Chap 5
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Identify the classes of lipids discussed in class (neutral, steroids and phospholipids) and summarize their functions in organisms.
1) neutral fats - energy storage - insulation against cold, cushion mechanical injury and buoyancy 2) steroids - cholesterol: common component of animal cell membranes - cholesterol transported in the blood by lipoproteins LDL and HDL - precursor form which most other steroids are synthesized (hormones, vitamins) - fluidity buffer in cell membranes 3) Phospholipid - amphipathic: non-polar hydrophobic tails (fatty acids), polar hydrophilic head (glycerol, phosphate, and organic base) - cell membrane (phospholipid bilayers) [phosphoglycerides = most abundant] [sphingolipids = mostly nervous system]
Describe the basic structure of a triglyceride, a phospholipid, and a steroid. Describe how the molecules can vary between and within each class.
Triglyceride: 3 fatty acids (hydrocarbon tail + COOH) , glycerol (3 carbon alcohol + 3 OH) = formed following three dehydration reactions = bonds are called ester linkage Phospholipid: phosphoglyceride (2 fatty acids tails, glycerol, phosphate and organic base = head) sphingolipids (1 fatty acid tail, sphingosine [a long chain amino alcohol] instead of glycerol) Steroid: characterized by a carbon skeleton of 4 interconnected hydrocarbon rings with various functional groups attached ( 3 rings = 6C, but last = 5C + R group)
Describe the structural differences between saturated and unsaturated fats and why these structural differences produce a solid or liquid fat at room temperature.
saturated: max number of H atoms bonded to the carbon skeleton. = solid = very linear (stacks on each other) unsaturated: double bonds (cis and trans) cis = olive oils, trans = becomes like butter
Describe the two outcomes of hydrogenation
unsaturated fats = become somewhat saturated (still leaving many unsaturated fatty acids) cis bonds into trans bonds (many not all)
From what molecule are steroids derived? What molecules in the body are made from steroids?
derived from cholesterol. makes hormones and vitamins D and E
How are fats digested? What is the structure and function of lipoproteins? How do chylomicrons, LDLs and HDLs differ from each other?
need to be emulsified (mixed) with the surrounding aqueous solution in the digestive tract. They’re hydrolyzed into fatty acids = absorbed into the mucosal cell lining the inner wall of the small intestine. after reassembled and packaged into lipoproteins (water-soluble lipid-carrying particles) = chylomicrons (contain cholesterol) lipoprotein: - a hydrophobic interior - a hydrophilic exterior composed in part by water-soluble protein HDL : mostly protein LDL: mostly lipid Chylomicron: remaining HDL/LDL and fatty acid
Describe the functions of HDL and LDL in the human body. Describe “bad” and “good” cholesterol and discuss its link with diet and health.
LDL = “bad”, carries cholesterol to various tissues such as the adrenal gland, gonads, muscle, and adipose tissue HDL = “good”, picks up excess cholesterol from body cells and blood and takes it to the liver = reduces the level of cholesterol in the blood omega 3 + 6 and exercise = increase HDL diets high in saturated and trans fats cause : increase LDL, decrease HDL, increase triglyceride levels
Describe the structures that phospholipids form in water. Indicate whether an energy input is required to form these structures.
heads out, tails in no need for energy
What two types of lipids make up the phospholipid bilayer?
phosphoglycerides and sphingolopids
Which cells have a higher abundance of sphingolipids? What happens to sphingolipids in patients with Tay-Sachs disease?
nervous system, spine, lungs accumulation of shingolipids in nerve cells which leads to the destruction of nervous system