Lecture 2a: Lipids Flashcards
What are lipids soluble in?
non-polar solvents (e.g. acetate, ether, chloroform)
Are lipids soluble in water?
No
What are lipids linked to?
Linked to or can be linked to fatty acids
Are lipids toxic?
Relatively non-toxic
What are lipids the main storage form of?
Energy in our body
What part of cells are lipids?
Component of cell membranes
What do lipids provide?
Insulation
What do lipids help control?
Body temperature
What do lipids provide protection for?
Internal organs
What do lipids form the basis of?
Many hormones
What absorption do lipids aid in?
Intestinal absorption of fat-soluble vitamins
What is the quality of lipids important for?
In terms of chronic disease risk
Why don’t we want to much fat?
To avoid a significant increase in body fat/weight
What do lipids provide in our food?
Enhance flavour/palatability and provide essential fatty acids
What are the 5 main types of lipids? (T, P, Sp, St, FSV)
Triacylglycerol
Phospholipids
Sphingolipids
Sterols
Fat soluble Vitamins
What are the fat soluble vitamins? (4)
A, D, E and K
What is the most common type of lipid in our body and in food?
Triglycerides
What are triglycerides made up of?
Glycerol and 3 fatty acids
What is the difference between triacylglycerol and triglyceride?
None, they mean the same thing
What is the Awater factor for TAGs?
37 kJ per gram
What are TAG’s the storage form of?
Fatty acids
What are TAG’s a structural component of?
Lipoproteins (how we carry fat around the body)
What percent of dietary lipids are TAG’s?
over 90%
What are phospholipids?
Major lipid class found in cell membranes
What is the structure of phospholipids?
2 fatty aids and a phosphate base
What can the bases of phospholipids be?
Choline
Inositol
Serine
Ethanolamine
What are phospholipids a source of?
Fatty acids
What are phospholipids a structural component of?
Membranes and plasma lipoproteins
What type of molecules are phospholipids?
Information molecules (eicosanoids)
What percent of dietary lipids are phospholipids?
5-10%
What is the structure of cholesterol?
Ring formation
Is cholesterol essential?
No, we make our own cholesterol
What is cholesterol a structural component of?
Membranes
What is cholesterol the backbone of?
Steroid backbone
What vitamin is cholesterol a precursor for the synthesis of?
Vitamin D
What acid is cholesterol a precursor for the synthesis of?
Bile acids
What structures are fatty acids part of?
phospholipid bilayers
What impact do fatty acids have on membranes?
Impact their fluidity
What type of molecules are fatty acids?
Information molecules (eicosanoids)
- prostaglandins
- thromboxanes
- leukotrienes
What is a short chain fatty acid?
C2-C6
What is a medium chain fatty acid?
C8-C12
What is a long chain fatty acid?
> C14
What is a very long chain fatty acid?
> C22
What length are most fatty acids in the diet?
C10-C22 (medium to very long)
Short to medium chains act more like what?
CHO as they go straight to the liver
What does the first number of the fatty acid notation mean?
Number of carbons (e.g. C18:0 = 18 carbons)
What does the second number of the fatty acid notation mean?
Number of double bonds (e.g. C18:0 = 0 double bonds)
What does it mean when a molecule has 0 double bonds?
It is completely saturated with hydrogens
When counting molecules what end do we count from?
The methyl end
What is the melting point of SAFA?
High
What is a common SAFA?
Stearic acid (C18:0)
What is the melting point of stearic acid?
69 degrees
Which SAFA is the primary product of fatty acid synthesis in the body?
Palmitate (C16:0)
How many double bonds do SAFA’s have?
Always 0
How many double bonds do Monounsaturated Fatty Acids have?
Mono = 1 cis or trans double bond
What is the melting point of MUFA?
intermediate melting points (olive oil)
What is a common MUFA?
Oleic Acid (C18:1n-9)
What is the melting point of oleic acid?
16 degrees
Are MUFA essential in the diet?
No they can be synthesised in the body
What does C18:1n-9 mean?
This molecule has 18 carbons, count from methyl end, on the 9th carbon there will be a double bond.
How many double bonds do polyunsaturated fatty acids have?
Poly = two or more cis or trans double bonds
How many carbons seperate double bonds in PUFA?
One carbon always separates the double bonds
How to read C18:3n-3
18 carbons, first double bond is 3 carbons away from the methyl end, all double bonds have one carbon in-between
What is the melting point of PUFA?
Low melting points
What is a common PUFA?
