The lipids are a group of organic macromolecules that are insoluble in water. There are three main types of lipids that are found in our diets and in our bodies. These are triglycerides or triacylglycerols or oils and fats, phospholipids and sterols. You can see that the fats and oils make up the majority of the lipids in our diet.
The triglycerides, which are the fats and oils, serve three major roles. They serve as a storage energy site to store energy for a long periods of time. They serve as a cushioning and protection structure tissue, which is found, like for example on the pads of our hands or the bottoms of our feet, as well as surrounding all of our vital organs to help cushion them against being bounced around when we are moving. They also, triglycerides are also found in the subcutaneous layer of our skin and play an important role in maintaining body temperature. Tri-glycerides have three main parts.
One of them is called glycerol, and that's shown in blue here. The other part are three fatty acids.
All fats and oils have that structure, but obviously, hopefully intuitively, you know that there is got to be a lot of differences going on as well. And those differences are all in these carbon chains, the fatty acids. So if we look at the fatty acids, they can vary in their length as well as their degree of saturation. So the carbon chain length can between, between four and 24 carbons long, the shorter the chain, the lower at which that fatty acid will melt and become a liquid. If you look in this top picture, it is a saturated fatty acid, and the reason why we say it is saturated is if you look at every single carbon, it is filled with the maximum possible number of hydrogens. So we say it is saturated with hydrogens. Unsaturated fats have one or more double bonds between carbons, so now those carbons cannot be filled with hydrogen. This is a mono- unsaturated fatty acid, because it only has one carbon to carbon double bond. Polyunsaturated fatty acids have two or more sets of carbon to carbon double bonds. And this is an example of Linoleic acid. We see there is one here and one here. Now you may have heard the term omega-3 and omega-6, and what these terms refer to is the location of the first carbon to carbon double bond in the chain. So this is an omega-6 fatty acid, so 1, 2, 3, 4, 5, 6. That is the sixth, so it is an omega-6, as opposed to 1, 2, 3. So there is that first carbon in the carbon to carbon double bond, so that is an omega-3 fatty acid.
Now remember that the fat molecule has the glycerol, so I am going to put that in the glycerol, with three fatty acids. So 1, 2, 3. But in the reality, there is not one type of fatty acid on one triglycerol molecule. You can have a mix. So for example, in corn oil, you have a little bit of saturated fatty acids. You have a fair amount of mono unsaturated fatty acids, and you have a lot of poly unsaturated fatty acids. Whereas if you look at coconut oil, it is mostly saturated fatty acids with a little bit of mono- unsaturated fatty acids, and a very tiny amount of polyunsaturated fatty acids. So when we talk about foods having saturated fats or unsaturated fats, what we are really talking about is the relative amount of unsaturated fatty acids in the triglycerols. And typically plants have more unsaturated fatty acids, and animals have more saturated fatty acids.
Another term you may have seen is the term hydrogenated or hydrogenation. And this refers to a process that humans and our ingenuity have come up with to make our foods more shelf-stabled in our highly processed foods. So what we do in making trans fats is we under pressure and heat change the arrangement of hydrogens in an unsaturated fatty acid to make that molecule behave like a saturated fatty acid. So here is a saturated fatty acid. You can see that it is nice and straight. It would stack together neatly and be solid at room temperature. If we look here at this cis, cis is a term for, in this case, both of the hydrogens being up, if you will, on this fatty acid. And because of the arrangement of those hydrogens in this unsaturated fatty acid, it makes it have this bend. And this is why plant oils, plant fats are typically liquid at room temperature is because of this structure. In a laboratory setting in industrial food production, we have figured out to change that cis confirmation into a trans confirmation so that the hydrogens are located at different places now. On that carbon and carbon libel bond and that leads to a very straight molecule that has an incredibly high stability at room temperature as well as at high heats. So trans fats became widely used in processed food in the 70s and 80s. They were used in everything from cookies and potato chips to ice cream to frozen dinners to pizza to McDonald's and all the fast food restaurants, frying their stuff in trans fats. They're very stable at high temperatures so you could fry 500 batches of french fries in one, you know, five gallons of trans fat. Whereas if you tried that in butter or olive oil, that oils or the butter would break down and would not be able to handle that much heat over long periods of time. Also, things like Twinkies and the hostess and the Entemanns and these other baked products that sit on shelves for a month or two without going bad, the trans fats allow them to do that. So it sounds like