Study guides › B/B › Biochemistry
Lipids & Membrane Biochemistry
Lipids store energy, build membranes, and carry signals. You will learn fatty acid and phospholipid structure, what controls membrane fluidity, how steroids, waxes and vitamins work, and how lipid messengers are made.
Study this chapter in PrepMed (free)
What this chapter covers
- Fatty Acids & Triacylglycerols. Chain length and double bonds decide melting point, fluidity, and how tightly fat can be stored.
- Phospholipids, Sphingolipids & the Bilayer. Amphipathic lipids assemble spontaneously into bilayers, and their tails set how fluid the membrane is.
- Steroids, Waxes & Lipid-Soluble Vitamins. One four-ring skeleton gives cholesterol and every steroid hormone, and four vitamins ride along with dietary fat.
- Signaling Lipids & Membrane Lipid Disorders. Membrane lipids are also raw material for second messengers, eicosanoids, and the sphingolipid storage diseases.
Key points to know
- Natural double bonds are cis and kink the chain
- More unsaturation and shorter chains mean a lower melting point
- Glycerophospholipid = glycerol + 2 fatty acids + phosphate head group
- Ceramide = sphingosine + fatty acid; sphingomyelin adds phosphocholine
- Cholesterol: 27 carbons, fused four rings, polar 3-OH
- Steroid hormones come from cholesterol and act on intracellular receptors
- Arachidonic acid comes from membrane phospholipids via PLA₂
- COX makes prostaglandins and thromboxanes; NSAIDs inhibit COX
Try a practice question
Which fatty acid has the lowest melting point?
- Stearic acid (18:0)
- Palmitic acid (16:0)
- Oleic acid (18:1)
- α-Linolenic acid (18:3)
Show the answer
D. Three cis double bonds give the most kinks and the weakest packing. Both saturated acids pack tightly and melt high.
Common questions
What does this chapter cover?
Lipids & Membrane Biochemistry covers Fatty Acids & Triacylglycerols, Phospholipids, Sphingolipids & the Bilayer, Steroids, Waxes & Lipid-Soluble Vitamins, Signaling Lipids & Membrane Lipid Disorders.
What should I know first?
Natural double bonds are cis and kink the chain More unsaturation and shorter chains mean a lower melting point Glycerophospholipid = glycerol + 2 fatty acids + phosphate head group
21 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.