Chem 5-Lipids
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- What are Terpenes/oids?
- Based on isoprene (c5h8, 2-methy-1,3-butadiene, tail bound to C1, head bound to C4). commonly occur in the oils that give plants their fragrance. Can be connected together to form polymeric isoprene derivatives incl. steroids, carotenoids, gibberelic acid, etc.
- What is the difference b/t a mixed triglyceride and simple triglyceride?
- In a simple transglyceride, all three fatty acids are the same.
- What are gangliosides?
- Like cerebrocides (glycosphingolidids), but with complex carb instead of simple sugar; usually found on the surface of the plasma membrane, particularly in nerve cells. Act as specific receptors; Probably play an important role in cell growth and differentiation
- Describe soaps
- They are alkali metal salts of fatty acids - their amphipathic nature makes them strong surfactants. Soaps decrease surface tension, improve wetting, and dissolve hydrophobic particles.
- How many calories do fats have per gram?
- 9 cal (carbs and protein only have 4 cal/g)
- What are detergents?
- Soaps, but formed w/ a stronger acid which makes them less sensitive to pH changes.
- What's special about phosphoglycerisdes?
- They spontaneously form lipid bilayers.
- What is the structure of steroids/ols?
- They have a perhydrocyclopenanophenanthrene nucleus (three cyclohexanes and one cyclopentane sharing sides)
- How do unsaturated fatty acids compare to saturated fatty acids?
- Unsaturated fatty acids have lower melting points, ergo they stay liquid at colder temperatures
- What does amphiphilic mean?
- Both hydrophilic and hydrophobic. Used to characterize fatty acids.
- What are gibberellins?
- A group of phytohormones
- What are fats?
- fatty acids and glycerol bound together by esther bonds (formed by dehydration); also called acyl-glycerols, neutral fats, glycerides.
- How was soap initially made?
- Saponification (base-catalyzed hydrolysis) or animal fat.
- What are sphingolipids?
- Composed of alcohol, NH head, and one fatty acid tail; second major type of membrane lipid.
- What configuration do saturated fatty acids have? Unstaturated?
- Saturated fatty acids have a zigzag conformation. Unsaturated fatty acids have a "kink" d/t the double bond.
- What is the difference b/t saturated and unsaturated fatty acids?
- saturated fatty acids have all carbons completely "saturated" with hydrogens - no double bonds.
- What are ceramides?
- A common type of sphingolipid; sphingomyelin is the major consistuent of myelin.
- What are cerebrocides?
- A common type of glycosphinolipid often found in the myelin sheath.
- Why do fats contain more energy?
- More C-H bonds, each of which is reduced, releasing energy (whereas carbs have more C-OH bonds, which are already oxidized)
- What are fatty acids?
- hydrocarbon chains w/ COOH group at end.
- What are the three essential fatty acids?
- Arachidonic acid, linoleic acid, lineolenic acid. Precursors of eicosanoids.
- What are waxes?
- Esthers of long-chain fatty alcohols and long-chain fatty acids [ROH+ RCOOH -> R-(C=O)-O-R + H2O]
- How do fatty acids tend to act on the surface of water?
- They spead out evely. Polar carboxyl groups are hydrogen-bonded to the surface of the water while hydrocarbon chains are aligned together away from the water d/t hydrophobic interactions.
- Do fats normally have an even or odd # of carbons?
- even
- What are surfactants?
- substance that accumulate at water surfaces and lower the surface tension of water, allowing it to penetrate and wet a variety of materials.
- What is hard water? What does it do?
- Hard water involves the presence of cations (Ca, Mg) in the water. Micelles are attracted to them, and scum is formed.
- Why does soap scum form?
- Alkali metal soaps are normally slightly alkaline. As the pH decreases, they dissociate, leaving an insoluble fatty acid precipitate.
- What structure do caretenoids have?
- They are tetraterpenes (carotenes are pure hydrocarbons; xanthophylls have O)
- What is the difference b/t fats and oils?
- Fats are made by animals (saturated, solid at room temp), oils by plants (unsaturated, liquid at room temp)
- Name six functions of lipids
- 1) structural 2) hormone/signal transduction 3) storage form of fuel (fat/oil) 4) transport form of fuel (fatty acids, lipoproteins) 5) non-energy nutrient [Vits D, E, A, K], 6) Protective components (fat as insulation, waxy coverings)
- What do caretenoids do?
- They are part of pigment systems - they also trap light (in photosynthesis, vision). Yellow color of flowers d/t carotenoid-containing chromoplasts (no chlorophyl).
- Are fatty acids soluble in water?
- If they are > 10 carbon atoms long, they are nearly insoluble in water. Because of their lower density, they float.
- What are phosphoglycerides?
- Like triglycerides, but have a hydrophilc phosphate instead of third fatty acid (may also have alcohol or amine esterfied to it)
- What are phopholipids used for?
- They are the major constitutents of membranes. Unsaturated phospholipids make the bilayer more fluid (have bent acyl groups that pack loosely)
- What structure do steroids have?
- They are triterpenes/oids
- What are glycolipids?
- They contain polar, hydrophilic carbohydrate head groups, but no phosphoric acid; found in plants and microorganisms