Lipids and Fatty Acids - Part 1 (Properties and Biological Roles)

A set of Q&A flashcards covering lipid types, fatty acid structure and saturation, essential fatty acids, membrane lipids and signaling, energy from fats, and related physiological concepts from Part 1 of the lecture.

What are the two main classes of phosphate-containing lipids in cellular membranes?

Glycerophospholipids and sphingolipids.

What is the backbone of glycerophospholipids and sphingolipids, respectively?

Glycerol for glycerophospholipids; sphingosine for sphingolipids.

What lipid serves as the main energy storage form and is rich in fatty acids?

Triacylglycerols (triglycerides).

What is the energy yield per gram for fatty acids compared with glucose?

Fatty acids yield about 9 kcal per gram; glucose yields about 4 kcal per gram.

What is beta-oxidation and where does it occur?

Beta-oxidation oxidizes fatty acids to acetyl-CoA in the mitochondria, providing substrates for the TCA cycle and oxidative phosphorylation.

Name the essential fatty acids in humans and why they are essential.

Linoleic acid (18:2, n-6) and alpha-linolenic acid (18:3, n-3); they cannot be synthesized and must be obtained from the diet.

Which fatty acid is a key precursor to eicosanoids and is abundant in membranes?

Arachidonic acid (20:4, n-6).

How is omega nomenclature defined for fatty acids?

Omega numbering counts from the methyl end; the position of the first double bond from that end defines the omega number (e.g., omega-3 has a double bond at the third carbon from the methyl end).

What is the difference between cis and trans configurations in fatty acids?

Cis double bonds have hydrogens on the same side, causing a kink; trans double bonds have hydrogens on opposite sides, giving a straighter chain.

How does saturation affect membrane fluidity and melting point?

More saturation increases tight packing and rigidity and raises melting point; more unsaturation introduces kinks that increase fluidity and lower melting point.

Which lipid is especially abundant in inner mitochondrial membranes and is important for electron transport?

Cardiolipin (diphosphatidylglycerol).

What is the role of cholesterol in membranes?

Modulates membrane fluidity and organization; acts as a precursor to steroid hormones and vitamin D.

What are the products of phospholipase C action on PIP2, and their signaling roles?

Diacylglycerol (DAG) and inositol trisphosphate (IP3); they act as second messengers to propagate signaling, including Ca2+ release.

What is the membrane model that describes a fluid lipid bilayer with proteins embedded in it?

The fluid mosaic model.

What are glycolipids without phosphate, and can you name examples?

Glycolipids such as galactosides, cerebrosides, and gangliosides (sphingolipids without phosphate).

Why are phospholipids signaling-active beyond their structural role?

They can be precursors to signaling molecules and participate in cascades (e.g., PIP2-derived DAG/IP3 signaling, Ca2+ signaling).

What is the significance of industrial trans fats?

Trans fats are produced by hydrogenation; they tend to straighten chains, impair membrane properties, and are linked to cardiovascular disease risk.

Why is arachidonic acid biologically important beyond being a membrane component?

It is a precursor to prostaglandins, thromboxanes, and leukotrienes, which are involved in inflammation, pain, and other signaling processes.