1. Why are the most unsaturated fatty acids found in phospholipids in the cis rather than the trans confirmation? Draw the structure of a 16-carbon fatty acid as saturated, trans monosaturated, and cis

1)(a) Saturated fatty acid tails have a different shape than unsaturated fatty acid tails. Briefly explain what this means in terms of chemical bonds.

(b) How does the difference in chemical bonds between saturated and unsaturated fatty acids affect the shape of these molecules.

(c) Cell membranes are made mostly of phospholipids (which contain fatty acids) that must maintain fluidity. What type of phospholipids would be better at maintaining fluidity: saturated phospholipids or unsaturated phospholipids? Explain your answer (and make sure your explanation relates to part b).

Compare the structure and functionof different types of lipids: triglycerides, phospholipids,steroids, and saturated and unsaturated fatty acids.

The table below shows the percent of each type of phospholipid fatty acid tail found in each type of the grass membranes on Oct. 2 and Dec. 8th. The first column in the table shows the length of the fatty acid tail and the number of double-bonds in the fatty acid. For example the fatty acid “16:0” would be a fatty acid that was 16 carbons long and had 0 double-bonds. The second and third columns show the percent of all phospholipid fatty acids that were of this type. For example, in grass collected on October 2nd, 23.9 % of the phospholipid fatty acids were 16 carbons long and had no double-bonds (16:0 type), and in the grass collected on Dec. 8^th, 21.0 % of the phospholipid fatty acids were 16 carbons long and had no double-bonds (16:0 type).

A. For each date the grass was collected, calculate the total percent of phospholipid fatty acids that were saturated fatty acids and the total percent of phospholipid fatty acids that were unsaturated fatty acids.

B. Draw a column graph that shows the total percent of phospholipid fatty acids that were saturated for each date that grass was collected and the total percent of phospholipids that were unsaturated for each date that grass were collected.

C. Why are the % of saturated and unsaturated fatty acid tails on the phospholipids of the Oct 2^nd collected grass and the Dec 8^th collected grass not the same? Use your understanding of membrane fluidity to address why these percentages have changed during this time period.

D. During this experiment the concentration of cholesterol found in the membranes of the grass was also measured. On Oct. 2^th the concentration of cholesterol was 1.10 umol/mg and on Dec. 8^th the concentration of cholesterol was 1.22 umol/mg. Why did the concentration of cholesterol change? Use your understanding of membrane fluidity to address why these concentrations have changed during this time period.