Lipids Lecture (BIOL-107 Topic 7)

Vocabulary flashcards covering key terms and definitions from the BIOL-107 Topic 7 Lipids lecture.

Lipids

Diverse group of hydrophobic organic molecules that includes fats, oils, waxes, steroids, and phospholipids.

Fats

Triglycerides used by animals for long-term energy storage, insulation, and organ protection (9 cal/g).

Oils

Plant triglycerides stored in elaioplasts; generally liquid at room temperature.

Waxes

Sticky lipids with high melting points that form protective, water-repellent layers in plants and animal ears.

Steroids

Lipids built on a four-carbon-ring skeleton; function varies with attached functional groups (e.g., cholesterol, hormones).

Phospholipids

Lipids containing two fatty acids and a phosphate group; primary components of cellular membranes.

Hydrophobic

Water-fearing; describes non-polar molecules that cannot form hydrogen bonds with water (e.g., most lipids).

Amphipathic

Molecule possessing both hydrophilic and hydrophobic regions, like phospholipids.

Micelle

Ring-shaped aggregate formed by amphipathic molecules with hydrophobic cores and hydrophilic exteriors; basis of soap action.

Functions of Lipids

Energy storage, nutrient absorption, padding, insulation, hormone synthesis, membrane structure, protection, waterproofing.

Caloric Density of Lipids

Lipids provide ~9 calories per gram, more than double carbohydrates’ 4 cal/g.

Steroid Skeleton

Characteristic four-fused-ring backbone common to all steroids.

Cholesterol

Membrane steroid that serves as precursor for estrogen, progesterone, etc.; excess can clog arteries and cause heart disease.

Glycerol

Three-carbon alcohol with three hydroxyl groups that forms the backbone of triglycerides.

Fatty Acid

Hydrocarbon chain with a terminal carboxyl (-COOH) group; can be saturated or unsaturated.

Triglyceride

Lipid formed when three fatty acids are ester-bonded to glycerol via dehydration synthesis.

Dehydration Synthesis

Reaction that joins molecules by removing water; three such reactions build a triglyceride.

Hydrolysis

Reaction that breaks covalent bonds by adding water; three hydrolyses fully digest a triglyceride.

Saturated Fatty Acid

Fatty acid with no C=C double bonds; straight chains pack tightly, yielding solid fats.

Unsaturated Fatty Acid

Fatty acid containing one or more C=C double bonds; kinks prevent tight packing, yielding liquids.

Monounsaturated Fat

Unsaturated fatty acid or fat with exactly one C=C double bond in its hydrocarbon chain.

Polyunsaturated Fat

Unsaturated fatty acid or fat with two or more C=C double bonds in its chain.

Hydrogenation

Industrial addition of H₂ to unsaturated oils to break C=C bonds, solidify the lipid, and create trans fats.

Cis Configuration

Arrangement where hydrogens attached to C=C are on the same side, causing a bend in the chain.

Trans Fat

Partially hydrogenated fat with hydrogens on opposite sides of C=C; raises LDL, lowers HDL, increases cardiovascular risk.

LDL Cholesterol

‘Bad’ cholesterol that transports lipids to tissues and contributes to arterial plaque formation.

HDL Cholesterol

‘Good’ cholesterol that carries excess lipids from tissues to the liver for removal.

Adipocyte

Specialized fat cell within adipose tissue that stores triglycerides.

Phospholipid Bilayer

Double layer of phospholipids forming cellular membranes with hydrophilic heads outward and hydrophobic tails inward.

Elaioplast

Plant plastid specialized for storing oil bodies.