Biological Molecules

Question 1

What is the test for reducing and non-reducing sugars?

Answer 1

BENEDICTS TEST

• A reducing sugar is one that can donate electrons, this includes all monosaccharides and disaccharides. An alkaline solution of blue copper sulfate (II) is added to the sugar and heated in water bath. If a reducing sugar is present a red precipitate of copper (I) oxide will form. In absence of a reducing sugar, Benedict’s reagent does not change colour at all.

Question 2

How do you test for proteins?

Answer 2

BIURET TEST

• A sample of the solution is placed in a test tube and an equal of NaOH is added. Then a few drops of dilute copper (II) sulfate solution is added and gently mixed. In presence of protein, solution turns lilac to indicate peptide bonds. In absence of protein, solution stays blue.

Question 3

How do you test for lipids?

Answer 3

• 2ml sample is added to 5ml of ethanol. Contents are mixed thoroughly by shaking to ensure that lipids have dissolved. When 5ml of water is added and mixed, solution turns cloudy to indicate presence of lipid due to formation of emulsion where light is refracted as it passes from droplets of oil to droplets of water.

Question 4

How is starch tested for?

Answer 4

• Tested for help with iodine colour of potassium iodide from yellow to black/blue.

Question 5

What is the stored energy source for plants called and what are the common polymers called?

Answer 5

Starch

• Amylose
• Amylopectin

Question 6

What is the stored energy source for humans called and what are it’s properties and why?

Answer 6

• Glycogen
• insoluble, compact, more branched than amylopectin.
• humans are mobile compared to plants so requires faster glycolysis.

Question 7

What differentiates amylose and amylopectin referring to structure?

Answer 7

• amylose has only 1,4 glycosidic bonds
• amylopectin has both 1,4 glycosidic bonds and 1,6 glycosidic bonds at every 1 in 25 glucose subunits.
• amylose is unbranched whereas amylopectin is branched and compact which is good for storage.

Question 8

What are the properties of ATP?

Answer 8

• Small - can move easily in and out of cell
• Water soluble - energy requiring properties happen in aqueous environments
• bonds between phosphates have intermediate energy - large enough for cellular needs but small enough to no have heat energy as waste
• Easily regenerated - can be recharged easily.