it's a great thing, but really the only person it's great for are the corporations making the food products; for our health, as I'll show you, they have a very negative effect. They're not widely used anymore and instead have been replaced by palm oil and palm oil actually is not that great for you either and has been associated with heart disease just in the same way that saturated fatty acids happen, not to mention the environmental issues surrounding the production of palm oil. There are two essential fatty acids that our bodies cannot synthesize these are linolenic acid and linoleic acid. And these are polyunsaturated fatty acids that play an important role as precursors to a group of compounds in our bodies called eicosenoids. And the eicosenoids are placed pivotal roles in things like nervous system function, our immune system, maintaining blood pressure, helping reduce inflammation and other sort of very important things related to our health like those. We can find them primarily in vegetable oils, nuts, seeds and whole grains and they are really pretty key for maintaining homeostasis in our bodies. I just want to remind you about the food label because when you look at a food label, you see that you have the total fat but they're not required to report the unsaturated fat. They're only required to report the saturated fat. So you're looking at this and you're like wait, it's got nine grams but I only see four and a half grams whereas the rest of the fat and it's because the other four and a half grams will be unsaturated fat and so they're not required to report that. They are required to report the trans fats but this is somewhat misleading because if there's less than two grams per serving I believe it doesn't count so they don't have to report it and they are also required to report cholesterol but as I'm about to tell you dietary cholesterol is generally not a problem for the majority of people. It is not the cause of high blood cholesterol.
So the triglycerides are going to vary in their degree of saturation and that's what gives them the liquid state. If they have a lot of unsaturated fatty acids in the triglyceride, they'll be liquid at room temperature. If they have a lot of saturated fatty acids, they will be solid at room temperature and this also feeds into their stability over time. So whether or not they go rancid which means they've gone bad and so yeah.
All right, two other groups of lipids are the phospholipids and the sterolsjust really briefly let's take a look at these. So the phospholipids consist also of a glycerol molecule just like the triglycerides but they also have two fatty acids and those fatty acids can be saturated and unsaturated they usually have a mix and then the last part of this molecule is this part which is the phosphate head. So this phosphate head gives this molecule the ability to dissolve in water and that helps us understand the important role of phospholipids which is to serve as the main structure of our plasma membranes, our cell membranes as well as the membranes of all of the organelles inside of our cells. The external environment of our cells is a watery solution and the inner cell inside of the cell is also primarily a watery solution. So we want to have molecules that can interact the hydrophilic with those outer and inner parts outside of the cell and the inside of the cell. So these phosphate heads are hydrophilic water loving the fatty acid tails here in the middle serve as a barrier and prevent most things from being able to easily pass through. So we want to have a molecule that can be used to dissolve into the cell or out of the cell. I will also just point out that there is cholesterol so cholesterol is not the thing you do get it measured with the doctor but it's not what we generally think of when we go to the doctor to get our blood fats measured. Cholesterol is a special type of lipid that helps maintain the fluidity of our plasma membranes and our cell membranes. Most of the other places where we see phospholipids is they behave as what are called emulsifiers and so they are things that help fats be small enough to fit in between spaces of water environment. So if you've ever had like a jar of oil and vinegar, you know they're separate but if you really, really shake it, shake it hard, hard, hard, that physical activity breaks the molecules of oil down into tiny enough droplets that they fit in amongst between the vinegar droplets. But if you let it sit, they will become, come out of emulsification. But this is also why we see emulsification in a lot of processed foods is they add things like lecithin so that ice cream has a smoother taste and yeah.
The last category of lipids are the steriles. So the sterolsare specifically four chain, four carbon rings. So that color is work for carbon rings. So one, two, three, four and from these four carbon rings, I have various things hanging off. So all of the sterolshave these same structure and cholesterol in addition to helping with the fluidity of our cell membranes also serves as the precursor for all of the steriles. So the categories of sterolsthat you may or may not be familiar with are the bile acids which are key in aridogenestine of fats. The sex hormones estrogen and testosterone are both steriles, adrenal hormones like cortisol and then some vitamins like vitamin D.
