7 - introduction to carbohydrates Flashcards
(24 cards)
why are carbohydrates important?
energy source
1g glucose = 4 Kcal/16 KJ
what are carbohydrates associated with?
important micronutrients and phytochemicals
…
carbohydrates are involved in cellular recognition (glycoproteins)
they provide flavour and sweetness
a source of dietary fibre: role in gut health
what is photosynthesis?
converting light energy into chemical energy
5 examples of sugars and sugar polymers:
- monosaccharides (monomer0
- disaccharides (dimer of 2 monomers)
- oligosaccharides (3-10 monomers producing an oligomer)
- polysaccharides (a polymer of >10 monomers)
- saccharide means end in ‘ose’
what are the properties of monosaccharides?
simple sugars (3-7 carbons)
=> triose (3), tetrose (4), pentose (5), hexose (6), heptose (7)
base unit (monomer) of all carbohydrates (polymers)
sweetness varies between sugars
they are water soluble
what are three common simple sugars?
glucose: blood sugar
galactose: milk sugar
fructose: fruit sugar
what group do aldoses contain?
an aldehyde group in position one.
what group to ketoses contain?
a ketone group at another C position.
how is starch formed?
alpha glucose molecules combine to form starch
how is cellulose formed?
beta glucose molecules combine to form cellulose
fructose
1.5 times sweeter than glucose
in fruit, serves as marker of rich nutrition
does not stimulate insulin
limited cell transport
where is fructose metabolised?
the liver (unlike glucose, which is metabolised in throughout the body) to produce glucose, glycogen and triglycerides
where is ribose found
in RNA
where is deoxyribose found
in DNA
what is an example of disaccharides?
an example is sucrose formed by the glycosidic linkage of one glucose and one fructose monomer:
a condensation reaction, requires energy and releases H2O.
how are disaccharides broken down into their constituent monosaccheerides?
by hydrolysis
this involved the addition of water, so is the opposite of condensation reaction (formation of water_
what are three natural disaccharides?
maltose, sucrose, lactose
what are some properties of natural disaccharides?
- water soluble
- sweet
- must be hydrolysed -> monosaccharides for use in the body
what are oilgosaccherides made from?
contain 3-10 monosaccharides: fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), maltodextrins from starch
what are some properties of oilgosaccharides?
Water soluble: can form gels
Important prebiotic
Increase mineral absorption
Slows glucose absorption
Link to proteins (forming glycoproteins) or lipids (forming glycolipids)
Roles in cell stability, call recognition, blood type, call binding and important for immune response.
properties of polysaccharides?
poly (many) saccharides (>10) - may be straight, helical, coiled, branched
insoluble in water
not sweet
physiologically inactive
important for bowl health and satiety
important role in energy storage:
- glycogen - stored in animals (liver and muscle)
- starch - stored in plants
what are triglycerides?
Triglycerides are lipids made from glycerol and three fatty acids = true fats or neutral fats
Glycerol, an alcohol that has a 3 carbon skeleton with hydroxyl (HO-) groups attached to each
The three fatty acids can be the same or different
Fatty acids consist of a carboxyl (-COOH) group attached to a long hydrocarbon skeleton; they are acidic
The fatty acids vary in length and can contain single or both single and double bonds (e.g. saturated vs unsaturated )
what is the function of carbohydrates?
1g of fat produces twice as much energy as 1g carbohydrate ie 9 Kcal/38KJ
Provides warmth (insulation) and buoyancy
Animals: long-term storage is in adipose call (adipocytes)
Plants store starch when mobility is not issue (e.g. tubers) and store oil when mobility and dispersal is required (e.g. seeds)
