Transcript True Fats

Dr. Tarek El Sewedy
Department of Medical Laboratory Technology
Faculty of Allied Medical Sciences
Lipids and Fatty acids
(2)
Intended Learning Outcomes
By the end of this lecture, students will learn:
• Fats and diet
• Classification of lipids
• Biological importance of true fats
• Chemical properties of true fats
• Complex Lipids
• Derived lipids
Lecture Content
• Fats and diet
• Classification of lipids
• Biological importance of fats
• Chemical properties of fats
• Complex Lipids
• Derived lipids
Omega-3 fatty acids
•
Omega-3 fatty acids (also known as n-3 fatty acids) are polyunsaturated fatty
acids that are essential nutrients for health. We need omega-3 fatty acids for
numerous normal body functions, such as controlling blood clotting and building
cell membranes in the brain, protection against heart disease .
•
Our bodies cannot make omega-3 fats, we must get them through food.
•
Alpha-linolenic acid (ALA) is the parent compound for Omega 3 fatty acid, is
found in some vegetable oils such as soybean, canola, and in walnuts.
Omega-3 fatty acids
•
For good health, we should aim to get at least one rich source of
omega-3 fatty acids in our diet every day. This could be through a
serving of fatty fish (such as salmon), a tablespoon of canola or
soybean oil in salad dressing or in cooking, or a handful of
walnuts.
Omega-6 fatty acids
•
Omega-6 fatty acids (also known as n-6 fatty acids) are also polyunsaturated
fatty acids that are essential nutrients, meaning that our bodies cannot make
them and we must obtain them from food.
•
Common dietary sources include safflower, corn, cottonseed, and soybean
oils.
•
Omega-6 fatty acids lower LDL cholesterol (the "bad" cholesterol) and reduce
inflammation, and they are protective against heart disease. So both omega6 and omega-3 fatty acids are healthy.
Cis and Trans Lipids
•
Naturally-occurring unsaturated vegetable oils have almost all cis bonds, but using oil for
frying causes some of the cis bonds to convert to trans bonds.
•
If oil is used only once like when you fry an egg, only a few of the bonds do this so it’s not
too bad. However, if oil is constantly reused, like in fast food French fry machines, more and
more of the cis bonds are changed to trans until significant numbers of fatty acids with trans
bonds build up.
•
Studies showed that fatty acids with trans bonds are carcinogenic and leads to significant
increase in heart disease by increasing levels of bad cholesterol (LDL). The levels of trans
fatty acids in highly-processed (hydrogenated oils), lipid-containing products such as
margarine are quite high.
•
Cholesterol
Cholesterol is a waxy substance your body uses to protect nerves, make cell tissues and
produce certain hormones.
•
A little cholesterol is essential for health.
•
The liver can manufacture all the cholesterol your body needs.
•
Low-density lipoprotein (LDL or 'bad') cholesterol can join with fats and other substances to build up in
the inner walls of your arteries. The arteries can become clogged and narrow, and blood flow is
reduced. High-density lipoprotein (HDL or 'good') carries harmful cholesterol away from the arteries
and helps protect you from atherosclerosis, heart attack and stroke.
Atherosclerosis
• A type of arteriosclerosis. Atherosclerosis causes arteries to
narrow, weaken and be less flexible. It's the term for the
process of fatty build-up in the inner lining of an artery. The
build-up that results is called plaque and reduces the amount
of blood and oxygen that is delivered to vital organs.
Triglycerides
• Triglyceride is a form of fat made in the body. Elevated
triglycerides can be due to overweight/obesity, physical
inactivity, cigarette smoking, excess alcohol consumption
and a diet very high in carbohydrates.
•
People with high triglycerides often have a high total
cholesterol level, including a high LDL (bad) level and a low
HDL (good) level. Many people with heart disease and/or
diabetes also have high triglyceride levels.
Fats and diet
•
Eating low fat food doesn’t mean we should give up fat entirely,
but we do need to educate ourselves about which fats should
ideally be avoided and which ones are more heart-healthy.
