Chapter 5: Lipid Structure and Function Flashcards
What are lipids?
Lipids as a class are characterized by insolubility in water and solubility in nonpolar solvents.
They serve a structural building blocks, signaling molecules, enzyme cofactors, light absorbing pigments, messengers, hormones, and energy storage.
What is an amphipathic molecule?
Which is which for membrane lipids?
What structures form due to amphipathic membrane lipids?
An amphipathic molecule has both hydrophilic and hydrophobic regions.
Polar head, non polar tail.
Liposomes, micelles, or phospholipid bilayer.
What elements make up a phospholipid?
A phosphate and alcohol that comprise the polar head, joined to a hydrophobic fatty acid tail by phosphodiester linkages.
Glycerophospholipids utilize glycerol as a backbone.
Sphingolipids have sphingoid base backbones.
What is glycerol and how does it relate to structural lipids?
Glycerol is a three carbon alcohol that forms phosphoglycerides (glycerophospholipids) and triglycerides (triacylglycerides).
What is a saturated fatty acid? Unsaturated fatty acid?
Solid or liquid at room temp?
Relate this to phospholipid bilayers.
Saturated fatty acid tails will have only single bonds, no pi bonds. Think butter, solid at room temp.
Unsaturated fatty acids tails include one or more double bonds, which contribute kinks in the structure. Think olive oil, liquid at room temp.
Unsaturated regions of the membrane will be more fluid while saturated regions will be less fluid.
What are glycerophospholipids?
Glycerophospholipids are phospholipids, but not all phospholipids are glycerophospholipids.
Glycerophospholipids (or phosphoglycerides) contain a glycerol backbone bonded by two fatty acids and buy a phosphodiester linkage to a highly polar head group.
What are sphingolipids?
What are some of the most well-known sphingolipids?
Sphingolipids have a sphingosine (or sphingoid) backbone, as opposed to a glycerol backbone of glycerophospholipids.
Some of the most well known sphingolipids are the cell surface antigens on red blood cells.
What are the four types of sphingolipids?
Ceramide. Single H atom as its head group.
Sphingomyelin. Phosphocholine or phosphoethanolamine as a head group. No net charge. Major component in the plasma membrane of cells producing myelin (oligodendrocytes and Schwann cells), the insulating sheath for axons.
Glycosphingolipids. No phophodiester linkage and therefore are not phospholipids. Found mainly on the outer surface of the plasma membrane.
Gangliosides are glycolipids that have polar head groups composed of a oligosaccharides with one or more N-acetylneuraminic acid (NANA, or sialic acid). Play a major role in cell interaction, recognition, and signal transduction.
What are waxes?
Waxes are esters of long chain fatty acids with long chain alcohols. They form pliable solids at room temperature.
Waxes function as protection for both plants and animals. They prevent dehydration as a water repellent to keep skin and feathers dry. Wax is also acted as a lubricant.
MCAT concept check structural lipids 5.1 page 169 question 1
Which component of membrane lipids contribute to their structural role in membranes which component contribute to function?
Membrane lipids are amphipathic: they have hydrophilic heads and hydrophobic tails allow, allowing for the formation of layers and aqueous solution.
Fatty acid tails form the bulk of the phospholipid bilayer, and play predominantly structural role.
On the other hand, the functional differences between membrane lipids are determined by the polar head group due to its constant exposure to the exterior environment of the phospholipid layer (either inside or outside of the cell).
The degree of unsaturation of fatty acid tails can also play a small role in function.
MCAT concept check structural lipids 5.1 page 169 question 2
What is the difference between a sphingolipid that is also a phospholipid and one that is not (like glycolipids).
The difference is the bond between the sphingosine backbone and the head group. When this is a phosphodiester bond (two ester bonds linked by a phosphate) it’s a phospholipid.
Nonphospholipid sphingolipids include glycolipids, which contain a glycosidic linkage to a sugar.
MCAT concept check structural lipids 5.1 page 169 question 3
MCAT concept check structural lipids 5.1 page 169 question 4
What would happen if an amphipathic molecule were placed in a nonpolar solvent rather than an aqueous solution ?
