This document summarizes a lecture on lipids and carbohydrates given by Dr. Arunima Karkun. It discusses the characteristics and classes of lipids, including their roles as energy sources and structural components. Specific fatty acids are identified, and the differences between saturated and unsaturated fatty acids are explained. The multi-step process of lipid digestion and absorption is outlined. Factors that influence the absorption of lipids are also reviewed. Finally, essential fatty acids and their importance for animals and crustaceans are described.

1. Lecture onLecture on LipidsLipids andand
CarbohydratesCarbohydrates
BY:-BY:-
Dr. Arunima KarkunDr. Arunima Karkun
Asst. ProfessorAsst. Professor
GDRCSTGDRCST

2. Part 1: LipidPart 1: Lipid
CharacteristicsCharacteristics
LipidLipid = a compound that is insoluble in= a compound that is insoluble in
water, but soluble in an organic solventwater, but soluble in an organic solvent
(e.g., ether, benzene, acetone,(e.g., ether, benzene, acetone,
chloroform)chloroform)
““lipid” is synonymous with “fat”, but alsolipid” is synonymous with “fat”, but also
includes phospholipids, sterols, etc.includes phospholipids, sterols, etc.
chemical structure: glycerol + fattychemical structure: glycerol + fatty
acidsacids

3. Lipid MoleculeLipid Molecule

4. Nutritional Uses of LipidsNutritional Uses of Lipids
We already know that lipids are concentrated sourcesWe already know that lipids are concentrated sources
of energy (9.45 kcal/g)of energy (9.45 kcal/g)
other functions:other functions:
1) provide means whereby fat-soluble nutrients (e.g.,1) provide means whereby fat-soluble nutrients (e.g.,
sterols, vitamins) can be absorbed by the bodysterols, vitamins) can be absorbed by the body
2) structural element of cell, subcellular components2) structural element of cell, subcellular components
3) components of hormones and precursors for3) components of hormones and precursors for
prostaglandin synthesisprostaglandin synthesis

5. Lipid ClassesLipid Classes
simplesimple:: FA’s esterified with glycerolFA’s esterified with glycerol
compoundcompound:: same as simple, but with othersame as simple, but with other
compounds also attachedcompounds also attached
phospholipidsphospholipids:: fats containing phosphoric acidfats containing phosphoric acid
and nitrogen (lecithin)and nitrogen (lecithin)
glycolipidsglycolipids:: FA’s compounded with CHO, but no NFA’s compounded with CHO, but no N
derivedderived lipidslipids:: substances from the above derivedsubstances from the above derived
by hydrolysisby hydrolysis
sterolssterols:: large molecular wt. alcohols found inlarge molecular wt. alcohols found in
nature and combined w/FA’s (e.g., cholesterol)nature and combined w/FA’s (e.g., cholesterol)

6. Saturated vs. Unsaturated Fatty AcidsSaturated vs. Unsaturated Fatty Acids
saturatedsaturated: the SFA’s of a lipid have no double: the SFA’s of a lipid have no double
bonds between carbons in chainbonds between carbons in chain
polyunsaturatedpolyunsaturated : more than one double bond: more than one double bond
in the chainin the chain
most common polyunsaturated fats contain themost common polyunsaturated fats contain the
polyunsaturated fatty acids (PUFAs)polyunsaturated fatty acids (PUFAs) oleicoleic,,
linoleiclinoleic andand linoleniclinolenic acidacid
unsaturated fats have lower melting pointsunsaturated fats have lower melting points
stearic (SFA) melts at 70stearic (SFA) melts at 70oo
C, oleic (PUFA) at 26C, oleic (PUFA) at 26oo
CC

7. Fatty Acids Commonly Found in LipidsFatty Acids Commonly Found in Lipids
Sat. Fatty Acids Formula Melting Point (o
C)
Butyric C4H8O2 Liquid
Palmitic C16H22O2 63
Stearic C18H36O2 70
Unsat. Fatty Acids Formula Melting Point (o
C)
Oleic C18H34O2 Liquid
Linoleic C18H32O2 Liquid
Linolenic C18H30O2 Liquid

8. Saturated vs. Unsaturated FatsSaturated vs. Unsaturated Fats
saturated fats tightly packed, clog arteries assaturated fats tightly packed, clog arteries as
atherosclerosisatherosclerosis
because of double bonds, polyunsaturated fats dobecause of double bonds, polyunsaturated fats do
not pack well -- like building a wall with bricks (sat.)not pack well -- like building a wall with bricks (sat.)
vs. irregular-shaped objects (unsat.)vs. irregular-shaped objects (unsat.)
plant fats are much higher in PUFA’s than animal fatsplant fats are much higher in PUFA’s than animal fats

