Lipids 1 Flashcards
<p>What are lipids?</p>
<p>Molecules that contain hydrocarbons and make up the building blocks of structures and function in a living cell</p>
<p>When are lipids soluble?</p>
<p>They are hydrophillic but are soluble in organic solution</p>
<p>Are lipids hydrophobic or hydrophillic?</p>
<p>Hydrophobic</p>
<p>Where can lipids be found?</p>
<p>Cell membranes</p>
<p>Adipose tissue</p>
<p>Blood lipoproteins</p>
<p>What are some functions of lipids?</p>
<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>
<p>What are the 5 lipid classes?</p>
<p>Fatty acids</p>
<p>Triacylglyderol</p>
<p>Phospholipids</p>
<p>Glycolipids</p>
<p>Steroids</p>
<p>What are the 2 forms of fatty acids?</p>
<p>Unsaturated (one or more double bonds)</p>
<p>Saturated (no double bonds)</p>
<p>How are fatty acids named?</p>
<p>By the number of carbons, number of double bonds and the position of the double bond</p>
<p>Give examples of lipid naming?</p>
<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>
<p>What are the 4 kinds of fatty acids in our diet?</p>
<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>
<p>What are saturated fats good for?</p>
<p>The nervous system</p>
<p>What are essential fatty acids?</p>
<p>Cannot be synthesised, need to be consumed in our diet</p>
<p>Why can essential fatty acids not be synthesised?</p>
<p>We cannot introduce double carbon bonds beyond carbon 9</p>
<p>What are omega-3 fatty acids derived from?</p>
<p>Linolenic acid (essential fatty acid)</p>
<p>What are omega-3 fatty acids good for, and omega-6?</p>
<p>Lowering blood cholesterol</p>
<p>What are triacylglycerols?</p>
<p>Esters of fatty acids and glycerol</p>
<p>What are triacylglycerols used for?</p>
<p>Storing energy and insulation</p>
<p>Are triacylglycerols water soluble?</p>
<p>No</p>
<p>What are phospholipids?</p>
<p>A lipid containing a phosphate group</p>
<p>How are phospholipids amphipathic?</p>
<p>They contain a hydrophillic head and a hydrophobic tail</p>
<p>Why are phospholipids often used in membranes?</p>
<p>They are amphipathic</p>
<p>What does amphipathic mean?</p>
<p>Has a hydrophillic and a hydrophobic component</p>
<p>What is the main site of lipid digestion?</p>
<p>Small intestine</p>
<p>Where does lipid digestion start?</p>
<p>In the mouth</p>
What is digestion by pancreatic enzymes (lipases) promoted by?
Emulsification (dispersion) by bile salts and peristalsis (mixing)
What pancreatic enzymes digest lipids?
Lipases
Where does some lipid digestion occur other than the mouth and the small intestine?
The stomach
What are bile salts?
Act as biological detergents to break down fatty acids
What are bile salts a derivative of?
Cholesterol
How are triacylglycerols digested?
Degraded in small intestine by pancreatic lipases to monoacylglycerol and two fatty acids
What are cholesterol esters digested into?
Digested to cholesterol and a free fatty acid?
How are phospholipids digested?
Hydrolysed to a fatty acid and lysophospholid
What does the digestion of lipids look like?
- Fat becomes emulsified fat in the duodenum (due to bile)
- Then broken down into fatty acids and glycerol in the small intestine (due to lipases)
What is the process of digested lipid uptake?
Form mixed micelles with bile salt which approach membrane and release lipid products which enter by diffusion
Short and medium chain fatty acids do not require micelles because they are more soluble
What is formed from digested lipids and bile salt?
Micelles
What could lipid malabsorption be due to?
Defect in bile secretion
Defect in pancreatic function
Defect in intestinal cells
What does lipid malabsorption cause?
A steatorrhea
What is a steatorrhea?
Excess fat in faeces
What secretes bile salt?
Gallbladder
What is the fate of absorbed lipids?
Resynthesised by intestinal cells for export
Packaged with apoB-48 into chylomicrons due to being insoluble
Why are absorbed lipids packaged with apoB-48 for export?
Because they are insoluble, this packaging makes them soluble
What does the packaging of absorbed lipids and apB-48 form?
Chylomicrons
How are chylomicrons released?
By exocytosis into the lymph and then the blood
What happens once chylomicrons reach the tissue?
- Hydrolysed to fatty acid and glycerol by lipoprotein lipase
- Resulting fatty acid is used for energy or resterfication to triacylglycerol for storage
What is a chylomicron renment?
Chylomicron depleted of tracylglycerol
Where do chylomicron renments go?
The liver where glycerol is used to produce glycerol-3-phosphate
Where is lipoprotein lipase normally found?
In capillaries of skeletal muscle and adipose tissue
What is the exact process of lipid digestion, absorption and transport summarised?
- Bile salts emulsify fats in small intenstine, forming micelles
- Intestinal lipases degrade triacylglycerol
- Fatty acids are taken up by intestinal mucosa and converted to triacylglycerol
- Triacylglycerol is incorporated with cholesterol and apolipoprotein into chylimicrons
- Move through lymphatic system, then blood to tissue
- Lipoprotein lipase converts tracylglycerol to fatty acid and glycerol
- Fatty acid enters cells
- Fatty acid oxidised for fuel or re-esterfied into triacylglycerol for storage
Why is triacylglycerol efficient for the storage of fats?
Highly reduced form
What is triacylglycerol stored as in adipose tissue?
Droplets
What is the process of fatty acids being released from adipose tissue?
- Hormone sensitive lipase (HSL) activated by phosphorylation in response to noradrenaline
- Fatty acid released from stored triacylglycerol by HSL
What deactivates hormone sensitive lipase (HSL)?
High plasma glucose and insulin by dephosphorylation
How is fatty acid transported in the blood?
In a complex with serum albumin, carried in lipoproteins
What are lipoproteins that transport fatty acids made of?
Hydrophobic cores (triacylglycerol and cholesterol esters)
Hydrophillic surface (unesterfied cholesterol, phospholipids, apolipoproteins)
What are the 4 classes of lipoproteins?
Chylamicrons
VLDL
LDL
HDL
Does density increase from chylamicrons to HDL or from HDL to chylamicrons?
Chylamicrons to HDL
What is the function of chylomicrons?
Transfer triacylglycerol from intestine to tissue, they are triacylglycerol rich
What is the function of VLDL?
Transfer triacylglycerol from liver to tissue, triacylglycerol rich
What is the function of LDL?
Transfer cholesterol to tissue, cholesterol rich
What is the function of HDL?
Transfer cholesterol from tissue to the liver for elimination, protein/cholesterol rich
What is a disease that too much LDL leads to?
Atherosclerosis