In a non-polar solvent, we would see the opposite of what happens in a polar solvent like water: the hydrophilic polar part of the molecules would be sequestered inside while the nonpolar hydrophobic part of the molecule would be found on the exterior and exposed to the solvent.
There are three categories of signaling lipids. What are they?
Steroids
Prostaglandins
Fat soluble vitamins
What are terpenes?
Terpenes are odiferous chemicals and are the metabolic precursor to steroids and other lipid signaling molecules.
They are built from isoprene (C5H8).
What are steroids?
What does steroid functionality depend on?
Are steroids polar or non polar?
Steroids are metabolic derivatives of terpenes and are very different from lipids mentioned earlier.
Steroids have four cycloalkane rings fused together: three cyclohexane and one cyclopentane.
The functionality of steroids is determined by the oxidation status of the structural rings as well as the functional groups they carry.
Steroids are non polar.
What are a few important steroid hormones listed in the book?
Testosterone, aldosterone, cortisol, estrogen.
What is cholesterol?
What molecules does cholesterol serve as a precursor for?
Cholesterol is a major component of the phospholipid bilayer and is responsible for mediating membrane fluidity.
Cholesterol is amphipathic molecule.
At low temperatures cholesterol keeps the cell membrane from solidifying. At high temperatures, cholesterol holds the membrane intact and prevents it from becoming too permeable.
Cholesterol service as a precursor to steroid hormones, bile acids, and vitamin D.
What are prostaglandins?
What do they have to do with cAMP? How does this relate to aspirin?
Where are they produced?
Prostaglandins are 20 carbon unsaturated carboxylic acid derivatives. Prostaglandins act as paracrine or autocrine signaling molecules.
As they act as a signaling molecule, their biological function is to regulate the synthesis of cyclic adenine monophosphate cAMP, which is a ubiquitous in intracellular messenger.
Downstream effects of prostaglandins include effects on smooth muscle function, influence over the sleep cycle, and the elevation of body temperature associated with fever and pain.
Nonsteroidal anti-inflammatory drugs, like aspirin, inhibit the enzyme cyclooxygenase COX, which aids in the production of prostaglandins.
Prostataglandins are produced by almost all cells in the body.
What is a vitamin?
Vitamin is an essential nutrient that cannot be adequately synthesized by the body, and therefore must be consumed in the diet.
Commonly divided into water soluble, and lipid soluble categories.
Lipid soluble vitamins can accumulate stored fat, whereas excess water soluble vitamins are excreted through the urine.
Briefly describe vitamin A, D, E, K.
Vitamin A: carotene. Important in vision, growth and development, immune function.
Vitamin D: cholecalciferol. Increases calcium and phosphate uptake in the intestines, which promotes bone production.
Vitamin E: tocopherols and tocotrienols. Characteristically hydrophobic, biological antioxidants. Prevents oxidative damage, which is an important contributor to the development of cancer and aging.
Vitamin K: phylloquinone and manquinones. Important clotting factor in the blood.
MCAT concept check signaling lipids 5.2 page 174 question 1
How many carbons are there in diturpene?
Diturpene has 20 carbon molecules in its backbone. One terpine unit is made from two isoprene units, each of which has five carbons.
MCAT concept check signaling lipids 5.2 page 174 question 2
What is the difference between a steroid and a steroid hormone?
A steroid is defined by its structure: it includes three cyclohexane rings and a cyclopentane ring.
A steroid hormone is a molecule within this class that also functions as a hormone, meaning that it travels in the bloodstream, is active at low concentrations, has high affinity receptors, and affects gene expression and metabolism.
MCAT concept check signaling lipids 5.2 page 174 question 3
NSAIDS block prostaglandin production in order to reduce pain inflammation. What do prostaglandins do to bring about these symptoms?
Prostataglandins regulate the synthesis of cyclic adenine monophosphate cAMP, which is involved in many pathways, including those that drive pain and inflammation.
