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Lecture 18 Supplemental Material Video Introduction to Lipids — Transcript

by Michelle Henderson · 3,031 words · 549 segments · language en · Watch on YouTube

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0:01so i wanted to walk through supplemental
0:02material
0:03for lipids and give y'all a quick recap
0:06when you look at
0:06structural differences as well as
0:08functional difference
0:10uh differences in lipids so a couple of
0:13things to remember when we look at
0:14lipids we can think about it in two
0:16different ways we can
0:17classify them based on their function
0:20and we can
0:21classify them based on structure
0:24when we look at function there's three
0:26major biological functions they can be
0:28associated with
0:29forming bilayers that become the basis
0:31of biological membranes
0:33we can look at them in terms of being
0:34major energy reserves
0:36based on energy contained in the
0:38hydrocarbon side chains
0:39and also the fact that they are involved
0:41in many
0:42intra as well as intracellular signaling
0:45events
0:46classifications we're going to see are
0:47going to be fatty acids which become
0:49major components in other classes of
0:51fatty acids
0:53triacylglycerols which are our energy
0:55storage
0:56and we have glycerophospholipids
0:59and sphingolipids both of which play in
1:02important roles in membranes
1:04and then we looked at the diverse class
1:06where we looked at steroids
1:08and again we're going to think about
1:11steroids
1:13in terms of steroid hormones
1:19we're going to think about these in
1:20terms of vitamins
1:24and we're also going to um think about
1:26these in terms of
1:29carcinoids those important
1:3220 carbon units as they're involved with
1:35the process
1:35of inflammation
1:38so when we think about fatty acids uh
1:41sorting them based on polarity becomes
1:43important in looking at structures so in
1:46this part we're going to
1:47focus on this top four
1:50we're going to look at fatty acids and
1:52how these become major components
1:55of the other classes of
1:58lipids so nonpolar lipids are the ones
2:00we think of
2:01for energy storage whereas polar lipids
2:03become the basis of bilayers
2:06when we look at the nonpolar lipids what
2:08we have
2:09are glycerol backbone esterified to
2:12three different fatty acids
2:14and these are going to be linked to each
2:16of the different carbons
2:17and this is going to be the formation of
2:19our ester bond
2:21when we look at these our polarity
2:24is now neutralized because of the ester
2:27bond that we formed between the charged
2:29fatty acid
2:30carboxylic acid head group and the ohs
2:32of the glycerol
2:34then what we start to see are the
2:35modifications that happen so the first
2:37thing that we see in
2:38changing is the fact that we've replaced
2:40a fatty acid
2:41with a phosphate containing head group
2:46and we can have some modifications in
2:48terms of what that head group is
2:50contained
2:51because these still have the glycerol
2:54backbone
2:55and ester bonds to our fatty acid we
2:58call these glycerol phospholipids
3:01glycerophospholipids are one of the
3:02major membrane components and make up
3:04part of what we call the phospholipids
3:06we also have sphingolipids these also
3:09are going to contain a phosphate
3:12phosphate containing head group but this
3:13time with choline and what we see
3:15is now the glycerol backbone and
3:19the c1 fatty acid has been replaced with
3:22the sphingosine unit
3:23and we have an n-linked an n-linked
3:27fatty acid
3:29and this phosphate containing head group
3:32the other rule that we see for
3:36sphingosine and our n-linked fatty acid
3:39and remember this
3:40is what we call a ceramide is that we
3:42can modify the head group to become a
3:43sugar
3:44so if it's a sugar head group it now
3:47becomes part of the glycolipid family
3:50and we can have cerebrosides
3:54in which we can look at monosaccharides
3:57like
3:58glucose and galactose modifying it or we
4:00can have
4:01gangliosides and this is where we have
4:05three or more sugar head groups
4:09and we call this the oligo mini
4:11saccharides
4:12and this is where we see our gm1
4:16gm2 and gm3
4:21and we did not cover these two classes
4:25so knowing the cartoon structure can be
4:27really helpful as you look through
4:29these different lipid structures and
4:31that's why i'm going to try to walk
4:32through in this
4:33supplemental materials to remind you
4:35these important structural
4:36characteristics as well as well as what
4:38their functions are
4:39in a cell so fatty acids we have our
4:42carboxylic acids these are our head
4:44groups that are going to be
4:45hydrophilic and also capable
4:49of forming esters ester bonds and amide
4:52linkages
4:54these we see are going to have these
