biology 1 : biological molecules - Carbohydrates Flashcards
what are monomers
smaller units from which large molecules are made from
name 3 examples of monomers
monosaccharides
amino acids
nucleotides
what are monosaccharides
monomers from which larger carbohydrates are made
give examples of monsaccharides
glucose fructose galactose
what happens in a condensation reaction between two monosaccharides
forms a 1-4 glycosidic bond
what are disaccharides
formed by the condensation of two monosaccharides
name all the diassacharides formed by the condensation of glucose
glucose + glucose -> maltose
glucose + fructose -> sucrose
glucose + galactose - > lactose
what are isomers
elements with the same chemical formula but different arrangement of atoms
what are the two types of glucose and what are they
alpha glucose
beta glucose
isomers
how are polysaccharides formed
condensation of many glucose units
what is formed at alpha condensation
glycogen and starch
what is formed at beta condensation
cellulose
what are reducing sugars
acts as a reducing reagent in chemical reactions (donates electrons to other molecules)
name all the reducing sugars
glucose fructose
lactose and maltose
how to test for reducing sugars
grind food in distilles water than filter out the solid particles
3 cm^3 of food solution into the boiling tube and add 3cm^3 of benedict solution
place boiling tube into boiling water for 5 min
if reducing sugar is present changes the colour will change depending on the amount of reducing sugar
green,yellow,orange,brick red
what makes the bendict solution blue
contains copper ion cu2+
why is the benedict test unreliable
Impossible to determine concentration of reducing Sugars
only gives a narrow range of colour changes
humans perceive colour differently
what is the test for non reducing sugars
add dilute hydrochloric acid
heat in a water bath
neutralize it using sodium hydrogencarbonate
complete benedict test
a positive result will form a colourful precipitate
why do you need to check if the solution is alkaline for the benedict test
benedict test will not work under acidic conditions
how to test for starch and how do you know if it is present
Add food solution then add iodine and potassium iodide
blue black if starch is present
stays orange is there is no starch
how to test for protein
Add food solution and then add biuret
Reagent
if protein is present solution will turn purple
if not solution will stay blue
what is biuret solution
sodium hydroxide and copper sulphate being premixed
what does the test for protein also test for
peptide bonds (protein has them amino acids don’t)
how to test for lipids
food mixture can not be mixed as lipids can stick to filter paper
leave food mixture to allow particles to settle
add 3cm^3 of food solution then add 3cm^3 of ethanol and water
shake solution
if lipids are present a white cloudy emulsion will form
if not it will stay clear
