Module 5 - Lipids Flashcards
Which products make up most of our fat intake?
Animal products (meat, fish, eggs, poultry, dairy)
What chemicals is a lipid composed of?
Carbon, Hydrogen and Oxygen
How long are most of the carbon chains found in fat?
4-24 carbons long
What are the three types of lipids?
- Triglycerides
- Phospholipids
- Sterols
What is the major form of lipid found in food?
Triglyceride
What is the major form of lipid found in the body (stored energy)?
Triglyceride
Why is fat, not CHO the major form of stored energy?
fat is more efficient form of storage because it has 9 calories per gram, also fat contains less water then glycogen which stores a lot of water
What is the chemical makeup of a triglyceride?
3 fatty acids attached to a glycerol molecule
Through what processes are triglycerides formed and broken down?
Formed: Condensation
Broken Down: Hydrolysis
What are the two ends of a fatty acid?
Methyl end (CH3) and Carboxyl end (COOH)
What end of the fatty acid is water soluble and binds to glycerol?
Carboxyl (COOH)
How are types of fatty acids determined?
- Length of carbon chain (4-26C)
- Number of C=C (degree of saturation)
- Location of Double Bonds
What are fatty acids with <10 carbons called?
Short Chain Fatty Acids (SCFA)
What are fatty acids with 10-15 carbons called?
Medium Chain Fatty Acids (MCFA)
What are fatty acids with >16 carbons called?
Long Chain Fatty Acids (LCFA)
How long is the carbon chain of a short chain fatty acid?
<10 carbons
How long is the carbon chain of a medium chain fatty acid?
10-15 carbons
How long is the carbon chain of a long chain fatty acid?
> 16 carbons
Every carbon must have __ bonds
4
Name 2 qualities that the number of C=C (carbon double bonds) determines in fats?
firmness (solid vs liquid at room temp)
melting point
stability
oxidation
What are saturated fatty acids?
fatty acids that carry maximum number of hydrogen atoms, no carbon double bonds, SATURATED with hydrogen
How many C=C in a saturated fatty acid?
0
When Saturated Fatty Acids are >10C long they are __ at room temperature
solid
When saturated fatty acids are <10C long, they are __ at room temperature
not solid
Give an example of a source of saturated fatty acid in food?
coconut oil, butter fat, meat fat
What is more stable, Saturated or Unsaturated Fats?
Saturated Fats
What is an unsaturated fatty acid?
a fatty acid with at least one C=C (carbon double bond)
What has a lower melting point, saturated or unsaturated fats? Why?
unsaturated fats, molecules are less tightly packed together because of the carbon double bonds which makes it easier to disrupt bonds
C=C (Carbon Double Bonds) create __ that make unsaturated fatty acids less firm at room temperature
kinks
Fatty acid must be __ C long to have C=C (Carbon double bonds)
12
Carbon double bonds are separated by 3C, true or false?
True
What is a Monounsaturated Fatty Acid (MUFA)?
fatty acid with only one C=C
What is a polyunsaturated fatty acid (PUFA)?
fatty acid with 2 or more C=C
What is a monounsaturated fat?
fat containing mostly monounsaturated fatty acids (MUFAs)
What is an example of a monounsaturated fat?
olive oil, canola oil, avocados, nuts
What is a polyunsaturated fat?
fat containing mostly polyunsaturated fatty acids (2 or more C=C)
What is an example of a polyunsaturated fat?
waluts
vegetable oil
sunflower seeds
What is the chemical make up of methyl end of fatty acid?
CH3
What is the chemical make up of Carboxyl end of fatty acid?
COOH
In the omega system of fatty acid nomenclature, numbering starts from ___ end of fatty acid
Methyl (CH3)
Search up the chemical structure of linolenic acid and name it using the omega system
18:3; n-3, 6, 9
Essential fatty acids are…
not made in sufficient amounts in the body to meet physiological need so must be consumed
Essential fatty acids are precursors to __
eicosanoids (EPA, DHA & AA), they are 20 carbons long
Eicosanoids like EPA and AA are required for…
components of cell membranes
regulation of blood pressure, clotting, lipid levels, immune responses
Name at least 3 things that Omega 3 or a-linolenic acid (ALA) is important for
protecting against heart disease and cancer, mental health, pregnancy and lactation, reducing inflamation
Omega 3 (ALA) converts to what eicosanoid in the body?
EPA and DHA, but this process is not efficient as only about 10% is converted
The Omega-3 in fish products are mostly
EPA and DHA
The Omega-3 in plant products is mostly
alpha-linolenic acid (normal Omega-3)
Omega-6 or linoleic acid is a LCFA that converts to what ecosanoid in the body?
