Which statement is true: a) all fatty acids in a triglyceride are unsaturated b) all lipids contain fatty acids c) all steroids contain a four ring region d) all phospholipids have one saturated fatty acid tail and one unsaturated fatty acid tail?

The correct answer is: c) all steroids contain a four ring region.

Let’s break this down:

• Option a: This is not true because triglycerides can have both saturated and unsaturated fatty acids. Depending on the source of the triglyceride, it may contain a mixture of both types of fatty acids.
• Option b: This statement is also false; while many lipids do contain fatty acids, not all lipids fall into this category. For example, steroids are lipids but do not contain fatty acids.
• Option c: This statement is true. Steroids are a class of lipids characterized by their structure, which includes a four-ring carbon skeleton. This is a defining feature of steroids, making this option correct.
• Option d: This is misleading because while many phospholipids contain one saturated and one unsaturated fatty acid tail, this is not universally true for all phospholipids. Variations exist in the structure of phospholipids.

In summary, the statement regarding steroids is the only one that holds true across the board.