Lab 3 Flashcards
Positive Control
something we know will give a positive reaction
Negative Control
something we know will NOT give a positive reaction
Why can water be used as a negative control?
water does not contain molecules that will react with any reagents, lack of reactivity will result in a color that shows a negative reaction
What does Iodine test for and what is a positive reaction
starch, deep blue-black colour
What are reducing sugars?
sugars that contain an aldehyde or ketone functional group which gives them the ability to reduce certain metallic ions when heated together
What is reduction?
a substance is reduced if it gains an electron through a chemical reaction
What does Benedict’s solution test for and what is a positive reaction
reducing sugars, green (weak), yellow ( stronger), and brown or red (strongly positive)
What happens when a reducing sugar is in presence of Benedict’s solution and heated together?
reducing sugar gives up an electron to Cu2+, reducing it to Cu+ and changing color of solution
Why can some sugars and starch not reduce benedict’s solution?
aldehyde or ketone functional group has been consumed during the formation of a glycosidic bond
What does the Biuret test test for and what is a positive reaction
biuret test detects peptide bonds between amino acids, violet colour if proteins are present
what does sudan IV test for and what is a positive reaction
lipids, pink or red
Acid hydrolysis
macromolecules being broken down into monomers in presence of heat AND acid
What are buffer systems?
systems that maintain pH of a solution by minimizing changes in H+ concentration
What effect does presence of a buffer have on amount of acid or base needed to change the pH?
solution requires more acid or base to change the pH compared to solution without a buffer
What effect would using a weaker acid or base have on a solution with a buffer system to change the pH?
solution would require even more acid or base to change pH because the weaker acids and bases do not dissociate 100%
