Lipids Flashcards
Define polymeric and why lipids are not
Polymers are chains bulit from small molecular units called monomers. Lipids are not polymers because they are not built from monomers
What is the function of lipids?
Form bilayers- essential components of cellular membranes ■ Hydrocarbon chains (in some lipids)- energy stores ■ Intra- and intercellular signaling events
o Fatty acids
Be able to name, or draw given either n or omega nomenclature
Carboxylic acids with long-chain hydrocarbon side groups Nomenclature: Stearic acid: 18:0 Oleic acid: cis-18:1Δ9 or 18:1ω-9
Describe the difference between saturated verses unsaturated. Which will have a higher melting point? Explain.
Saturated – Fully reduced Pack tightly – form rigid, organized membranes • Saturated fatty acids tend to be fats • m.p. increases as chain lengthens ■ Unsaturated – Contain double bonds – Almost always a cis configuration Less ordered packing • Greater potential for motion • Unsaturated fatty acids tend to be oils • m.p. decrease with number of double bonds
o Triacylglycerols
Be able to draw
Understand what makes them major energy storage molecules
Non-polar, water insoluble fatty acid triesters of glycerol
■ Fatty acid linked to glycerol via dehydration reaction
Major energy source (most abundant
lipid class in animals)
– No solvation required
– More efficient packing
– Most reduced form of carbon
o Glycerophospholipids
Where are they commonly found?
What makes them unique from triacylglycerols?
what is the cleavage sites for the phospholipases?
Major lipid component of membranes ■ Amphiphilic ■ Saturated C16 or C18 most common at C1 ■ Unsaturation most common at C2 ■ Head groups that attach to phosphate at C3 are commonly derived from polar alcohols Cleavage Phospholipiase C activation – Cleaves PI (4,5) P2 into DAG and IP3 Powerful detergents- destroy lipid membranes
o Sphingolipids
Where are they commonly found in a cell?
Be able to identify the structure of sphingosine
How are ceramides distinct from sphingosine?
• Be able to identify sphingomyelin
Major membrane components
■ Most are derivatives of the C18 amino alcohol sphingosine
N-acyl fatty acid derivatives of sphingosine are termed ceramides
– Parent of more abundant sphingolipids
plasma membranes
Sphingolipids are structural components in the plasma membranes of eukaryotic cells. Their metabolism produces bioactive signaling molecules that modulate fundamental cellular processes.
Shingolipids: Sphingomyelin
Sphingophospholipids ■ Found in animal cell membranes ■ Enriched in myelin sheaths ■ Deficiencies in sphingomyelinases cause Niemann-Pick Disease
o Glycospingolipids
Be able to recognize cerebrosides and gangliosides
glycosphingolipids ■ Ceramide with a single sugar residue linked to the primary alcohol via an acetal linkage – Glucose and galactose are the most common sugars added
Glycoshingolipids: Cerebrosides
Glycoshingolipids: Gangliosides
Ceramide with attached oligosaccharides that include
at least one sialic acid residue
o Eicosanoids
Be able to describe and recognize the structure
Describe some of their functions within cells
are involved in vasodilation and vasoconstriction, promotion of sleep, pain and fever. They pay a role in up- or down-regulating inflammatory cytokines.
Signaling molecules derived from
the oxidation of arachidonic acid
■ Behave as hormones
o Waxes
Be able to recognize their structures and describe their function
Esters of long-chain alcohols with longchain fatty acids ■ Waxes are insoluble in water Plants – Wax coating prevents plant from becoming water logged or dehydrating ■ Animals – Water proof coating
o Steroids
Functions
Core structure
Steroids are isoprene-based molecules ■ Core structure - three 6-membered rings and one 5-membered ring fused together Cholesterol Most common in animals ■ 30-40% lipid membranes ■ Weak amphiphilic character
o Isoprenoids
Be able to identify the carbon skeleton that they are composed of
How distinct from other lipid classes discussed?
Built from five-carbon units with the same carbon skeleton as isoprene ■ Non-structural components of membranes