9. Saturated vs. Unsaturated FA’sSaturated 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.

10. LipidLipid
Digestion/AbsorptionDigestion/Absorption
Fats serve a structural function in cells, as sources ofFats serve a structural function in cells, as sources of
energy, and insulationenergy, and insulation
the poor water solubility of lipids presents a problemthe poor water solubility of lipids presents a problem
for digestion: substrates are not easily accessible tofor digestion: substrates are not easily accessible to
digestive enzymesdigestive enzymes
even if hydrolyzed, the products tend to aggregate toeven if hydrolyzed, the products tend to aggregate to
larger complexes that make poor contact with the celllarger complexes that make poor contact with the cell
surface and aren’t easily absorbedsurface and aren’t easily absorbed
to overcome these problems, changes in the physicalto overcome these problems, changes in the physical
state of lipids are connected to chemical changesstate of lipids are connected to chemical changes
during digestion and absorptionduring digestion and absorption

11. Lipid Digestion/AbsorptionLipid Digestion/Absorption
Five different phases:Five different phases:
hydrolysishydrolysis of triglycerides (TG) to free fatty acidsof triglycerides (TG) to free fatty acids
(FFA) and monoacylglycerols(FFA) and monoacylglycerols
solubilizationsolubilization of FFA and monoacylglycerols byof FFA and monoacylglycerols by
detergents (bile acids) and transportation from thedetergents (bile acids) and transportation from the
intestinal lumen toward the cell surfaceintestinal lumen toward the cell surface
uptakeuptake of FFA and monoacylglycerols into the cell andof FFA and monoacylglycerols into the cell and
resynthesis to triglycerideresynthesis to triglyceride
packagingpackaging of TG’s into chylomicronsof TG’s into chylomicrons
exocytosisexocytosis of chylomicrons into lymphof chylomicrons into lymph

12. Enzymes Involved in DigestionEnzymes Involved in Digestion
of Lipidsof Lipids
lingual lipaselingual lipase: provides a stable interface with: provides a stable interface with
aqueous environment of stomachaqueous environment of stomach
pancreatic lipasepancreatic lipase: major enzyme affecting: major enzyme affecting
triglyceride hydrolysistriglyceride hydrolysis
colipasecolipase: protein anchoring lipase to the lipid: protein anchoring lipase to the lipid
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, activated: cleave phospholipids, activated
by trypsinby trypsin

13. What about Bile???What about Bile???
These areThese are biological detergentsbiological detergents synthesized by the liversynthesized by the liver
and secreted into the intestineand secreted into the intestine
they form the spherical structures (they form the spherical structures (micellesmicelles) assisting in) assisting in
absorptionabsorption
hydrophobic portion (tails of FA) are located to the inside ofhydrophobic portion (tails of FA) are located to the inside of
the micelle, with heads (hydrophillic portion) to the outsidethe micelle, with heads (hydrophillic portion) to the outside
they move lipids from the intestinal lumen to the cellthey move lipids from the intestinal lumen to the cell
surfacesurface
absorption is by diffusion (complete for FA andabsorption is by diffusion (complete for FA and
monoglycerides, less for others)monoglycerides, less for others)

14. 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 agentsemulsifying 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) at double(rancidification (rot) at double
bond)bond)
optimaloptimal dietary calciumdietary calcium = optimal FA absorption (high Ca == optimal FA absorption (high Ca =
 absorption)absorption)

15. Lipid Metabolism/AbsorptionLipid Metabolism/Absorption
short chain FA’s are absorbed and enter the portalshort chain FA’s are absorbed and enter the portal
vein to the livervein to the liver
those FA’s with more than 10 carbons arethose 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 andthey are then converted into chylomicrons and
pass to the lymphatic systempass to the lymphatic system
some FA’s entering the liver are oxidized forsome FA’s entering the liver are oxidized for
energy, others storedenergy, others stored
blood lipids: 45% P-lipids, 35% triglycerides, 15%blood lipids: 45% P-lipids, 35% triglycerides, 15%
cholestrol esters, 5% free FA’scholestrol esters, 5% free FA’s

