T1 - 1.2 carbohydrates Flashcards
uses of carbohydrates
- energy source e.g. glucose
- energy storage e.g. glycogen
- constituents of DNA and RNA
- glycolipids and glycoproteins are used in cell membranes for recognition
- cell walls use cellulose
what are 2 examples of monosaccharides
alpha glucose, beta glucose
what does alpha glucose look like
what does beta glucose look like
characteristics of monosaccharides
sweet, soluble, can crystallise easily
what is a condensation reaction
forms a covalent bond between monomers to form a larger molecule and release water
what do condensation reactions form between carbohydrates
glycosidic bonds:
di/polysaccharides
what is a hydrolysis reaction
forms smaller molecules by breaking covalent bonds USING WATER
how does maltose breakdown
glucose + glucose by maltase
how does sucrose breakdown
glucose + fructose by sucrase
how does lactose breakdown
glucose + galactose by lactase
what is a qualitative test for reducing sugars
- add Benedict’s solution
- heat at 80C for 3 mins
- turns from blue to orange-red precipitate
what is a qualitative test for non-reducing sugar
- boil in HCl which hydrolyses the sucrose
- cool and neutralise by adding sodium hydrogen carbonate
- add Benedict’s solution
- heat at 80C for 3 mins
- turns from blue to orange-red precipitate
what is a polysaccharide
many monosaccharides joined together with glycosidic bonds
what is starch
a polysaccharide found in plants with subunits of alpha glucose
what is amylose/starch
straight chain molecules of alpha glucose in starch
made of 1,4 glycosidic bonds
what is amylopectin
branched chain molecules of alpha glucose in starch
made of 1,6 glycosidic bonds
function of starch
energy storage, insoluble, compact, can be hydrolysed easily
what is glycogen
a polysaccharide found in animals that is made of subunits of alpha glucose
how does glycogen differ to starch
more branches and more compact in glycogen
function of glycogen
- stored in muscles and liver for energy storage
- smaller chains and branches make it easier to be hydrolysed
- spherical so more compact for storage in cells
what is cellulose
a polysaccharide found in plant cell walls made up of subunits of beta glucose
what is cellulose made up of
1,4 glucan chain - long and unbranched chains
what happens when glucan chains line up parallelly
they form hydrogen bonds between each chain making microfibril (24-36 glucan chains)
what happens when microfibril chains line up parallelly
they form hydrogen bonds between them to produce macrofibril
what is the benefit of macrofibrils in cell walls
creates a strong and rigid structure which prevents bursting in cell walls
how does it benefit starch and glucose to have alpha glucose monomers
can provide respiratory substrate rapidly
how do the branches benefit starch and glucose
can fit many glucose molecules into a small space
are starch and glucose insoluble
yes therefore doesn’t affect the water potential
why are glycogen and starch large molecules
cannot cross cell membranes and diffuse
