Steroids - Online Tutor, Practice Problems & Exam Prep

Steroids are lipids characterized by a steroid nucleus, consisting of three fused cyclohexane rings and one cyclopentane ring. Cholesterol, the most abundant steroid in the human body, plays a crucial role in maintaining cell membrane integrity and serves as a precursor for bile acids and steroid hormones. Bile acids, synthesized from cholesterol, emulsify lipids for digestion. Steroid hormones, including sex hormones and adrenocorticosteroids, act as chemical messengers regulating various physiological functions, such as glucose metabolism and sexual characteristics.

Steroids Concept 1

Now, steroids are lipids that contain the steroid nucleus. If we're talking about the steroid nucleus, that is where we have 3 Cyclohexane Rings and 1 Cyclopentane ring fused together. This configuration gives us these 4 rings fused together overall. And remember, when we're looking at lipids, lipids are broken down into fatty acids with its continued breakdown into these 4 different groups. And then, we also have our steroids, which we are currently focusing on, that are broken down into cholesterols, bile acids, and steroid hormones. They all have this nucleus involved because they're all steroids.

Now, if we look at the numbering, we're going to say rings are designated A, B, C, and D, and numbered in alphabetical order. We start off with carbon 1, and move this way. We can see that the line color gets more intense as we reach the end at carbon 10. Then, we continue to carbon 11. It's going to take this path. Again, it's trying to count to carbon number 17, and as it does, the color intensifies to more red. This highlights a path in how we number this particular structure from Carbon 1 all the way to Carbon 17. Remember, this represents our steroid nucleus, which essentially consists of 3 Cyclohexane Rings connected with 1 Cyclopentane ring, and they're all fused together.

Steroids Concept 2

Now, here we're going to take a look at cholesterol. We're going to say cholesterol is the most abundant steroid in the human body. Remember, because it is a type of steroid it will have the steroid nucleus. We have our 4 fused rings together. Remember, if we're going to number this, we start out here with 1, 2, 3, 4, 5, 6, 7, 8, 9, and then this here would be 10. Then we'd have here 11, 12, 13, 14, 15, 16, and 17.

Based on the numbering, we're going to say that the OH group is at carbon number 3, as we can see here. We're going to say we have a double bond that starts at carbon number 5, C₅. We have two methyl groups at carbons 10 and 13; so here goes a methyl group on Carbon 10 and one on 13. And then we have a hydrocarbon chain at carbon 17, which is this chain right here.

Now, we're going to say that cholesterol helps maintain the structural integrity of the cell membrane. It can help with the rigidity of the cell membrane based on the amount of cholesterol that's within that cell membrane. We're also going to say here that it is the precursor of bile salts or acids and steroid hormones. Alright. So keep this in mind when we're discussing cholesterols, which are part of steroids.

Steroids Example 1

In this example, let's say, explain why cholesterol is a lipid but does not undergo saponification with aqueous base. Remember, with saponification, what are we trying to do? We're trying to cut a fatty acid that we've seen before in the past into glycerol and its salt of fatty acids. If we take a look here, the cholesterol molecule is decomposed under strong basic conditions. Note that this would not be a valid reason for why it does not undergo saponification. Cholesterol can only be hydrolyzed under acidic conditions. Again, that would not be the correct answer and why saponification will not happen with cholesterol. The side chain of the steroid skeleton is very stable and does not undergo hydrolysis. So, yes, we have an alkyl chain on carbon number 17. So that tends to make it more non-polar, but it doesn't necessarily have to do with stability or not being able to undergo hydrolysis. The best answer here is that cholesterol is not a fatty acid ester that undergoes hydrolysis. Remember, what's the whole point of hydrolysis? In basic hydrolysis or saponification. It is to sever ester linkages in the formation of a glycerol molecule and salts of fatty acids. Because cholesterol does not represent a fatty acid ester, we wouldn't have this type of cleavage going on with saponification. So that's why this is the best answer out of all the options provided.

Steroids Concept 3

Now the next group of steroids that we'll take a look at are our bile acids. They're synthesized in the liver from cholesterol and stored in the gallbladder. Here, they emulsify lipids in the small intestines and increase their surface area for digestion. We're talking about an emulsifying agent; this helps a hydrophobic substance to remain dispersed in an aqueous medium. We're going to say here that emulsifying agents can have nonpolar as well as polar regions in their structures. Observing some types of bile acids, the first structure has its steroid nucleus with the 4 fused cells. However, there are highlighted groups. For instance, there is still an OH on carbon 3. We also observe the presence of additional OH groups, and a slightly altered alkyl group here. Bile acids are also referred to as bile salts because they exist as an anion in intestinal pH. Since it exists as a salt, this would be a carboxylate anion here, as well as here. We also have Cholic Acid in this region, which is just a modified version of it called Chenodeoxycholic Acid. 'Deoxy' indicates the loss of an oxygen, noting that there was an OH here, but now it's no longer there. Finally, there is Ursodeoxycholic Acid. Here, glycine is the new group attached, resulting in it being an O negative. What's important here is that bile acids help in the absorption of cholesterol. So, that's their significance. Remember, these are the important aspects of bile salts, also known as bile acids, when discussing this type of steroid.

