Lipids 1 Flashcards

1
Q

<p>What are lipids?</p>

A

<p>Molecules that contain hydrocarbons and make up the building blocks of structures and function in a living cell</p>

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2
Q

<p>When are lipids soluble?</p>

A

<p>They are hydrophillic but are soluble in organic solution</p>

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3
Q

<p>Are lipids hydrophobic or hydrophillic?</p>

A

<p>Hydrophobic</p>

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4
Q

<p>Where can lipids be found?</p>

A

<p>Cell membranes</p>

<p>Adipose tissue</p>

<p>Blood lipoproteins</p>

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5
Q

<p>What are some functions of lipids?</p>

A

<p>Stored form of energy</p>

<p>Structural element of membreanes</p>

<p>Enzyme cofactors</p>

<p>Hormones</p>

<p>Vitamins A, D, E and K</p>

<p>Signalling molecules</p>

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6
Q

<p>What are the 5 lipid classes?</p>

A

<p>Fatty acids</p>

<p>Triacylglyderol</p>

<p>Phospholipids</p>

<p>Glycolipids</p>

<p>Steroids</p>

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7
Q

<p>What are the 2 forms of fatty acids?</p>

A

<p>Unsaturated (one or more double bonds)</p>

<p>Saturated (no double bonds)</p>

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8
Q

<p>How are fatty acids named?</p>

A

<p>By the number of carbons, number of double bonds and the position of the double bond</p>

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9
Q

<p>Give examples of lipid naming?</p>

A

<p>18:0 - 18 carbons, no double bonds</p>

<p>18:3 (9, 12, 15) - 18 carbons, 3 double bonds, double bonds between 9/10, 12/13 and 15/16</p>

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10
Q

<p>What are the 4 kinds of fatty acids in our diet?</p>

A

<p>Essential fatty acids (linoleic eg)</p>

<p>Good fats (high in polyunsaturated fats such as olive oil)</p>

<p>Bad fats (high in saturated fatty acids such as beef)</p>

<p>Very bad fats (trans fatty acids such as hard margarine)</p>

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11
Q

<p>What are saturated fats good for?</p>

A

<p>The nervous system</p>

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12
Q

<p>What are essential fatty acids?</p>

A

<p>Cannot be synthesised, need to be consumed in our diet</p>

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13
Q

<p>Why can essential fatty acids not be synthesised?</p>

A

<p>We cannot introduce double carbon bonds beyond carbon 9</p>

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14
Q

<p>What are omega-3 fatty acids derived from?</p>

A

<p>Linolenic acid (essential fatty acid)</p>

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15
Q

<p>What are omega-3 fatty acids good for, and omega-6?</p>

A

<p>Lowering blood cholesterol</p>

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16
Q

<p>What are triacylglycerols?</p>

A

<p>Esters of fatty acids and glycerol</p>

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17
Q

<p>What are triacylglycerols used for?</p>

A

<p>Storing energy and insulation</p>

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18
Q

<p>Are triacylglycerols water soluble?</p>

A

<p>No</p>

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19
Q

<p>What are phospholipids?</p>

A

<p>A lipid containing a phosphate group</p>

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20
Q

<p>How are phospholipids amphipathic?</p>

A

<p>They contain a hydrophillic head and a hydrophobic tail</p>

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21
Q

<p>Why are phospholipids often used in membranes?</p>

A

<p>They are amphipathic</p>

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22
Q

<p>What does amphipathic mean?</p>

A

<p>Has a hydrophillic and a hydrophobic component</p>

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23
Q

<p>What is the main site of lipid digestion?</p>

A

<p>Small intestine</p>

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24
Q

<p>Where does lipid digestion start?</p>

A

<p>In the mouth</p>

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25
Q

<p>What is digestion by pancreatic enzymes (lipases) promoted by?</p>

A

<p>Emulsification (dispersion) by bile salts and peristalsis (mixing)</p>

26
Q

<p>What pancreatic enzymes digest lipids?</p>

A

<p>Lipases</p>

27
Q

<p>Where does some lipid digestion occur other than the mouth and the small intestine?</p>

A

<p>The stomach</p>

28
Q

<p>What are bile salts?</p>

A

<p>Act as biological detergents to break down fatty acids</p>

29
Q

<p>What are bile salts a derivative of?</p>

A

<p>Cholesterol</p>

30
Q

<p>How are triacylglycerols digested?</p>

A

<p>Degraded in small intestine by pancreatic lipases to monoacylglycerol and two fatty acids</p>

31
Q

<p>What are cholesterol esters digested into?</p>

A

<p>Digested to cholesterol and a free fatty acid?</p>

32
Q

<p>How are phospholipids digested?</p>

A

<p>Hydrolysed to a fatty acid and lysophospholid</p>

33
Q

<p>What does the digestion of lipids look like?</p>

A

<ol> <li>Fat becomes emulsified fat in the duodenum (due to bile)</li> <li>Then broken down into fatty acids and glycerol in the small intestine (due to lipases)</li></ol>

