Module 7 Flashcards
What are triglycerides?
- main dietary lipids
- contains a glycerol backbone with three fatty acids attached to it
Are all fatty acids the same?
No, fatty acids can differ in length, degree of saturation and geometric organization
What are saturated fatty acids?
does not contain any double bonds
What are unsaturated fatty acids?
one or more double bonds
monounsaturated fatty acids - one double bond
polyunsaturated fatty acids - more then one double bond
What are essential fatty acids?
polyunsaturated fatty acids with a double bond before the 9th position
body cannot make itself
What are the two essential fatty acids?
omega 3 and omega 6
What is alpha-linolenic acid?
- omega 3 fatty acids
- can be used to synthesize other omega 3 fatty acids DHA and EPA
- found in chia and flax seeds
What is linoleic acid?
- omega 6 fatty acids
- can be used to synthesize another omega 6 fatty acid arachidonic acid
- found in soybeans, corn and vegetable oil
What are eicosanoids?
hormone like molecules that are synthesized from omega 3 and omega 6 fatty acids
What properties do omega 3 fatty acids have?
anti-inflammatory
What properties do omega 6 fatty acids have?
pro-inflammatory
What are the different lengths of fatty acids?
long chain - 14 or more carbon atoms
medium chain - 6-12 carbon atoms
short chain - 2-4 carbon atoms
most fatty acids we consume have 18-22 carbon atoms
What food is categorized in long chain?
animal products, some plant
What food is categorized in medium chain?
tropical oils
What food is categorized in small chain?
bacteria when they ferment indigestible carbs
What is the cis configuration of a fatty acid?
hydrogen are on the same side of the double bond
What is the trans configuration of a fatty acid?
hydrogens are on the opposite of the double bond
What is hydrogenation?
converting cis fatty acids into trans fatty acids
What is the purpose of hydrogenation?
trans fatty acids are more stable therefore have a longer shelf life
but they increase risk of CVD
What are Sterols?
- ring formation made up of a hydrocarbon chain
- can be consumed from both plant and animal
All lipids are what?
hydrophobic
What are some roles of sterols?
cell membrane structure, hormone formation
What is the most common animal-derived sterols?
cholesterol
What is cholesterol?
cell membrane structure, precursor for vitamin D, estrogen and testosterone
Is cholesterol an essential nutrient?
No because liver and other body structures can synthesize cholesterol
What foods are plant-derived sterols found in?
vegetable oils, buts, seeds, fruits
What are plant-derived sterols?
slightly different molecular structure then animal-derived sterols
What happens when we consume plant sterols?
it competes with cholesterol which limits absorption
What are phospholipids?
critical component of the cell membrane, not an essential nutrient
What are the similarities and differences of phospholipids and triglyceride?
similarities - both have fatty acids attached to a glycerol backbone
differences
- triglyceride has three fatty acids while phospholipids have two fatty acids
- triglyceride are entirely hydrophobic while phospholipids only have a hydrophobic tail
What does amphiphilic mean?
hydrophilic head and hydrophobic end
What are the functions of the phospholipid bilayer?
- allows water content inside the cell to be separated with water on the outside
- can act as an emulsifier
- carry lipids around the body
What can pass through the membrane?
water and non polar substances like fats
What are the fat soluble vitamins?
A, D, E, and K
Can triglycerides be absorbed?
Triglycerides cannot be absorbed as ingested but must first be broken into fatty acids and their glycerol backbone
What are the steps of lipid digestion?
- mouth - lingual lipase chemically digests medium and short chain fatty acids, mechanical digestion separates lipids
- stomach - gastric lipase digests medium and short chain fatty acids
- liver - bile is produced and secreted
- gallbladder - bile is stored
- pancreas - secretes pancreatic lipase
- small intestine - majority of lipid digestion, bile emulsifies lipids, pancreatic lipase digests remaining lipase
- large intestine - minimal lipid digestion and absorption
What are the steps of lipid absorption?
