Lab 2: Chemical Composition of Cells

Question 1

Test for proteins, starch and sugar:

Answer 1

Proteins: Biuret Test
Starch: IKI
Sugar: Bendict

Question 2

What color does the Reagan turn if there is a protein or peptide present?

Answer 2

Purplef= for protein, pinkish-purple for peptide. (biuret Reagant)

Question 3

What color does the reagant turn if starch is present?

Answer 3

Blue-black (iodine solution)

Question 4

What color does the Reagant turn if there is sugar present?

Answer 4

green (very low), yellow (low), yellow-orange (moderate), orange (high), orange-red (very high).

Question 5

In what form are carbohydrates found in onions and potatoes?

Answer 5

Onions are positive in sugar and the potato is positive in starch.

Question 6

Test for lipids:

Answer 6

fats and oils do not evaporate from brown paper, instead, they leave an oily spot

Question 7

Emulsifier:

Answer 7

causes fats and oils to disperse in water. Contains molecules with both a polar and non polar end.

Question 8

What kind of bond forms during a dehydration synthesis reaction involving two amino acids?

Answer 8

Peptide bond.

Question 9

What molecule do plants store glucose?

Answer 9

Starch

Question 10

What is the name used for plant fats?

Answer 10

Oil.

Question 11

What must be present to successfully break down fats during digestion?

Answer 11

Bile salts

Question 12

Why won’t an oil stain come out of your shirt when you dab it with water?

Answer 12

Oil is insoluble in H2O.

Question 13

As what molecule do plants store glucose?

Answer 13

Starch

Question 14

What kinds of molecules are insoluble in water but soluble in alcohol or ether?

Answer 14

Lipids