Lipids. Lipids: Defined. ClassificaCon by FuncCon 10/19/09. Chapter 21

Transcription

1 Lipids Chapter 21 Lipids: Defined They are a family of substances that are insoluble in water, but soluble in non polar solvents and solvents of low polarity ClassificaCon by FuncCon Energy storage Lipids hold more energy per gram than carbohydrates Lipids are long term energy storage Membrane Components Due to there hydrophobic nature lipids allow the cell membrane to keep control on the exit and entry of substances Messengers Primary messenger: steroid hormones Secondary messenger: prostaglandins and thromboxanes 1

2 ClassificaCon by Structure Simple lipids: fats and waxes Complex lipids Steroids Prostaglandins, thromboxanes and leukotrienes Animal fats and plant oil are triglycerides They are triesters of glycerol and long chain carboxylic acids called famy acids The famy acids are unbranched carbon in length Even number of carbons If a double double, then mainly cis form Triglycerides ProperCes of Triglycerides Physical State Most animal fats are solid at room temperature Fats from plants and fish are usually liquid The two main types of fats are: Saturated: single bonds Unsaturated : one or more double bonds HydrogenaCon A carbon carbon double bond can be reduced by treacng them with hydrogen and a catalyst Unsaturated oil can be converted to solid fats by this reaccon 2

3 Rancidity When unsaturated fats go bad due to exposure of the double bond to oxygen. More of ClassificaCon Complex Lipids Mainly these are found in membranes There is two main groups Phospholipids: an alcohol, famy acid and a phosphate group Glycerophospholipids Sphingolipids Glycolipids: an alcohol, famy acid and a carbohydrate 3

4 Membranes: A Lipid Bilayer Membrane Transport Membranes are not stacc structures Gap junccon: allows control of passive transport Facilitated transport: a transporter assists in crossing AcCve transport: ions through a gradient Myelin Sheath and MulCple Sclerosis A nerve axon wrapped in a white lipid is called white mamer. This coacng is called a myelin sheath and produced outside the brain by a Schwann cell In MulCple Sclerosis the myelin sheath deteriorates Similar demyelinizacon occurs in Guillain Barre syndrome 4

5 Steroids consist of three cyclohexane rings fused to a cyclopentane ring Steroids Lipid Storage Diseases Complex lipids are constantly being synthesized and decomposed In Lipid storage diseases some of the enzyme necessary to decompose lipids are defleccve or missing Lipid accumulacon causes enlarged liver and spleen, mental retardacon, blindness and early death More on Steroids Cholesterol The most abundance steriod in the human body Serves as a plama membrane component Serves as the raw material for other steriod hormone and bile salts It exist in constant circulacon Lipoproteins: transport cholesterol High density lipoprotein (HDL) good cholesterol Low density lipoprotein (LDL) bad cholesterol Very low density lipoprotein (VLDL) Chylomicrons carry dietary lipids synthesized in the intescnes 5

6 Transport of Cholesterol LDL Transport of cholesterol starts out as very large VLDL parccles VLDL become LDL HDL These transport cholesterol from peripheral Cssues to the liver and transfer cholesterol to LDL Roles of Steroid Hormones AdenocorCcoid Produced in the adrenal glands Two types MineralocorCcoids: regulate Na + and K + GlucocorCcoids: control carbohydrate metabolism Sex Hormone Important male hormone is testosterone Important female hormone is estridiol, this with progesterone regulates menstrual cycle Anabolic Steroids Testosterone is used by athletes to build up muscle Two big disadvantages: It affects secondary sexual characterisccs Not very effeccve when taken orally Side effects Facial hair, baldness, deepening of the voice, and menstrual irregularices 6

7 Oral ContracepCon Progesterone prevents ovulacon during pregnancy SyntheCc analogs of progesterone are oien used in the pill What are Bile Salts? These are oxidacon products of cholesterol They are powerful detergents One end is strongly hydrophilic and the rest of the molecule is hydrophobic They are responsible for forming the needed emulsion of lipids digescon in the small intescne Secondary Messengers Prostaglandin: scmulates uterine contraccons, induces labor, lowers blood pressure, can be used to treat asthma, can be used as a decongestant, etc. Thromboxanes: induce platelet aggregacon Leukotrienes: occur mainly in white blood cell, they produce long lascng muscle contraccons and can cause asthma like amacks, can cause inflammacon and fever 7