- the micelle breaks down and its lipid contents are absorbed into the small intestine cells through passive diffusion
- lipids get wrapped in phospholipids as they exit the small intestine cell and enter the centre of the villus. the resulting structure is called a chylomicron
- chylomicrons are too large to enter the blood instead they enter lacteals
What is the main purpose of a lipoprotein?
to carry lipids around the body
What is required to transport lipids?
lipoprotein molecules
What is the benefit of a hydrophobic nature of lipids?
incapable of dissolving in watery environments of the small intestine lumen, blood and lymph
What happens when there are more lipids in the lipoprotein?
less dense
What is the transport of chylomicron?
small intestine villus –> lymph –> blood –> body cells –> liver
What is the transport of very low density lipoprotien (VLDL)
made in liver –> body cells –> becomes LDL as it losses triglycerides
What is the transport of low density lipoprotein (LDL)
from VLDL –> delivers cholesterol to body cells or returns to the liver or gets deposited in artery walls
What is the transport of high density lipoprotein (HDL)
made in liver –> picks up cholesterol from body cells –> returns it to the liver
What are the steps of Lipoproteins transport and deliver lipids?
- Chylomicrons transport lipids between the small intestine and liver
- They are absorbed into lacteals, one way lymphatic vessels found within the villi
- Once chylomicrons are deposited into the bloodstream from the lymphatic vessels, they circulate through the body dropping off lipids to body tissues
- Remaining chylomicrons end up at the liver
What is the main triglyceride delivery system from the liver?
VLDL
What are the contents of HDL?
high in protein and lower lipid content
How much energy do lipids provide?
9 kcal/gram
What is the main lipid we use for energy?
triglyceride
How does carb diet affect metabolism of triglycerides?
Adequate diet = citric acid cycle
Inadequate = ketones are formed
Where is extra energy stored as lipids?
adipose tissue delivered by chylomicrons
How are fat soluble vitamins transported?
since they are hydrophobic, they require a lipoprotein for their transport and are stored in adipose tissue
What is atherosclerosis?
the narrowing of the artery
What causes atherosclerosis?
fatty materials building up in artery walls narrowing the arteries and restricting blood flow
What are the impacts of trans fatty acids?
increase risk of CVD, ratio of LDL to HDL
What are the impacts of diets that are high in saturated fats?
increase LDL –> increases CVD risk = lipid hypothesis
What are the contents of LDL?
fewer triglycerides and is higher in cholesterol
What are the contents of VLDL?
mainly triglycerides
What are the impacts of diets that are high in polyunsaturated fatty acids?
decrease LDL –> decrease CVD risk
What hormone does essential fatty acids synthesize?
eicosanoids
What are the impacts of diets that are high in cholesterol?
has minimal effect on increasing LDL and CVD risk
the body makes less cholesterol when more is consumed, LDL levels don’t rise
What are the complications of a diet that is high in cholesterol?
25-30% of people are cholesterol hyperresponders meaning their LDL goes up when more is consumed
What are the impacts of diets that are high in plant sterols?
reduce LDL levels by competing with cholesterol for absorption
What are the recommendations for lipids?
- 20-35% of calories come from lipids (higher in children)
- consume lipids from whole sources
- eliminate artificial trans fat, minimizing processed food
- unsaturated fat over saturated fat, more plants then animals
- consume fish, nuts, vegetable oils to get adequate amount of omega 3 and omega 6 fatty acids
What is the path for lipids?
- Chylomicrons are the lipoproteins that deliver triglycerides from the small intestine
- Lipoprotein lipase breaks down triglycerides into fatty acids and glycerols
- The remaining chylomicrons are sent back to the liver
- VLDL is created in the liver and is the main delivery system of triglycerides
- Lipoprotein lipase breaks down triglycerides and is released to cells
- VLDL becomes smaller losing more triglycerides and eventually becomes LDL which is the main delivery system of cholesterol
- Three potential fates of LDL
- LDL is used up by other cells
- LDL returns to the liver
- LDL is oxidized, can lead to narrowing of artery
- Liver can also make HDL which picks up cholesterol and returns it to the liver
