week 5 lipids Flashcards
what are the good lipids
unsaturated
what are the bad lipids
saturated
the very bad lipids
trans
functions
-energy, 9kcal/g. takes less energy to store and holds less water than carbohydrates
-makes up the lipid bilayer in cell membrane
- protection ans insulation
-adds taste, texture and smell to food
-aids in satiety -convert to other molecules needed by the body
-carries and stores soluble vitamins
- myelin sheath is made out of fat
the fatty acid structure
the basic building block of a lipid is called a fatty acid
- made of carbon, hydrogen and oxygen
the chemistry of lipids
the structure resembles the letter E, with one glycerol and 3 fatty acid chains attached
- FAs can be 4-24 carbons long , 18 C are most common
- can be saturated or unsaturated
unsaturated fatty acids
- a carbon-carbon double bond is a point of unsaturation. Fatty acids that have a double bond are unsaturated fatty acids
- theses cab be monounsaturated or polyunsaturated
location of the =
- identified by the position of the double bond nearest the methyl end, which is described by an omega number
- first = 3 carbon away from the methyl end us an omega 3fatty acid
naming fatty acids
short chain < 6C
medium chain6-12C
Long Chain > 12C
degree of saturation
the degree of saturation influences the firmness of fats at room temp
- the shorter the chain, the softer the fat is at room temperature
-butter = saturated = solid at room temp
- olive oil = unsaturated = liquid at room temp
saturated (health)
solid at room temperature, can stick to artery walls
-found mostly in animal products
- generally less healthy
unsaturated (health)
liquid at room temp
found mostly in plant foods
generally more healthy
stability
saturation influences stability, all fats spoil when exposed to oxygen
- poly unsaturated fats spoil faster due to unstable double bonds
hydrogenation
point of unsaturation are saturation by adding H. protects against oxidation and makes liquids more solid, improving texture of foods
trans fats
most often a fat is partially hydrogenated and some double bonds that remain after processing change from cis to trans
- in nature most double bonds are cis configuration
what are transfats
- made by the process of hydrogenation
- in the body, behave like saturated fats = raise blood cholesterol
- a small amount of trans fats come from natural sources and at current levels of consumption, natural trans fats have little, if any effect on blood lipids
butter
all natural right from cow
tastes great, conjugated linoleic is naturally found, some evidence to help prevent cancer
saturated
MARGARINE
could be hydrogenated or not
- plant fat , unsaturated
doesn’t provide same effect in food products
triglycerides
FAs often occur as free FAs, most often they are incorporated into triglycerides
- lipids composed of 3 FAs attached to a glycerol molecule
-condensation reaction combines a H form from the glycerol and an OH form the fatty acid, forming H2O and a bond between the glycerol and FA
Phospholipids
Lecithin
The most common phospholipid
One glycerol, 2 FAs, one P group with a
molecule of choline
FAs make phospholipids soluble in fat,
while the P group allows them to dissolve
in water
Adds versatility in the food industry
Phospholipids act as emulsifiers to mix
fats with water
Mayo and chocolate bars
Phospholipids
phospholipids in food
Found naturally in eggs, liver, soybeans, wheat germ, peanuts. As
lecithin.
phospholipids role
Major parts of our cell membranes - help vitamins and hormones to
pass in/out of cells, & help keep fats suspended in blood & body fluids
phospholipids in the liver
The liver makes all the lecithin that a person needs. Lecithin
supplements are pointless because the intestine hydrolyzes most of it
before it passes into the tissues. Lecithin is NOT an essential nutrient.
