Module 4- Lipid Digestion Flashcards
T or F: lipids are soluble in organic solvents such as ether & chloroform
T
what are the 2 most important energy sources in the diet?
lipids & carbs
phospholipids allow the cell membrane to be
selectively permeable
what are the 4 fat soluble vitamins?
ADEK
lipids are substrates for
cholesterol
cholesterol is important in the formation of ( ) hormones
sex
3 components of lipids
C, H, O2
why do lipids have more oxygen
required for oxidation for energy production
what is the simplest lipid
fatty acid
what is the simplest carb
glucose
fatty acids are ( ) to make energy
oxidized
what are the 3 types of simple lipids
1) fatty acids
2) tri, di & monoglycerols
waxes
sterol vs non-sterol wax ester
sterol: precursors for corticosteroids
non-sterol: functional
T or F: waxes do not provide energy but they are functional
T
lipoproteins & their functions (2)
lipids conjugated to a protein
- lipid absorption in small intestine & transport into bloodstream
what are the 2 ends of a fatty acid & what property do they each give the fatty acid?
1) methyl -> CH3
- hydrophillic: attracts water
2) carboxylic -> COOH
- hydrophobic: repels water
saturated vs unsaturated FA
saturated: no C-C double bonds
unsaturated: 1 or more C-C double bond
acetic acid
CH3COOH
cis vs trans
cis: H on same side of C-C double bond
trans: H on different sides of C-C double bonds
trans fatty acids are a result of ( ) of cis fatty acids
microbial fermentation
the presence of a C-C double bond means the fatty acid will be
kinked, not linear
naturally occurring fatty acids are in the ( ) configuration
cis
fatty acids that have more than 1 C-C double bond will always be separated by ( ) carbon atoms
3
C 16: 0
palmitic acid
C 18: 0
stearic acid
C18: 1
oleic acid
C18: 3
alpha linoleic acid
C18: 2
linoleic acid
2 essential fatty acids
1) linoleic acid = C18: 2 delta 9,12
2) a-linoleic acid = C18: 3 delta 9,12,15
what 2 desaturase enzymes do animals lack?
delta 12 & delta 15
what desaturase enzyme do animals have?
delta 9
desaturase enzyme function
inserts a C-C double bond into C9 starting from COOH end
T or F: plants can synthesize both essential FA so animals on plant diet get both
T
3 symptoms of FA deficiency
1) retarded growth
2) reproductive failure
3) necrosis of tail
what 2 beneficial effects do omega 3 fatty acids have on human health?
1) brain development
2) anti-carcinogenic effects
what omega FA is linked to negative health impacts?
omega 6
what ratio of omega 3 : omega 6 fatty acids reduce negative health impacts?
4:1
T or F: lipid content is most plants is relatively high
F
major form of lipid storage in plants
triglycerides
ideal lipid % in animal feeds
2-3%
silages have (%) lipids
2-4
T or F: oil seed lipid content is very high
T
as animals get older, water ( ) and fat ( )
decreases, increases
why will dry cows have a higher adipose tissue reserve compared to lactating animals?
b/c they mobilize adipose tissue during early lactation to support milk production
what are the structural lipids in an animal?
phospholipids
T or F: storage lipids are variable, not constant
T
list 3 major functions of FA in the body?
1) insulation
2) component of steroid hormones
3) fat soluble vitamin absorption
2 types/components of lipids
1) fats-> solid at room temp
2) oils -> liquid at room temp
difference between fats & oils
chain length & degree of saturation
lipids composed of longer chain FA / saturated are ( ) while lipids composed of short chain FA / are unsaturated are ( ) at room temperature
long- solid = fat
short= liquid = oil
triglyceride structure
glycerol backbone with 3 FA attached in an ester linkage
T or F: the FA attached in a triglyceride can be all the same or different
T
what happens to a triglyceride during lipid digestion?
lipase breaks ester linkage to release 3 free FA
monoglyceride
1 FA is attached to glycerol backbone
phospholipids heads are ( ) while tails are ( )
hydrophillic, hydrophobic
2 reasons why phospholipids are important for cell membranes
1) provide structure
2) give it selective permeability
cell membrane is composed of a
bilayer of phospholipids
why are phospholipids soluble in aqueous environments?
bc hydrophilic ends are in contact with aqueous environment inside & outside the cell
lipoproteins have a hydro( ) core
hydrophobic
glycolipids contain a ( ) component in their structure
- list an example
carbohydrate such as glucose or galactose
2 important glycolipids
cerebrosides & gangliosides
what feed source is rich in glycolipids?
grasses
what 2 forms can cholesterol exist in?