•
We need fat in our diet. As the most concentrated source of calories
(nine calories per gram of fat compared with four calories per gram for
protein and carbohydrates), it helps supply energy.
•
Fat provides linoleic acid, an essential fatty acid for growth, healthy skin
and metabolism.
•
It also helps absorb fat-soluble vitamins (A,D,E and K).
•
And fat adds flavour and is satisfying, making us feel fuller
Although all fats have the same amount of calories, some are more
harmful than others: saturated fats and trans fats in particular.
Saturated fats
•
These fats are derived from animal products such as meat, dairy and
eggs. But they are also found in some plant-based sources such as
coconut, palm oils. These fats are solid at room temperature. Saturated
fats directly raise total and LDL (bad) cholesterol levels. Conventional
advice says to Avoid them as much as possible
A meta-analysis published in 2003 found a direct relationship
between saturated fat and breast cancer. In 2007, a systematic
literature review published by the World Cancer Research Fund
and the American Institute for Cancer Research found consistent
evidence for a direct relationship between animal fat and
colorectal cancer.
The Ugly fats
Trans Fats or Hydrogenated Fats
Trans Fats are typically found in packaged goods and fast food restaurants
They all have/use the ugly fats…
TRANS FATS!
The Ugly fat
•
scientists discovered that they could create a fat that would
prolong the spoiling of packaged goods by simply adding a
hydrogen atom to an unsaturated fat.
• The partially hydrogenated fat creations wouldn’t spoil as easily
as non-hydrogenated fats, plus they didn’t break down during
temperature changes, which made transporting them easier, and
they were less expensive than animal fat.
Another ugly man-made invention!
Trans Fats or Hydrogenated Fats
•
Are actually unsaturated fats, but they can
raise total and LDL (bad) cholesterol levels
while also lowering HDL (good) cholesterol
levels.
•
Trans fats are used to extend the shelf life
of processed foods, typically cookies,
cakes, fries and donuts. Any item that
contains “hydrogenated oil” or “partially
hydrogenated oil” likely contains trans fats.
•
Hydrogenation is the chemical process
that changes liquid oils into solid fats.
•
Since January 2006, all food
manufacturers are required to list trans fat
content on food labels.
Butter
Margarine, tub
Margarine, stick
Unsaturated fats
•
Monounsaturated fats and polyunsaturated fats are two types of
unsaturated fatty acids. They are derived from vegetables and
plants.
•
Monounsaturated fats:
•
This type of fat is preferable to other types of fat and can be found in olives, olive oil, nuts, peanut oil, canola oil
and avocados. These kinds of fats can lower LDL (bad) cholesterol and maintain HDL (good) cholesterol.
•
Polyunsaturated fats:
•
These are found in sesame, corn, cottonseed and soybean oils. This type of fat has also been shown to reduce
levels of LDL cholesterol, but too much can also lower your HDL cholesterol
Butter Vs. Margarines
•
Margarine tops butter when it comes to heart health.
•
Margarine is made from vegetable oils, so it contains no cholesterol.
•
Margarine is also higher in "good" fats — polyunsaturated and
monounsaturated.
•
Butter, is made from animal fat, so it contains cholesterol and high levels
of saturated fat.
•
Some margarines contain trans fat. In general, the more solid the
margarine, the more trans fat it contains. So skip the stick for soft or
liquid margarine instead.
•
Look for a spread that doesn't have trans fats and has the least amount
of saturated fat. When comparing spreads, be sure to read the Nutrition
Facts panel and check the grams of saturated fat and trans fat.
Eat Healthy
Stay Healthy
lipids
simple
True fat
derived
complex
waxes
steroids
glycolipids
phospholipids
sulfolipids
lipoproteins
Fat sol
vitamins
Classification of lipids
• LIPIDS ARE CLASSIFIED AS SIMPLE OR COMPLEX Or DERIVED
A. Simple lipids: Esters of fatty acids with various alcohols.
1. True Fats: Esters of fatty acids with glycerol.
2.
