to draw a 3d molecule in two dimesntions.

the rule for drawing the haworth perspective is to always put the oxygen at the top right of the mocluela dn the rest of the mocleusla re going to be draw at a counterclock wise manenr. thats the standard way of drawing cyclic sugar mjolecules . if u follpow this rule all the Oh groups that are on the righ side end up at the bottom plane of the ring and everything at the left side is going to end up above the plane of the sugar ring. the terminal CH2OH group so were talking about this CH2OH group it prjects upwars so uy can see that cH2OH is above the plane of the ring and that is true for all D sugars. if u cyclise the L sugar the Ch2OH is going to be at the bottom of ht ering. when the anomeric Oh of the D sugar is on the opposite side of the ring as the c6 carbon the structure is defined as alpha. So the OH that is attached ot the anomeric carbon is located below the plan. the temrinal ch2oh is above and that is opposide sides therefore that is called alpha. so if they are above the plane they are beta.

if u investiage the abunance of these structure in aquous solution what u find , only .02% s oalmost nothing is in linera form and 99.9% is in the cyclic form and the distrbution between the alpha amd beta is 36 % alpha dn 64% beta. why its not 50/50. this is becayse of stability . so for nay cyclic hexane the more stable structure is when the substrituen is in the equatorial position like the B. so glycose when it cycliszes it likes to form six member ring sugars , soem sugars will form five membered ringd like fructose . we have a name for this, six member suvar are called pyranoses because it resmbles the organic molcule pyran. sugar molcuels that are cyclic but have five memebred rings are called furanoses. and tha comes from the organic molecule called furan. so for glucose the dominant structure is the pyranose structure. for glucose the dominant structure is the pryanose structure hoewver it is possible to form furan forms of glucose, and thsi si so little that it is hard to detect. there is a tiny amount of hte five ring glucose sugar but its neglibly small. thats bc thermanodyly fromation of the six ring sugar is more faborable in the case of glucose. as mentioned before all these five differenter forms of glucose are in dynamic equilibium. theyre constnatly interconveritn from one form to another. but hte final abundace is rouhgtly

most in the pyrnaose and slighhly in the beta compared to the alpha.

in ur body u will enocuter the various sugars as well as sugar derivates . this is also the case witha mino acids which are modified . so the glucosamine is where hte oH group usually found in carbon 2 is exchanged with an amino group. that where the name glucosamine comes from. t

acetyl glucosamein u exchagne the OH with an amino group and further youve acetyalted that amino group forming this sugar derivative. and various other example are shown . dont have to memorize the structure of names but u should recognize them if u know the structure names of hte og unmodified monosacchrides

The second common reaction that sugar moelcules under is the redox reaction. the aldehyde groups reacts with copper to conver copper 2 plus to copper plus. this is very visually stricking conversion. so CU2 plus has this disitnct blue color apearance and its very clear but once u conver it to coppoer 1 plus u get this red solution and it perceipates and u get thise reaciton readily obserable witht he naked eye. if u add ur sugar solution and add coper 2 plus to it u can know whether ur sugar contains an aldehyde group or not . its a easy test , aldose and sugars can form aldehyces are called reducing sugars so all aldehudes sugars are reducing sugars. but it turns out that ketone sugars will have this postive reation to conver clear blue to red cloudy liquid. bc ketoses will undergo. a tautomerization rection to convert back and forth between the aldehyde and the keton form. this is a dynamic equilium. and once a little bit of the ketone sugar is converted to the aldhyde form , that cna react with coppera dn give u a psotive resutl. so ketose sugar will show u the same result, not bc the keton can direcly react with copper but bc ketone can conver to the aldehyde from, and thea ldhyde from cna react with copper. and thats going to beocme importnat when we talk about longer saccharides. so here u have two mono sacchrides .or two glucuse molcuels. that bonine to from maltose which is a dissachride which is analgous. to two amino acids being linked together to form a dipeptide. the linage that conencts two sugar mocluels is caleld O glycosidc bond. this is a sugar equivalent of the peptude bond. this is a condenstaion reaciotn becayse in the process u remove or u generate a water mocluel.

This is also a reversible reaction. You

can start with a disaccharide, add a water molecule

across the O-glycosidic bond, and return to

the two individual monosaccharides. That reaction

is called hydrolysis. So it's very analogous to

what we talked about for amino acids and peptides