CHO (structure, nomenclature, and properties)

carbs energy per gram

4kcals/gram

ADMR for carbs

45-65% of energy

carbs are _____ compounds

organic

carbs are classified as _________ or __________—

available and unavailable

what are available carbs?

 hydrolyzed by enzymes of the human GI tract to monosaccharides that are absorbed and metabolized

in terms of available carbs, what are the two rates of digestion

rapidly and slowly digestible carbs

what are rapidly digestible carbs

simple sugar (mono and di-saccharides) that are readily and rapidly cleaved by the enzymes and absorbed to contribute to blood glucose levels very quickly

what are slowly digestible carbs

those found in starches or complex carbs that are broken down more slowly and have weaker response to blood glucose concentrations

what are unavailable carbs?

not hydrolyzed by human enzymes but may be fermented by gut bacteria forming SCFA

carbs help spare

protein (as an energy source)

what happens when we fast?

When we fast and lack available glucose, we will break down muscle and use glucogenic amino acids as precursors to glucose

glucose provides energy for what tissues (most important)

nervous tissue and RBC (solely rely on glucose for energy)

where are carbs derived from (3 sources)

• Diet (starches and sugars)

• Glycogen (stored in liver and muscle as this form)

• Gluconeogenic precursors (amino acids that have at least 3Cs in their skeleton)

all carbs are _____ and _____

hydrophilic, organic

organic =

contains carbon

what are the monosaccharides

glucose, fructose, and galactose

what are the disaccharides

sucrose, lactose, maltose

what are oligosaccharides

3-10 units

what are polysaccharides

>10 units (starches usually)

based on carbons, what are the carb classes?

• 3 carb units: triose

• 4: tetra

• 5: pentose

• 6: hexose

based on components in their simple structure, sugars are either what of 2 options??

aldoses or ketoses

what are aldoses?

have Aldehyde (carboxylic group at the end of the structure)

what are ketoses

have Ketone (carboxylic acid at the middle of the structure)

glyceraldehyde structure

glyceraldehyde

• aldose or ketose?

• # of carbons?

• chiral carbons?

• aldose

• 3C

• one (C2)

how do you number the linear monosaccharide

start with the C of the carboxylic group and work your way down

what is chirality

Ability turn light when is solution

a chiral molecule is identified by

has 4 different functional groups surrounding a carbon

the carbon having 4 different functional groups attached is known as

chiral carbon

D vs L: where do you look?

the most distal chiral carbon from the carboxyl group (C1)

When is it D? when is it L?

when hydroxyl (OH) group is on the right = D

when hydroxyl (OH) group is on the right = L

D stands for?

dextrorotatory

D formation means what?

means that when molecule is placed in solution and light is shined down, it will reflect the light to the right

L stands for

levorotatory

L formation means what?

 reflect light towards the left

which configuration will we look at and why?

D, because they are the only carbs that are biologically relevant

what comes from/ happens to glyceraldehyde?

We can reduce it and ultimately get a bunch of different monosaccharides

what are the 3 monosaccharides we will focus on?

D-glucose, D-mannose, D-galactose

D-glucose, D-mannose, and D-galactose

• have how many carbons

• how many chiral carbons

• 6 Cs

• 5 chiral carbons

D-glucose and D-mannose are

epimers

what is an epimer

2 molecules that differ in one chiral carbon

what is stereochemistry

when a chiral molecule has optical ability or the ability to rotate the plane of linear polarized light as it travels through a solution

aka: means a special molecule can twist a beam of light as the light passes through a liquid

what will always exhibit stereochemistry

All chiral carbons (or chiral molecules)

what is an enantiomer?

are stereoisomers that vary in configuration at all chiral centers (are mirror images)

what happens when we add glucose to a solution (what will it want)

to react

how does glucose react in a solution (how does it react)

The aldehyde group of aldehydo-D-glucose (aka D-glucose) will react with its hydroxyl group attached to the chiral carbons

what are the 4 molecules D-glucose will make when in a solution?

• B-D-glucopyranose

• a-D-glucopyranose

• B-D-glucofuranose

• a-D-glucofuranose

In solution, the linear monosaccharides tend to

cyclize

what are the types of configurations?

Fischer, Haworth, and chair formula

what is the  Fischer formula

Linear structure configuration

what is the Haworth formula

Cyclized structure

what is the chair formula

3D structure (most stable)

how does the process of cyclization occur? (with glucose as example)

Hydroxyl group on carbon 5 can react with the carboxyl group to cyclize

what happens to the carboxyl group carbon

it is now chiral

C1 is now called what?

the anomeric carbon

aka, the carboxyl group that reacted to cyclize, is called the anomeric carbon now

in Haworth formula, how do you know if sugar is D or L?