When we eat fat, it goes into our mouth. It's mostly mechanical digestion. There's a little bit of salivary lipase or lingual lipase that helps start to break it down, but it's it's pretty minor.
In our stomach, again, it's more physical mechanical digestion. There's a little bit of gastric lipase, but it's still not really doing that much. As is the case for most of the nutrients, it's really in the small intestine where we see the vast majority of the activity occurring. So in our small intestine, it is a multiplied using bile pancreatic lipases, which are enzymes secreted from the pancreas specifically to breaking down triglycerides will break down those triglycerides and then my cells are small structures that will help with absorption.
Let's take a look at how bile works. If we start out up here, we have a big old blob of fat that we've just swallowed. Let's say some butter that we ate on a piece of toast. Now, because of the way the fat is and the way the enzymes are, the enzymes can't really get hold of these fat molecules to start breaking them down. And this is where the bile salts become important. So this is a bile molecule. It's made from cholesterol. Here are those four rings. And it has this amphipathic part. This hydrophilic part is an amphipathic molecule so that the bile can actually attach to the fat and then still be dissolved in the water and cause it to break into small droplets.
So this is a most fied fat. And now, because they're most fied, those enzymes can interact with the fat and break it down into glycerol and fatty acids. So once the fats have been digested, depending on what product we're talking about, they can take one of two pathways to get into our bodies. The short chain fatty acids and the medium chain fatty acids and glycerols can pass directly through the intestinal cells and into the bloodstream where they will be taken to the liver. The larger lipids, such as the monoglycerides and long chain fatty acids, will be organized into these structures called micelles, which have hydrophobic tails, sort of all the fatty parts are inside and the hydrophilic heads are facing on the outside. These allow them to be water soluble enough that they can diffuse into the intestinal cells. So that's what this is showing. They're going into the intestinal cells. And the bile salts will go back out into the intestinal lemon, the space of the intestine and the delivered fats, the monoglycerides and fatty acid chains will be organized into what are called a chylomicron. Those chylomicrons can then be transported into the lymphatic system and travel where they will ultimately end up meeting with the blood and go to the liver to be formally to be used again. So the chylomicron is one type of what's called a lipoprotein, lipoprotein, and lipoproteins are basically blobs of lipids and proteins that are lipid delivery systems in our bodies. So the chylo- micron delivers the lipids from our digestive processes into our bloodstream or a lymphatic system in that our bloodstream, but we have some others that we also have to think about. So we have several kinds. One is called the VLDLs, which stands for very low density lipoprotein, which means there is a low density of protein and a high density relatively of triglyceride. The VLDLs are made in the liver and they go around the body dropping off triglycerides to where they're needed in our body for whatever they're needed for. The ideal, which stands for intermediate density lipoprotein, is basically a broke down VLDL, so it's going to go back to the liver and from the liver it will either gain more triglycerides or it will be recycled for its parts. The third type is called the LDL, the low density lipoprotein, and if you look at the low density lipoprotein, you see that it actually doesn't have too much triglyceride, but it has a lot of cholesterol. And that's what it's job is, the LDL is to deliver cholesterol to cells for either synthesis of hormones or for maintaining the fluidity of membranes. And then last but not least, we have the HDL, which is the high density lipoprotein, which has mostly protein and less of different lipids. And the job of the HDL is to pick up any excess cholesterol that hasn't been used and take it back to the liver for disposal. Now you may have heard LDL and HDL and other contacts. Sometimes we call LDL, the so-called bed cholesterol and the HDL is the good cholesterol, but it's sort of a misnomer because neither of them is actually cholesterol. They both contain cholesterol, but neither of them is actually cholesterol. So with lipid metabolism, once the fat has been taken to our liver, it will be shipped out in LDLs and LDLs to go do things around our body. Some of it will go into what are called adipocytes, which are fat cells, and this is an adipocyte and adipose tissue. And so you can see that the job, as I showed you in that slide earlier, is really a storage job. So the whole point of an adipocyte is to store fat. So that's most of the organelles and everything are just kind of squished off to the side. Here's the little nucleus. And these are pretty metabolically inactive cells. But when the call comes, they're ready for action. One of the biggest places that we see the adipose tissue play a role is in supplying 60% of our energy at rest. This includes when we're vaginat in front of the TV or watch or taking a nap or sleeping or just sitting and watching videos about lipid metabolism. They're also used during prolonged exercise. So