Biology 101 – Quiz on Exercise 6 – Nutrient Analysis of Foods
Name _____KEY_______________________________________
1. To your experimental test tube, you add the following:
 5 mL distilled water
 5 mL starch solution
 An enzyme that hydrolyzes starch
 Benedict’s solution
You let the test tube sit for 30 minutes and then you place it in the boiling water. Do you expect the
solution to change color? Why/Why not? (5 points)
Starch is a polymer of glucose monomers. Thus, when starch is hydrolyzed, the result will be a
lot of glucose molecules. Since glucose is a simple sugar, the Benedict’s solution will change from
blue to orange (a positive result)
2.
True or False (2 points each)
a.
Biuret solution tests for the presence of molecules made when amino acids have been
joined together by peptide bonds TRUE
b.
Iodine tests for a carbohydrate
TRUE
c.
Sudan IV tests for lipids TRUE
d.
4 grams of fat have more kilocalories than 5 grams of protein but less kilocalories than 6
grams of carbohydrate
FALSE
e.
Nucleic acids often serve as an important food source for embryos
FALSE
f.
A plant product cannot test positive for protein because plant products lack muscle tissue
FALSE
g.
If a food tests positive with the Sudan IV, then it must test negative with the Benedict’s
solution
FALSE
h.
The actual color of the food itself can interfere with the interpretation of the color
changes in these nutrient analysis experiments
TRUE
3.
You come across an unrecognizable mass of food on the sidewalk. Before you eat it, you decide to
analyze the nutrients in it to see if it is a wise dietary choice. Here are the results of your 4 tests:
 Sudan IV  Positive
 Benedict’s Solution  Negative
 Iodine  Negative
 Biuret Solution  Positive
Is it likely that this food came from a green plant? (1 point) NO
Why/Why not? (3 points) B/C IODINE TEST (STARCH) WAS NEGATIVE
Does this food probably contain the simple sugar galactose? (1 point) NO
Why/Why not? (3 points) B/C BENEDICT’S TEST (SIMPLE SUGAR) WAS NEGATIVE
Could “regulation of chemical reactions” have been the original function (in the living organism
from where this food came) of any of the organic molecules in this food? (2 points) YES
What organic molecule type typically performs such a function? (2 points)
PROTEINS
Did the organism that this food came from perform cell respiration? Explain your answer. (2
points) YES! ALL LIVING ORGANISMS PERFORM CELL RESPIRATION
Bonus Question: You weighed this piece of food and discovered it had a mass of 30 grams.
Suppose 10 grams of an organic molecule is necessary for a positive test result. What is the
maximum number of calories that this piece of food could provide?
a.
220 kilocalories
b.
210 kilocalories
c.
305 kilocalories
d.
170 kilocalories
e.
80 kilocalories
f.
680 kilocalories