1. Give some differences between a triglyceride and a phospholipid.
Answer
Triglyceride contains three fatty acid chains, while phospholipid only contains two. Triglyceride is non polar, while phospholipid is polar. Triglyceride is hydrophobic, while phospholipid has a hydrophilic head and hydrophobic tail.
2. A fatty acid can be represented by the formula R-COOH. What does the letter R represent ?
Answer
The variable region of the fatty acid, which is the hydrocarbon chain.
3. Identify which of the two fatty acids shown below is saturated. Explain your answer.
Answer
Fatty acid A because it has no C=C bonds.
4. Olestra is a fat substitute. It is made from a molecule of sucrose with fatty acids attached. Its structure is shown in the figure below. "X" represents the positions where fatty acids are attached. Name the bond at position Y.
Answer
Glycosidic bond.
5. Olestra is not digested in the gut. Explain why.
Answer
Olestra has a different shape from normal sucrose or lipids, so it does not fit into the active site of digestive enzymes such as lipase or sucrase.
6. Describe a test you could carry out to show that biscuits have lipids present.
Answer
Grind and mix with alcohol. Add equal volume of water, shake and positive result is a white emulsion.
7. Draw a phospholipid molecule and label it to explain why it can be called a polar molecule.
Answer