Arachidonic Acid (AA)
Name 3 things that Omega-6 or linoleic acid helps in the body
cell signaling
cell membranes
regulates fatty acid synthesis
Which essential fatty acid is a precursor to eicosanoids that are more inflammatory?
Omega-6
What is the range for ideal ratio of Omega 6 and Omega 3?
1:1 to 5:1, however western diets provide ratios of 30:1!
What types of fatty acid are essential fatty acids?
Polyunsaturated fatty acids
What is the biggest source of omega-6 fatty acid in U.S
Soybean oil
What are sources of omega-3?
fish like salmon, trout, anchovies
Unsaturated fatty acids (contain double bonds), can be found in Cis and Trans configurations, explain both cis and trans fatty acids.
Cis fatty acids have the H atoms on the same side of the C=C
Trans fatty acids have the H atoms on opposite sides of the C=C
Which type of unsaturated fatty acid has a lower melting point: cis or tran?
Cis (since the hydrogen atoms are in the same side, a kink is formed)
Which type of unsaturated fatty acid has a higher melting point: cis or trans?
Trans (the hydrogen atoms are on opposite sides of the bond so no kink is formed)
Is there many trans fats found in nature?
No
Most trans fats are formed by a process called…
partial hydrogenation
Explain hydrogenation that produces trans fats
Hydrogen is bubbles through unsaturated oil and breaks many C=C bonds and adds H, some of the C=C bonds change to trans (H on opposite sides)
What is the effect of hydrogenation of fats?
longer shelf life (increased stability against rancidity and higher melting point)
Partial Hydrogenation vs Total Hydrogenation
In partial hydrogenation only some carbon double bonds are broken and in total hydrogenation all the carbon double bonds are broken
What health risks are associated with trans fatty acids?
increased blood cholesterol and risk of heart disease
When was trans fat banned in Canada
2018
What is chemical structure of phospholipid?
glycerol attached to 2 fatty acids and a phosphate group
What is a defining feature of phospholipids?
they have a water soluble end and also a fat soluble end, allowing them to mix in both water and fat (important functions in body and food)
What end of the phospholipid is water soluble and hydrophilic?
phosphate group (N+PO4)
What is one important part of the body that phospholipids make up?
Phospholipid bilayer of cell membrane (hydrophilic head faces outwards to the watery areas oustide and inside cell while the hydrophobic tail faces inwards)
What is function of phospholipid bilayer?
helps regulate what can pass into/out of the cell, water can come in but proteins and other substances are kept from leaking out
What is a use of phospholipids in food?
they are used as emulsifiers (allow water and oil to mix)
How is a sterol arranged?
arranged in 4 rings shape with various side chains
Do sterols dissolve in water?
No, not well
What are the 2 well known sterols?
Vitamin D, Cholesterol
Are sterols found in plant and animal sources?
Yes
Where is cholesterol found in food?
only in animal products
Do humans make cholesterol?
yes in the liver
Where is most of thecholesterol found in the body?
cell membranes and myelin (material that covers spinal cord)
Cholesterol is important for…
sex hormones
vitamin d in skin
cholic acid (component of bile)
cortisol
Dietary cholesterol (found in foods) has a BIG influence on blood cholesterol: true or false?
False, very little influence
Are some people more predisposed to creating more cholesterol endogenously in the liver?
Yes
What are risks of high cholesterol circulation in blood?
increased risk of Cardiovascular disease
What should you do when you have high cholesterol?
- reduce overall fat intake (particularly SFA and TFA)
- increase plant sterols intake (reduces cholesterol absorption as plant sterols look similar)
- increase soluble fibre intake (it attaches to cholesterol and is excreted)
Why are plant sterols important in reducing cholesterol levels?
they are structurally similar to cholesterol to the point where the body can not differentiate them, so they compete in absorption, more plant sterols = less cholesterol absorbed
In lipid digestion, what does the gallbladder release into the chime when fatty chyme is present in duodenum?
Bile (bile salts emulsify lipids into smaller particles)
What does the pancreas release to digest lipids?
