Lecture 7 Flashcards by Arden Pappot

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

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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

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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

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What is the general structure of a fatty acid?

Hydrophilic end: carboxyl group
Hydrophobic end: carbon chain

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What is a monounsaturated fatty acid

one double bond

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What is a polyunsaturated fatty acid?

Two+ double bonds

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What is cis vs trans unsaturated FA?

Cis: kinks in the structure
trans: no kinks in the structure (produced in the industry - unhealthy)

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What do the kinks in FA help with?

fluidity

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What are the two types of FA nomenclature?

Omega
Delta

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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

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What is the delta system nomenclature?

Numbering starts from the carboxyl end of fatty acid
numbercarbons:numberdoublebonds delta(position of double bonds)

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Why are essential fatty acids essential?

humans ack enzymes necessary to insert double bonds beyond the delta-9 position of a fatty acid

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What are two essential fatty acids?

linoleic acid and alpha linolenic acid

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What delta bonds are produced in plants?

delta-12 and delta-15

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What are the signs of n-6 essential FA deficiency?

Skin: dermatitis
Growth: low
repro maturity: low
CNS development: ok
retinal development: ok

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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?

1. Bile acids are made in the liver from cholesterol 2. Bile salts are stored in the gallbladder (get there through bile duct) 3. Bile salts enter small intestine through bile duct and breaks down food, 5% is lost in feces 4. 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?

1. Mixed micelle is brought to water layer - digestive enzymes break down lipid 2. Mixed micelle is brought to the brush border membrane 3. 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