Lipids Part 1: TAGs, Fatty Acids, and Terpenes

Summary

In this educational video, Professor Dave delves into the world of lipids, highlighting their nonpolar nature and diverse types, including triacylglycerols (TAGs), which can be oils or fats. He explains the difference between saturated and unsaturated fatty acids, the health implications of trans fats, and the role of lipids in energy storage. The video also touches on the formation of soap from fatty acids and introduces terpenes and terpenoids, showcasing lipids' importance in our daily life and health.

Takeaways

• 🧪 Lipids are a class of biomolecules that include fats, oils, and steroids, and are largely nonpolar with long hydrocarbon chains or ring systems.
• 🍯 Triacylglycerols (TAGs) are lipids with three ester groups and can be found in oils and fats, with the state depending on the saturation of their fatty acids.
• 🌡 Saturated fatty acids have higher melting points than unsaturated ones due to the lack of kinks in their structure, allowing for tighter packing and stronger van der Waals forces.
• 🔁 Unsaturated fatty acids can be further classified into monounsaturated and polyunsaturated, with the presence of one or multiple double bonds, respectively.
• 🚫 Trans fats are harmful as they have a linear shape that increases their melting point, making them more solid and difficult to metabolize, and are associated with cardiovascular disease.
• 💡 Omega-3 fatty acids have a double bond on the third carbon from the end of the chain and are important for health.
• 🧼 The sodium salt of fatty acids, when deprotonated, forms soap molecules that can clean by forming micelles which trap dirt and grease, making it water-soluble.
• 🌿 Terpenes and terpenoids are lipids made up of repeating isoprene units, with terpenoids containing oxygen atoms and found in various plants and fruits.
• 🔬 Hydrogenated vegetable oils are derived from polyunsaturated fats by adding hydrogen, but partial hydrogenation can create trans fats.
• 🔋 TAGs serve as energy storage in the body, releasing more energy upon metabolism than carbohydrates due to the abundance of carbon-hydrogen bonds.
• 🍽 The discussion on the ideal ratio of saturated to unsaturated fats in the diet is ongoing and requires further examination.

Q & A

What are lipids?

Lipids are a group of biomolecules that include fats, oils, and steroids. They are characterized by being largely nonpolar and composed predominantly of long hydrocarbon chains or ring systems.

Why are lipids not typically classified as macromolecules?

Lipids are usually not big enough to be classified as macromolecules because their molecular size is generally smaller compared to polymers like proteins or nucleic acids.

What is the difference between oils and fats?

Oils are triacylglycerols (TAGs) that are liquid at room temperature, while fats are TAGs that are solid at room temperature.

What happens when TAGs are hydrolyzed?

When TAGs are hydrolyzed, glycerol and three fatty acids are produced. This process involves a hydroxide attacking each carbonyl group in the TAG.

What are fatty acids and why are they important in TAGs?

Fatty acids are carboxylic acids with long nonpolar hydrocarbon tails. They are important in TAGs as they form the ester groups that make up the TAG structure.

What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids have only single bonds in their hydrocarbon chains, maximizing the number of hydrogen atoms. Unsaturated fatty acids have one or more double bonds, which can be either monounsaturated or polyunsaturated.

Why are trans fats considered harmful?

Trans fats are harmful because their linear shape gives them a higher melting point, making them more likely to remain solid and more difficult to metabolize. They are associated with cardiovascular disease.

How do the physical properties of fatty acids affect the melting points of fats?

Saturated fatty acids have higher melting points than unsaturated ones. Double bonds in unsaturated fatty acids restrict rotation and cause a kink in the chain, interfering with crystal packing and lowering the melting point.

What is the role of fats in energy storage in the human body?

Fats, like TAGs, serve as energy storage in the human body. When metabolized, they release twice as much energy as carbohydrates due to the numerous carbon-hydrogen bonds.

What is the significance of the sodium salt of fatty acids in soap formation?

When the carboxyl group of fatty acids is deprotonated to form the sodium salt, soap molecules are created. These molecules have a polar head and a nonpolar tail, which help in forming micelles that trap and remove nonpolar dirt or grease.

