Lecture 6 CHO Classification & Function Flashcards
What are the main elements contained in CHO, proteins, lipids and vitamins?
- Hydrogen
- Carbon
- Nitrogen
- Oxygen
- Phosporus
- Sulphur
Why is CHO considered hydrated carbon?
H to O ratio is 2:1 just like water
Macronutrient DRIs of digestible CHO
~130 AI
Macronutrient DRIs for fibre
CHO AMDRs
45-65%
Classification of CHO
Classified as either simple or complex
* simple: monosaccharides and disaccharies
* complex: oligosaccharides and polysaccharides
Common monosaccharides
- glucose
- fructose
- galactose
Common disaccharides
- lactose
- sucrose
- maltose
Common oligosaccharides
- raffinose
- stachyose
- verbascose
Common polysaccharides
- Starch
- glycogen
- dietary fibre
Basic features of monosaccharides
- Aldose (-ose, 1 aldehyde, 1C) or ketose (-ulose, 1 ketone, 2C)
- Triose, tetrose, pentose, hexose, heptose, octose, nonose
- D or L- based on the chirality
Identify
monosaccharide - glucose
Identify
Galactose
Identify
Fructose
What is bond that links monosaccharides?
glycosidic bonds
Formation of glycosidic bonds
Formed by condensation reaction of hydroxyl (-OH) of one molecule with a hydrogen atom (H) of another s and forming a molecule of water
How are glycosidic bonds named?
The numbers in a glycosidic bond refer to the carbon atoms that form the bond.
* glycosidic bond facing down: 𝝰 glycosidic bond
* glycosidic bond facing up: β glycosidic bond
What is the glycosidic bond of maltose?
a-1,4 glycosidic bond
Basic features of disaccharides, oligosaccharides and polysaccharides?
- Consists of 2+ monosaccharides formed via glycosidic linkages
- Require specific enzymes for hydrolysis during digestion
- Reducing or non-reducing
What are the branching structures of polysaccharides?
- Linear polysaccharides
- Alternating single sugar unit branches on linear polysaccharide
- Blocks of consecutive single sugar unit branches on linear polysaccharide
- Ramified structure, branches on branches
What are reducing sugars?
Sugars that contain aldehyde groups & have an open chain form and can therefore react. The free anomeric -OH are free to react
* reduction
* oxidation
* isomerization
Maillard reaction
Reaction between a CHO and an amine group to form glycosides
Louis Camille Maillard
Maillard reaction
Shows how reducing sugars reacted whereby they reacted with glycoproteins to create a browning effect
Louis Camille Maillard
Reactivity of amines with aldoses
Initiation of the Maillard reaction
* aminoketose formed can undergo a cascade of reactions
What are advanced glycation end products?
proteins or lipids that become glycated after exposure to sugars which often occurs after prolonged exposure (diabetes) and can minimize original properties and functions
* can collect in collagen rich tissue (joints, blood vessel walls, lens)
What are the common reducing and non reducing sugars?
reducing
* lactose
* maltose
nonreducing
* sucrose
* trehalose
What is used as a proxy for the rate of progression of diabetes?
Glycosylation of HbA1C
* glycation of Hb in the periphery is best indicator of whole body glycation as a result of excess glucose and is a marker of how poorly one is manageing diabetes
Most abundant macronutrient
CHO
What are the types of polysaccharides?
- digestible: starch (amylose & amylopectin), resistant starch, glycogen
- non-digestible: dietary fibres