Linoleic acid (C18:2n-6)
What is the melting point of linoleic acid?
-5 degrees
Are PUFA’s essential in the diet?
Body cannot synthesise n-6 and n-3 PUFA
=C18:2n-6 and C18:3n-3 are essential fatty acids (EFA)
What are the essential fatty acids human need?
omega-3 fatty acids (a-linolenic acid)
omega-6 fatty acids (linoleic acid)
Why are some fatty acids essential?
Humans are not able to produce a double bond before the 9th C from the methyl (CH3) or omega (w) end.
How much energy intake should essential fatty acids make up?
At least 1-3%
What are the symptoms of essential fatty acid deficiencies?
– Growth retardation
– Reproductive failure
– Skin lesions (dry skin)
– Kidney and liver disorders
– Neurological and visual problems
Are essential fatty acid deficiencies common?
No, most diets meet the minimum requirements more than adequately
What are trans fatty acids?
a type of unsaturated fatty acid that contain at least one double bond in the trans configuration
What does trans mean?
opposite sides
What is a common trans fatty acid?
Elaidic Acid (C18:1n-9)
What is a cis fatty acid?
a type of unsaturated fatty acid in which the hydrogen atoms attached to the carbon atoms of the double bond are on the same side of the bond
What is a common cis fatty acid?
Oleic acid (C18:1n-9)
What has a higher melting point, cis or trans fatty acids?
Trans bonds have higher melting points
How do we get fat?
By eating it and also biosynthesising some
What do we use fat for?
Energy
How do we store fat?
As TAG’s in adipose tissue
What is desaturation of fatty acids?
adding on double bonds
What is elongation of fatty acids?
the addition of two-carbon units (acetyl-CoA) to the carboxyl end of a fatty acid chain, resulting in the extension of the chain length
What oils are very high in SAFA?
Coconut oil, butter, palm oil, lard
What oils are very high in MUFA?
Olive oil, canola oil, peanut oil
What oils are very high in PUFA?
Seed oils (e.g. flaxseed oil, sunflower oil, corn oil)
What type of fat increases blood cholesterol?
Saturated fat
If you want to decrease cholesterol, what oil should you pick?
An oil that is rich in polyunsaturated omega - 6 (e.g. sunflower oil)
What cholesterol is considered bad?
LDL
Which cholesterol is lower risk?
HDL
What receptor does SAFA decrease?
Decreases LDL receptor activity (therefore there will be lots more cholesterol floating around), this will eventually cause damage to vessel walls
What does SAFA suppress? (A)
Suppresses ACAT (rate limiting enzyme of cholesterol esterification), resulting in greater proportion remaining in the regulatory pool. These enzymes normally get rid of cholesterol.
What do trans fatty acids increase?
Cholesterol synthesis
Which omega PUFA decreases cholesterol?
PUFA n-6 by
How does PUFA omega 6 decrease cholesterol in terms of receptors?
Increased LDL receptor activity, this is good as there will be less cholesterol floating around
What enzyme do PUFA omega 6 increase?
Increased CYP7 (rate limiting enzyme in converting cholesterol to bile acids), these are involved in digestion and therefore help to get rid of cholesterol
What receptor regulator does PUFA omega 6 decrease?
decrease in Proprotein convertase subtilisin/kexin type-9 (PCSK9) – a hepatic LDL-receptor regulator which degrades the receptor
What do PUFA omega 3’s decrease?
TAG levels
What secretion does PUFA omega 3 increase?
increased lipogenesis and VLDL secretion
Omega 3 PUFA’s increase the activity of what?
- Increased lipoprotein lipase activity – increased hepatic clearance of lipoproteins
- Increased reverse cholesterol transport
What percent of fatty acids in our blood is undesirable?
0-4%
What do PUFA omega 3’s decrease?
Reduce inflammation
What percent of fatty acids in our blood is intermediate?
4-8%
What percent of fatty acids in our blood is desirable?
Above 8%
What should protein intake be?
15-25% of energy
What should fat intake be?
20-35% of energy
What should omega 6 fat intake be? (linoleic acid)
4%-10% of energy
What should omega 3 fat intake be? (a-linolenic acid)
0.4-1%
What does fat intake look in New Zealand
All age groups are at the upper level - closer to 35
What is the threshold that we would like SAFA to be?
Not over 10%
What does SAFA intake look like in NZ?
All age groups are over the threshold that we would like (over 10%) - this could be why our heart disease rates are so high
