Lipids and Membranes Study Flashcards

Comprehensive vocabulary flashcards covering lipid classification, functions, dental relevance, and associated biochemical structures from the Week 3 DS1101 intro lecture.

Lipids

A diverse group of naturally occurring organic molecules that do not dissolve in water but do dissolve in organic solvents like diethyl ether, benzene, and chloroform/methanol.

Dental Calculus

Hardened dental plaque (tartar) containing a dry matter organic portion composed of $54.9\%$ protein and $10.2\%$ lipid.

Early Childhood Caries (ECC)

A condition in children associated with higher total lipid and triglyceride levels in saliva compared to children without the condition.

Adipocytes

Fat cells that store lipids as a long-term fuel reserve for intracellular energy storage.

Fatty Acids

Long-chain carboxylic acids, typically with a chain length greater than $10$ carbons and nearly always an even number of carbons ranging from $C12$ to $C20$.

Palmitic acid

A saturated fatty acid with the naming code $16:0$.

Stearic acid

A saturated fatty acid with the naming code $18:0$, solid at $37^{\circ}\text{C}$ due to tight, ordered packing.

Oleic acid

An unsaturated fatty acid with the naming code $18:1$, liquid at $37^{\circ}\text{C}$ due to loose packing caused by a double bond.

Saturated Fatty Acids

Fatty acids with no double bonds $(C=C)$ that have higher melting points and whose water solubility decreases as chain length increases.

Unsaturated Fatty Acids

Fatty acids with one or more double bonds $(C=C)$ that have lower melting points and whose water solubility increases with more double bonds.

Triglycerides

Also known as triacylglycerols, these are molecules composed of glycerol and three fatty acids; they are the most abundant lipids in humans and provide $9\,\text{kcal/g}$ of energy.

Chylomicrons

The form in which triglycerides are transported in the blood.

Lipases

Enzymes that hydrolyse (break down) lipids to release their fatty acid components.

Glycerophospholipids

Also called phosphoglycerides, these are the second most abundant lipids in nature and are a major complex lipid found in membranes.

Lecithin

Also known as phosphatidylcholine, it is the most common glycerophospholipid and the most abundant lipid in cell membranes.

Sphingomyelin

A sphingolipid built on sphingosine (a long-chain amino alcohol) that is found in the myelin sheath coating nerve axons.

Amphipathic

A characteristic of complex lipids having both a polar (water-loving) head group and non-polar (water-hating) hydrocarbon tails.

Cerebrosides

Glycolipids containing sphingosine and a sugar (glucose or galactose) found in brain cell membranes and the myelin sheath of oligodendrocytes.

Perhydrocyclopentaphenanthrene

The characteristic 4-ring (tetracyclic) carbon skeleton found in all steroids.

Cholesterol

The most abundant and important steroid in the human body, present in all animal cell membranes and a precursor to all steroid hormones and bile acids.

Androgens

Male sex hormones, such as testosterone, that develop male secondary sex characteristics.

Estrogens

Female sex hormones, such as estradiol, that develop female secondary sex characteristics and control the menstrual cycle.

Mineralocorticoids

Steroid hormones, such as aldosterone, that regulate $\text{Na}^{+}$ and $\text{K}^{+}$ levels.

Glucocorticoids

Steroid hormones, such as cortisol, produced in the adrenal cortex that regulate carbohydrate metabolism.

Anabolic steroids

Steroids like Dianabol that build large molecules and increase protein body mass.

Second Messenger Lipids

Intracellular signaling molecules such as $\text{IP}_3$ (Inositol 1,4,5-trisphosphate) and $\text{DAG}$ (Diacylglycerol) produced by the hydrolysis of glycerophospholipids.

Multiple Sclerosis (MS)

A disease characterized by the destruction of the myelin sheath (demyelination) in the nervous system.

Vitamin A

A lipid-soluble polyene formed from beta-carotene; essential for vision via retinal; deficiency causes night blindness and enamel hypoplasia.

Rhodopsin

A pigment in the rod cells of the retina formed from retinal and the protein opsin; it triggers optic nerve impulses via cis-trans isomerisation at $C11\text{-}C12$.

Vitamin D3

A lipid-soluble molecule formed from cholesterol and UV radiation that increases calcium absorption; deficiency causes rickets and enamel defects.

Vitamin E

A lipid-soluble vitamin that acts as an antioxidant and may be needed for reproduction.

LDL (Low Density Lipoprotein)

A lipoprotein that stays in plasma for $2.5$ days and carries about $50\%$ of the blood's cholesterol to cells; normal plasma level is $175\,\text{mg/100 mL}$.

Apolipoprotein B100 (ApoB-100)

The protein component of LDL, consisting of a single peptide chain of $4,636$ amino acids with a molecular weight of $513\,\text{kDa}$.

Catabolism

The metabolic process of breaking down large molecules to release energy.

Anabolism

The metabolic process of building up large molecules using energy.

Phosphoanhydrides

The high-energy $\text{P-O-P}$ linkages found in ATP (adenosine triphosphate) that release energy for cellular work when broken.