Lecture 5: Lecture 5: LipidsLipids and and CarbohydratesCarbohydrates

Craig KasperCraig Kasper

Fish NutritionFish Nutrition

Part 1: Lipid Part 1: Lipid CharacteristicsCharacteristics

LipidLipid = a compound that is insoluble in = a compound that is insoluble in water, but soluble in an organic water, but soluble in an organic solvent (e.g., ether, benzene, acetone, solvent (e.g., ether, benzene, acetone, chloroform)chloroform)

““lipid” is synonymous with “fat”, but lipid” is synonymous with “fat”, but also includes phospholipids, sterols, also includes phospholipids, sterols, etc.etc.

chemical structure: glycerol + fatty chemical structure: glycerol + fatty acidsacids

Lipid MoleculeLipid Molecule

Nutritional Uses of LipidsNutritional Uses of Lipids We already know that lipids are concentrated We already know that lipids are concentrated

sources of energy (9.45 kcal/g)sources of energy (9.45 kcal/g)

other functions:other functions:

1) provide means whereby fat-soluble nutrients 1) provide means whereby fat-soluble nutrients (e.g., sterols, vitamins) can be absorbed by the (e.g., sterols, vitamins) can be absorbed by the bodybody

2) structural element of cell, subcellular 2) structural element of cell, subcellular componentscomponents

3) components of hormones and precursors for 3) components of hormones and precursors for prostaglandin synthesisprostaglandin synthesis

Lipid ClassesLipid Classes simplesimple: : FA’s esterified with glycerolFA’s esterified with glycerol compoundcompound: : same as simple, but with other same as simple, but with other

compounds also attachedcompounds also attached phospholipidsphospholipids: : fats containing phosphoric acid fats containing phosphoric acid

and nitrogen (lecithin)and nitrogen (lecithin) glycolipidsglycolipids: : FA’s compounded with CHO, but no FA’s compounded with CHO, but no

NN derivedderived lipidslipids: : substances from the above substances from the above

derived by hydrolysisderived by hydrolysis sterolssterols: : large molecular wt. alcohols found in large molecular wt. alcohols found in

nature and combined w/FA’s (e.g., cholesterol)nature and combined w/FA’s (e.g., cholesterol)

Saturated vs. Unsaturated Fatty Saturated vs. Unsaturated Fatty AcidsAcids

saturatedsaturated: the SFA’s of a lipid have no : the SFA’s of a lipid have no double bonds between carbons in chaindouble bonds between carbons in chain

polyunsaturatedpolyunsaturated: more than one double : more than one double bond in the chainbond in the chain

most common polyunsaturated fats contain most common polyunsaturated fats contain the polyunsaturated fatty acids (PUFAs) the polyunsaturated fatty acids (PUFAs) oleicoleic, , linoleiclinoleic and and linoleniclinolenic acid acid

unsaturated fats have lower melting points unsaturated fats have lower melting points stearic (SFA) melts at 70stearic (SFA) melts at 70ooC, oleic (PUFA) at C, oleic (PUFA) at

2626ooCC

Fatty Acids Commonly Found in Fatty Acids Commonly Found in LipidsLipids

Sat. Fatty Acids Formula Melting Point (oC) Butyric C4H8O2 Liquid Palmitic C16H22O2 63 Stearic C18H36O2 70 Unsat. Fatty Acids Formula Melting Point (oC) Oleic C18H34O2 Liquid Linoleic C18H32O2 Liquid Linolenic C18H30O2 Liquid

Saturated vs. Unsaturated Saturated vs. Unsaturated FatsFats

saturated fats tightly packed, clog arteries as saturated fats tightly packed, clog arteries as atherosclerosisatherosclerosis

because of double bonds, polyunsaturated fats because of double bonds, polyunsaturated fats do not pack well -- like building a wall with do not pack well -- like building a wall with bricks (sat.) vs. irregular-shaped objects bricks (sat.) vs. irregular-shaped objects (unsat.)(unsat.)

plant fats are much higher in PUFA’s than plant fats are much higher in PUFA’s than animal fatsanimal fats

Saturated vs. Unsaturated FA’s Saturated vs. Unsaturated FA’s Plant vs. Animal FatPlant vs. Animal Fat

corn soy tallow lard Sat. FA’s Myristic 3 Palmitic 7.0 8.5 27 32.2 Stearic 2.4 3.5 21 7.8 Unsat. FA’s

Oleic 45.6 17 40 48 Linoleic 45.0 54.4 2 11 Linolenic 7.1 0.5 0.6 Arachid.

