6. Lipids

What are lipids and their defining properties?

Lipids are hydrophobic or amphipathic molecules that are insoluble in water, soluble in nonpolar solvents, and include fats, oils, steroids, waxes, and related compounds.. Higher in energy then proteins and carbs.

Why are many lipids amphipathic?

They contain both hydrophilic (polar) and hydrophobic (nonpolar) regions, allowing membrane formation.

What are the major physiological roles of lipids?

Energy storage, thermal insulation in adipose tissue, myelination, membrane structure, lipid transport, and vitamin A/D/E/K (esential aa) absorption.

What diseases are associated with lipid imbalance?

Obesity, diabetes mellitus, atherosclerosis, and heart disease.

How are lipids classified?

• Simple lipids: fatty acids + alcohol

• Complex lipids: fatty acids + alcohol + additional groups

• Derived lipids: hydrolysis products of simple/complex lipids

What are examples of complex lipids?

Phospholipids, glycolipids, and lipoproteins.

What are examples of simple lipids?

Triacylglycerols (fats/oils) and waxes.

what do fats contain, what are oils

fatty acids with glycerol (alcohol). oils are just fats at liquid room temp state

what are waxes

fatty acids with monohydric alcohols

what do phospholipds contain

phosphoric acid residue, nitrogen-containing bases, alcohol

what do glycolipids contain

fatty acid, spingoshpine, carbohydrate

What are examples of derived lipids?

Fatty acids, steroids, eicosanoids, ketone bodies.

What are key characteristics of fatty acids?

Unbranched chains with an ionizable carboxyl group; usually even-numbered carbons; esterified in fats but circulate as free fatty acids.

What is the general structure of a fatty acid?

ionizable carboxyl group at the α end (second carbon) and hydrocarbon chain ending at the ω end (last carbon); typically 14–24 carbons.

Difference between saturated and unsaturated fatty acids? and naming

• Saturated: no double bonds

• Unsaturated: one or more double bonds

Geneva system: –anoic (saturated) and –enoic (unsaturated).

What are the functions of TAGs?

Primary energy storage, thermal insulation, stored in adipose tissue.

how are tags formed

dehydration synthesis— 3 h2o removed

What are the two main types of phospholipids?

• Glycerophospholipids

• Sphingolipids

Structure of glycerophospholipids?

Two fatty acids esterified to glycerol + phosphate + polar head group.

What defines sphingolipids?

Sphingosine backbone + fatty acid (ceramide) attached in ester linkage and + head group through phosphodiester linkage.

In glcerophospholipids, what is attached to the 3′ carbon via a phosphodiester linkage?

A highly polar or charged head group is attached to the 3′ carbon of glycerol through a phosphodiester bond.

Where are sphingolipids abundant?

Central nervous system (CNS). think sphingomyelin

What are glycolipids? where are they

Lipids with carbohydrate chains attached; found in the outer leaflet of membranes. abundant in nerve tussue

What are glycosphingolipids?

Major glycolipids in animal tissues composed of ceramide linked to one or more sugars.

What is galactosylceramide and where is it found?

A glycosphingolipid found primarily in the brain and nervous tissue.

What are gangliosides and what are their functions?

Glycosphingolipids abundant in nervous tissue that mediate cell–cell recognition and communication and act as receptors for hormones and bacterial toxins (e.g., cholera toxin).

What are lipoproteins?

Complexes of lipids and proteins that transport lipids in blood.

Why are lipoproteins necessary? how does their density vary

Lipids are water-insoluble and require transport carriers. More proteins, more dense

What defines a steroid structurally?

cyclic nucleus. Four fused rings (three hexagons + one pentagon).

Major functions of steroids?

Growth, metabolism, homeostasis, reproduction.

What is cholesterol’s significance?

Membrane and lipoprotein component; precursor of bile acids, steroid hormones, vitamin D; linked to atherosclerosis.

What is the clinical relevance of cholesterol and ergosterol?

Cholesterol is associated with atherosclerosis and heart disease, while ergosterol is a cholesterol-like sterol found in plants and yeast.

What are eicosanoids?

Bioactive lipids derived from 20-carbon polyunsaturated fatty acids (arachidonic acid).

arachidonic acid

Cyclooxygenase (COX) produces prostaglandins and thromboxanes, while lipoxygenase (LOX) produces leukotrienes and lipoxins.

What are prostaglandins and how are they synthesized?

Local hormones with diverse physiological effects.

, synthesized in vivo by cyclization of the central carbon chain.

Functions of thromboxanes?

blood clotting, Platelet aggregation and vasoconstriction.

Have the cyclopentane ring interrupted with an

oxygen atom

Functions of leukotrienes and lipoxins?

hree or four conjugated double bonds .Pro-inflammatory; bronchoconstriction; involved in asthma.

Common lipid structures formed in water?

Plasma membranes (bilayers), micelles, liposomes (spheres of lipid bilayers enclosing different molecules).