34
Q

<p>What is the process of digested lipid uptake?</p>

A

<p>Form mixed micelles with bile salt which approach membrane and release lipid products which enter by diffusion</p>

<p>Short and medium chain fatty acids do not require micelles because they are more soluble</p>

35
Q

<p>What is formed from digested lipids and bile salt?</p>

A

<p>Micelles</p>

36
Q

<p>What could lipid malabsorption be due to?</p>

A

<p>Defect in bile secretion</p>

<p>Defect in pancreatic function</p>

<p>Defect in intestinal cells</p>

37
Q

<p>What does lipid malabsorption cause?</p>

A

<p>A steatorrhea</p>

38
Q

<p>What is a steatorrhea?</p>

A

<p>Excess fat in faeces</p>

39
Q

<p>What secretes bile salt?</p>

A

<p>Gallbladder</p>

40
Q

<p>What is the fate of absorbed lipids?</p>

A

<p>Resynthesised by intestinal cells for export</p>

<p>Packaged with apoB-48 into chylomicrons due to being insoluble</p>

41
Q

<p>Why are absorbed lipids packaged with apoB-48 for export?</p>

A

<p>Because they are insoluble, this packaging makes them soluble</p>

42
Q

<p>What does the packaging of absorbed lipids and apB-48 form?</p>

A

<p>Chylomicrons</p>

43
Q

<p>How are chylomicrons released?</p>

A

<p>By exocytosis into the lymph and then the blood</p>

44
Q

<p>What happens once chylomicrons reach the tissue?</p>

A

<ol> <li>Hydrolysed to fatty acid and glycerol by lipoprotein lipase</li> <li>Resulting fatty acid is used for energy or resterfication to triacylglycerol for storage</li></ol>

45
Q

<p>What is a chylomicron renment?</p>

A

<p>Chylomicron depleted of tracylglycerol</p>

46
Q

<p>Where do chylomicron renments go?</p>

A

<p>The liver where glycerol is used to produce glycerol-3-phosphate</p>

47
Q

<p>Where is lipoprotein lipase normally found?</p>

A

<p>In capillaries of skeletal muscle and adipose tissue</p>

48
Q

<p>What is the exact process of lipid digestion, absorption and transport summarised?</p>

A

<ol> <li>Bile salts emulsify fats in small intenstine, forming micelles</li> <li>Intestinal lipases degrade triacylglycerol</li> <li>Fatty acids are taken up by intestinal mucosa and converted to triacylglycerol</li> <li>Triacylglycerol is incorporated with cholesterol and apolipoprotein into chylimicrons</li> <li>Move through lymphatic system, then blood to tissue</li> <li>Lipoprotein lipase converts tracylglycerol to fatty acid and glycerol</li> <li>Fatty acid enters cells</li> <li>Fatty acid oxidised for fuel or re-esterfied into triacylglycerol for storage</li></ol>

49
Q

<p>Why is triacylglycerol efficient for the storage of fats?</p>

A

<p>Highly reduced form</p>

50
Q

<p>What is triacylglycerol stored as in adipose tissue?</p>

A

<p>Droplets</p>

51
Q

<p>What is the process of fatty acids being released from adipose tissue?</p>

A

<ol> <li>Hormone sensitive lipase (HSL) activated by phosphorylation in response to noradrenaline</li> <li>Fatty acid released from stored triacylglycerol by HSL</li></ol>

52
Q

<p>What deactivates hormone sensitive lipase (HSL)?</p>

A

<p>High plasma glucose and insulin by dephosphorylation</p>

53
Q

<p>How is fatty acid transported in the blood?</p>

A

<p>In a complex with serum albumin, carried in lipoproteins</p>

54
Q

<p>What are lipoproteins that transport fatty acids made of?</p>

A

<p>Hydrophobic cores (triacylglycerol and cholesterol esters)</p>

<p>Hydrophillic surface (unesterfied cholesterol, phospholipids, apolipoproteins)</p>

55
Q

<p>What are the 4 classes of lipoproteins?</p>

A

<p>Chylamicrons</p>

<p>VLDL</p>

<p>LDL</p>

<p>HDL</p>

56
Q

<p>Does density increase from chylamicrons to HDL or from HDL to chylamicrons?</p>

A

<p>Chylamicrons to HDL</p>

57
Q

<p>What is the function of chylomicrons?</p>

A

<p>Transfer triacylglycerol from intestine to tissue, they are triacylglycerol rich</p>

58
Q

<p>What is the function of VLDL?</p>

A

<p>Transfer triacylglycerol from liver to tissue, triacylglycerol rich</p>

59
Q

<p>What is the function of LDL?</p>

A

<p>Transfer cholesterol to tissue, cholesterol rich</p>

60
Q

<p>What is the function of HDL?</p>

A

<p>Transfer cholesterol from tissue to the liver for elimination, protein/cholesterol rich</p>

61
Q

<p>What is a disease that too much LDL leads to?</p>

A

<p>Atherosclerosis</p>