Lipid Lipid Digestion/AbsorptionDigestion/Absorption

Fats serve a structural function in cells, as sources Fats serve a structural function in cells, as sources of energy, and insulationof energy, and insulation

the poor water solubility of lipids presents a the poor water solubility of lipids presents a problem for digestion: substrates are not easily problem for digestion: substrates are not easily accessible to digestive enzymesaccessible to digestive enzymes

even if hydrolyzed, the products tend to aggregate even if hydrolyzed, the products tend to aggregate to larger complexes that make poor contact with to larger complexes that make poor contact with the cell surface and aren’t easily absorbedthe cell surface and aren’t easily absorbed

to overcome these problems, changes in the to overcome these problems, changes in the physical state of lipids are connected to chemical physical state of lipids are connected to chemical changes during digestion and absorptionchanges during digestion and absorption

Lipid Lipid Digestion/AbsorptionDigestion/Absorption

Five different phases:Five different phases: hydrolysishydrolysis of triglycerides (TG) to free fatty of triglycerides (TG) to free fatty

acids (FFA) and monoacylglycerolsacids (FFA) and monoacylglycerols solubilizationsolubilization of FFA and monoacylglycerols by of FFA and monoacylglycerols by

detergents (bile acids) and transportation from detergents (bile acids) and transportation from the intestinal lumen toward the cell surfacethe intestinal lumen toward the cell surface

uptakeuptake of FFA and monoacylglycerols into the of FFA and monoacylglycerols into the cell and resynthesis to triglyceridecell and resynthesis to triglyceride

packagingpackaging of TG’s into chylomicrons of TG’s into chylomicrons exocytosisexocytosis of chylomicrons into lymph of chylomicrons into lymph

Enzymes Involved in Enzymes Involved in Digestion of LipidsDigestion of Lipids

lingual lipaselingual lipase: provides a stable interface : provides a stable interface with aqueous environment of stomachwith aqueous environment of stomach

pancreatic lipasepancreatic lipase: major enzyme affecting : major enzyme affecting triglyceride hydrolysistriglyceride hydrolysis

colipasecolipase: protein anchoring lipase to the : protein anchoring lipase to the lipidlipid

lipid esteraselipid esterase: secreted by pancreas, acts on : secreted by pancreas, acts on cholestrol esters, activated by bilecholestrol esters, activated by bile

phospholipasesphospholipases: cleave phospholipids, : cleave phospholipids, activated by trypsinactivated by trypsin

What about Bile???What about Bile??? These are These are biological detergents biological detergents synthesized by the synthesized by the

liver and secreted into the intestineliver and secreted into the intestine they form the spherical structures (they form the spherical structures (micellesmicelles) )

assisting in absorptionassisting in absorption hydrophobic portion (tails of FA) are located to the hydrophobic portion (tails of FA) are located to the

inside of the micelle, with heads (hydrophillic inside of the micelle, with heads (hydrophillic portion) to the outsideportion) to the outside

they move lipids from the intestinal lumen to the they move lipids from the intestinal lumen to the cell surfacecell surface

absorption is by diffusion (complete for FA and absorption is by diffusion (complete for FA and monoglycerides, less for others) monoglycerides, less for others)

Factors Affecting Absorption of LipidsFactors Affecting Absorption of Lipids

amount of fat consumedamount of fat consumed ((fat=fat=digestion=digestion=absorption)absorption)

age of subjectage of subject ( ( age = age = digestion) digestion) emulsifying agents emulsifying agents (( digestion = digestion = absorption) absorption) chain length of FA’schain length of FA’s (> 18C = (> 18C = digestibility) digestibility) degree of saturation of FAdegree of saturation of FA ( ( sat = sat = digestibility) digestibility) overheating and autooxidationoverheating and autooxidation (rancidification (rot) (rancidification (rot)

at double bond)at double bond) optimal optimal dietary calciumdietary calcium = optimal FA absorption = optimal FA absorption

