Question
A student conducts an experiment to compare the melting points of an
unsaturated fatty acid and a saturated fatty acid. The data are shown in
the table.
| Fatty Acid | Melting Point \((^o C)\) |
| Oleic acid (unsaturated) | 16.3 |
| Stearic acid (saturated) | 69.3 |
(a) Describe the structural differences between an unsaturated fatty
acid and a saturated fatty acid.
(b) Identify the independent variable and the dependent variable in
this experiment.
(c) The membrane surrounding cell A contains a much higher
percentage of unsaturated fatty acids than the membrane
surrounding cell B. Predict which cell would have a more flexible
membrane.
(d) Justify your prediction from part (c).
▶️Answer/Explanation
Ans:
(a) Saturated fatty acids have a chain of carbon atoms connected by
single bonds. Unsaturated fatty acids have carbon chains that
contain at least one double bond between the carbon atoms.
(b) The independent variable is the type of fatty acid. The dependent
variable is the melting point in degrees Celsius.
(c) Cell A would have a more flexible cell membrane.
(d) Cell A would have a more flexible cell membrane because it
contains more unsaturated fatty acids. Unsaturated fats contain
double bonds in random locations, causing bends in the long
chains. These bends in the fatty acid chains prevent unsaturated fats
from forming tightly packed sheets, which leaves some spaces
between the fatty acid chains. Saturated fats, on the other hand, are
straight chains; they form tightly packed sheets and have less space
between their fatty acid chains. Since unsaturated fats cannot pack
tightly like saturated fats, this allows unsaturated fats to be more
flexible and thus be liquid at room temperature.