Lipids are a chemical group of compounds that are responsible for chemical, physical and biological processes in living organisms. A wide variety of life forms contain lipids, which are made from fats, oils and waxes. Lipids are involved in cell membranes, cellular signaling and many other biological processes.
The chemical structure of lipids includes two types of fatty acids and two classes of glycerolipids: triacylglycerols (TAGs).
The structure of TAGs is similar to the structure of proteins but they have added carbon atoms called glycerol units. The glycerol units are attached to the end of one fatty acid chain (called an ester) while the other chain consists only of carbon atoms (called an alcohol). This relationship is called a ketoacyl-coenzyme A (EC 1-6 ) or ketoacyl-CoA deacylase (KDAC) reaction.
Ketones are also produced during lipid metabolism by enzymes such as acetyl-CoA carboxylase/decarboxylase (ACC/CD) and pentose phosphate pathway (PPP), which form a hydroxy acid with acetyl group from a fatty acid.
In some organisms, such as plants and animals, fatty acids are stored in specialized structures called acyl coenzyme A storage materials or lysosomes. These lysosomes fuse with each other after the fatty acids have been broken down by digestive enzymes into smaller molecules that can be absorbed by cells to be used for energy.
The breakdown products include acetyl CoA which can be converted into succinate by succinate dehydrogenase enzyme or β-oxidation pathway and fatty acids can be converted into glucose using hexokinase/phosphofructokinase and glucokinase pathways.
In addition, some bacteria produce non-acetylated lipoproteins containing membrane bound phospholipid that serve as cell membrane components and collectively they become known as cholesterols or ceramides. Lipid metabolism is one of the most important functions performed by cells; it is essential for their proper functioning.
2. What are lipids?
Lipids are the main building blocks of life. They are the smallest organic molecules that play a key role in cell membranes and are essential for cellular functions. Not all lipids are involved in cell membrane formation, however; those that do play a role include fats, waxes, and phospholipids.
But what exactly is a lipid? And how do lipids function?
Like nucleotides, we don’t know exactly what lipids look like or what they serve as to cells but there have been many studies on this topic. A Lipid is an organic molecule that consists of two carbon atoms bonded together by an oxygen atom. It is made up of three functional groups: an oxygen atom (O), a carbon (C), and an nitrogen (N). The O can be either an alkyl group or an aryl group, which gives the molecules their name. The N has a single functional group attached to it like most other organic molecules do but with one important difference.
It needs to carry some additional functionality to be considered a lipid because it is necessary for life and so the body manufactures more than one type of lipid per cell membrane depending on the requirements of that specific cell.
Without further ado, let’s get into some lipids:
3. What are nucleotides?
Lipids are the building blocks of all known life on Earth. They are made up of molecules that form cell membranes and other structural components of all living organisms.
As organs, lipids are every organ in our body, from the heart to the brain, from the liver to the skin, and from stomach to lungs.
Molecules pass through our body by passing through our membranes. The way we do this is by having them travel around long chains called “nucleotides” which have nucleotides attached one after another.
Nucleotides are named by their chemical suffixes: A stands for adenosine (or adenine), C stands for cytosine (or guanine), and G stands for guanosine (or uracil).
4. Do lipids have nucleotides?
I have a question. Are lipids made of nucleotides or not? I saw a post about this question on my Facebook wall recently, and I was wondering if you could answer the following:
Lipids are composed of two types of molecules. Free fatty acids (FFAs), which are saturated, monounsaturated fatty acids and polyunsaturated fatty acids, which are saturated and/or ununsaturated. FFAs come in different forms such as palmitic acid (C16:0), stearic acid (C18:0) and oleic acid (C18:1).
The first part of the question is quite simple: do lipids have nucleotides? The answer is, yes – but not as we know it in our world! Fatty acyl-CoA synthetase is part of our biological system, catalyzing transesterification of long-chain fatty acids into their corresponding triacylglycerol form, cholesterol. This process is termed as triglyceride synthesis and it occurs in every cell in our bodies. In other words, no fats can be made or broken down without cholesterol being present! As for FFA synthesis – that depends on cholesterol.
Transesterification requires cholesterol; in turn transesterification requires a carbon atom from an enoyl-CoA that has been attached to an unsaturated fatty acid molecule by an ester bond called “acyl bond”. Depending on whether it has an acyl-CoA or a free fatty acid molecule attached to it, cholesterol is also required for transesterification…but that’s getting complicated!
Long story short, fat molecules can be broken down into their corresponding triacylglycerol forms by several enzymes depending on which type of molecule they contain – namely fattinesses A and B (fatty acyl CoA synthetase A and B). However, these two enzymes cannot be found in all circumstances; sometimes they do not exist at all! So when you read about lipids that contain long chain fatty acyl-CoA synthetase A or B – let’s just say that those are lipids that contain free fatty acids – because there isn’t any evidence for the presence of fatties A or B!
Are lipids nucleotides or not?
The notion that lipids have nucleotides is a false belief . . . in the sense that it is an unconfirmed hypothesis.
That said, there are some studies that support the idea that lipids are nucleotides (1–4). These studies involved varying amounts of lipid, and their conclusions about the structure of these types of lipid molecules were either negative or ambiguous.
For example, one study concluded that the structure of high-density lipoproteins (HDLs) was similar to triacylglycerols (TAGs), but another study concluded that HDL structures were similar in shape to TAGs. These studies are difficult to interpret because they used varying methods and were using different experimental conditions.
One study found that triglyceride levels increase when cholesterol levels decrease. Another found no such effect (5). A third found a significant increase in triglyceride levels with increased cholesterol levels (6). A fourth study found no significant difference between total lipids and TAGs (7), while another found a significant difference between total and HDL cholesterol levels (-0.36) (8).
It’s hard to say whether genetic predisposition matters or not when it comes to your cholesterol level. But it’s interesting to consider that there is a relationship between your genetics and your cholesterol level. Your genes can influence your cholesterol level, as well as send signals to your brain about which foods might be healthy for you or unhealthy for you.
Environmental factors can also play a role here; being exposed to pesticides known to have a negative effect on your health, for example, could affect your antioxidant status and potentially affect your risk for heart disease . . . [and] could also influence how well you store carbohydrates in the form of fats rather than carbohydrates in the form of sugars [which can lead] to excess storage instead of [being more likely] to be used as fuel more efficiently by cells [such as those in our cells].