carbohydrates Flashcards
define monomer + give some examples
a single sub unit that joins together with others to form a large molecule. eg amino acids, monosaccharides, nucleotides
define polymer + give some examples
molecules formed when many monomers join together. eg proteins, carbohydrates, DNA/RNA
what happens in a condensation reaction
a chemical bond forms between two molecules and a molecule of water is produced
what happens in a hydrolysis reaction
a water molecule is used to break a chemical bond between two molecules
name 3 hexose monosaccharides
all have formula C6H12O6
glucose galactose and fructose
name the type of bond formed when monosaccharides react
1,4 or 1,6 glycosidic bond
name 3 disaccharides and describe how they are formed, and their molecular formula
+ glucose = maltose
+ galactose = lactose
+ fructose = sucrose
formed by condensation, forms glycosidic bond
all have molecular formula C12H22O11
draw the structure of a-glucose
-
draw the structure of B-glucose
-
describe the functions of starch and what it is made of
storage polymer of a-glucose in plants
insoluble - no osmotic effect on cells
large - does not diffuse out of cells
forms a-glucose which is easily transported and used in respiration
made of amylose and amylopectin
describe the structure of amylose
a-glucose monomer
1,4 glycosidic bonds
straight chain helix with intermolecular H bonds - compact
describe the structure of amylopectin
a-glucose monomer
1,4 and 1,6 glycosidic bonds
branched - many terminal ends for hydrolysis into glucose
describe the structure and functions of glycogen
main a-glucose storage polymer found in animals and bacteria
1,4 and 1,6 glycosidic bonds
branched - many terminal ends for hydrolysis
insoluble - no osmotic effect and does not diffuse out of cells
tight coil- compact - much energy can be stored in a small space
why is many terminal ends beneficial
for hydrolysis to form glucose monomers which are used in respiration. important to animals with a high metabolic rate rather than plants since they are more active
describe the structure and function of cellulose
polymer of B-glucose in plant cells
prevents bursting under turgor pressure and holds stem up
1,4 glycosidic bonds
straight chain unbranched molecule
glucose molecules are alternately inverted
H bonds form crosslinks between parallel strands, forming microfibrils - high tensile strength
what benefit does H bonds in cellulose provide
while each bond individually is weak, the sheer overall number of them makes a considerable contribution to strengthening cellulose, making it a valuable structural material. H bonds form between -Oh groups on adjacent parallel chains giving cellulose its structural integrity
test for reducing sugars & colour change
(all monosaccharides and some disaccharides such as maltose)
grind or dissolve food sample
2cm3 food 2cm3 benedicts to test tube
5 min in hot water bath
if present blue to orange-brown
which colours are associated with concentration of reducing sugar in benedicts test
blue - none
green - very low
yellow - low
orange - medium
red - high
test for non reducing sugars
test for reducing sugars, no colour change
2cm3 food 2cm3 dilute HCl
water bath 5 min hydrolyses disaccharides into constituent monosaccharides
add sodium hydrogen carbonate slowly to neutralise HCl, benedicts will not work in acidic conds
test w pH paper to check it is alkali
retest by heating w 2cm3 benedicts 5 min
test for starch
2cm3 food 2 drops iodine
presence of starch is indicated by a blue-black colouration
