Quiz 6 Flashcards
packet 8 and 9
CHO vs proteins?
CHO: made of sugar molecules (mainly glucose) broken down to release energy
proteins: chain of amino acids that have structural and functional roles in the body
what does amphipathic mean?
when a lipid has both hydrophobic and hydrophilic regions, this allows them to interact with both water and fats
what are the main types of lipids?
triglycerides, phospholipids, steroids and waxes
what are triglycerides?
fats and oils, the most abundant lipid in the body and food, serve as the primary energy storage molecule in the body, made up of glycerol and 1-3 fatty acids (depending on monoglyceride, diglyceride, or triglyceride)
what are phospholipids?
amphipathic lipids made up of glycerol, 2 fatty acids, and a phosphate group, phosphate head is hydrophilic and fatty acids are hydrophobic
what are the functions of phospholipids?
- cell membranes: structural component of cell
membranes that form the lipid bilayer 2 (phospholipids) - bile: component of bile that aids in lipid digestion by breaking up (emulsifying) dietary lipids into lipid droplets (micelles)
- lipoproteins: phospholipids form lipoproteins, complexes that transport insoluble lipids in the
blood
what is cholesterol?
the most abundant sterol in the body, an important components in cell membranes that maintain stability and fluidity, acts as parent compound to make other sterols (such as vitamin D, cortisol, estrogen and testosterone), is a nonessential nutrient made by the liver
what is the composition of fatty acids?
carbon, hydrogen, and oxygen atoms with an acid (COO-) group and a methyl (CH3) group, double or single carbon bonds, the number of carbons in the chain (fewer carbon atoms = more soluble fatty acid), and essential vs nonessential determines the kind of fatty acids
what are the different types of fatty acids?
saturated: single bonds between carbon atoms, maximum number of hydrogen atoms
monounsaturated: one double bond
polyunsaturated: with two or more double bonds
for each double bond there are 2 less hydrogen atoms compared to a saturated FA with an equal number of carbon atoms
what determines if a food is liquid or solid (fat) at room temperature?
ratio of saturated to unsaturated fatty acids since unsaturated fatty acids have bends and kinks that prevent close orderly packing
fats are solid at room temperature since they have a high percentage of saturated fatty acids
oils are liquid at room temperature because they have a high percentage of unsaturated fatty acids
what is the fatty acid nomenclature?
number of carbon atoms, number of double bonds, omega-# refers to the # of the carbon atom before the first double bond from the methyl end
what makes a fatty acid essential/nonessential?
essentiality is based on the position of the first double
bond from the methyl end, if the first double bond
occurs before the 9th carbon atom the FA is
essential, humans lack the enzymes needed to synthesize double bonds occurring before C-9
what are the 2 essential fatty acids?
linolenic acid: 18:3 omega-3 FA
linoleic acid: 18:2 omega-6 FA
why are linolenic and linoleic acids important?
they can lead to the formation of other omega-3 or omega-6 FAs by elongation (increasing the number of carbon atoms) or desaturation (increasing double bonds by removing hydrogen atoms)
ex:
linoleic acid + 4 carbons and 2 double bonds = arachidonic acid
linolenic acid + 2 carbons and 2 double bonds = eicosapentaenoic acid
linolenic acid + 2 carbons and 1 double bond = docosahexaenoic acid
why are omega-3s (linolenic acid, EPA, and DHA) so important?
some evidence for lower cardiovascular disease risk, strong evidence for brain and eye development in fetus and brain development throughout infancy
EPA and DHA are added to foods since conversion to make them naturally is slow and limited
how are supplements used to increase omega-3s?
salmon, tuna, mackerel, herring and sardines contain EPA and DHA (>- two 3.5 ounce servings per week to prevent cardiovascular disease is recommended), fish oil supplements are purified to remove heavy metals, algal oil DHA is a safer and cleaner alternative, DHA concentration in breastmilk is influenced by DHA in the mothers diet (recommended that pregnant women consume fish 2-3 times per week or take a supplement)
how are triglycerides digested?
digested in small intestine where emulsification disperses fat globules, when fat-rich chyme reaches the SI, cholecystokinin signals the gallbladder to release bile, bile is amphipathic which allows fat globules to disperse in the aqueous environment, results in the formation of small lipid spheres (droplets) called micelles, pancreatic lipase hydrolyzes the ester bonds that attach fatty acids to the glycerol and results in 2 free FAs and 1 monoglyceride
how are dietary lipids circulated?
monoglycerides and free fatty acids are absorbed into the enterocyte (intestinal cell), inside the enterocyte, fatty acids are reattached to monoglycerides forming triglycerides, lipids are packaged into particles
called chylomicrons, which are released from enterocytes into the lymphatic system
what is the exogenous pathway?
transport of dietary lipids as chylomicrons, circulating chylomicrons interact lipoprotein lipase (LPL), an enzyme
along the lining of capillaries associated with adipose tissue and muscle cells, LPL hydrolyzes the ester bonds,
which enables fatty acids to be taken up by muscle and adipose tissue, chylomicron remnants are taken up
by the liver
what is the endogenous pathway?
delivery of lipids made in the liver, in addition to dietary lipids, the liver synthesizes lipids (triglycerides and cholesterol) from excess carbohydrates and amino acids, lipids made by the liver must also be transported to peripheral tissues, to transport lipids in the blood,
the liver packages triglycerides and cholesterol into particles called very-low-density lipoproteins (VLDLs)
what is the morphology of very-low-density lipoproteins (VLDLs)?
VLDL particles consist of a central lipid core (TG and Chol) encased in phospholipids and proteins, phospholipids and proteins are water soluble, which enable lipids to circulate in the blood, surface proteins called apolipoproteins allow cells to identify VLDLs which then
take up triglycerides via lipoprotein lipase
how are VLDLs converted to IDLs?
removal of triglycerides (TG) from VLDLs changes the size (smaller), composition (ratio of lipid:protein ), and function, after losing some TG, VLDLs converted
into Intermediate Density Lipoproteins (IDLs), some IDLs taken up by liver, remaining IDLs lose more TG and
become Low Density Lipoproteins (LDLs), the main role of LDLs is to deliver cholesterol to peripheral tissue, cells with LDL receptors removed LDL particles from the blood where it is used to make hormones, components of bile, and components of cell membranes
what is atherosclerosis?
when LDL particles not efficiently cleared from the blood can infiltrate the arterial wall triggering inflammation which can eventually obstruct blood flow, if blood flow to the heart or brain is interupted it can lead to heart attack or stroke
what are high density lipoproteins (HDLs)?
HDLs particles (high protein, low lipid) help remove excess cholesterol from blood vessels and tissues and transport it to the liver to be reused or eliminated, high HDL levels associated with lower risk of atherosclerosis and heart disease