1) free form
2) cholesterol ester
cholesterol is made of a ( ) ring structure
4
cholesterol ester function
synthesis of a variety of compounds
bile acids functions
digestion of lipids
building block of bile acids
cholesterol
what is the active form of vitamin D
vitamin D3
how are fat soluble vitamins absorbed?
absorbed in micelles
primary triglyceride
C18: 2
T or F: phospholipids are high in ruminal bacteria
T
short, medium & long chain FA lengths
short: 0-8 carbons
med: 10-16 carbons
long: 18+ carbons
animal based lipid supplements contain ( ) fats while plant based lipid supplements contain ( ) fats
saturated, unsaturated
digestibility of fats and oils is affected by what 2 factors
1) degree of saturation
2) chain length
longer FA chain lengths ( ) digestibility
increases
what type of lipids are most digestible?
unsaturated
why are saturated lipids less digestible than unsaturated?
saturated FA are packed tightly due to kinks = less surface area = less area for enzymes to penetrate = less digestible
lipids are added to livestock diets in what form?
oil seeds
3 reasons for adding lipids to livestock diets
1) increase palatability
2) alleviate heat stress
3) dust control
why would feed intake be greater with higher fat content?
bc fat increases palatability
T or F: supplementation of lipids in the diet improves absorption of fat soluble vitamins
T
why are essential FA essential?
animals do not have enzymes to synthesis delta 12 & 15
T or F: lipids increase biosynthesis of steroid hormones
T
90% of lipids in diets fed to livestock are in the form of
triglycerides
total dietary lipid content is (%) in monogastric diets after supplemental lipids are added
6-7%
primary location of lipid digestion in monogastrics
small intestine
serous gland
secretes lingual lipase
gastric lipase is secreted by
chief cells in stomach wall
one major difference between salivary amylase and lingual lipase
salivary amylase is completely digested once it gets to the stomach but lingual lipase is not
emlusification
break large fat globules into fat droplets
where does most emulsification take place in monogastrics
duodenum
what organ initiates emulsification? how?
muscular contractions of stomach wall break them into fat droplets
major substrate for lipid digestion in monogastrics
triglycerides
what 2 things are flowing out of monogastric stomach during lipid digestion?
1) intact triglycerides
2) small amounts of di & monoglycerides
reason for emlusification
increases surface area for enzyme activity
why do oil & water not mix?
fat globules are hydrophobic = limits enzyme penetration
where are micelles produced vs stored?
produced: liver
stored: gallbladder
how are micelles reabsorbed?
through the ileum
pancreatic lipase function
digests triglycerides
where is co-lipase produced? what is its function?
produced by pancreas
removes bile salts attached to fat droplets to allow lipase to attach & start digesting the lipid
end products of triglycerides
- NEFA
- small amounts of mono & diglycerides
T or F: there is complete removal of all 3 FA after triglycerides are digested in monogastrics
F
product of phospholipase
lipophospholipids
lipophospholipids
phosphate group + 3 FA
cholesterol esterase function & products (2)
digests cholesterol esters
free cholesterol & FA
core of micelle is made of what 4 things?
1) NEFA
2) monoglycerides
3) cholesterol
4) lipophospholipids
T or F: mixed micelles are absorbed
F
where does re-synthesis of TG occur?
endoplasmic reticulum
what does the disintegration of micelles release?
end products of lipid digestion which will be absorbed
chylomicron function
allows micelle to migrate towards cell membrane & allow access into lymphatic system through exocytosis
why is the outside of a chylomicron made of phospholipids?
their hydrophillic ends allow it to interact with aqueous environment in bloodstream
chylomicron functions (2)
- facilitate absorption of lipids of feed origin
- transport lipids into bloodstream
lipoprotein function
transport endogenous lipids that are packaged into VLDLs, LDLs, HDL, etc
endogenous lipids
lipids synthesized in liver, skeletal muscle & adipose tissue
short chain vs long chain FA absorption
short: absorbed directly into portal system -> liver
long: absorbed into lymphatic system -> peripheral tissues -> thoracic duct
2 mechanisms of FA absorption
1) passive diffusion
2) facilitated diffusion
facilitated diffusion of FA uses what transporter?
