Question

1. examine the phospholipids below. identify which image (a or b) contains saturated fatty acids chains and which contains unsaturated fatty acid chains? 3. justify your answer to question #2 by labeling the structural component in the image that differentiates saturated fatty acid chains from unsaturated fatty acid chains. 4. the heads of phospholipids contain a phosphate group, as seen below (r represents variable molecules the phosphate group can be attached to). using this image and your knowledge of chemistry from unit 1, justify why the heads of phospholipids are hydrophilic. r—o—p=o o- o-

Explanation:

Step1: Identify saturated and unsaturated fatty - acid chains

Saturated fatty - acid chains have single bonds only and are straight. Unsaturated fatty - acid chains have double bonds which cause kinks. Image A has straight chains, so it has saturated fatty - acid chains. Image B has a kink due to a double bond, so it has unsaturated fatty - acid chains.

Step2: Justify the difference in structure

The key structural component is the presence of double bonds. In image B, the double bond creates a kink in the fatty - acid chain, while image A has no double bonds and thus straight chains.

Step3: Justify hydrophilicity of phospholipid heads

The phosphate group in the phospholipid head has a negative charge (as seen in the structure $R - O - P=O$ with two $O^-$). Water is a polar molecule. Polar molecules are attracted to charged molecules. So, the charged phosphate group in the phospholipid head is attracted to water, making the head hydrophilic.

Answer:

1. A contains saturated fatty - acid chains, B contains unsaturated fatty - acid chains.
2. The presence of a double bond in B creates a kink, while A has no double bonds and straight chains.
3. The phosphate group in the phospholipid head is charged (negatively), and water is polar. Charged molecules attract polar water molecules, making the head hydrophilic.