structure of carbohydrates (monosaccrides)

[MedGrl@2022]

From AAMC:

"A. Carbohydrates
1. Description
a. nomenclature, classification, common names
b. absolute configurations
c. cyclic structure and conformations of hexoses
d. epimers and anomers
2. Hydrolysis of the glycoside linkage
3. Reactions of monosaccharides"

Just wondering is it necessary to memorize the structure of the common monosaccrides for the MCAT. If so, does anyone know a good way to do this? TBR has this hand thing. But I am really confused how it works. Let me know, what you have come up with...

Thank you,

Verónica

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[image187]

yeah I wouldn't memorize structures of too many things. Maybe remember glucose and how the different groups are used in linkages, but seriously though anything more than that is probably unnecessary

 

[MedPR]

Be able to identify glucose and fructose.

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[Jepstein30]

Be able to identify glucose and fructose.

Sent from my SGH-T999 using SDN Mobile

as well as (IMO) what makes up common disaccharides like sucrose and galactose.

don't think you'll get much else

 

[BerkReviewTeach]

TBR has this hand thing. But I am really confused how it works.

It's actually a simple trick that is amazing for glucose, mannose, ribose, and galactose.

For D-glucose, start with your right hand and flip off the page in front of you and hold your hand in place (sideways, with your middle finger pointing left). With your palm facing you and your middle finger pointing to the left, hold you hand in that position and compare the position of each of your fingers to the OH groups on glucose (in the Fischer projection).

Your thumb is pointing up like the carbonyl on C-1, your index finger is folded and pointing to the right like the hydoxyl group on C-2, your middle finger is straight and pointing to the left like the hydoxyl group on C-3, your ring finger is folded and pointing to the right like the hydoxyl group on C-4, and your pinky is folded and pointing to the right like the hydoxyl group on C-5. It's simply a matter of matching the OH groups to your fingers. Given that you used your right hand, you made right-handed glucose, better known as D-glucose.

Hopefully this makes sense and seems easy, If so, then go back to the pages in the BR book that describe other monosaccharides and the Haworth projections. They will hopefully be much easier this time as long as your hand is oriented as described above.

 

[MedGrl@2022]

It's actually a simple trick that is amazing for glucose, mannose, ribose, and galactose.

For D-glucose, start with your right hand and flip off the page in front of you and hold your hand in place (sideways, with your middle finger pointing left). With your palm facing you and your middle finger pointing to the left, hold you hand in that position and compare the position of each of your fingers to the OH groups on glucose (in the Fischer projection).

Your thumb is pointing up like the carbonyl on C-1, your index finger is folded and pointing to the right like the hydoxyl group on C-2, your middle finger is straight and pointing to the left like the hydoxyl group on C-3, your ring finger is folded and pointing to the right like the hydoxyl group on C-4, and your pinky is folded and pointing to the right like the hydoxyl group on C-5. It's simply a matter of matching the OH groups to your fingers. Given that you used your right hand, you made right-handed glucose, better known as D-glucose.

Hopefully this makes sense and seems easy, If so, then go back to the pages in the BR book that describe other monosaccharides and the Haworth projections. They will hopefully be much easier this time as long as your hand is oriented as described above.

Thank you so much! I understand it now. Do you know if I should memorize the monosaccrides that make up common disaccrides? AAMC says know "reactions of monosaccrides" I wasn't sure if this was what they were referring to.

 

[Postictal Raiden]

It's actually a simple trick that is amazing for glucose, mannose, ribose, and galactose.

For D-glucose, start with your right hand and flip off the page in front of you and hold your hand in place (sideways, with your middle finger pointing left). With your palm facing you and your middle finger pointing to the left, hold you hand in that position and compare the position of each of your fingers to the OH groups on glucose (in the Fischer projection).

Your thumb is pointing up like the carbonyl on C-1, your index finger is folded and pointing to the right like the hydoxyl group on C-2, your middle finger is straight and pointing to the left like the hydoxyl group on C-3, your ring finger is folded and pointing to the right like the hydoxyl group on C-4, and your pinky is folded and pointing to the right like the hydoxyl group on C-5. It's simply a matter of matching the OH groups to your fingers. Given that you used your right hand, you made right-handed glucose, better known as D-glucose.

Hopefully this makes sense and seems easy, If so, then go back to the pages in the BR book that describe other monosaccharides and the Haworth projections. They will hopefully be much easier this time as long as your hand is oriented as described above.

wow, this is amazing. I'm wondering if there's an easy, similar way to remember the ring structure?

 

[AFLATPEG]

wow, this is amazing. I'm wondering if there's an easy, similar way to remember the ring structure?

ring structure, i always look at carbons C-2, C-3, and C-4 for positioning of the up/down groups. when drawn from straight chain to ring structure, the groups from the right side of the straight chain goes down on the ring structure, and groups drawn on the left, goes up.

C-6 is drawn up for D-sugars, and down for L-sugars.

C-1 is anomeric so you need to see if your C-1 -OH group is cis or trans with your C-6. (cis=beta, trans=alpha)

hope this helps!