IB Docs (2) Team MC test: Lipids
Multiple choice test on B.3 Lipids
Use the following 'quiz' to test your knowledge and understanding of this sub-topic. As this relates to a sub-topic on the options you may need access to the IB data booklet.
If you get an answer wrong, read through the explanation carefully to learn from your mistakes.
Which are roles of lipids?
I. energy storage
II. structural components of cell membranes
III. thermal insulation
Lipids are also electrical insulators, act as hormones and transporters of lipid-soluble vitamins.
Which is not a lipid?
A lipid is a substance of biological origin that is soluble in nonpolar solvents. Starch is polar and is a carbohydrate.
Which is the correct formula for the fat made by condensing propan-1,2,3-triol with a fatty acid, RCOOH?
The three ester links will be −C−O−CO−R not −C−CO−O-R and all carbon atoms can only have four bonds.
Which can store the most energy (per g of substance) in the human body?
Fats contain more than twice as much energy weight for weight than proteins, carbohydrates and DNA as they are in a more reduced form (i.e. contain less oxygen).
Which row correctly describes both hydrolytic and oxidative rancidity?
| Row | Hydrolytic rancidity | Oxidative rancidity |
| 1 | Caused by the formation of aldehydes and ketones when fats react with water and an enzyme such as lipase. | Caused by the formation of free fatty acids when the C=C double bonds in unsaturated fats react with oxygen. |
| 2 | Caused by the formation of aldehydes and ketones when the C=C double bonds in unsaturated fats react with oxygen. | Caused by the formation of free fatty acids when fats react with water and an enzyme such as lipase. |
| 3 | Caused by the formation of free fatty acids when fats react with water and an enzyme such as lipase. | Caused by the formation of aldehydes and ketone when the C=C double bonds in unsaturated fats react with oxygen. |
| 4 | Caused by the formation of free fatty acids when the C=C double bonds in unsaturated fats react with oxygen. | Caused by the formation of aldehydes and ketone when fats react with water and an enzyme such as lipase. |
The rank smell when butter undergoes hydrolytic rancidity in the presence of water and an enzyme is due to the formation of short chain fatty acids. Unsaturated fats undergo oxidative rancidity when the C=C double bonds are oxidized to produce aldehydes and ketones.
Phospholipids are made up of four major components condensed together. What is the correct order of these components starting at the hydrophobic 'tail' of a phospholipid molecules and ending at its hydrophilic 'head'?
An example of a phospholipid is phosphatidyl choline: .jpg)
What is the iodine number of linoleic acid, CH3(CH2)4(CH=CHCH2)2(CH2)6COOH?
The molar molecular mass of linoleic acid is 280 g mol−1.
Linoleic acid contains two C=C bonds so two moles of iodine react with 1 mole of linoleic acid. One mole of I2 has a mass of 254 g so 508 g of iodine react with 280 g of linoleic acid and the iodine number, which equals the number of grams of iodine that add to 100 g of linoleic acid, = (508 ÷ 280) x 100 = 181.
Which fatty acid has the lowest melting point?
The more unsaturated the acid the lower the melting point as the molecules of acid are less able to pack closely together due to the 'kinks' in the carbon chain caused by the C=C double bonds.
Which are steroids?
I. 
II. 
III. 
Steroids must posses the four membered ring system 
.
Which are generally thought to be bad for human health?
I. low density lipoproteins
II. trans-fats
III. high density lipoproteins
HDL particles can remove cholesterol from the arteries thus lowering the chances of cardiovascular disease whereas LDL particles and trans-fats can cause the arteries to become lined with cholesterol.
Twitter
Facebook
LinkedIn