Concept 3.4: Lipids are a diverse group of hydrophobic molecules

What are lipids?

A diverse group of hydrophobic molecules that do not form true polymers.

What trait do all lipids share?

They mix poorly with water due to their hydrophobic nature.

What types of lipids are most biologically important?

Fats, phospholipids, and steroids.

Why are lipids hydrophobic?

Lipids are hydrophobic because they consist mainly of hydrocarbon chains, which are nonpolar and do not interact well with water.

What is the structure of a fat?

A fat consists of a glycerol molecule linked to three fatty acids.

What does a fatty acid consist of?

 A fatty acid consists of a long hydrocarbon chain with a carboxyl group at one end.

Why do fats seperate from water?

Fats separate from water because their long hydrocarbon chains are nonpolar and hydrophobic, causing them to cluster together and exclude water.

What is glycerol?

An alcohol with three carbons, each bearing a hydroxyl group.

How are fatty acids defined?

Long carbon chains, usually 16 or 18 carbons long, ending with a carboxyl group.

What is an ester linkage?

A bond formed between a hydroxyl group and a carboxyl group during fat formation.

What are saturated fats?

Fats with fatty acids that have no double bonds, fully saturated with hydrogen.

What are unsaturated fats?

Fats with one or more double bonds in their fatty acid chains, resulting in fewer hydrogen atoms.

Why are most plant fats liquid at room temperature?

They contain unsaturated fatty acids that create kinks in the chains, preventing tight packing.

What are trans fats?

Unsaturated fats that have been hydrogenated to become solid, often associated with health risks.

What is the primary function of fats?

Energy storage; fats store more energy per gram than polysaccharides like starch

What are phospholipids?

Lipids that are major constituents of cell membranes, consisting of two fatty acids and a phosphate group.

What distinguishes the two ends of a phospholipid?

The hydrocarbon tails are hydrophobic, while the phosphate group forms a hydrophilic head.

What is the phospholipid bilayer?

A double-layered sheet formed by phospholipids in water, crucial for cell membrane structure.

How do phospholipids arrange themselves in a cell membrane?

Hydrophilic heads face outward towards water, while hydrophobic tails point inward, away from water.

What are steroids?

Lipids characterized by a carbon skeleton with four fused rings.

What is cholesterol?

A crucial steroid in animal cell membranes and a precursor for other steroids like hormones.

How is cholesterol obtained?

It is synthesized in the liver and also obtained from dietary sources.

What are some potential health risks associated with high cholesterol levels?

Elevated cholesterol may contribute to atherosclerosis and cardiovascular disease.

How do fatty acids contribute to the properties of fats?

The presence of double bonds in fatty acids influences whether fats are saturated or unsaturated.

Why is fat an efficient energy storage molecule?

Its hydrocarbon chains are rich in energy, storing more energy per gram than carbohydrates.

What is the role of lipids in cells?

Lipids form cell membranes, store energy, and serve as signaling molecules.

What happens during the hydrogenation process?

Unsaturated fats are converted to saturated fats by adding hydrogen, altering their structure.

A phospholiipid has __ fatty acids and a phosphate group attatched to glycerol.

 A phospholipid has two fatty acids and a phosphate group attached to glycerol.

Proteins account for more than __% of the dry mass of most cells

Proteins account for more than 50% of the dry mass of most cells.

 How do phospholipids contribute to cellular function?

They create a barrier that separates the cell from its environment and compartmentalizes internal processes.