Pancreatic lipase
How does pancreatic lipase digest lipids?
lipase removes two fatty acids from each triglyceride molecule, converting most fat into monoglycerides and “free“ fatty acids
What are the major products of lipid digestion?
glycerol, monoglycerides, fatty acids
What are the smaller products of lipid digestion that pass easily and directly though the cells of intestinal lining into bloodstream, where they travel to liver?
glycerol and shorter chain fatty acids
What is a micelle?
water soluble particle formed by bile salts surrounding fatty acids and monoglycerides
What does a micelle do?
transports the lipids to edge of the absorptive cell which takes the monoglycerides and fatty acids from micelles
What do the end products of lipid digestion do after they are removed from micelle?
combine to become triglyceride, then the absorptive cell packages triglyceride with cholesterol, phospholipids and protein to form a chylomicron
What is the goal of the absorptive cells in lipid digestion?
to strip the micelle of the lipid digestion end products (monoglycerides and fatty acids which combine into triglyceride) and repackage them as chylomicron (with protein, phospholipid and cholesterol)
Where does the chylomicron, formed by the absorptive cells, go?
enters the lacteal (vessels of the small intestine that absorb digested fat) and eventually the bloodstream
Larger digested lipids (monoglycerides and long chain fatty acids) must form ___ before they can be released into lymph that leads to blood
lipoproteins (such as chylomicrons)
What is a chylomicron?
large triglyceride rich lipoprotein formed by the absorptive cells in lipid digestion, they are made up by triglycerides, protein, phospholipids and cholesterol
what is the major function of lipoproteins?
transport triglycerides (fat) to cells
As chylomicrons are so large that they can not move directly into the bloodstream, they instead go to the __
larger openings of the lacteals
What is a lacteal?
lymph vessel located in centre of each villus
The lymphatic system plays a role in lipid digestion by ___
transporting chylomicrons (which are too large to go to blood) to thoracic duct where they enter bloodstream
The lymphatic system plays a role in lipid digestion by ___
transporting chylomicrons (which are too large to go to blood) to thoracic duct where they enter bloodstream
As chylomicrons circulate blood, what substance breaks down the triglycerides in chylomicron into fatty acids and glycerol for use of nearby cells?
lipoprotein lipase (not to be confused with pancreatic lipase)
After fat is removed from chylomicrons by lipoprotein lipase, where does the remaining portion of chylomicron go?
to the liver to be broken down
where are the other lipoproteins (not including chylomicrons) produced? Name them
Liver
- VLDL (very low density lipoprotein)
- LDL (low density lipoprotein)
- HDL (high density lipoprotein)
Rank the lipoproteins by size
- chylomicrons
- VLDL
- LDL
- HDL
Which lipoprotein has most proportion of fat?
chylomicron
After chylomicron remnants travel to liver and are disassembled, what role do VLDLs play?
VLDLs transport lipids away from liver so lipoprotein lipase can break down any remaining triglycerides, they pick up cholesterol and become LDL
What is the role of LDL lipoproteins?
transport cholesterol to body cells
What is the role of HDL lipoproteins?
picks up and transports cholesterol to the liver for reuse or elimination
Give a summary of the proportions in each lipoprotein
Chylomicrons: little protein and high amounts of triglycerides - lowest in density
VLDL: half triglycerides
LDL: half cholesterol (bad cholesterol)
HDL: half protein (good cholesterol) - highest density
As lipoproteins get smaller, proportion of protein ___
imcreases, due to less fat content
After VLDL come across lipase, they become ___
IDL (intermediate density lipoprotein) that can turn into LDL
Are some people predisposed to creating more cholesterol in their body?
Yes
What is the risk of high cholesterol levels circulating in blood?
- may increase risk of cardiovascular disease
- oxidized LDL involved in atherosclerosis
Step1 of Atherosclerosis (thickening/hardening of arteries)
- Inflammation of endothelium and uptake of LDL
- infiltration of LDL into subendothelial region
Step 2 of Atherosclerosis (thickening/hardening of arteries)
- LDL oxadized
- macrophages (immune cells) activated
- macrophages engulf LDLs and become foam cell in arterial wall
Step 3 of Atherosclerosis (thickening/hardening of arteries)
- accumulation of foam cells leads to production of fatty streak
Step 4 of Atherosclerosis (thickening/hardening of arteries)
- formation of a fibrous plaque which protrudes into vessel lumen
- smooth muscle cells and extra cellular matrix cover the fatty streak
- plaque ruptures, thrombus forms
- if thrombus large enough it can affect blood flow of vessel
- if thrombus breaks off, it will become an embolus (which can block smaller blood vessels in the body)
Why is trans fat horrible for cholesterol?
