Ch 5: Lipids Flashcards
chem structure of fatty acids
organic acid
C chains w H attached
- carboxylic acid group
- methyl group
fatty acid chain length
even # of C 18-C is most abundant found in food Long 12-24 C Medium 6-10 C Short less than 6 C
degree of unsaturation of fatty acids
amt of double bonds present
unsaturated fatty acids
monounsaturated- 1 double bond (point of unsaturation)
polyunsaturated- 2+ double bonds
saturated fatty acids
no double bonds b/w carbons
naming polyunsaturated fatty acids
- from first unit of unsaturation from methyl end
- omega number for monounsaturated FAs
triglycerides chemical structure
glycerol backbone w 3 fatty acids
- very few fatty acids are free in the body, most are part of triglycerides
how are triglycerides formed?
condensation reactions
- produce water from H and hydroxyl (OH-)
factors contributing to functional properties of triglycerides
chain length
degree of saturation
position of double bonds
properties of saturated triglycerides ex
the more saturated TG, the more solid at room temp it is
ex. animal fat
coconut and palm oil structures
firmer than most veg oils but still softer than animals fats
- bc of shorter chain length
8-14C
palm oil almost 50/50 saturated to polyunsaturated
shorter chain length = ?
softer at room temp
saturation of triglycerides provides __?
stability
unsaturated fatty acids oxidize more easily, causes spoiling
– manufactures place their products in air tight containers, add antioxidants, or hydrogenate their products to prevent spoiling
hydrogenation
H atoms added to unsaturated fatty acids
- makes liquid fat more solid at room temp.
- increases the shelf life of food
Trans - fatty acids
from partially hydrogenated, rather than completely hydrogenated fatty acids
- behave like saturated fats in the body
- cis bonds are not as negative healthwise as trans fatty acids
Phospholipids
plus ex.
act as emulsifier
- fatty acid portion makes fat soluble
- phosphate portion makes water soluble
ex. our cell membranes, allows water & fat soluble vit & hormones to pass through
ex 2. lipoproteins in our blood, transport fats through bloodstream
emulsifier
- a substance w both water-soluble and fat-soluble portions
- promotes the mixing of oils and fats in watery solutions
Lecithin
supplementation is problematic bc our liver makes all the lecithin that we need, therefore it is not an essential nutrient
micelle
emulsified fat
sterols
have multi ring structure
ex. cholesterol
cholesterol
- from animal prod. only
- made by liver, 800-1500mg/day
- used to make bile acids, sex and adrenal hormones, vitD
- procides structural support for our cell membranes
plant sterols
shown to decrease cholesterol levels and inhibit cholesterol absorption
- thus has been added to food such as margarine in an effort to decrease blood cholesterol
emulsification of fat
occurs in sm intestine
bile emulsifies fat, breaks down into fat droplets (micelles) that repel one another
enterophatic circulation
bile in GI tract has 2 possible fates:
- reabsorbed by sm intestine and sent back to liver to be recycled
- excreted (absorbed by soluble fibres) , may lower cholesterol levels
lipid digestion in the mouth
- body temp causes fat to become more fluid
- salivary glands produce lingual lipase that hydrolyzes fats
lipid digestion in the stomach
constant churning muscular action of stomach causes fats to be dispersed into smaller fat droplets to be exposed to gastric lipase
lipid digestion in small intestine
- when fat enters, it stimulates the release of cholecystokinin (CCK) which causes the gallbladder to release bile
- bile acids pair up w amino acids to emulsify fat
- amino end attracts water and sterol end attracts fat, this draws fat into lumen (water-based) and allows pancreatic and intestinal lipases to further digest fat droplets
end products of lipid digestion
- monoglycerides
- some fatty acids
- very little glycerol
triglyceride digestion
- pancreatic and intestinal lipases hydrolyze each fatty acid on the TG
gives 2 free fatty acids and a monoglyceride
phospholipid digestion
2 fatty acids and a phospholipid component are absorbed
sterol digestion
- absorbed as is