What are terpenes and terpenoids, and how do they differ from each other?

Terpenes and terpenoids are polymers made up of repeating isoprene units. Terpenes are hydrocarbons, while terpenoids contain oxygen atoms. Terpenoids can be found in various plants and fruits, such as menthol in peppermint.

What is the role of steroids in lipids?

The script does not provide specific details about the role of steroids in lipids, but generally, steroids are a type of lipid that includes cholesterol and other compounds with a characteristic ring structure.

Outlines

00:00

🧪 Lipids: Structure and Types

Professor Dave introduces lipids, a class of biomolecules that includes fats, oils, and steroids. Lipids are nonpolar and typically composed of long hydrocarbon chains or ring systems, and they are not large enough to be considered macromolecules. The video explores different lipid types, starting with triacylglycerols (TAGs), which have three ester groups and can be oils or fats depending on their state at room temperature. TAGs are hydrolyzed into glycerol and fatty acids, which can be saturated, unsaturated, or polyunsaturated, with the latter often containing trans fats that are harmful to health. The melting points of these fats are influenced by the presence of double bonds, which affect their ability to form solid structures. Omega-3 fatty acids are highlighted for their unique double bond placement. Hydrogenated vegetable oils are discussed as a source of trans fats due to partial hydrogenation. The energy storage role of fats in the body is emphasized, noting that they provide more energy than carbohydrates upon metabolism. The discussion concludes with the role of fatty acids in soap production, where their deprotonated form helps in forming micelles that trap and remove nonpolar dirt.

05:02

🌿 Terpenes and Terpenoids: Diversity in Lipids

The second paragraph delves into terpenes and terpenoids, lipids formed from repeating isoprene units. Terpenes, such as myrcene and farnesene, are varied in structure, with examples like limonene showcasing ring formation. Larger structures like beta-carotene, composed of eight isoprene units, are also highlighted. Terpenoids differ from terpenes by incorporating oxygen atoms, with menthol from peppermint being a notable example. The paragraph emphasizes the diversity and ubiquity of these lipids in plants and fruits, contributing to their flavors and other biological functions. The video concludes with an invitation to subscribe for more tutorials and to contact Professor Dave for further inquiries.

Keywords

💡Lipids

Lipids are a class of biological molecules that include fats, oils, and steroids. They are characterized by being largely nonpolar and composed predominantly of long hydrocarbon chains or ring systems. In the context of the video, lipids are not typically large enough to be classified as macromolecules, which is a key distinction from other biomolecules like proteins and nucleic acids. Lipids play a crucial role in energy storage, cell membrane structure, and as signaling molecules.

💡Triacylglycerols (TAGs)

Triacylglycerols, or TAGs, are a type of lipid that consist of three ester groups. They are found in substances like peanut oil, corn oil, butter, and lard. TAGs that are liquid at room temperature are referred to as oils, while those that are solid are called fats. The video explains that TAGs can be hydrolyzed to yield glycerol and three fatty acids, highlighting their role in energy storage and their different states based on the type of acyl groups they contain.

💡Ester Groups

Ester groups are chemical structures found in TAGs, where a hydrocarbon chain is linked to a carboxylic acid through an ester bond. The video mentions that TAGs have three ester groups, and their hydrolysis results in the release of glycerol and fatty acids. The nature of these ester groups, including the presence of double bonds, determines whether the TAG is a saturated or unsaturated fatty acid.

💡Fatty Acids

Fatty acids are carboxylic acids with long nonpolar hydrocarbon tails. They are derived from TAGs through hydrolysis and can vary in their structure, particularly in the number and arrangement of carbon-carbon bonds. The video discusses saturated fatty acids, which have no double bonds and a high hydrogen content, and unsaturated fatty acids, which contain one or more double bonds, affecting their melting points and health implications.