4:56hydrocarbon side chains
4:57and these are going to be what are
4:59hydrophobic and therefore in cellular
5:02environment
5:03are going to aggregate and seek out
5:05other hydrophobic interactions
5:07we also see we look at fatty acids the
5:10two important things to ask
5:12number of questions sorry two important
5:14questions to ask
5:15the number of carbons that exist and the
5:18number of double bonds
5:20which we can also think of as the degree
5:23of saturation
5:25when we look at this first example we
5:27see that we have carbon 18
5:29and then this tells me the number of 18
5:31carbons in the fatty acid
5:33colon and the number is going to tell me
5:34the number of double bonds
5:36you should know that this is stearic
5:37acid and then in this example we have
5:40c18
5:40we have one double bond and i can use my
5:42delta symbol to tell me this is that
5:44carbon 9
5:45and this would be oilic acid these are
5:47major components these fatty acids that
5:50form other various lipid structures
5:52and again can be saturated or
5:54unsaturated
5:55we then go to trisoglycerols these are
5:58fatty acid triesters of glycerol these
6:00are nonpolar
6:02highly water water insoluble
6:06these are found in cells called
6:07adipocytes
6:09which make up adipose tissue
6:14these become our major energy reserves
6:17when we look at the cartoon structure we
6:19see our glycerol bond
6:21our glycerol backbone our ester bond and
6:24we have
6:25three different fatty acids linked at
6:28carbons one carbons two and carbon three
6:31and these fatty acids can either each be
6:34unique or
6:34sometimes we'll see that two are the
6:36same and then the third one is unique
6:38here we have our example of a true fatty
6:41acid so again
6:42looking at our glycerol backbone we note
6:44our ester bonds
6:46we see in this case that we have one
6:48palmittoyal two
6:49in oil three sterile glycerol so
6:52remember you need to know those basic
6:54fatty acid structures that were covered
6:56in the lecture video
6:57and once you know these and you can read
7:00nomenclature
7:01you know what location they would have
7:03or i could give you the structure and
7:04you could count
7:05your carbons and make sure that
7:08you know you understand what fatty acid
7:10that you're looking at when we look at
7:12triazole glycerols as major inner
7:13reserves we've actually talked about two
7:15sources of
7:15energy one is glycogen
7:19and this is our carb energy source
7:23and the second we have is our fats which
7:26is in the form
7:27of glycerol
7:32when we look at these they both allow
7:34for energy
7:35glycogen breaks down to allow for
7:38glucose to be formed and your body has
7:40about one day
7:41supply of glucose from this
7:44tricyl glycerols are going to break down
7:46and we're going to get from that
7:48acetyl or acetyl coa
7:51and your body is going to have from that
7:54about two to three months supply of
7:56energy
7:57when we look at the two versions
8:00what we see is that your body is going
8:03to toggle between these based on energy
8:06needs and what's happening what your
8:08diet is like
8:09so for most if we have a balance of
8:11glycogen and fat supply
8:13plan a is going to be that we're going
8:14to utilize carbohydrates first
8:17because these are our readily mobilized
8:19energy form
8:24however it's meant to be short-term so
8:26if your body is not able to keep up
8:29with supplying energy to all of your
8:31different cell types using carbs your
8:33body will flip
8:34over to what's called fat burning mode
8:36and we can think about this as being
8:38plan b of course the type of exercise
8:40that you do
8:41as well as the type of diet you have and
8:44also adding into that the amount of rest
8:45and proper sleep that you get is always
8:47going to
8:47play a role in how your body toggles
8:49between
8:50utilizing carbs and fats as an energy
8:53source
8:55so when we look at fats glycerol
8:57backbone identified with the esterified
8:59fatty acid
9:00and then your fatty acid chains next
9:03what we have are glycerophospholipids
9:05these are the major lipid components of
9:06biological membranes
9:08and we have replaced one of the fatty
9:10acids with a phosphate containing head
9:12group
9:13when we look at these we are going to
9:15have two different
9:17uh fatty acids that are linked to
9:19carbons one and two
9:20we have our phospha containing head
9:22groups our phosphate
9:24and it is linked to a head group that
9:26can be
9:27many different things there's a table
9:29that outlined those for you
9:30and these can have a range in terms of
9:33structure
9:34so variation and structure and this is
9:37important because it can play a
9:39different role in terms of specificity
9:41and interactions so here
9:44we have an example of one steroid to
9:47arroyo iii
9:47phosphatidylcholine so the first thing
