Lecture 7 Flashcards
What are some characteristics of lipids?
- soluble in organic solvents
- wide variety of structures and functions
- source of energy
- major component of cell and organelle membranes
What are the functions of lipids?
- concentrated source of energy
- palatability of foods and increase satiety
- source of essential fatty acids - omega 3 and omega 6
- source of fat-soluble vitamins (A,D,E,K)
- necessary for growth and development
- important precursors for production of hormones
- affect inflammation and blood clotting
- key roles in disease development
What are the two types of fatty acids?
Saturated
- max # of H atoms
- only single bonds
Unsaturated
- missing H atoms
- double bonds: monounsaturated, polyunsaturated
- cis or trans configuration
What is the general structure of a fatty acid?
Hydrophilic end: carboxyl group
Hydrophobic end: carbon chain
What is a monounsaturated fatty acid
one double bond
What is a polyunsaturated fatty acid?
Two+ double bonds
What is cis vs trans unsaturated FA?
Cis: kinks in the structure
trans: no kinks in the structure (produced in the industry - unhealthy)
What do the kinks in FA help with?
fluidity
What are the two types of FA nomenclature?
Omega
Delta
What is the omega system nomenclature?
carbons:# double bonds n-location of 1st double bond
numbering starts from the methyl end of fatty acid
numbercarbons:numberdoublebonds n-locof1stdoublebonds
What is the delta system nomenclature?
Numbering starts from the carboxyl end of fatty acid
numbercarbons:numberdoublebonds delta(position of double bonds)
Why are essential fatty acids essential?
humans ack enzymes necessary to insert double bonds beyond the delta-9 position of a fatty acid
What are two essential fatty acids?
linoleic acid and alpha linolenic acid
What delta bonds are produced in plants?
delta-12 and delta-15
What are the signs of n-6 essential FA deficiency?
Skin: dermatitis
Growth: low
repro maturity: low
CNS development: ok
retinal development: ok
What are the signs of n-3 essential FA deficiency?
Skin: ok
growth: ok
repro maturity: ok
CNS development: low IQ
retinal development: low visual activity
What is EFA desaturation and elongation?
Desaturation: insert double bond, remove 2H
elongation: add 2 carbons
What EFA’s are converted to eicosanoid’s?
Omega 6 (linoleic acid) - arachidonic acid
Omega 3 (alpha linolenic acid) - eicosapentaenoic acid
How are the omega EFA’s converted to eicosanoid’s?
desaturation by delta-6 desaturase
elongation by elongase 5
desauration by delta-5 desaturase
What is the process of omega 6 to arachidonic acid?
linoleic acid (omega 6)->gamma linolenic acid->dihomo-gamma-linolenic acid->arachidonic acid
What is the process of converting alpha linolenic acid (omega 3) to eicosapentaenoic acid?
alpha linolenic acid-> stearidonic acid-> eicosatetraenoic acid-> eicosapentaenoic acid
What are some characteristics of eicosanoids?
- metabolites of 20-carbon FA’s
- produced by most cells in the body
- hormone-like but function locally
- role in inflammation
- implications for disease
What are triglycerides?
glyceride + 3 FA
main dietary lipid
major storage lipid
What are TAG’s critical for?
- lipogenesis
- lipolysis
- transported in lipoproteins
What is the naming system for TAG’s?
sn-1, sn-2, sn-3
denotes the FA position
What are the structure of phospholipids?
- more polar than TAGS
- hydrophillic head
- hydrophobic tail - FA
What are primary functions of phospholipids?
- Components of membranes
- Source of physiologically active fatty acids for eicosanoid synthesis
- Anchors membrane proteins
- Intracellular signalling
What are the structural features of sterols?
- free or esterified with a FA
- cholesterol ester (CE)
What are the primary functions of sterols?
- essential components of membranes
- precursor for:
- bile acid production
- steroid sex hormone production
- vitamin D synthesis
What are the four organs in the body that participate in lipid digestion?
Mouth: lingual lipase, continuously secreted
Stomach: gastric lipase, continuously secreted, lipases stable at low pH
Liver and Gallbladder: storage of bile salts, release of bile triggered by hormones
Small intestine: pancreatic enzymes include pancreatic lipase (breaks TAGs), cholesterol esterase (breaks cholesterol ester)
What are mixed micelles?
small, spherical complexes containing lipid digestion products plus bile salts
What is the function of mixed micelles?
digested lipids are emulsified by ocnjugated bile acids, micelles engulf these and can access the spaces between microvilli in the intestine, transport mechanism
What is a summary of the process of enterohepatic circulation?
- Bile acids are made in the liver from cholesterol
- Bile salts are stored in the gallbladder (get there through bile duct)
- Bile salts enter small intestine through bile duct and breaks down food, 5% is lost in feces
- The rest are reabsorbed by the small intestine through a portal vein and make their way back to the liver
What is enterohepatic circulation?
the movement of bile acid molecules from the liver to the small intestine and back to the liver
What are the three brush border enzymes?
Pancreatic lipase - works on TAG
Cholesterol esterase - works on cholesterol esters
Phospholipase - works on phospholipids
What is the process of lipids absorption from the small intestine?
- Mixed micelle is brought to water layer - digestive enzymes break down lipid
- Mixed micelle is brought to the brush border membrane
- Broken-down lipids pass through and are repackaged in the enterocyte into a chylomicron (lipoprotein) and are brought into lymphatic circulation
What is a chylomicron?
small globules composed of protein and lipid (ie. triglyceride with a lipid coating) - water-soluble coat so it can leave cell and enter the lymphatic system