FATP -> fatty acid transport protein
how many FATPs are there?
4
T or F: absorption of lipids is an energy-independent mechanism
T
T or F: glycerol is not used in adipose tissue, it goes to the bloodstream instead
T
fatty acyl-Coa is activated in the ( ), then transported into ( ) for ( )
cytosol, mitochondria matrix, oxidation
2 ATP =( ) AMP
1
beta oxidation of oleic acid
releases acetyl CoA so it can enter TCA cycle
most FA have an (even/odd) number of carbon atoms for beta oxidation
even
how many cycles of beta oxidation does palmitic acid go through? how many acyl CoA are produced?
8, 8
2 examples of when overproduction of acyl CoA can occur?
1) early lactation
2) keto diet
what happens with excessive catabolism of adipose tissue?
acyl CoA is used to make ketones bc it exceeded capacity of TCA cycle
3 ketone bodies
1) acetone
2) b-hydroxybutyrate
3) acetoacetate
what are products of triglycerides used for?
beta oxidation to produce ATP
what is the 1st important step in the synthesis of FA?
malonyl CoA
what is malonyl CoA important for?
milk synthesis in mammary gland
T or F: there is complete degradation of TG into glycerol + 3 FA in ruminants
T
saturated vs unsaturated FA in rumen
saturated: no transformation, go to small intestine
unsaturated: undergo transformation through biohydrogenation to convert to saturated FA
biohydrogenation
conversion of unsaturated FA to saturated by adding 2 H
glycolipid digestion in rumen
instantaneously fermented to produce VFAs
T or F: rumen bugs can synthesis sufficient lipids
T
what lipids do rumen bugs mostly synthesize?
microbial phospholipids
T or F: very little unsaturated FA in diet end up in small intestine
T
why do very little unsaturated FA in ruminant diets make it to the small intestine?
b/c most are biodehydrogenated due to activity of microorganisms
T or F: FA composition in a pig reflects very closely to the FA composition of the diet, but this does not occur in ruminants
T
how does biohydrogenation alter methanogenesis?
reduces methane production bc it is using up H ions in rumen instead of them going towards supporting methane production
how to reduce methane production in the diet using lipids?
feed diet high in unsaturated FA
T or F: more unsaturated FAs will be in the small intestine than what the ruminant actually consumed
T
why will more unsaturated FAs be in the small intestine than in the feed?
b/c of biohydrogenation
2 intermediates of biohydrogenation under normal conditions
1) cis-9 trans 11 C18: 2
2) trans-11 C18:1
what causes the biohydrogenation pathway to change?
high amounts of linoleic acids
2 intermediates formed by the altered biohydrogenation pathway
1) trans 10 cis 12 CLA
2) trans 10 C 18:1
anti-lipogenic
suppress lipogenesis in adipose tissue/mammary gland = milk fat depression
what are the 2 anti-lipogenic intermediates of biohydrogenation
1) trans 10 cis 12 CLA
2) trans 10 C18:1
beneficial effects of cis 9 trans 11
1) reduce blood pressure
2) reduce cancer
3) improve heart health
most important animal product source of cis 9 trans 11 for human consumption
milk
what animal products have a high level of CLA?
bovine products
total fat in ruminant diets should be (%)
6-7
4 impacts of too much fat in ruminant diet
1) reduced fiber digestion
2) lower production of VFA
3) reduced DMI & milk yield
4) milk fat depression
what 4 things are a mixed micelle composed of
1) free fA
2) monoglycerides
3) diglycerides
4) cholesterol
order of lipid digestion in small intestine (4)
1) bile salts
2) co-lipase
3) pancreatic lipase
4) micelles
what do micelles transport
microvilli
why is fiber digestion decreased with a high fat diet
microbial enzymes cannot access feed due to lipid layer around feed particles
T or F: unsaturated FA are toxic to protozoa
T
a decrease in protozoa = ( ) in fiber digestion
decrease
high fat diet reduces what ratio of VFAs? why?
acetate : propionate
- less acetate due to less fiber
T or F: small intestine lipid absorption is the same in ruminants & monogastrics
T
