LAUREN, MAY, ANNIE, & ANJANETTE FAT DIGESTION LAUREN, MAY, ANNIE, & ANJANETTE

WHY ARE FATS IMPORTANT? Helps to absorb vitamins and minerals Needed to build cell membranes and myelin sheath around nerves Essential for blood clotting, muscle movement, and inflammation

SATURATED FATS Contain all possible hydrogens in carbon chains (All Single Bonds) No kinks due from double bonds tend to be solid at room temperature Ex: Meats, butter, cheese, cream, coconut oil.

UNSATURATED FATS do not have as many hydrogen as possible, contain double bond Polyunsaturated Transunsaturated Monounsaturated

MONOUNSATURATED one unsaturated carbon, one double bond Liquid at room temperature Ex: Olive oil, peanut oil, canola oil, avocados, most nuts

POLYUNSATURATED Two main types of polyunsaturated fats are omega-3 and omega-6 fatty acids The numbers refer to the distance between the beginning of the carbon chain and the first double bond found in walnuts, sunflower and flax seeds, oils, salmon, tuna, trout. The human body can produce all the fatty acids it needs, except for two: linoleic acid (LA), an omega-6 fatty acid, and alpha-linolenic acid (ALA), an omega-3 fatty acid. These must be consumed from the diet and are therefore termed “essential fatty acids”.

TRANS FATS Not typically found in nature. These fatty acids are created by adding hydrogen to liquid oils to make them solid. Consumption of trans fats has been shown to increase the risk of coronary artery disease in part by raising levels of the lipoprotein LDL, lowering levels of the lipoprotein HDL, increasing triglycerides in the bloodstream and promoting systemic inflammation. Ex: Donuts, margarine, cake mixes and frostings, cookies…(Anything with hydrogenated or partially hydrogenated oils).

SHORT CHAIN FATTY ACIDS Short-chain fatty acids are fatty acids with fewer than 6 carbon (C) atoms They are produced when the friendly gut bacteria ferment fiber in your colon, and are the main source of energy for the cells lining your colon. Absorbed directly into the villi of the intestinal mucosa. About 95% of the short-chain fatty acids in your body are: Acetate (C2). Propionate (C3) Butyrate (C4). Propionate is mainly involved in producing glucose in the liver, while acetate and butyrate are incorporated into other fatty acids and cholesterol High-fiber foods, such as fruits, veggies, legumes and whole grains, encourage the production of short-chain fatty acids

LONG CHAIN FATTY ACIDS Long-chain fatty acids are those with at least 14 or more carbons in their tail which makes up most saturated and unsaturated fats Used for esterification to form triacylglycerols, phospholipids and cholesteyl esters Long-chain fatty acids cannot cross the blood–brain barrier (BBB) and so cannot be used as fuel by the cells of the central nervous system while short-chain fatty acids can.

LIPID DIGESTION IN MOUTH & STOMACH lingual lipase secreted by von Ebner's glands stable in acidic environment and can remain active in stomach and small intestine digests short and medium chain fatty acids gastric lipase secreted by chief cells of gastric mucosa digest short and medium chain fatty acids

IT BEGINS IN THE SMALL INTESTINE… EMULSIFICATION OF FATS BY BILE STORED IN GALL BLADDER

SMALL INTESTINE – PANCREATIC LIPASE occurs in jejunum optimum pH of 7.0-8.8 inhibited by bile salts colipase allows for lipase to get past inhibitory bile salts

ABSORBTION IN SMALL INTESTINE

CHOLESTEROL SYNTHESIS ESTERS transport form of cholesterol HMG CoA reductase controls speed of cholesterol synthesis Statins inhibit this, reducing cholesterol synthesis transport form of cholesterol allows more cholesterol molecules to fit into lipoprotein high levels of cholesterol esters are associated with atherosclerosis

CHYLOMICRON Chylomicrons are the largest and least dense of the lipoproteins and have the highest triglyceride content Chylomicrons are coated with proteins and leave the epithelial cell via exocytosis Once in the bloodstream, chylomicrons are removed from the blood and processed/broken down by lipoprotein lipase in the endothelial cells of the liver

LACTEALS – LYMPH TRANSPORT OF CHYLOMICRONS

VLDL, LDL, & HDL VLDL – Very low density lipoprotein is composed of protein, fats and cholesterol synthesized in the liver These are then shuttled to the tissues to be stored or used as energy LDL- Low density lipoprotein contains mostly cholesterol. Carry fats and cholesterol produced in the liver to the tissues High VLDL and LDL are associated with atherosclerosis and heart disease HDL- High density lipoprotein has the highest protein:lipid ratio and so is the densest This is the so-called good cholesterol because it carries cholesterol away from the tissues to the liver, lowering blood cholesterol levels High HDL levels are associated with a lowered risk of cardiovascular disease

LIPOGENSIS Process of converting acetyl coA into fatty acids Acetyl coA obtained from glycolysis Takes place in cytoplasm Acetyl coA cannot cross mitochondrial membrane so it is transported out as citric acid and then split into oxaloacetate and acetyl coA Glycerol backbone is added to form triglycerides

KETOGENESIS Creation of ketone bodies from excess acetyl co A