Lipids Flashcards
how many calories do dietary lipids provide?
9 kcals/g
what does hydrophobic mean?
doesn’t dissolve in water
where is energy stored?
adipose tissue
what are the 3 types of lipids?
- triglycerides
- phospholipids
- sterols
describe the structure of a triglyceride?
a glycerol head with 3 fatty acid tails attached
what is the structure of a phospholipid?
a glycerol head attached to a phosphate and nitrogen-containing group along with 2 fatty acid tails
what is the structure of a sterol?
conencting rings of carbon and hydrogen
true or false: the longer a fatty acid chain is, the harder it is to digest?
true
what are the different types of fatty acids?
- saturated fat
- unsaturated fat
what is saturated fat?
fatty acids that dont contain a double bond; saturated with hydrogens; solid at room temperature
what is unsaturated fat?
fatty acids that contain double bonds; less saturated with hydrogens; liquid at room tempertature
describe the different types of unsaturated fats
- monounsaturated fat (MUFA) = unsaturated fats that contain one double bond
- polyunsaturated fats (PUFA) = unsaturated fats that contain multiple double bonds
double bonds are ____ stable and are more likely to be ____
less; oxidized
unsaturated fats are more likely to form ____
free radicals
what prevents the oxidation of double bonds and the formation of free radicals?
antioxidants
what are the essential fatty acids?
- omega-3
- omega-6
what are the different forms of omega-3?
- alpha-linolenic acid (ALA)
- eicosapentaeonic acid (EPA)
- decosahexaenoic acid (DHA)
what are the different forms of omega-6?
- linoleic acid
- Arachidonic acid
what is lingual lipase?
enzyme that breaks down fatty acids in the mouth (minor role)
what is gastric lipase?
enzyme that breaks down fat in the stomach
how does hydrolysis contribute to the digestion of triglycerides?
breaks the triglyceride into free fatty acids, monoglycerides, and a glycerol
what are chief cells?
cells in the stomach that produce digestive enzymes
where does most of the digestion and absorption of lipids occur?
small intestine
what is the function of cholecystokinin (CCK)?
stimulates the gallbladder to release bile
what is the function of pancreatic lipase?
hydrolyzes lipids into monoglycerides
what are phospholipases?
enzyme that hydrolyzes phospholipids into 2 fatty acids and a phospholipid remnant
what is the function of bile?
breaks down large fat globules into smaller spheres
what are micelles
small spherical globules of fat that consist of monoglycerides, cholestrol, and phospholipids
in terms of lipid digestion, what occurs in the small intestine?
- cholecystokinin (CCK) is secreted which stimulates the gallbladder release bile into the small intestine
- fat globules form due to the aqueous environement in the small intestine
- bile breaks up fat globules and prevents them from re-merging
- pancreatic lipase hydrolyzes the triglycerides into monoglycerides
- the monoglycerides bond with cholesterol and phosolipids to form micelles
- the micelles diffuse into the enterocyte
once the micelle has been absorbed, what happens to the different parts of the micelle?
- glycerol heads and short/medium chain fatty acids diffuse into the portal vein and head over the liver
- the long chain fatty acids combine with the monoglycerides to reform triglycerides
- the triglycerides combine with cholesterol, phospholipids and proteins to form chylomicrons
what are lipoproteins?
complexes made out of both lipids and proteins
where do chlyomicrons go after their formation in the enterocyte?
they are absorbed into the lacteal and are transported into the lymph system
how do chylomicrons enter the bloodstream?
through the thoracic duct
what is lipoprotein lipase (LPL)?
a lipoprotein that hydrolzes triglycerides in chylomicrons; seperates the fatty acids from the glycerol head
where do the triglycerides go after being hydrolyzed by LPL?
the cells where they are used
what are very-low density lipoproteins (VLDL)?
lipoproteins that are formed from the chylomicron remnants and lipids and in the liver; transport triglycerides to the peripheral cells
what are low-density lipoproteins (LDL)?
lipoproteins that are made from VLDLs; transports cholesterol to peripheral cells
what are high-density lipoproteins (HDL)?
a lipoprotein that is formed from the cholesterol that is cleaved from artery walls and tissues; removes cholesterol from cells
describe the process of lipid transportation after absorption in the enterocyte?
- chylomicrons enter the lymph system via the lacteal and exit the lymph system through the thoracic duct into the bloodstream
- while in the bloodstream chylomicrons are exposed to lipoprotien lipase (LDL) which hydrolyzes triglycerides
- the chylomicron goes to liver where VLDL, LDL, and HDL are formed
what is the connection between LDL/HDL and cholesterol?
- LDL is associated with high levels of cholesterol since it transports cholesterol to peripheral cells and remains in the bloodstream longer than HDL
- HDL is associated with lower levels of cholesterol since it removes cholesterol from the cells/bloodstream and bring it back to the liver where it is excreted or recyled
what are adipocytes?
the primary site of storage for triglycerides
the release of fatty acids from the adiposecytes is stimulated by what?
glucagon
what is the AMDR for dietary fat?
20-35% of daily kcal needs
what are the sources of dietary fat to limit? State the amounts to which they should be limited?
- saturated fat= <10% of total kcals
- trans fat = <1% or none
what are the essential fatty acids?
- arachidonic acid
- esicosapentaenoic acid
- dosahexanoic acid
what is the AI for the essential fatty acids?
- linoleic acid: 17g for adult men, 12g for adult women
- alpha-linoleic acid: 1.6g for adult men, 1.1g for adult women
what are the AMDRs for the essential fatty acids?
- linoleic acid: 5-10% of total kcals
- alpha-linoleic acid: 0.6-1.2% total kcals
what is atherosclerosis?
the hardening of the coronary arteries due to plaque buildup
what happens during the injury and inflammation at an arterial wall?
- LDLs and other lipids infiltrate the injured wall
- the injury attracts macrophages
- the mixture of macrophages and LDL causes foam cells to form
- foam cells and platelets build up to form plaque
what are endothelial cells?
blood cells
what is the pathphysiology behind inflammation?
- chemical messengers (histamine, prostaglandins, and cytokines) are released
- these messengers activate immune cells which activates the inflammatory response
- vasodilation also occurs - increased blood flow to injury
what is oxidative stress?
the imabalance in the production of reactive oxygen species exceeding antioxidant capacity
what are polyphenols?
a plant-based chemical that contains antioxidants
what is atherosclerotic cardiovascular disease?
atherosclerosis that leads to cardiovascular disease
what are the risks factors for cardiovascular disease?
- diet
- phsyical activity
- smoking
- high blood pressure
- high levels of LDL cholesterol
- stress
- weight status
- non-modfiable factors
what are the benefits of having higher levels of HDL?
- inhibition of LDL oxidation - less inflammation
- inhibits vascular inflammation
- promotes efflux of cholesterol from macrophages in arteries
- promotes epithelial repair and function
how are trans fatty acids formed?
hydrogenation of unsaturated fats
what is the impact of trans fat on the body?
- increased ratio of LDL to HDL
- increased levels of LDL and triglycerides
- increased inflammation at site of arterial wall
- endoplasmic recticulum stress
- increased storage of fat in liver
true/false: high triglyceride levels are associated with CVD risk?
true