(high Ca = (high Ca = absorption) absorption)

Lipid Lipid Metabolism/AbsorptionMetabolism/Absorption

short chain FA’s are absorbed and enter the short chain FA’s are absorbed and enter the portal vein to the liverportal vein to the liver

those FA’s with more than 10 carbons are those FA’s with more than 10 carbons are resynthesized by the liver to triglyceridesresynthesized by the liver to triglycerides

they are then converted into chylomicrons they are then converted into chylomicrons and pass to the lymphatic systemand pass to the lymphatic system

some FA’s entering the liver are oxidized for some FA’s entering the liver are oxidized for energy, others storedenergy, others stored

blood lipids: 45% P-lipids, 35% triglycerides, blood lipids: 45% P-lipids, 35% triglycerides, 15% cholestrol esters, 5% free FA’s15% cholestrol esters, 5% free FA’s

Lipid Lipid Digestion/Digestion/AbsorptioAbsorptio

n n

Lipid Lipid Digestion/Digestion/AbsorptioAbsorptio

nn

Characteristics of Fat Characteristics of Fat StorageStorage

Most of the body’s energy stores are Most of the body’s energy stores are triglyceridestriglycerides

storage is in adipose, source is storage is in adipose, source is dietary or anabolism (synthesis) from dietary or anabolism (synthesis) from COH or AA carbon skeletonsCOH or AA carbon skeletons

remember obesity?remember obesity? adipose can remove FA’s from the adipose can remove FA’s from the

blood and enzymes can put them blood and enzymes can put them back back

Fatty Acid Fatty Acid NomenclatureNomenclature

Nomenclature reflects location of Nomenclature reflects location of double bondsdouble bonds

also used are common names (e.g., also used are common names (e.g., oleic, stearic, palmitic)oleic, stearic, palmitic)

linoleic is also known as 18:2 n-6linoleic is also known as 18:2 n-6 this means the FA is 18 carbons in this means the FA is 18 carbons in

length, has 2 double bonds, the first of length, has 2 double bonds, the first of which is on the 6th carbonwhich is on the 6th carbon

arachidonic = 20:4 n-6arachidonic = 20:4 n-6

What’s in a Name??What’s in a Name??

Fatty Acid NomenclatureFatty Acid Nomenclature

Essential Fatty Essential Fatty AcidsAcids

Only recently determined as essential (1930)Only recently determined as essential (1930) body can synthesize cholesterol, body can synthesize cholesterol,

phospholipidsphospholipids research: same as AA’s but via addition research: same as AA’s but via addition

(EFA’s added improved growth, NEFA’s (EFA’s added improved growth, NEFA’s didn’t)didn’t)

requirement determined by depleting fat requirement determined by depleting fat reserves of subject animal: difficultreserves of subject animal: difficult

Essential Fatty Acids Essential Fatty Acids (fish)(fish)

Most NEAA found in marine food websMost NEAA found in marine food webs Essential fatty acids (to date):Essential fatty acids (to date):

– linoleiclinoleic (18:2 n-6; terrestrials; fish - not really) (18:2 n-6; terrestrials; fish - not really)– linoleniclinolenic (18:3 n-3; terrestrials; fish) (18:3 n-3; terrestrials; fish)– arachidonic arachidonic (20:4 n-6; marine maybe)(20:4 n-6; marine maybe)– eicosopentaenoiceicosopentaenoic acid (20:5 n-3, marine) acid (20:5 n-3, marine)– docosohexaenoicdocosohexaenoic (22:6 n-3, marine) (22:6 n-3, marine)

Why? Because elongation beyond 18 carbons is Why? Because elongation beyond 18 carbons is very difficult in marine fish (lack pathways)very difficult in marine fish (lack pathways)

actual EFA requirement is a matter of whether the actual EFA requirement is a matter of whether the fish is FW/SW or WW/CWfish is FW/SW or WW/CW

Essential Fatty Acids (most Essential Fatty Acids (most animals)animals)

salmonids need n-3 FA’s for membrane salmonids need n-3 FA’s for membrane flexibility in cold water (why does this work?)flexibility in cold water (why does this work?)