sterol - compounds
multiple ring structure
cholesterol
sterol in food
plant and animal foods contain sterol, but only those from animals contain cholesterol
-plant sterols inhibit cholesterol absorption
sterol roles
bile acid, hormones, vitamin D, cholesterol… cholesterols made in the body and consumed(exogenous). our liver produces and contributes far more cholesterol to the body’s total than our diets
cholesterol
serves as starting material for vitamin D and hormones
-90% of the bodys cholesterol resides in the cells
- DV is 300mg
-structural component of cell membranes
-cannot be used for energy
- can accumulate in artery walls and form plaque leading to atherosclerosis
lipid digestion goal
- goal is to dismantle the triglycerides into monoglycerides, fatty acids and glycerol that the body can use
digestion mouth
hard fats begin to melt as they warm us, lingual begins some fat digestion
digestion stomach
stomach shunning and chyme disperse fat into small droplets expose it to gastic lipase
small intestine digestion
hormone cholecystokinin signals gallbladder to release bile, bile acid are made from cholesterol
where are fats fully digested
in SI as they encounter lipase from the pancreas and SI
bile
-enters small intestine and emulsifies fat
-bile that reaches the large intestine helps control bacterial overgrowth
-most bile is reabsorbed into blood and recycled to liver
- some bile is trapped by dietary fiber= helps reduce blood cholesterol
lipid absorption
-glycerol and SCFA are absorbed directly into bloodstream
-micelles permit solubility in watery digestive fluids and transportation to intestinal cells
- once inside, monoglycerodes and LCFA reform new triglycerides
- monoglycerides and LCFA are emulsified by bile, forming micelles
- lipid contents of micelles diffuse into cells upon arrival
lipid transport
lipoprotein transport fat through the watery bloodstream
- 4 main types of lipoproteins, distinguished by size and density of proteins
- chylomicron
chylomicrons
- largest and least dense
- transport diet derived lipids from SI and are releases into the blood the rest of the body cells remove TGs from chylomicron as they pass, so they get smaller
- once TGs have been depleted proteins receptors remove theses remnants form the blood
VLDL
Very low density lipoproteins
Lipids made in lover and those
from chylomicron remnants are
packaged with proteins as
VLDLs
Cells remove TGs, cholesterol
becomes predominant and they
become LDLs
VLDL
LDL
low density lipoproteins
- circulate and make contents available to the cells of all tissues
- cells use TG, cholesterol, and PL from the LDL for energy to build membrane , make hormones or stores
- LDL receptors on the liver help control blood cholesterol by removing LDL from circulation
HDL
- liver makes theses to remove cholesterol from cells and carry it back to liver
- helps to prevent plague buildup by clearing cholesterol
- also has anti- flammatory properties that keep plaque from breaking apart and causing heart attack
health implication
The blood cholesterol linked to heart
disease is LDL
HDL also carries cholesterol but elevated
HDL represents cholesterol returning
from the body back to the liver for
breakdown and excretion
High LDL and low HDL are associated
with high risk of heart disease
Adequate HDL alongside low LDL reduce
risk of heart disease
what can we do to lower LDL and/or raise HDL
- monounsaturated or polyunsaturated instead of saturated
-soluble dietary fiber
-PA
Roels of TGs
- provide cells w/ energy at 9 kcal
- fat accumulation in non adipose tissue is toxic and impairs health
- when body fat is reduced or excessive, these secretion changes
- fat provides a cushion for bones and organs
- body fat stores have unlimited capacity thanks to adipose tissue
-adipose tissue also secrete severals hormones that regulate the body from temperature extremes - provides structural materical for cell membrane
lipid metabolism as a whole
go to slides
heart disease
elevated LDL is a major risk factor. Cholesterol accumulates in artries, restricting blood flow and raising BP. The more saturated fat in the diet the higher LDL levels
dietary cholesterol
unlike saturated and trans fats, dietary cholesterol only raises blood levels modestly no cleat relationship between dietary cholesterol and heart disease
cancer
relationship between dietart fat and cancer is weak and inconclusive. More evidence likes adipose tissue as a contributor to cancer risk. More evidence for increased risk of cancer from dietart saturated fats
weight
due to fat being 9kcal excessive fat intake can result in exceeding energy needs ans increased adipose storage
recommendation
AMDR = 20-35% of kcal intake
Less than 10% from saturated fat
As little trans fats and dietary
cholesterol as possible
Diets with up to 35% intake from fat
can be compatible with good health
only if energy intake is reasonable
and saturated/trans fat intakes are
low
Health Canada:
