Biochem ch10
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11 questions
| 🇬🇧 | 🇬🇧 |
| 8 examples of biological functions of lipids? | • Storage of energy • Insulation from environment – Low thermal conductivity – High heat capacity (can “absorb” heat) – Mechanical protection (can absorb shocks) • Water repellant – Hydrophobic nature: keeps surface of the organism dry • Prevents excessive wetting (birds) - Prevents loss of water via evaporation Buoyancy control and acoustics in marine mammals – Increased density while diving deep helps sinking (just a hypothesis) Membrane structure acts as a cofactor for enzymes Signaling molecules Pigments Antioxidants |
| How are lipids classified? | Based on the structure and function • Lipids that do not contain fatty acids: cholesterol, terpenes, ... • Lipids that contain fatty acids (complex lipids) – can be further separated into: – storage lipids and membrane lipids |
| How are fatty acids classified? | Carboxylic acids with hydrocarbon chains containing between 4 to 36 carbons • Almost all natural fatty acids have an even number of carbons • Most natural fatty acids are unbranched • Saturated: no double bonds between carbons in the chain • Monounsaturated: one double bond between carbons in the alkyl chain • Polyunsaturated: more than one double bond in the alkyl chain |
| PUFA nomenclature. | Slides 10-1 slides (12-15) |
| How double bonds and length affect melting and membrane fluidity? | • Melting Point – decreases as the chain length decreases – decreases as the number of double bonds increases |
| How cholesterol contributes to membrane fluidity and structure? | Cholesterol, the major sterol in animal tissues, is amphipathic, with a polar head group (the hydroxyl group at C-3) and a non- polar hydrocarbon body (the steroid nucleus and the hydrocarbon side chain at C-17) It lies alongside the phospholipids in the membrane and tends to dampen the effects of temperature on the membrane. Thus, cholesterol functions as a buffer, preventing lower temperatures from inhibiting fluidity and preventing higher temperatures from increasing fluidity too much. |
| Why storage lipids are efficient as fuel storage? | Fatty acids carry more energy per carbon because they are more reduced – Fatty acids carry less water per gram than carbohydrates because they are nonpolar – 2g of water/g of glycogen is needed • Glucose and glycogen are for short-term energy needs, quick delivery • Fats are for long-term (months) energy needs, good storage, slow delivery |
| Examples of Hormones (initiate signal)? | Steroid Hormones Testosterone, the male sex hormone, is produced in the testes. Estradiol, one of the female sex hormones, is produced in the ovaries and placenta. Cortisol and aldosterone are hormones synthesized in the cortex of the adrenal gland; Cortisol regulates glucose metabolism and suppresses inflamation Aldosterone regulates salt excretion by kidneys. |
| Examples of Signaling intermediates (participate in transmitting signal)? | Phosphatidylinositol 4,5-bisphosphate in the cytoplasmic (inner) face of plasma membranes serves as a reservoir of messenger molecules that are released inside the cell in response to extracellular signals interacting with specific surface receptors inositol 1,4,5-trisphosphate (IP3), which is water-soluble, and diacylglycerol, which remains associated with the plasma membrane. IP3 triggers release of Ca2+ from the endoplasmic reticulum, and the combination of diacylglycerol and elevated cytosolic Ca2+ activates the enzyme protein kinase C. phosphatidylinositol 3,4,5-trisphosphate is a product of PI3K that serves as binding site for PH domain in several signal transduction molecules that propagate signal downstream of PI3K. |
| Examples of Lipids as vitamins? | Vitamin A (Retinol) • Involved in visual pigment • Precursor for other hormones involved in signaling Vitamin E, K, and other lipid quinones are antioxidants |