Macronutrients Part 2 - Lipids

Vocabulary flashcards covering the chemistry, digestion, transport, and metabolism of lipids as presented in Lecture 4.

Lipid

A broad category of macronutrients characterized by its solubility in organic solvents (ether, chloroform, acetone) and its insolubility in water.

Fatty acid

A simple lipid consisting of a straight chain of carbons with an acid group ($OOH$) at the end.

Saturated Fats

Fatty acids where every available carbon location is attached to a hydrogen atom, making them chemically stable under high heat; sources include butter, coconut butter, and lard.

Monounsaturated fatty acids (MUFAs)

Fatty acids with one double bond between two carbon atoms, making them liquid at room temperature and medium-stable for cooking.

Polyunsaturated fatty acids (PUFAs)

Fatty acids with two or more double bonds, making them highly unstable and reactive with oxygen to create free radicals.

Free radicals

Highly reactive molecules with an unpaired electron, often created when PUFAs are exposed to heat, light, or oxygen, potentially leading to atherosclerosis.

Essential Fatty Acids (EFAs)

Fatty acids the body cannot synthesize itself, categorized into omega-3 and omega-6 lineages.

Alpha-linolenic acid

A form of omega-3 fatty acid derived from seeds such as linseeds (flax seeds).

EPA and DHA

Eicosapentaenoic acid and docosahexaenoic acid; forms of omega-3 fatty acids found in marine algae and fish oils.

Arachidonic acid

An omega-6 fatty acid found in animal fats like egg yolks, dairy fat, and meat.

Trans-fat

Harmful fats resulting from the hydrogenation of vegetable oils to make them solid at room temperature.

Cholesterol

A complex multiple ring-structure lipid used for cell membranes, bile salts, and as a precursor for vitamin D and steroid hormones.

Phospholipids

Complex molecules containing a phosphate group with both hydrophobic and hydrophilic parts, serving as the main component of cell membranes.

Emulsification

The process of mixing oil and water facilitated by an emulsifier, such as bile salts, to allow lipid digestion in an aqueous environment.

Triglycerides

The complex form of fatty acids consisting of three fatty acids attached to a 3-carbon glycerol backbone.

Cholecystokinin (CCK)

A hormone stimulated by fat that slows stomach emptying (increasing satiety) and signals the gall bladder to secrete bile salts.

Micelles

Small spherical particles formed by bile salts and digested lipids that fuse with enterocyte cells for absorption.

Chylomicrons

A type of lipoprotein created in the enterocyte to transport repackaged triglycerides into the lymphatic system.

Low-density lipoprotein (LDL)

Commonly known as "bad cholesterol," it takes cholesterol from the liver and distributes it around the body.

High-density lipoprotein (HDL)

Commonly known as "good cholesterol," it returns cholesterol from the periphery to the liver for excretion.

Fatty acid oxidation

The enzymatic process of breaking down fatty acids to release stored energy, often referred to as "burning fat."

Carnitine

A carrier molecule synthesized from lysine and methionine that transports fatty acetyl-CoA across the mitochondrial membrane.

Beta-oxidation

The mitochondrial process that chops long-chain fatty acyl-CoA into many smaller Acetyl CoA units.

Ketosis

An overflow metabolic pathway where Acetyl-CoA is converted into ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone) for energy.

Palmitate

A 16-carbon saturated fatty acid that is the usual end product of fatty acid synthesis in the cytoplasm.

Insulin

The main control hormone that turns intracellular lipase OFF, thereby blocking the breakdown of stored fats.

HMG-CoA reductase

The key enzyme and control point in cholesterol synthesis that is inhibited by statin drugs.

Satiety

The clinical term for the feeling of being full and satisfied after eating.

Lecithin

A phospholipid found in egg yolks and soybeans used by the liver to make bile salts.

Energy density of fat

Fat provides $9\text{ kcal/gram}$, compared to $4\text{ kcal/gram}$ for carbohydrates and proteins.