Lipids - Online Tutor, Practice Problems & Exam Prep

Lipids

In this video, we're going to begin our lesson on lipids. And so of course, you guys have learned about lipids before in your previous biology courses, and so you probably already know that lipids are just one of the 4 major macromolecules that are found in all living organisms. And really, when it comes down to it, lipids are defined as hydrocarbon-based molecules that are water insoluble or hydrophobic for that matter. And recall that hydrophobic just means that they are water-fearing, meaning that they do not mix well with water. Now, although all lipids have some region or group that is water insoluble or hydrophobic, there are also some lipids that can also be amphipathic, which you might recall just means that they contain both hydrophobic and hydrophilic groups.

And another thing to note about lipids is that unlike the other 3 major categories of macromolecules — proteins, carbohydrates, and nucleic acids — lipids actually do not form polymers or long chains of repeating monomer subunits. And that is one reason for why lipids are some of the most structurally and functionally diverse classes of macromolecules or biomolecules. And so, if we take a look at our image down below, what you'll notice is at the top, we have the other 3 major macromolecules, proteins, carbohydrates, and nucleic acids. Notice that all of these form polymers, and so, they are long chains of repeating subunits. And, this is going to, again, be very different from the lipids that we see down below. It's very important to note that lipids do not form polymers.

And what you'll notice is that we've got all of these different structures here and all of these are lipids, and they are very diverse in their structure. So this over here, it looks very different than this structure over here, which looks very different than this structure over here. But one thing that they have in common is that they all contain hydrocarbons, and you can see the hydrocarbons here in these molecules, and they're all going to have some kind of water insoluble or hydrophobic group. Now, again, they can also be amphipathic because notice that these hydrocarbon chains here are hydrophobic or water-fearing just like this little kid here is afraid of the water. But these hydrophobic regions can also be linked to hydrophilic or polar groups that are water-loving. And so, that is what can make some lipids amphipathic.

Moving forward in our course, we're going to be talking about lots of different types of lipids and different groups, and we'll be able to see that these indeed are the most structurally and functionally diverse class of biomolecules. And so, this here concludes our introduction to lipids, and we'll continue to learn more about them as we move forward in our course. So I'll see you guys in our next video.

Lipids

Alright. So now that we've briefly introduced lipids, in this video we're going to talk about the functional diversity of lipids. We already know from our last lesson video that lipids are the most structurally and functionally diverse class of biomolecules, which means that lipids must display an enormous variety of biological functions. They display such a large amount of biological functions that it's not possible to list all of the biological functions on this page. Instead, we're going to talk about some of the primary functions that lipids have, and we'll talk more about these primary functions as we move along through our course.

The first primary function of lipids is one that you guys probably already know about from your previous biology courses - the function that allows some lipids to act as long-term energy storage molecules. Just like batteries are capable of storing energy over long periods of time, some lipids can store energy over long periods of time in their hydrocarbon chains. We'll discuss more about this function as we progress in our course.

Lipids are also going to be the major structural component of membranes. We'll explore more about membranes later in our course. Lipids play a crucial role in regulating temperature; they can regulate the temperature of an entire organism, and they are also vital for regulating the temperature of individual cells. They are also important for managing biological activity under different types of temperatures. We'll delve deeper into this as we continue through our course.

Lastly, some lipids are very important for bio-signaling, which allows cells to communicate with each other. You can see below two separate cells that are capable of communicating with each other. We'll discuss more about this function later in our course. But for now, you have a general idea of what lipids are capable of doing for a cell, and we'll be able to talk more about lipids as we move along.

So, I'll see you guys in our next video.

Amphipathic molecules can interact with both lipids and water because they:

a) Function as nucleic acids. 

b) Contain hydrophobic and non-polar groups. 

c) Contain polar and hydrophilic groups.

d) Contain non-polar and hydrophilic groups.

e) Function as long-term-energy-storage molecules.

• A. Function as nucleic acids.
• B. Contain hydrophobic and non-polar groups.
• C. Contain polar and hydrophilic groups.
• D. Contain non-polar and hydrophilic groups.
• E. Function as long-term-energy-storage molecules.

Lipids

Alright, so now that we've introduced lipids and some of their biological functions, in this video we're going to introduce a critical lipid map that's going to be super helpful for you guys as you move forward throughout our entire lesson on lipids. It's important to note that there are actually thousands of different molecules that are classified as lipids. There are so many different molecules that it makes it really challenging to categorize lipids in a simple way. These thousands of different molecules can be categorized based on similarities in their biological functions, or they could be categorized based on similarities in their chemical structures. You might find that your textbooks or your professors categorize lipids in slightly different ways. However, here at Clutch Prep, we've specifically chosen to categorize these thousands of different molecules based on similarities in their chemical structures. The map you see down below is based on these similarities, and we believe this is the easiest way for you to learn about lipids and how they relate to each other structurally. We'll also talk about the biological roles of these lipids as we move through our course.

What you'll notice down below is a flowchart, which is really just a map, of our entire lesson on lipids. You can use this flowchart or map continuously throughout our entire lesson on lipids. This will be a super helpful guide to ensure that you don't get lost as we maneuver our way through our lesson on lipids. Taking a closer look at our lipid map down below, at the very top we have lipids, and immediately the lipids can be branched into two different groups. We have this left branch over here, which are the fatty acids and the fatty acid-based lipids, and then we have this right branch over here which are the isoprenes and the isoprene-based lipids. Moving forward in our course, we're first going to explore all of the fatty acid-based lipids, and after that, we'll zoom back out and explore the isoprene-based lipids. We're going to cover the isoprenes last and, moving forward in our course, we'll see different versions of our map and we're going to abbreviate the isoprenes using this molecule right here, which is an isoprene molecule. Again, we're going to explore all of the fatty acid-based lipids first.

Another really cool feature of this map is that it's a reflection of the order that we're going to cover these topics. You can actually use this lipid map to make predictions about what we're going to cover next. For example, we know that we're going to explore the fatty acid-based lipids first. In our next lesson video, you should expect to see fatty acids. After we've finished talking about fatty acids, the next thing that you should expect to see are glycerolipids. We're going to be covering the furthest branches to the left in their entirety and then zoom out and start to cover all of these other branches in this fashion. Once we make our way through all of the fatty acid-based lipids, we're going to finally zoom out and take the right branch and explore the isoprenes. Because this lipid map here is continuously referring to this map, I'll be continuously referring to this map as we move along through our course. This concludes our introduction to this lipid map, and we'll be able to get a little bit of practice before we actually move forward and start exploring the fatty acid-based lipids. So, I'll see you guys in our next video.

Lipids include a wide range of compounds including which of the following?

a) Cholesterol, cellulose, cerebrosides, and fats. 

b) Chitin, starch, polysaccharides, and glucose. 

c) Waxes, fats, phospholipids, and steroids.

d) Nucleic acids, triacylglycerols, and gangliosides. 

• A. Cholesterol, cellulose, cerebrosides, and fats.
• B. Chitin, starch, polysaccharides, and glucose.
• C. Waxes, fats, phospholipids, and steroids.
• D. Nucleic acids, triacylglycerols, and gangliosides.

Using the lipid map above, which of the following types of lipids is NOT derived from a fatty acid precursor?

a) Steroids.

b) Waxes.

c) Glycerolipids.

d) Eicosanoids.

e) Sphingolipids. 

• A. Steroids.
• B. Waxes.
• C. Glycerolipids.
• D. Eicosanoids.
• E. Sphingolipids.