Lipid Structure and Function Flashcards
What does amphiphatic mean?
If a molecule is amphiphatic, it contains both a hydrophobic and hydrophilic region. Lipids are amphiphatic.
Lipids form a variety of structures in aqeous solution. What are the main structures?
- Micelles
- Liposomes
- Lipid Bilayers
Compare saturated lipids and unsaturated lipids.
What determines a phospholipid’s properties?
A phospholipid’s properties are determined by the degree of saturation and the functional groups to which the fatty acid chains are bonded.
What is the difference between a sphingolipid that is a phospholipid and one that is not?
A sphingolipid that is a phospholipid contains a phosphodiester bond whereas a sphingolipid that is not a phospholipid does not contain a phosphodiester bond.
- Ex: Glycosidic linkages to a sphingolipid produces a glycosphingolipid that is a phospholipid.
- Ceramide is also a sphingolipid that is not a phospholipid because only a hydrogen atom is bound to the sphingosine backbone.
What composes terpenes and how are they made?
Terpenes are made of isoprene (C5H8) moieties and are named based on the fact that 1 terpene is made of 2 isoprene subunits.
- Monoterpene = 2 isoprene subunits
- Sesquiterpenes = 3 isoprene subunits
- Diterpenes = 4 isoprene subunits
- Triterpenes = 6 isoprene subunits
- Tetraterpenes = 8 isoprene subunits
What are the main types of sphingolipids and their characteristics?
- Ceramide - only a hydrogen atom is bound to the sphingosine backbone
-
Sphingomyelin - either phosphatidylcholine or phoshpatidylethanolamine is bound to the sphingosine backbone
- Neutral (have no net charge)
- Produced by oligodendrocytes and Schwann cells
- Cerebroside - a monosaccharide is bound to the sphinosine (neutral)
- Globoside - more than one sugar is bound to the sphingosine (neutral)
- Ganglioslide - an oligosaccharide with one or more N-acetylneuranminic acid (NANA; also called sialic acid) is bound to the sphingosine backbone (negatively charged)
Vitamin A is what type of lipid and what is one of its most important roles in the body?
Vitamin A is a diterpene that derives retinal which is a visual pigment for sight.
What is the structure of steroids?
Steroids are metabolic derivatives of terpenes that are characterized by having 4 cycloalkane rings (3 cyclohexane, 1 cyclopentane).
- Functionality of steroids is determined by the oxidation status of these rings, as well as the functional groups they carry.
- Steroids are nonpolar
What are steroid hormones?
Steroid hormones are steroids that are released by an endocrine gland and travel through the bloodstream on protein carriers to distant sites, where they bind to specific high-affinity receptor to alter gene expression levels and metabolism.
- Some important steroid hormones are testosterone, estrogen, cortisol, and aldosterone.
What is cholesterol?
Cholesterol is a steroid that has a major component of the phospholipid bilayer and is responsible for mediating membrane fluidity. It is an amphipathic molecule composed of a polar head and a hydrophobic tail.
- At low temperatures, cholesterol prevents the cell membrane from solidifying, and at high temperatures cholesterol holds the membrane intact preventing it from becoming too permeable.
What are some of the important molecules that cholesterol serves as a precursor to?
Cholesterol is an important precursor to steroid hormones, bile salts, and vitamin D.
What is the main function of prostaglandins and what are some of the main powerful downstream effects they induce?
In many tissues, prostaglandins main function is to regulate the synthesis of cAMP. The downstream affects of this is smooth muscle function, influence over the sleep-wake cycle, and the elevation of body temperature associated with fever (inflammation) and pain.
- Nonsteroidal anti-inflammatory drugs (NSAIDs), like aspirin, inhibit the production of prostaglandins.
How many carbons are in a diterpene?
In a diterpene, there are:
20 carbons = 5 carbons x 4 isoprene subunits
- 2 isoprene subunits per terpene
- Each isoprene subunit is composed of 5 carbons
What are the name and function of the four fat-soluble vitamins?
- Vitamin A (carotene)
- Derivative for retinal which serves as a visual pigment in sight
- Derivative for retinoic acid which regulates gene expression during epithelial development
- Vitamin D (Cholecalciferol)
- Derivative for calcitriol which increase the uptake of calcium and phosphate in the small intestines, which promotes bone production.
- Vitamin E (tocopherols)
- Antioxidants that use their aromatic rings to react with free radicals, destroying them.
- Vitamin K (Phylloquinone and menaquinones)
- Vital to posttranslational modifications required to form prothrombin, an important clotting factor in the blood.
- It is also required to introduce calcium-binding sites on several calcium-dependent proteins