9:50that we see is carbon one
9:52uh stearic acid is the fatty acid that's
9:55going to be esterfied to the cholesterol
9:56backbone
9:57we see at carbon one in general we see
9:59fatty acids ester fiber that are going
10:01to be saturated
10:03so that means zero double bonds and
10:06containing 16 or 18 carbons
10:08we can compare that at carbon 2 where we
10:10have oilic acid
10:12this is going to be a carbon 2 a fatty
10:14acid that's going to be unsaturated
10:17and is esterified and usually contains
10:1916 or 18
10:20carbons long and then in this case at
10:22carbon 3 where a head group exists we
10:24have phosphatidylcholine
10:26so this is our phosphate containing head
10:28group and in this case
10:29we see a structure of choline
10:35then we have sphingolipids sphingolipids
10:38are a major
10:40class of membrane lipids
10:43that exist that are broken down into
10:45three different groups
10:47the similarity in all of these is that
10:49we introduced
10:53sphingosine and this is the portion that
10:56is shown here
10:57in black that serves as the backbone so
10:59we've replaced glycerol and the c1 fatty
11:02acid
11:03and you can have attached to this an
11:05amide linked
11:07fatty acid and those together are going
11:10to give you
11:10the ceramide and the ceramide is what
11:13becomes the basic
11:15building block
11:20for this particular class of single
11:23lipids
11:24and the variation between them is going
11:26to come to what is attached at
11:28carbon 3 in terms of the head group so
11:30the first example we see
11:32is sphingomyelins this is a type of
11:34single lipid that's particularly found
11:35in
11:36central nervous system and makes up the
11:39myelin sheath
11:40when we look at its structure what we
11:43see is
11:44a phosphate head group and attached to
11:46that choline
11:48then what we have is and again i'm sorry
11:51this becomes the
11:52ceramide unit and so we're looking at
11:56the modifications here
11:57of our head group and then we have the
11:59two other classes
12:01ribosides and gangliosides and these are
12:03going to have
12:04saccharides as their head group so if
12:07it's monosaccharide we call that a
12:10cerebroside
12:11monosaccharide here and we can see
12:14glucose
12:15or galactose serve as the
12:19monosaccharide attachment and then we
12:21can also have oligosaccharides and this
12:23is going to be what makes up
12:24gangliosides
12:25one of the sugars is going to be xylic
12:27acid
12:28and when we look at these they can have
12:30either three
12:31four or five sugars that make up
12:35our uh different gm
12:38that we label one two three and these
12:41can function in different ways they can
12:43serve as receptors for hormones
12:45uh also surface entry point for toxins
12:47they can play a role in cell growth they
12:49can play a role in cell differentiation
12:51for that reason we also have important
12:52studies that are tying it now to
12:55carcinogenesis uh cancer cells and we
12:58talked about the fact that for decades
13:00the structure
13:00of gangliosides has been noted
13:04but even today we're still having
13:05hundreds of articles every year come out
13:08in terms of scientific publications
13:10figuring out the role in which these
13:11gangliosides play because there's still
13:13much to be learned
13:14in terms of what these uh lipids do
13:18and then the fifth class was looking at
13:20sterols so we have these
13:23different sterile derivatives that have
13:24unique functions
13:26and this is going to come from those
13:28four rings
13:31um that are fused together and we can
13:33look at different modifications and it
13:34can occur
13:36so the first class we looked at are what
13:37we call steroid hormones
13:40and most of you have heard of estrogen
13:44and testosterone and know the importance
13:45that that plays
13:46in sexual maturation and development
13:50but we also talked about glucocorticoids
13:51and mineral corticoids and how these are
13:53made of the adrenal glands so i wanted
13:55to expand upon that a little bit
13:57as a reminder your adrenal glands are
13:59located just above the kidneys
14:01and these adrenal glands release
14:04different signal molecules that are
14:06related to stress
14:08now we've actually talked about
14:09epinephrine a little bit norepinephrine
14:12and we can talk about adrenal
14:16adrenaline rushes and we can talk about
14:19this as
14:20fight or flight response
14:25and what this does is a short-term
14:27response in which your central nervous
14:29system your
14:30your brain perceives something that's
14:32sent through the body of the message
14:34and what it does is to increase your
14:37breathing rate and your blood pressure
14:38change your heart rate speeds up
14:41and it's going to cause alterations in
14:42your blood flow patterns and the reason
