Carbohydrates Flashcards
what are the functions of carbohydrates
energy and carbon source
energy store
flavouring
functional ingredient (gum, probiotics)
what are the 4 types of carbohydrate
monosaccharide
disaccharide
oligosacchardie
polysaccharides
outline the characteristics of monosaccharides
- simple, one sugar unit
- C3H6O3
- aldoses and ketoses
what are the characteristics of aldoses
has a carbon and a double bonded oxygen at the end of the chain
contains an aldehyde group
what are the characteristics of ketoses
has a carbon and double bonded oxygen in the middle of the chain
contains a ketone group
define chiral
cannot be placed on top of its mirror image
examples of stereoisomers
D-…
L-…
what are the two chiral forms
enantiomers
epimers
what is an enantiomer
mirror reflection
compounds related by inverting the configuration at all asymmetric carbons
OH group pointing left = L-glucose
OH group pointing right= D-glucose
what is an epimer
disastereomers with an inverted configuration at one asymmetric carbon
what is a disastereomer
compounds related by inverting configuration at one or more chiral centres
what is meant by the cyclic structure of monosaccharides
reaction occurs between -OH at C-5 and the aldehyde at C-1, producing a pyranose ring
this produces an new asymmetric centre at C1, with two new alpha and beta stereoisomers- called anomers
alpha anomer- above the ring
beta anomer- below the ring
the anomie’s are interchangeable by mutarotation
give an example of a reducing sugar
all monosaccharides
glucose, fructose maltose, lactose
give examples of naturally occurring food monosaccharides
glucose, fructose, lactose, ribose
how is the anomeric carbon configuration determined
glucose
- CH2OH and OH are on opposite sides on the anomeric carbon
- 6 membered ring= pyranose
fructose
- CHOH and OH are on the same side of the anomeric carbon
- 5 membered ring= furanose
example of a disaccharide
maltose
how are disaccharides formed
the hemiacetal end is free to open or close
the hemiacetal group of the alpha-delta-glucose reacts with the OH group of the beta-delta-glucose and forms a glycosidic bond
two monosaccharides formed by the glycosidic bond
how is sucrose formed
glucose and fructose = sucrose head to head no free anomeric carbon so is non-reducing inversion on heating made by plants
sugar beet is…
UK grown and processed in 6 factories
seasonal (Sept- March)
sugar cane is…
a tropical plant that is shipped raw to the UK
processed all year in 1 UK factory
has many uses (flavour, colour, sweetener)
how is lactose made
glucose and galactose
head to tail
reducing sugar
give an example of a non-reading sugar
sucrose, trehalose
how is trehalose made
glucose and glucose
head to head
energy storage in insects
non-reducing sugar
what are polyols
sugar alcohols
how are polyols produced and what are they used for
produced by the hydrogenation if sugars and syrups
used to replace sugars
fewer calories
small effect of blood glucose and insulin levels
non-cariogenic (no tooth decay)
in chewing gum, toothpaste
what are oligosaccharides
3-10 covalently linked monosaccharides
found in artichokes, garlic, onions
e.g galactooligiosaccharide
what are polysaccharides
10+ monosaccharides homopolysaccharides - single type of monomer - straight or branched chain - e.g starch and cellulose
heteropolysaccharides
- two or more different monomers
- straight or branches chain
- e.g gellan gum
