Chem Chapter 19 Final - Chapter 19: Lipid terminology, melting points of fatty acids, phospholipid properties

What are lipids?

Organic compounds that are soluble in nonpolar solvents (like hexane) but not in polar solvents (like water).

They include fats, oils, phospholipids, and sterols.

What is a fatty acid?

A carboxylic acid with a long hydrocarbon chain, typically with an even number of carbons.

It can be saturated or unsaturated.

What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids have no double bonds between carbon atoms (e.g., stearic acid).

Unsaturated fatty acids contain one or more double bonds (e.g., oleic acid for monounsaturated, linoleic acid for polyunsaturated).

What is the term for fatty acids with one double bond?

Called monounsaturated fatty acids (MUFA).

An example is oleic acid (18:1 Δ9).

What are polyunsaturated fatty acids (PUFAs)?

Two or more double bonds.

Examples include linoleic acid (18:2 Δ9,12) and linolenic acid (18:3 Δ9,12,15).

What does "cis" vs. "trans" refer to in fatty acids?

"Cis" refers to the hydrogen atoms on the same side of a double bond, causing a bend.

“Trans" refers to hydrogen atoms on opposite sides of the double bond, resulting in a more linear structure.

How do double bonds in unsaturated fatty acids affect their melting point?

More double bonds (unsaturation) lower the melting point of fatty acids because they create kinks that prevent tight packing

How does the length of a carbon chain affect the melting point of fatty acids?

Longer carbon chains result in higher melting points due to stronger London dispersion forces between the molecules

What is the melting point of stearic acid (C18:0)?

Stearic acid, a saturated fatty acid, has a higher melting point (around 69-70°C) compared to unsaturated fatty acids of the same length.

How does the saturation of fatty acids affect their state at room temperature?

Saturated fatty acids are typically solid at room temperature (e.g., butter), while unsaturated fatty acids are liquid (e.g., olive oil)

What are phospholipids?

Lipids that contain a phosphate group

They are essential components of cell membranes and have both hydrophilic (polar) and hydrophobic (nonpolar) regions

What are the two major types of phospholipids?

Glycerophospholipids

Sphingolipids

Sphingolipids

Contain sphingosine as the backbone

Glycerophospholipids

Contain glycerol as the backbone (e.g., lecithin)

What is the structure of glycerophospholipids?

Glycerophospholipids have a glycerol backbone, two fatty acid tails (nonpolar), and a phosphate group (polar) that may have additional groups like choline.

What is lecithin?

A type of glycerophospholipid with a choline group attached to the phosphate, and it is often used as an emulsifier in food and cosmetics

What is the role of phospholipids in cell membranes?

Phospholipids form a bilayer in cell membranes

Hydrophilic (polar) heads facing the aqueous environment and the hydrophobic (nonpolar) tails facing inward, creating a semi-permeable barrier

What is the significance of the amphipathic nature of phospholipids?

Allows phospholipids to form bilayers and act as effective membrane components

How do phospholipids help membrane structures in the body?

Forming the basis of cell membranes

How do phospholipids help emulsification in the body?

Aiding in fat digestion by emulsifying fats in the intestines

How do phospholipids help signal transduction in the body?

Involved in cell signaling pathways

How do phospholipids help with emulsification?

Phospholipids have both hydrophilic and hydrophobic parts, which allows them to stabilize mixtures of water and oil, creating emulsions (e.g., in digestion or food preparation)

What is a phospholipid bilayer?

A two-layered structure that forms the core of cell membranes, with hydrophilic heads facing outward and hydrophobic tails facing inward

What is the role of phosphatidylcholine in the body?

A major phospholipid in cell membranes and plays a role in maintaining membrane integrity and function

How do fatty acid chains affect the properties of phospholipids?

The length and saturation of the fatty acid chains affect the fluidity and stability of the phospholipid bilayer.

Shorter, unsaturated chains increase fluidity

Longer, saturated chains make the membrane more rigid.