14:44for this
14:45is to allow for metabolic rate to be
14:47increased
14:48because it's really all about gaining
14:50energy
14:52and what happens is your body's going to
14:54start to utilize glycogen reserves and
14:56break it down
14:57activate glycogen phosphorylase to allow
15:00for amounts of glucose to be released
15:02and for blood glucose levels to go up so
15:04that energy molecules are being sent
15:06and your body can fight or flight
15:08response
15:10then what we also have are
15:11glucocorticoids and mineral corticoids
15:14glucocorticoids if you'll remember uh
15:16one of the more commons is cortisol
15:19and these are involved in also allowing
15:21for energy to be gained where
15:23proteins and fats are utilized in order
15:27to allow for
15:28glucose to be made and also conserve to
15:32suppress immune system responses mineral
15:35corticoids affect how kidneys function
15:37particularly as it relates to sodium ion
15:39concentrations in water
15:41and these also are going to affect blood
15:43volume as well as blood pressure
15:45when we look at these classes of steroid
15:48hormones we realize that these have to
15:49be regulated
15:51we have to make sure that enough are
15:53being made and not too much long term
15:56or they can have potentially unintended
15:59side effects we talked about
16:00the disease state of addison's disease
16:03as well as cushing's
16:05the second group that we talked about
16:06are the lipid soil vitamin
16:08soluble vitamins and these you get from
16:11your diet
16:12vitamin a i always hear people tell you
16:14eat your carrots so you have good vision
16:17this plays a role in visual pigment
16:20particularly
16:21low light receptors so that you're able
16:23to see we have vitamin d that plays an
16:25important role in how your body absorbs
16:27calcium and we know calcium is important
16:30in different metabolic pathways we're
16:32about to look at this in membrane
16:34transport
16:34but also plays a role in bone growth too
16:37much calcium can have an issue in terms
16:39of affecting solubilities
16:42and too little can lead to improper bone
16:45growth so we have to have the body get
16:46those levels
16:48correct we talked about vitamin e how
16:50this serves as an antioxidant it
16:52associates with other membrane lipids
16:54and proteins
16:55so when things like reactive oxygen
16:57species that can either be produced
16:59within the mitochondria
17:00of the cell or from the environment that
17:03can do damage
17:04that we hope that this vitamin e uh will
17:07react with the ros
17:08and allow for it to be damaged and
17:10therefore protect
17:11membrane components from any kind of
17:13damage and the last one we talked about
17:15was vitamin k
17:17you also get about half of your daily
17:19supply
17:21is going to come from bacteria
17:25that exists in your gut part of your gi
17:28tract
17:30and this plays an important role in
17:33serving to allow for
17:35activation of coagulation factors so
17:37that blood clotting can occur
17:40and the third thing that we introduced
17:42was talking about signaling so i like
17:45this image because i want to put some
17:46things together for you for us when we
17:47talk about lipids everything has really
17:49started with the fatty acid structure
17:51so i wanted to point out that acetyl-coa
17:54is a two-carbon unit and this is which
17:56uses the building block to make fatty
17:57acids this is why fatty acids exist in
17:59even number carbons
18:01when we um biosynthesize them
18:04and when we look at fatty acids we see
18:06that these can be
18:08a basis for glycerol lipids or
18:11phospholipids and sphingolipids
18:13all which are going to have a function
18:15as part of the membrane structure
18:18but we're also going to see that fatty
18:20acids can
18:21allow for modification to sterols
18:24cholesterol esters is an example of this
18:26as well as break down and allow for uh
18:29formation of it carcinoids
18:31they're again the 20 carbon unit this is
18:34where we have leukotrienes thromboxanes
18:37prostaglandins
18:38and they can play a role in inflammation
18:41they can play a role in
18:44isodilation and also a role in
18:49vasoconstriction
18:52and then we also can see that fatty
18:54acids can be broken down into acetyl-coa
18:56and then these units can be used to make
18:57something called isopentyl pyrophosphate
19:00and this becomes the basis by which your
19:02body can make
19:04sterols and we're going to
19:07continue to talk about cholesterol in
19:09particular
19:10as we look at the role it also can play
19:13in membrane function so hopefully this
19:16serves as a good reminder
19:17remember to look not only at structure
19:21but also how differences in structure
19:23allow for
19:24different functions physiologically

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