Carbohydrates Flashcards
(27 cards)
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
