3.1.2 carbohydrates Flashcards
define monosaccharide
monomers from which larger carbohydrates are made
give examples of monosaccharides
glucose, galactose and fructose
what bond does a condensation reaction between 2 monosaccharides form?
glycosidic
what is formed by the condensation of 2 monosaccharides?
disaccharide
give examples of disaccharides
sucrose, maltose and lactose
what monosaccharides make up sucrose?
glucose and fructose
what monosaccharides make up lactose?
galactose and glucose
what monosaccharides make up maltose?
glucose and glucose
what are the two isomers of glucose?
alpha glucose and beta glucose
define polysaccharide
molecules formed by the condensation of many glucose units
give examples of polysaccharides
starch
glycogen
cellulose
outline the structure and function of starch
structure : 2 polymers - amylose & amylopectin alpha glucose
function: energy source
what type of bonds does starch have?
amylose : alpha 1:4 glycosidic bonds
amylopectin : alpha 1:4 and 1:6 glycosidic bonds
how is the structure of starch suited to its function?
amylose : long, unbranched chains of glucose, coiled so compact and able to hold a lot of glucose good for energy storage
amylopectin : branched meaning there are free ends allowing enzymes to hydrolyse to get the glucose, faster hydrolysis= good for respiration
extra : starch is insoluble, molecules are large & compact
outline the structure and function of glycogen
structure : alpha glucose
function : storage molecule (in liver & muscles )
what type of bonds does glycogen have?
alpha 1:4 and 1:6 glycosidic bonds
how is the structure of glycogen related to its function?
compact so more can be stored
insoluble so doesn’t allow water into cells
more branched so ends can be acted on by enzymes
outline the structure and function of cellulose
structure : beta glucose
function : provides rigidity to the plant cell wall & also prevents the cell from bursting as water enters it
what type of bonds does cellulose have?
hydrogen bonds
how is the structure of cellulose related to its function?
cellulose is made up of beta glucose and so form long straight unbranched chains
the cellulose molecules run parallel to each other and are cross linked by hydrogen bonds
the are grouped together to form microfibrils giving more strength
how would you test for reducing sugars?
add Benedict’s reagent to the sample solution
heat the test tube in a water bath
if reducing sugar is present a coloured precipitate will form (copper sulfate reduced to copper oxide)
positive result : blue to brick red
what are the reducing sugars?
galactose
glucose
fructose
maltose
how would you test for non reducing sugars?
add dilute hcl to the sample and heat in a water bath that has been brought to a boil
neutralise the solution with sodium hydrogen carbonate
then carry out the Benedict’s test as normal
what is a non reducing sugar?
sucrose