increases LDL (“bad cholesterol”) and decreases HDL (“good cholesterol”)
Why are monounsaturated fatty acids (MUFAS) great? List health benefits
- part of myelin (structural lipids)
- improved cognitive function
- anti-inflammatory
- reduced cardiovascular risk
Why are Polyunsaturated fatty acids (PUFAs) great? List Benefits
- regulates blood pressure, blood clotting, blood lipid levels, immune responses
- omega-3 reduces CVD risk; beneficial for brain health
All SFAs (Saturated fatty acids) are bad for you
No, stearic acid (18:0) reduced cdv risk
To reduce CVD risk we should:
- reduce blood cholesterol
- reduce SFA consumption by reducing total fat consumption *dietary cholesterol has little effect on blood cholesterol
List 5 of the Roles of Lipid in the Body
- Energy Source (9kcal/gram)
- Energy Reserve (body fat stores energy)
- Carry fat soluble vitamins (A,D,E,K)
- Satiety (feeling of fullness, fats stay in stomach longer then carbs)
- Component of all body cells (phospholipids, sterols)
- Cholesterol is used to make several hormones (estrogen, testosterone)
- Regulate body functions (flow of molecules in/out of cells)
- Provides essential fatty acids (linolenic, linoleic), precursors to eicosanoids (EPA and AA)
- Insulation - subcutaneous fat insulated body against heat loss
- Protection - fat deposits help hold organs in place
- Lubrication - mucous membranes of eyes
Is there an AI or RDA for total fat intake? if so what is it?
No there isn’t an AI or RDA for total fat intake
Is there a UL for total fat intake? if so what is it?
There is no UL as there is no specific amount known where negative health effects occur
What is the AMDR for total fat intake for adults?
20-35%
Why is <20% fat harmful?
increased risk of CVD due to increased atherogenic lipoprotein
Why is >35% fat harmful?
- risk of obesity
- high intake of SFA (raises LDL levels)
What is the AMDR for both omega-6 (linoleic acid) and omega-3 (linolenic acid)
omega-6: 5-10% of total energy
omega-3: 0.6-1.2% of total energy
Should SFAs be replaced with PUFAs and MUFAs?
YES
Is there a DRI for SFA and TFA?
No, they can not be isolated in food as food is mix of fats, however TFA intake should be as low as possible
What is the recommendation for dietary Cholesterol?
no DRI or UL, as low as possible while eating nutritious diet
State 3 ways to lower fat intake?
- eat plenty of fruits and veg
- reduce invisible and visible fat intake
- consumer lower fat dairy
- choose lean meat
- less fried foods
What type of fatty acid are omega-3 and omega-6?
Polyunsaturated fatty acid (multiple carbon double bonds)
What hormone stimulates secretion of pancreatic lipase and bile to digest triglycerides and phospholipids in duodenum?
CCK
Where are bile salts reabsorbed?
Ileum (section of small intestine that absorbs vitamins like B12 and bike salts)
Is cholesterol broken down?
No, it is packed in chylomicrons (along with monoglycerides, fatty acids, protein, phospholipid fragments) in small intestine and enters lymphatic system
The liver uses ___ to make other lipoproteins
Chylomicrons
Why does the body need lipids? State at least 3 reasons
energy (triglycerides)
proper growth and development
skin and nail maintenance
production of bile and hormones
What cholesterol is generally “good” and “bad”?
Good: HDL (absorbs cholesterol and carries to liver which flushes it from body)
Bad: LDL (Part of plaque build up in arteries - atherosclerosis)
How can someone with elevated blood cholesterol and/or triglyceride levels reduce risk of CDV?
replace SFA with MUFA/PUFA
increase soluble fibre and plant sterol intake
lose excess mass and increase physical activity
Is Omega-3 fatty acid good or bad for CVD?
Good, as it is precursor to EPA and DHA, can slow build of plaque in arteries, lower blood pressure etc.
Partial hydrogenation turns __ into __
cis unsaturated (C=C) fatty acids to trans unsaturated fatty acids (hydrogen configuration changes to trans) making them more stable and increasing shelf life - unhealthy
Total hydrogenation turns _ into _
usaturated fatty acids into saturated fatty acids by removing all carbon double bonds making it more stable against rancidity (and unhealthy)
Limiting artificial trans fats could prevent …
many heart attacks and deaths
What are the eicosanoids of Omega-3 and Omega-6?
Omega-3: EPA and DHA (anti-inflammatory, prevent blood clots)
Omega-6: AA (arachidonic acid - cell signalling)
Partial and total hydrogenation to produce trans fatty acids – how does this change the structure/function of the fatty acid?
Hydrogen is bubbled through breaking carbon double bonds ands add H, some remaining carbon double bonds change to trans configuration, makes fatty acid more linear and stable against rancidity
The fat soluble and water soluble end of phospholipids allows it to act as a..
Phospholipid Bilayer in cell
Emulsifier in Food
Do sterols (like cholesterol and Vitamin D) dissolve well in water?
No
Where is cholesterol found?
Only in animals (made in liver) / animal products
High circulating levels of cholesterol (produced endogenously) can increase risk of…
CVD (Cardiovascular Disease)