💡Saturated Fatty Acids

Saturated fatty acids are a type of fatty acid that contains only single carbon-carbon bonds in their hydrocarbon chain. This means they have the maximum number of hydrogen atoms possible, leading to higher melting points. The video uses butter as an example of a saturated fat, explaining that its solid state at room temperature is due to the neat packing of these fatty acids, maximizing van der Waals attractions.

💡Unsaturated Fatty Acids

Unsaturated fatty acids are fatty acids that contain one or more double bonds in their hydrocarbon chain. The presence of these double bonds introduces a 'kink' in the chain, preventing tight packing and thus lowering the melting point. The video contrasts saturated fatty acids with unsaturated ones, using olive oil as an example of a liquid oil due to its unsaturated nature.

💡Trans Fats

Trans fats are a type of unsaturated fat where the hydrogen atoms in the double bond are on opposite sides of the carbon-carbon bond, giving a linear shape. The video mentions that trans fats are harmful to the human body, as they have a higher melting point and are more difficult to metabolize. They are associated with cardiovascular disease and are formed when cis double bonds in unsaturated fats are isomerized.

💡Omega-3 Fatty Acids

Omega-3 fatty acids are a type of polyunsaturated fatty acid where the first double bond is located at the third carbon from the end of the hydrocarbon chain. The video briefly mentions omega-3 fatty acids without detailed explanation, but they are known for their health benefits, such as reducing inflammation and supporting brain function.

💡Hydrogenated Vegetable Oils

Hydrogenated vegetable oils are fats that have undergone a process of hydrogenation, where some of the double bonds in polyunsaturated fats are converted to single bonds. The video warns that partial hydrogenation can lead to the formation of trans fats, which are detrimental to health. This process is used to increase the shelf life and stability of oils.

💡Terpenes and Terpenoids

Terpenes and terpenoids are a class of lipids that are polymers made up of repeating isoprene units, a 5-carbon diene. Terpenes are hydrocarbons, while terpenoids contain oxygen atoms. The video provides examples such as myrcene, farnesene, and limonene, which are found in various plants and fruits. Terpenoids like menthol are also mentioned, illustrating the diversity of these lipids in nature.

💡Steroids

Steroids are a type of lipid characterized by a ring structure composed of four fused carbon rings. The video briefly mentions steroids as another type of lipid, but does not delve into their specific functions or examples. Steroids are known for their roles in various biological processes, including hormone production and cell membrane integrity.

Highlights

Lipids are nonpolar biomolecules composed of long hydrocarbon chains or ring systems.

Triacylglycerols (TAGs) are the main type of lipids, including peanut oil, corn oil, butter, and lard.

TAGs can be oils or fats, depending on their state at room temperature.

Fatty acids are carboxylic acids with long nonpolar hydrocarbon tails, varying in saturation.

Saturated fatty acids have the maximum number of hydrogen atoms and higher melting points.

Unsaturated fatty acids contain one or more double bonds, affecting their structure and properties.

Trans fats are harmful due to their linear shape, increasing the risk of cardiovascular disease.

Saturated fatty acids can form an orderly solid lattice due to their ability to maximize van der Waals attractions.

Omega-3 fatty acids have a double bond at the third carbon from the end of the chain.

Hydrogenated vegetable oils can lead to the formation of trans fats through partial hydrogenation.

TAGs serve as energy storage, releasing more energy than carbohydrates during metabolism.

Stored body fat provides long-term energy, sustaining life for up to a month without food intake.

The role of fatty acids in soap formation through the creation of sodium salts and micelles.

Terpenes and terpenoids are lipids made of repeating isoprene units, found in various plants and fruits.

Terpenoids differ from terpenes by containing oxygen atoms, such as in menthol.

Steroids, another type of lipid, will be discussed in further tutorials.

Transcripts

Professor Dave here, let's learn about lipids.

As we continue our survey of biomolecules, we arrive at lipids.

Lipids include things like fats, oils, and steroids, and the key characteristic that

defines them is that they are largely nonpolar, composed predominantly of long

hydrocarbon chains or ring systems, and unlike the two types of polymers we've

discussed, lipids are usually not big enough to be classified as

macromolecules. Let's take a look at some different types of lipids.