16. LipidLipid
Digestion/Digestion/
AbsorptionAbsorption

17. LipidLipid
Digestion/Digestion/
AbsorptionAbsorption

18. Characteristics of FatCharacteristics of Fat
StorageStorage
Most of the body’s energy stores areMost of the body’s energy stores are
triglyceridestriglycerides
storage is in adipose, source is dietarystorage is in adipose, source is dietary
or anabolism (synthesis) from COH oror anabolism (synthesis) from COH or
AA carbon skeletonsAA carbon skeletons
remember obesity?remember obesity?
adipose can remove FA’s from theadipose can remove FA’s from the
blood and enzymes can put them backblood and enzymes can put them back

19. Fatty AcidFatty Acid
NomenclatureNomenclature
Nomenclature reflects location of doubleNomenclature reflects location of double
bondsbonds
also used are common names (e.g., oleic,also used are common names (e.g., oleic,
stearic, palmitic)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 length,this means the FA is 18 carbons in length,
has 2 double bonds, the first of which is onhas 2 double bonds, the first of which is on
the 6th carbonthe 6th carbon
arachidonic = 20:4 n-6arachidonic = 20:4 n-6

20. What’s in a Name??What’s in a Name??
Fatty Acid NomenclatureFatty Acid Nomenclature

21. Essential Fatty AcidsEssential Fatty Acids
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 additionresearch: 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 fatrequirement determined by depleting fat
reserves of subject animal: difficultreserves of subject animal: difficult

22. Essential Fatty AcidsEssential 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)
– arachidonicarachidonic (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 veryWhy? Because elongation beyond 18 carbons is very
difficult in marine fish (lack pathways)difficult in marine fish (lack pathways)
actual EFA requirement is a matter of whether the fish isactual EFA requirement is a matter of whether the fish is
FW/SW or WW/CWFW/SW or WW/CW

23. Essential Fatty Acids (mostEssential Fatty Acids (most
animals)animals)
salmonids need n-3 FA’s for membranesalmonids 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’strout 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 inaddition of arachidonic is also helpful in
deficient diets, but can be synthesized fromdeficient 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

24. Essential Fatty AcidsEssential Fatty Acids
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!

25. Lipids as Crustacean EnergyLipids 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 foras 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 HUFA’scold water species = increased dietary HUFA’s
maturation animals: increased requirement formaturation animals: increased requirement for
20:4 n-6, 20:5 n-3 and 22:6 n-3 for proper20:4 n-6, 20:5 n-3 and 22:6 n-3 for proper
spawningspawning

26. Part 2: CarbohydratePart 2: Carbohydrate
CharacteristicsCharacteristics
From: Lovell; D’Abramo et al.From: Lovell; D’Abramo et al.

27. General CommentsGeneral Comments
Carbohydrates often written as “COH”Carbohydrates often written as “COH”
much of what we need to know aboutmuch of what we need to know about
them, besides their structure, wasthem, besides their structure, was
covered in “Bioenergetics, Parts 1&2”covered in “Bioenergetics, Parts 1&2”
here, we cover structurehere, we cover structure

28. Carbohydrate StructureCarbohydrate Structure
Basic chemical structure consists ofBasic chemical structure consists of
sugar unitssugar units
found as aldehydes or ketones derivedfound as aldehydes or ketones derived
from polyhydric alcoholsfrom polyhydric alcohols
contain: C, H, Ocontain: C, H, O
often shown as aliphatic or linearoften shown as aliphatic or linear
structures, but exist in nature as ringedstructures, but exist in nature as ringed
structuresstructures

29. Glucose StructureGlucose Structure
O
C-H
H- C-OH
HO-C-H
H-C-OH
H-C-OH
CH2OH
CH2OH
O
H
HO
OH
H
H
OH
H
OH
Haworth perspective

30. Carbohydrate ClassificationCarbohydrate Classification
Usually by the number of sugar units in theUsually 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 animals aremost important polysaccharides to animals are
starch and cellulosestarch and cellulose

31. StarchStarch andand CelluloseCellulose
CH2OH
O
H
OH
H
H
OH
H
CH2OH
O
H
OH
H
H
OH
H
OO O
CH2OH
O
H
OH
H
H
OH
CH2OH
O
OH
H
H
OH
H
O
O
H
H
O
starch
cellulose

32. Starch and CelluloseStarch and Cellulose
Starch containsStarch contains αα-D-glucose linkage-D-glucose linkage
Cellulose has aCellulose has a ββ-D-glucose linkage-D-glucose linkage
we store starch in muscle tissues aswe store starch in muscle tissues as
glycogenglycogen, peeled off by enzymes when, peeled off by enzymes when
neededneeded
cellulose is primary component of plantcellulose is primary component of plant
tissue, largely indigestible to monogastricstissue, largely indigestible to monogastrics
must have enzyme, “must have enzyme, “cellulasecellulase””