Biochemistry Chapter 5: Lipid Structure and Function Flashcards
Are lipids soluble in water? nonpolar organic solvents?
Water - no
Nonpolar organic solvents - yes
What does it mean to be amphipathic?
Both polar and nonpolar
What are lipids composed of?
hydrophilic (polar) head group and a nonpolar hydrophobic tail
How is the head group attached?
Via a phosphodiester linkage
What determines the fluidity of the membrane?
saturation – saturated are less fluid than unsaturated.
What are sphingolipids?
contain a sphingosine backbone – many are also phospholipids - called sphingophospholipids.
What are sphingomyelins?
Major class of sphingolipids and contain a phosphatidycholine or phosphatidylethanolamine head group – main component of the myelin sheath.
What are glycosphingolipids?
Attached to sugar moieties instead of a phosphate group. Cerebrosides have one sugar connected to sphingosine.
What is a cerebrosides?
have one sugar connected to sphingosine
What are globosides?
Have two or more sugars connected to sphingosine
What are gangliosides?
contain oligosaccharides with at least one terminal N-acetylneuraminic acid (NANA); also called sialic acid
What are waxes?
contain long-chain fatty acids esterified to long-chain alcohols. They are used as protection against evaporation and parasites in plants and animals.
What are terpenes?
Odiferous steroid precursors made from isoprene; a 5-C molecule. 1 terpene unit = 2 isoprene units)
What are terpenoids?
derived from terpenes via oxygenation or backbone rearrangement.
Steroids
Contain 3 cyclohexane rings and one cyclopentane ring. Their oxidation state and functional groups may vary.
What are steroid hormone characteristics?
- high-affinity receptors
- work at low concentrations
- affect gene expression and metabolism
What is cholesterol?
important to membrane stability and fluidity; serves as a precursor to a host of other molecules.
What are prostaglandins?
autocrine and paracrine hormones that regulate cAMP levels. They have powerful effects on muscle contraction, body temperature and sleep-wake cycle and pain.
What are fat-soluble vitamins?
A, D, E, K
What is vitamin A for?
aka carotene
metabolized to retinal for vision and retinoic acid for gene expression in epithelial development
What is vitamin D for?
aka cholecalciferol
metabolized to calcitriol in the kidneys and regulates calcium and phosphorus homeostasis in the intestines (increasing calcium and phosphate absorption) promoting bone formation.
What is vitamin E for?
aka tocopherols
acts as biological antioxidants – their aromatic rings destroy free radicals, preventing oxidative damage.
What is vitamin K for?
aka phylloquinone and menaquinones
helps with formation of prothombin, a clotting factor. It performs posttranslational modifications on a number of proteins
What are triacylglycerides?
Preferred method of storing energy for long term use. They contain one glycerol attached to three fatty acids by ester bonds.
Why do lipids have so much energy?
The carbon atoms are more reduced than in carbohydrates
Why are they easier to store?
Triacylglycerols are very hydrophobic, so they are not hydrated by body water and do not carry additional water weight.
What are adipocytes?
cells specifically used for storage of large triacylglycerol deposits
Saponification
the ester hydrolysis of triacylglycerols using a strong base, like sodium or potassium hydroxide
Micelle
can dissolve a lipid-soluble molecule in its fatty acid core and washes away with water because of its shell of carboxylate head groups