First, triacylglycerols, or TAGs.

These are molecules with three ester groups, and examples include peanut oil,

corn oil, butter, and lard. TAGs that are liquid at room temperature are called

oils, and if they're solid, they're called fats. These molecules can differ in the

type of acyl groups they possess, which is this portion of the molecule, which

will always be a hydrocarbon chain of some length. If these ester groups are

hydrolyzed, meaning a hydroxide attacks each carbonyl, kicking off this portion

of the molecule, we get glycerol and three fatty acids. They're called fatty acids

because they are carboxylic acids but they also have long nonpolar hydrocarbon

tails, which can vary depending on the TAG the fatty acid is derived from. Most of

the time this tail is unbranched and contains an even number of carbons. If it

contains all carbon-carbon single bonds, this would be a saturated fatty acid

because it contains the maximum number of hydrogen atoms possible. If there's a

double bond

it's an unsaturated fatty acid. Sometimes there are two or three double bonds,

which would make it a polyunsaturated fatty acid. In naturally occurring fats

the double bonds are almost always cis. When we hear about trans fats, these are

the ones that seem to be harmful to the human body, as their linear shape gives

them a higher melting point, so they are more likely to remain solid and more

difficult to metabolize.

These are associated with cardiovascular disease. In general, saturated fatty acids

have higher melting points than unsaturated ones, because the double

bonds restrict rotation and therefore cause a kink in the chain, which

interferes with crystal packing. Saturated fatty acids can pack neatly

and maximize van der Waals attractions.

That's why butter, which is fully saturated, is a solid at room temperature

whereas olive oil, which has a degree of unsaturation in one of its hydrocarbon

chains, is less able to form an orderly solid lattice and is therefore a liquid

at room temperature. An omega-3 fatty acid is one where the third carbon from

the end of the chain is participating in a double bond. When we talk about

hydrogenated vegetable oils, these are derived by hydrogenating some of the

double bonds in polyunsaturated fats. One problem with partial hydrogenation is

that it can sometimes isomerize double bonds, turning cis into trans, resulting

in trans fats, which as we said, should be avoided. In general fats like TAGs are

used as energy storage. When these are metabolized in our bodies, they release

twice as much energy as carbohydrates, since there are so many carbon-hydrogen bonds.

Furthermore, polysaccharides like glycogen only provide energy for about a

day, whereas the fats we store that make up around twenty percent of our body

mass provide long-term energy storage, which would keep us alive for up to a

month without any food intake if necessary.

Still, there is much discussion about how much saturated fat and unsaturated fat

should be in our diet, but we will have to examine that another day.

Another interesting aspect of fatty acids is that when the carboxyl group is

deprotonated to form the sodium salt, you get soap molecules, which have a polar

head and a nonpolar tail. These work by forming micelles in solution, where many

soap molecules orient themselves with the negatively charged carboxylate

groups all facing outwards to maximize ion-dipole interactions with

water molecules, while the hydrophobic hydrocarbon chains point inwards by

exclusion, making van der Waals interactions with one another.

Any nonpolar dirt or grease which is normally not water-soluble can get

trapped inside and willl then wash away with the micelle, which is water-soluble.

That's why washing your hands with just water alone won't do anything, but add

some soap and the dirt gets transported away in little spheres of soap molecules.

Let's discuss another type of lipid: the terpenes and terpenoids. These are

polymers made up of repeating isoprene units, which is this 5 carbon diene.

Here we can see myrcene, a terpene consisting of two isoprene units.

Farnesene, found in apples, has three. The units can be linked to form rings such

as in limonene, which is found in lemons. These can get much larger such as with

beta-carotene, comprised of eight isoprene units, which is found in various

plants and fruits. Terpenoids are similar to terpenes but they contain oxygen

atoms, such as with menthol, found in peppermint. Those are just a few types of

lipids found in our bodies.

Let's continue with lipids as we take a look at steroids.

Thanks for watching, guys. Subscribe to my channel for more tutorials, and as always, feel free to email me: