Carbohydrates & Lipids Flashcards
what are carbohydrates?
molecules containing carbon, hydrogen and oxygen
include sugars and long-term polymers (polysaccharides)
what are the two types of sugars?
monosaccharides - glucose, fructose & galactose
disaccharides - sucrose, maltose & lactose
what are the two types of polysaccharides?
storage - glycogen & starch
structural - cellulose
what are monosaccharides?
soluble in water
have a sweet taste
form crystals
3 carbons = triose sugars
5 carbons = pentose sugars (ribose / deoxyribose)
6 carbons = hexose sugars (glucose)
general formula = (CH2O)n - n is greater than or equal to 3
how can alpha glucose and beta glucose be distinguished?
by the arrangement of the OH and H groups
in alpha glucose the OH group on carbon 1 is below the plane of the ring
in beta glucose the OH group on carbon 1 is above the plane of the ring
what is the function of alpha glucose in living organisms?
the main energy source in plants and animals
how does the structure and properties of alpha glucose relate to its function?
forms hydrogen bonds with H/OH groups of water so is soluble
can easily be moved around the organism & within cells
bonds contain energy
bonds broken down by enzymes to release energy - produces ATP
molecules of glucose can join together via condensation reactions to form polysaccharides and disaccharides
what are pentose monosaccharides?
monosaccharides that contains five carbon atoms
eg - ribose and deoxyribose
what are disaccharides?
sugars composed of two monosaccharides covalently bonded together by a glycosidic bond
maltose = glucose + glucose
lactose = glucose + galactose
sucrose = glucose + fructose
how are alpha-glucose monosaccharides joined together?
how is an a-1,4-glycosidic bond formed?
condensation reactions
two alpha-glucose monomers joined together at carbon 1 of one monomer & carbon 4 of another with an oxygen in the centre (C-O-C)
forms an a-1,4-glycosidic bond
forms a disaccharide
the OH group bonded to 1 carbon atom is removed, the H in the OH bonded to the other carbon is removed, they form water
what is a hydrolysis reaction?
one molecule of water is used to break the glycosidic bond
catalysed by enzyme eg - maltase
forms monosaccharides from a disaccharide
OH bond in water breaks, leaves a H atom & an OH group
1 of the CO bonds of the glycosidic bond breaks
H bonds to O, OH bonds to C
what needs to happen to beta glucose so it can form a glycosidic bond with galactose?
beta glucose is flipped 180° so OH groups are next to each other
forms a beta glycosidic bond
forms lactose
hydrolysis reaction
what is starch?
found in plants
carbohydrate made up of 2 different polysaccharides:
amylose - coiled
amylopectin - coiled & branched
stored in chloroplasts
stored in the cell as starch grains
broken down into a-glucose molecules which can be respired to produce ATP
what is amylose?
polysaccharide - makes up starch
made of a-1,4-glycosidic bonds
alpha glucose
coiled
hydrogen bonds keep the chain in a coiled structure
what is amylopectin?
polysaccharide - makes up starch
a-1,4 & a-1,6-glycosidic bonds
coiled & branched
branches bonded between carbon 1 & 6
what is glycogen?
referred to as animal starch
same structure as amylopectin but has more branching
a-1,4 & a-1,6-glycosidic bonds
glucose is stored as glycogen granules in large amounts in liver & skeletal muscles
insoluble, compact & energy dense
doesn’t allow osmosis
how do the structures of glycogen and starch relate to their function?
both are storage polysaccharides
both are made by bonding many thousands of alpha-glucose molecules together through condensation reactions
the alpha glucose that is stored is used in respiration
how do the properties of glycogen and starch relate to their function?
compact - lots of glucose and energy can be stored (energy dense)
metabolically inactive
insoluble in water
chain molecules - can be hydrolysed / built up by enzymes