EXCEPT when fatty acid is attached then is need to be hydrolyzed first and both components can be absorbed
lipid transport
by way of lipoproteins, 4 types: chylomicrons Very Low Density Lipoprotein Low Density Lipoprotein High Density Lipoprotein
Absorption of lipids
the larger the molecule, the harder it is to absorb
- monoglycerides and long chain fatty acids are broken down by bile into micelles to be able to diffuse easily across cell membrane
lipoproetin lipase
- enzyme activated in response to insulin
- hydrolyzes triglycerides, allowing components to move into cell
- located on an endothelial cell lining capillaries around adipose, muscle and heart
chylomicrons
- largest, least dense
- transport diet-derived lipids to the body for immediate use
- as tissues (muscle, adipose) remove triglycerides, chylomicron becomes known as chylomicron remnant (now smaller and more dense)
- liver collects remnants, breaks down and recycles
VLDL
- made from chylomicron remnants
- travel in blood to tissues where they lose TG (deliver to body tissues)
- as lipids are removed from VLDL, it becomes dense and full of cholesterol, smaller = LDL
LDL
transport cholesterol to body cells or returns to liver to be removed from circulation
- (bad) cholesterol
HDL
- smallest, most dense
- formed by liver cells, pick up cholesterol from the body cells and brings it back to the liver for excretion
- anti-inflammatory properties
- (good) cholesterol
inflammation
fat that has oxidized,
oxidized fat sticks better to artery walls
factors that lower LDL/raise HDL
- weight control
- mono- or polyunsaturated fats in diet rather than saturated
- soluble dietary fibres
- phytochemicals
- moderate alcohol consumption
- physical activity
- medication can lower LDL but does not increase HDL
health effects of lipids
hint: think cholesterol
heart disease
- major risk factor is elevated blood cholesterol
- this is bc it accumulates in arteries, restricts bloodflow and can lead to heart attack or stroke
- over 40% of canadians ages 20-75 have unhealthy blood cholesterol levels
the process of atherosclerosis
see notes this is quite a lot
RDA and UL for fat
no RDA or UL for fat
- the general public does not know the difference bw good and bad fats, risks restricting good fats
role of triglycerides in the body
provide energy (9kcal/g)
unlimited storage form of energy
Adipose tissue:
- stores fat, serve as insulation, shock absorption, cell membrane structures, secrets hormones
adipokines: regulate energy balance, feelings of satiety
essential fatty acids in the body
linoleic acid - omega 6
linolenic acid - omega 3
eicosanoids - made from n-6 and n-3
linoleic acid
omega 6
component of membrane phospholipids
make arachidonic acid
linolenic acid
omega 3
component of membrane phospholipids
make EPA and DHA
eicosanoids
- made from n-6 and n-3
- hormone like inflammatory mediating compounds
- if made w n-6 are inflammatory, n-3 are anti-inflammatory
olive oil
positive impacts on vascular system, healthy arteries
- in countries where olive oil consumption in increased they have lower BP, lower rates of heart disease, lower LDL oxidation, etc
nuts
- energy dense, high in fat, healthy fat
- mono and polyunsaturated fats
- fibre, protein and more stuff
- contain plant sterols
- phytochemicals that act as antioxidants
the Mediterranean diet
lowers risk of developing chronic diseases
- high in fat but lower in saturated and trans fats
- rich in monounsaturated fat
- rich in complex CHO and fibre
- nutrients and phytochemicals from fresh fruits, veg
fish
contain EPA and DHA (long chain fats) that benefit heart
- reduce blood TG
- prevent blood clots
- decrease BP
- defend against inflammation
our high omega 6/ omega 3 ratio
not good, bc they compete for the same biosynthetic enzymes and we consume a lot more omega 6
- high consumption of omega 6 (meats) leads to obesity
- should increase omega 3 consumption (oils like flax, chia) and oils high in monounsaturated fats (olive, sunflower)
insulin
released from beta cells of pancreas
- causes glucose from the blood and moves it into cells or skeletal muscle
glucagon
released when the glucose is gone
released from the alpha cells of the pancreas
- causes glucose to be released from cells of the liver into the blood