trout can elongate and desaturate n-3 FA’s trout can elongate and desaturate n-3 FA’s Linoleic acid (18:2 n-6) is the most essentialLinoleic acid (18:2 n-6) is the most essential addition of arachidonic is also helpful in addition of arachidonic is also helpful in

deficient diets, but can be synthesized from deficient diets, but can be synthesized from linoleic (maybe sparing effect)linoleic (maybe sparing effect)

EFA’s, like EAA’s, must be dietaryEFA’s, like EAA’s, must be dietary

Essential Fatty Essential Fatty AcidsAcids

LINOLEIC CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH

18:2 n-6

LINOLENIC CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH

18:3 n-3

EICOSOPENTAENOIC ACID

CH3CH2CH=CHCH2CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)3COOH

20:5 n-3

DOCOSOHEXAENOIC ACID - YOU CAN DO THIS ONE!

Lipids as Crustacean Energy Lipids as Crustacean Energy SourcesSources

Largely, n-6 FA’s (linoleic) used for energyLargely, n-6 FA’s (linoleic) used for energy as temperature drops, requirement for as temperature drops, requirement for

monounsaturated and PUFA’s increasesmonounsaturated and PUFA’s increases change in temperature = change in dietchange in temperature = change in diet cold water species = increased dietary cold water species = increased dietary

HUFA’sHUFA’s maturation animals: increased maturation animals: increased

requirement for 20:4 n-6, 20:5 n-3 and requirement for 20:4 n-6, 20:5 n-3 and 22:6 n-3 for proper spawning22:6 n-3 for proper spawning

Part 2: Carbohydrate Part 2: Carbohydrate CharacteristicsCharacteristics

From: Lovell; D’Abramo et al. From: Lovell; D’Abramo et al.

General CommentsGeneral Comments

Carbohydrates often written as “COH”Carbohydrates often written as “COH” much of what we need to know about much of what we need to know about

them, besides their structure, was them, besides their structure, was covered in “Bioenergetics, Parts 1&2”covered in “Bioenergetics, Parts 1&2”

here, we cover structurehere, we cover structure

Carbohydrate StructureCarbohydrate Structure

Basic chemical structure consists Basic chemical structure consists of sugar unitsof sugar units

found as aldehydes or ketones found as aldehydes or ketones derived from polyhydric alcoholsderived from polyhydric alcohols

contain: C, H, Ocontain: C, H, O often shown as aliphatic or linear often shown as aliphatic or linear

structures, but exist in nature as structures, but exist in nature as ringed structuresringed structures

Glucose StructureGlucose Structure

O

C-H

H- C-OH

HO-C-H

H-C-OH

H-C-OH

CH2OH

CH2OH

OH

HO

OH

H

H

OH

H

OH

Haworth perspective

Carbohydrate Carbohydrate ClassificationClassification

Usually by the number of sugar units in the Usually by the number of sugar units in the molecule:molecule:– monosaccharidesmonosaccharides (glucose) (glucose)– disaccharidesdisaccharides (2 units) (2 units)

maltose (2 glucose units)maltose (2 glucose units) sucrose (glucose + fructose)sucrose (glucose + fructose)

– polysaccharidespolysaccharides (long chain polymers of (long chain polymers of monosaccharidesmonosaccharides

– most important polysaccharides to most important polysaccharides to animals are starch and celluloseanimals are starch and cellulose

Starch Starch and and CelluloseCelluloseCH2OH

OH

OH

H

H

OH

H

CH2OH

OH

OH

H

H

OH

H

OO O

CH2OH

OH

OH

H

H

OH

CH2OH

O

OH

H

H

OH

H

OO

H

H

O

starch

cellulose

Starch and CelluloseStarch and Cellulose Starch contains Starch contains -D-glucose linkage-D-glucose linkage Cellulose has a Cellulose has a -D-glucose linkage-D-glucose linkage we store starch in muscle tissues as we store starch in muscle tissues as

glycogenglycogen, peeled off by enzymes when , peeled off by enzymes when neededneeded

cellulose is primary component of plant cellulose is primary component of plant tissue, largely indigestible to tissue, largely indigestible to monogastricsmonogastrics

must have enzyme, “must have enzyme, “cellulasecellulase””