once you've passed a couple of hours of exercise, your body will preferentially switch to burning fat for energy. All right. You've probably heard a lot about issues associated with high-fat diets and disease. And these are not totally unfounded worries because the top causes of death in the United States are heart disease, cancer, and stroke. But the, it turns out in the last five years or so that we learned that while you do want to limit fat in your diet, fat isn't really the enemy as much as sugar is and that the sugar industry has been suppressing lots of research and data showing that high sugar high refined carbohydrate diets are actually probably play equally if not stronger role in the development. So it's a part of some of these diseases. So heart disease is a broad category that refers to anything that causes heart failure. It could be a heart attack or it could be COPD, which is product obstructive pulmonary disorder and a whole host of other things. Basically your heart's just not doing what it's supposed to be doing. Certain types of cancer associated with high-fat diets, like colon cancer, for example, strokes, which is basically some blockage to blood. And blood flow in your brain can be caused by high-fat diets. A metabolic syndrome, which is a precursor to diabetes. Usually a metabolic syndrome as the person has high blood sugar, high blood fats, high blood pressure, has a lot of visceral fats who fat around their organs can be very dangerous. And then high blood pressure is a disease or hypertension is the same thing that is also. So it's really important to know your numbers. A normal blood pressure is below 120 for your systolic number and below 80 for your diastolic number. And then as you go up from there, it changes. I do want to make a point that you should know your normal blood pressure levels. As well as recognize like when you go to a doctor, you're stressed out. I'm often running up the stairs because I'm late. So that can cause your blood pressure to get elevated by knowing your regular blood pressure levels, your normal levels. You will be able to tell whether your blood pressure is abnormal at the doctor or not. And a lot of times if my blood pressure is pretty high when they measure it, they'll just wait 15 minutes and measure it again. So I know they usually be back down to normal. Another thing that happens when you go to the doctor is they measure your blood -lippered profile. And these are the numbers that you want to shoot for in that. So the milligrams per desolate is the US measure. And the millimoles per desolate is European Union and Canadian measure of those. Usually when you get these results, they give you like an interpretive table to tell you where you find in, where you fill in. So optimally, your total cholesterol, which is actually the sum of your LDL and HDL is going to be less than 200. And you want your LDL to be less than 130 and your HDL to be higher than 60. If you have like I often have HDL of 110 and 120, that's fine. It doesn't matter at least to some level. It doesn't really measure how high your HDL is. What's important is that your LDL is low and the total is below 200. They also will measure your triglycerides, which is the free fat molecules that are circulating in your bloodstream. And so you want those to be less than 150. So here's what happens to fats in your bloodstream when you eat different kinds of fats in your diet. So when you eat a lot of saturated fats like cheese and cream and beef and you know ribs and stuff like that, that's going to cause your, your bad cholesterol, your LDL levels to go up. It doesn't really have any effect on your HDL. When you eat a lot of unsaturated fats in your diet like those from plants other than palm and coconut oil, this is going to cause your LDL to go down because your HDL is going up. And if you remember HDL's job is to grab excess LDL and take it back to the liver. This is why the trans fats are so bad for you is because the trans fats have the opposite effect. They raise your LDL and they lower your HDL. And so they're actively like a double whammy relative to saturated fat. So remember back in the 70s and 80s, everybody's like, I'm going to eat hard drink because it's so much healthier. But it turns out you were actually causing more harm. You may as well just eat in the butter because at least it wasn't affecting your levels of HDL. So outcomes of this, particularly this is called atherosclerosis, which is the hardening and the damage of your arteries. This is showing that from the perspective of your cardiac arteries. Basically with the excess fats as well as excess sugars with high blood sugar in your blood, these damage the lining of your arteries. And as that happens, inflammation occurs and fats in the blood will be attracted to those and sort of like lay down a wall, if you will. And then your immune system goes that doesn't belong there. So it covers them all up. And so then you can see now you have less space in your artery for blood to flow because you've had these blockages formed. And this is a rough surface. So now you have the opportunity to put more fats on this and until you ultimately get a fully clogged artery. This is what a fully clogged artery looks like. This in addition, even if they're not fully clogged, if you have some blockage, it's likely more likely that they can break off or blood clots can form and block blood flow. And that's what leads to things like heart attacks and strokes.
