Lab 3 Flashcards
What does Benedict reagent test for?
Reducing sugars that have been heated.
What are reducing sugars? Are sucrose and starch reducing sugars?
- Sugars that contain aldehyde or ketone functional grps.
- No, they don’t test positive with Benedicts solution.
What is a negative and positive result for Benedict’s?
Negative: Light blue
From weak to strong positive:
* Green.
* Yellow.
* Orange, brown, red.
What does Biuret test for?
Proteins (peptide bond between amino acids).
What is a negative and positive result for Biuret?
Negative: dark blue (darker than Benedict).
Positive: purple.
What does Sudan IV test for?
Lipids.
What is a negative and positive result for Sudan IV?
Negative: Red flakes floating in clear liquid.
Positive: Red/pink layer on top, clear liquid on bottom.
What is acid hydrolysis?
When macromolecules break down into their monomers in the presence of heat and acid.
What happens when HCL is added to starch and heated? What result would adding iodine give?
- Starch is hydrolyzed into glucose thru acid hydrolysis.
- A negative result.
What is an acidic solution?
A solution that contain a higher concentration of H ions than OH ions.
What is a basic solution?
A solution that contains ahigher concentration of OH ions than H ions.
What is an acid?
A substance that that dissociates in water and yelds H or OH ions.
What is a strong acid?
What is a weak acid?
- A substance that completely dissociates in water.
- A substance that doesn’t dissociate completely in water.
What do buffers do?
Maintains pH of a solution by minimizing changes in concentration of H ions.
How do buffers work?
Absorbs excess H+ ions or releases H+ ions when there’s too little.