Waxes: Esters of fatty acids with higher molecular weight alcohols.
Glycerol
High M.W
alcohol
Fatty
acid
Fatty
acid
True fat
WAX
Simple lipids
Waxes are esters of
FA with high M.W
alcohol
True fats are esters of
FA with glycerol
•Usually solid.
Simple: has one type of
FA in all positions
•Alcohol such as myricyl
Mixed : has different types of FA
alcohol (1-triacontanol,
C30H61OH) or ceryl alcohol
(1-hexacosanol, C26H53OH).
True Fats “Acylglycerides”
1. Monoacylglcerols
2. Diacylglycerols
3. Triacylglycerols
Biological importance of true fats
 Reserve food in animals and plants.
 Supporting and protection materials around organs e.g. kidney.
 Source of energy
*
* Non polar.
* Tasteless, odorless, colorless.
* Neutral in reaction.
* Specific gravity˂1 (float on water).
* Low melting point.
lipids
simple
True fat
derived
complex
waxes
steroids
glycolipids
phospholipids
sulfolipids
lipoproteins
Fat sol
vitamins
Complex lipids
Lipids containing group in addition to
fatty acids and alcohols as phosphate,
sulfate, carbohydrates and protein.
Complex lipids
phospholipids
sulfolipids
glycolipids
lipoproteins
CH-O-C-R1
O
CH-O-C-R2
O
Glycolipids are lipids with a
carbohydrate attached
CH2-O-C-R3
O
lipids
simple
True fat
derived
complex
waxes
steroids
glycolipids
phospholipids
sulfolipids
lipoproteins
Fat sol
vitamins
carotenoids
• They include complex compounds: sterols, fatty aldehyde and ketone
bodies, lipid–soluble vitamins and hormones.
• Cholesterol, is a derived lipid and an
important component of cell membranes, it
is an amphipathic molecule because it
contains a polar hydrophilic hydroxyl group
and 4 hydrophobic rings. Cholesterol is also
a precursor to the steroid hormones, such
as testosterone.
*
All students has been given assignments , any student that was not given an
assignment should prepare an assignment on any of the topics on the next
slide and deliver it by next week.
ASSIGNMENTS
• Selected students are requested to prepare slides about one of the
following topics (To be delivered before next lecture):
• Cholesterol and disease
• Lipoproteins
• Bee Wax
• Essential Fatty Acids
Study Questions
 Complete:
 Glycerol is an organic compound, has three -------------




groups.
----------------and --------------are saturated fatty acids.
--------------and ----------------------are true lipids.
Cholesterol belongs to-----------------lipids
1gram of ----------- yields 4.1Kcal while 1 g of ----------yield 9 Kcal.
----------------are esters of fatty acids with higher
molecular weight monohydric alcohols.
Choose:
1-Beewax belongs to
 a-Compound lipids.
 b-Simple lipids.
 c-Derived lipids.
2. -------------------------is an essential fatty acid.
 a-Linoleic acid.
 b-Oleic acid.
 c-Palmitic acid.
3-LDL and HDL belong to ---------------- a-Sulpholipids.
 b-Lipoproteins
 c-Phospholipids.
 4-Cholesterol belongs to-------------- a-Simple lipids.
 b-Complex lipids.
 c-Derived lipids.
 Correct the incorrect word:
 Arachidonic acid is monounsaturated fatty acid.
 Oxidation of 1 g of Carbohydrate yields 9 Kcal.
Write the chemical formula of the following:
 Palmitoleic acid (16:1n;∆9)
 α linolenic acid (18:3n;∆9,12,15)
 linoleic acid (18:2n; ∆9,12)
 Arachidonic acid (20;4n;5,8,11,14)
Mention points about:
 1-Function of lipids.
 a b c 2-Lipids are classified into
 a b c-
Principles of Biochemistry, Donald J. Voet, Judith
G. Voet, Charlotte W. pratt; Willey, 3rd ed.