D is when CH2OH group attached to C5 is sticking out of the ring

L is when the CH2OH group attached to C5 is projecting inside of the ring

what is alpha configuration

when the hydroxyl group of a cyclized sugar’s anomeric carbon is projected down

what is beta configuration

when the hydroxyl group of a cyclized sugar’s anomeric carbon is projected up

what are reduced sugar derivatives?

sugar alcohols (reduced sugars)

what are 3 examples of reduced sugars?

D-xylitol, D-glucitol (D-sorbitol), Myo-inositol

D-sorbitol comes from

reducing glucose (6C)

D-xylitol comes from:

reducing fructose (5C)

what is a glycosidic linkage

a link that forms between anomeric carbon of one sugar and another molecule, releasing water in the process (condensation)

what are the types of glycosidic bonds (4)

• O-glycosidic bond (C-O)

• N-glycosidic bonds (C-N)

• S-glycosidic bonds (C-S)

• C-glycosidic bonds  (C-C)

what is condensation

linking 2 molecules by removing water

what is hydrolysis

 bond occurs when we remove water and get the starting 2 molecules

Glycosidic bonds can be hydrolyzed by

enzymes

enzymes and glycosidic bonds (how they work)

they are highly specific for the type of linkage  (will care if it is alpha or beta!!)

The specificity to the beta or alpha will determine if

 the carb is available or non-available (if we can break it down or not)

unavailable would mean

it is a fiber that the body cannot break down in the SI

how does uridine diphosphate (UDP) form glycosidic bond and what type of bond is it?

anomeric carbon of D-ribose forms linkage with N of uracil

-forms N-glycosidic bond

what does AGEs stand for

advanced glycation end points

what are AGEs?

very reactive and harmful molecules that form from glucose and protein forming a N-glycosidic bond nonenzymatically

what is glycation

nonenzymatic glycosidic bond formation

what is glycosylation?

enzymatic glycosidic bond formation

process of AGEs forming

glucose + protein react —> form schiff base —> form unstable Amadori product —> after weeks to months for AGEs

why are AGEs bad (what do they do)

• contribute to inflammation

• Stiffen the artery walls, lungs, joints

• contribute to vascular and eye complications in adults with DM

AGEs not only occur in the body, where else?

in food with the Maillard reaction (reaction of heating up glucose with protein that results in the browning color seen in bread)

what is Hemoglobin A1c (HbA1c)

 a nonenzymatic glycation reaction of glucose  to valine in one of the b-chains of hemoglobin

hemoglobin structure

• 4 chains

• 2 beta and 2 alpha

• each chain contains heme group that attaches to iron (holds the oxygen)

how does HbA1c form?

Elevated glucose --> nonenzymatically attaches to Hgb via valine in beta chain via glycation

HbA1c criteria

• normal

• prediabetes

• diabetes

• Normal: <5.7%

• Pre-diabetes: 5.8-6.4%

• Diabetes: ≥ 6.5%

maltose (characteristics- 5)

• Glucose + glucose

• Alpha 1,4 glycosidic bond

• Is a component of starch

• Is a reducing sugar (has free hydroxyl group on the end)

• Broken down by maltase

maltose is made up of

glucose + glucose

maltose type of bond

a-1,4-glycosidic bond

maltose is a component of

starch

maltose is a ______ sugar

reducing sugar

what is a reducing sugar

has a free hydroxyl group at the anomeric carbon

maltose is broken down by what enzyme

maltase

sucrose characteristics (5)

• Glucose + fructose

• Alpha 1,4 glycosidic bond

• Found in table sugar (sugar in food = sucrose)

• Nonreducing sugar

• Broken down by sucrase

sucrose is made up of

glucose + fructose

sucrose has what type of bond

a-1,4-glycosidic bond

sucrose is found in

table sugar

sucrose is a __________ sugar

nonreducing

sucrose is broken down by

sucrase

lactose characteristics (5)

• Glucose + galactose

• Beta 1,4 glycosidic bond

• Is a reducing sugar (has free hydroxyl group on the end)

• Not as sweet as sucrose

• Broken down in SI by lactase

lactose is made up of

glucose and galactose

lactose type of linkage

b-1,4-glycosidic bond

lactose is a _________ sugar

reducing

lactose sweetness level compared to sucrose

less sweet