So you want to focus on lean or round designations for meat, fish and chicken and turkey are all good options. Tofu, you do need to have some fat in your diet. Nuts and seeds are excellent sources and plant-paste oils as well as avocados. And then for dairy, just limit your dairy, but you want to eat relatively small amounts of dairy.
triglycerides
energy
protection
insulation
maintaining body temperature
Triglyceride => glycerol other are 3 fatty acids
fatty acid= carbon change link
saturated fatty acids maximum hydrogen one or more double bond
monoone saturated fatty acid
poly saturated carbon double bond omega 6 fatty acid
poly saturated carbon
fat molecule has glycerol with 3 fatty acid
in reality there is not one type of fatty acid
for example corn oil little bit of fatty acid
coconut oil mostly saturated fatty acid very tiny of poly fatty acid
relative amount of unsaturated fatty in triglycerides
animal has more saturated fatty acid
hydrogenic
trans fat
hydrogen and fatty acid
here is saturated fatty acid
room temperature
hydrogen been up
hydrogen unsaturated fatty
plant fat are liquid
cis conformation
straight molecule
high heat
very stable at high temperature
transfat-
olive oil
transfat
cooperation food product give negative affect our health
essential fatty acid body cannot synthesis
nervous system , immune , homeostasis of the body we can find them in vegetable oil
total fat only require saturated
9g
trans fat
dietary cholestrol
TG - alot of unsaturated fatty acid
solid in room temperature
Degree of saturation
two other group of lipd
phospholipid - two fatty acid can be saturated and unsaturated
last molecule this phosphate has dissolved in water
main structure of membrane
membrane of organalle
watery solution
we want to have molecules can interact hydophillis
fatty acid tail middle can easily pass through
blood test
cholesterol- help to maintain the plasma membrane
help that small enough to fit in watery environment
oil and vinegar molecules are tiny amount to fit in
phospholipid
sterols
four carbon rings
adrenal hormone
vitamin D
when we eat fat mechanical digestion , lingual lipase start to break down
little bit of
inner small intestine
pancreatic
triglyceride
break down those
small structure will help
bile molecule - hydrophilic can attacch to fat can dissolved in water
emulsifed fat- break down into glycerol and fatty acid
can take one or two path way
can pass through intestine cell
organzied into hydrophobic
water soluable not
into the intestinal cell
back out into the intestinal lumen
organized transported into lymphatic system
chylomicron
lypofat protein
lipid and protein
delivery system
digestive process in our blood stream
we have several kind
very low density of lipoprotein
VLDL made in liver
intermediate density of lipoprotein to broke down the LDL
thrid type LDL too much triglyceride - too much cholestrol
HDL high density lipoprotein
the job of HDL
any access cholesterol
you may have heard HDL and LDL
HDL good cholesterol
LDL to go
adipose tissue
the whole point to store fat
nucleus pretty metabolic
biggest place adipose tissue 60% energy during rest -
During prolong exercise -
High fat diet
Heart disease , cancer and stroke
we learned that limit fat
limit sugar
refine carb diet
Heart failure
high fat diet
stroke
basically
metabolic syndrome
high blood sugar
high blood pressure
important to know your number (Blood pressure)
cheesse cream
bread - bad cholesterol go up
when you eat alot coconut oil LDL down HDL going up
transfat they raise your LDL and they lower your HDL
lining of the artery ,fats in the blood attracted to those
lay down to wall
you have less
artery and blood flow blockage of blood flow
block artery - lead to heart attack and stroke
chicken, turkey, tofu
plant base oil
diary limit amount
choose food high in unsaturated fat
meat and meat alternative - Lean, round, herring salmon, tuna, chicken, tofu
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