Card Set Information
Structure, function, metabolism
Give 2 examples of SFA, MUFA and PUFA.
: butyric acid, palmitic acid
: oleic acid, elaidic acid
: linoleic acid, arachdonic acid
What is the delta and omega system of FA nomenclature?
: starts at the carboxyl end
: starts from methyl end
What are the two essential FA? Why are they essential?
Linoleic acid (omega 6) and Alpha linolenic (omega 3)
They are essential because human enzymes lack the ability to insert a double bond beyond the delta 9 position (at delta 12 and delta 15 positions) therefore aren't produced in the body
This enzyme is only found in plants
We receive these nFA from plants
What are the signs of n-6 deficiency and n-3 deficiency?
: dermatitis, decreas in growth and reproductive maturity - FA incorprates into cell membrane of skin cells
: decrease in IQ (affects CNS development) and decreases visual acuity (affects retinal development) - FA associated with membranes in the brain
FA get incorporated into cell membranes
What are the desaturation and elongation pathways for EFA (abbreviated)?
Repetitive series of desaturations and elongation by 2Cs coming from acetyl CoA
Linoleic acid (n-6) gets converted eventually to arachidonic acid which get converted to pro-inflammatory eicosanoids
Alpha linolenic acid (n-3) gets converted to eicosapentanoic acid (EPA) and docosahexanoic acid (DHA)
EPA is a precursor for anti-inflammatory eicosanoids
DHA is involved in the development of brain cell membranes - related to CNS and retinal development
Usually have more n-6 FA
What is the difference between pro and anti inflammatory eicosanoids?
: important physiological response to fighting infections and mounting inflammation - thermal biological response
: dampen inflammation response in the body - important in arthritis
What is an eicosanoid?
20 carbon metabolite of AA and EPA
Produced by most cells in the body
Hormone like, local function
Role in inflammation, platelet aggregation and blood pressure
Implcations for disease
Pro inflamm causes too much aggregation
After FA are incorporated into cell membranes, the cell will convert them eicosanoids
How are TAGS used?
Main dietary form and major storage form
used in lipolysis and lipogenesis (in adipose tissues)
Can have MAG, DAG, TAG
What are the main functions of phospholipids?
Main compoenents if cell membranes - lipid bilayers
Source of physiological active compounds (eicosanoids)
Anchors membrane proteins
What is the role of phosphotidyl choline?
Found in diet and plays a role as an emulsifier
What are the sources and principal functions of sterols? What are the structural features?
40% diet and 60% endogenous production
Components of membranes
Steriod sex hormones
Also has teriod nucleus - 4 ring structure - animal cholesterol is seen as bad and plant cholesterols as good
The liver produces sufficient cholesterol for body
What are the 7 lipid functions?
1.Concentrated source of energy
2. Palatability and satiety
3. Source of FA
4. Carrier of fat soluble vitamins (A, D, E, K)
5. Involved in hormone production
6. Affect blood clotting and inflamation
7. Associated with disease development
: obesity, diabetes, heart disease
At what organs does lipid digestion occur and how?
: secretes lipases
: gastric lipases
: production of bile salts and salts which allows alipids to come into contact with enzymes in the rest of digestion
: stores the bile - source - bile allows for emulsification
: pancreatic lipases - main site of lipid digestionand cholesterol estrase - breaks down cholesterol as most in the form of a cholesterol ester
How are digested lipids stabilized? What are mixed micelles?
Stabilized by bile salts = conjugate of bile acids
Small, spherical complexes containing lipid digested products and bile salts
Can access intramicrovillus spaces of the membrane
originally thought the lipids were delivered into intestinal mucosal cell through passive diffusion, but carrier mediated transporters have been identified
Bile salts are reabosrbed
Describe the structure of a micelle?
Have amphipathic phospholipids and bile salts on outside surrounding and stabilizing the structure
FA, MAG, lysolecithin and cholesterol inside
What happens once lipids are absorbed into the intestinal mucosal cell?
Enters the cell as a micelle
They are resynthesized into cholesterol esters, TAGs and phosphotidyl choline and packaged into a chylomicron and enters lymphatic system
Short chain FA can pass directly through the membrane but then attach to albumin which then transports it through portal circulation
What is a chylomicron?
It is a lipoprotein
Synthesized directly in intestinal mucosal cell
Phsopholipids play structural role on outside
Have apoproteins either on inside of membrane or outside - allow stabilization within the blood circulationand provide recognition functions
What is the affect on chylomicrons after a meal?
The amount of chylomicrons increases
Clearance is due to lipoprotein lipases (LPL)
Found on endothelial cell surface of small blood vessels and capilleries
LPL in adipose and muscle tissue NOT liver
LPL releases a FA and DAG from a TAG which can then be absorbed by the body
Chylomicron remnants are removed from the blood at the liver
What happens when the chylomicron remnant reaches the liver?
The contents along with lipids from other sources get repackaged into VLDL which forms LDL
Some HDL is produced as well
The chylomicron remnants are resynthsized to larger structure to form a FA pool leading to a TAG pool which are then repackaged into VLDL and taken up by the hepatic cells into circulation
What lipid metabolism occurs in the adipose tissues?
Contents of VLDL, LDL and HDL are broken down by LPL, taken up by adipose tissues and resythnesized as TAG and stored in TAG pool - can be used for energy later on
What is LDL? It's main function?
VLDL is the main transporter of newly syntheized TAGs from the liver
LDL delivers cholesterol in essential places but if no more requirements for cholesterol, will begin to deposit it anywhere - seen as bad
What is the function of HDL?
Produced in liver and involved in reverse choelsterol transport - picks up remnants of cholesterol and brings it back to the liver to be used in bile acids or excreted
Lecithin cholesterol acetyl transferase converts it to cholesterol esters - form of transportation
What is the effect of lowering dietary cholesterol?
In most cases, this has little effect on cholesterol levels as most if produced by your body
Exception is the dietary gene interaction in which there is a polymorphism that causes lowering dietary cholesterol to effectively lower blood level cholesterols (10-25% of people)
Where do trans FA occur?
naturally in ruminant fat (4-8% of ruminant milk are trans FA) - most common is elaidic acid
Also made through partial dehdrogenation processes which convert cis FA to trans form
This is done to increase stability and shelf life
What are the health risks associated with trans FA?
Double negative - increases LDL and decreases HDL which is linked to cardiovascular disease