Steroids Example 2

Which one of the following statements is incorrect about bile acids? Bile acids are emulsifying agents and help in fat digestion. This is one of the key things we talked about when it comes to bile salts. They're going to help to emulsify lipids in the small intestines and increase the surface area for digestion. Bile acids act as coenzymes for lipases. Nowhere do we mention the enzyme of lipases and their cooperation with bile salts. So this would be our answer. Bile acids exist as their salts in the intestinal pH. That is true because it is basic enough that we can deprotonate the carboxylic acid portions of these bile acids, converting them into bile salts. Bile acids are produced from cholesterol in the liver. Yes. And they're stored in the gallbladder, so this statement is true. The only statement here that's incorrect would have to be option b.

Steroids Concept 4

This video we're going to take a look at steroid hormones. Now hormones themselves represent chemical messengers that help one part of a body communicate with the other. When it comes to steroid hormones, they can be broadly classified into 2 groups. We have them represented as sex hormones as well as adrenocorticosteroids. Now, here we're talking about sex hormones; these control sexual characteristics and regulate muscle growth. And in red, we have our adrenal corticosteroids; well, these regulate a wide range of physiological functions. If we take a look here at this chart at different types of steroid hormones, the first three deal with our sex hormones. We have Androgens which are produced within the testes and because of that their function is in the sexual development in males and they help in the control of muscle growth. A good example of this would be testosterone. Now, of course, women do produce testosterone as well or females produce testosterone as well, just not to the same extent on an average basis. Now, Estrogens. These are produced within the ovaries. They help to control sexual development in females. A good example of this is Estradiol. Notice the subtle differences in the structures. All of these are steroid hormones and because of that, they're going to have our steroid nucleus where we have our 4 fused rings. Differences come with what's attached to those 4 fused rings. Next, we have Progestins; these are also produced within the ovaries and here they control the menstrual cycle and pregnancy in females. A good example here is Progesterone. Next too, we have are our adrenocorticosteroids, We have Glucocorticoids, so these are produced in the adrenal glands. Gluco helps to regulate glucose metabolism and another important feature is that it helps to reduce inflammation. A good example of this is Cortisol. Next, we have mineralocorticoids, So these are also produced within the adrenal glands. They help to regulate the balance of sodium and potassium ions in cells and in body fluids. Here we have Aldosterone as the best example in terms of this type of adrenal corticoid steroid. Now, here are memory tools 1 and 2. Memory tool 1 deals with our sex hormones and it is, ANDI test strange program. ANDI stands for androgens which are produced within the testes. The female version of that would be estrogen. So you have androgens in males, estrogen in females. And then program here would be our progestins here. And again, the most common one would be progesterone. Memory tool 2 is Glucose Control and Mineral Doses. Glucose control deals with Glucocorticoids, remember they help with the regulation of glucose metabolism and inflammation. And then mineral doses, mineral because of mineralocorticoids. And then here we have Aldosterone is the common example used for mineralocorticoids. So, we utilize these 2 memory tools to help us group together the sex hormones versus the adrenal corticoid steroids and helps us to remember the names that exist within each of these two groups.

Steroids Example 3

It says, which one of the following statements is an incorrect description of a function of a steroid hormone?

First, we have, "Cortisol is a glucocorticoid and regulates glucose metabolism." Yes, cortisol is indeed a glucocorticoid. From the name, it deals with glucose, and it does help with the regulation of its metabolism.

Aldosterone helps to maintain the balance of sodium and potassium ions. Memory tool 2 tells us glucose control and mineral doses. From the portion of mineral doses, we're referencing Aldosterone. Aldosterone is a mineralocorticoid. It does help with maintaining sodium and potassium ions within the cell and the surrounding fluids.

We're being told that Estradiol is going to help to stimulate the breaking down of glycogen within the liver. This process deals with the breaking down of glycogen. Now, we know that estradiols are part of estrogens, right? That's the best example for it. Estrogens have more to do with sexual development in females, not with the breaking down of glycogen within the liver. So this statement is false.

Testosterone contributes to the regulation of muscle growth. Testosterone is the big example when it comes to androgens, which are produced within the testes and have to do with sexual development in males. They also deal with the regulation of muscle growth. So this statement is true.

The only statement here that is false would be (c). Estradiol does not deal with the breaking down of glycogen within the liver. So, this statement is incorrect.

Which of the following compounds is not a steroid hormone?

• A. Cortisol
• B. Testosterone
• C. Phenazone
• D. Aldosterone

Which of the following compounds is not a bile acid?

• A. Cholic acid
• B. Glycocholic acid
• C. Chenodeoxycholic acid
• D. Glycyrrhizinic acid

Here’s what students ask on this topic:

What is the structure of the steroid nucleus?

The steroid nucleus is a core structure found in all steroids, consisting of three cyclohexane rings and one cyclopentane ring fused together. These rings are labeled as A, B, C, and D in alphabetical order. The numbering of carbon atoms starts from carbon 1 in ring A and continues sequentially through the rings, ending at carbon 17 in ring D. This unique arrangement forms the backbone for various steroids, including cholesterol, bile acids, and steroid hormones.

What role does cholesterol play in the human body?

Cholesterol is the most abundant steroid in the human body and plays several crucial roles. It helps maintain the structural integrity and rigidity of cell membranes. Cholesterol is also a precursor for the synthesis of bile acids, which aid in lipid digestion, and steroid hormones, which regulate various physiological functions. Additionally, cholesterol is involved in the formation of vitamin D and certain signaling molecules.

How are bile acids synthesized and what is their function?

Bile acids are synthesized in the liver from cholesterol and stored in the gallbladder. Their primary function is to emulsify lipids in the small intestine, increasing the surface area for digestion. Bile acids act as emulsifying agents, possessing both polar and non-polar regions, which help disperse hydrophobic substances in an aqueous medium. This emulsification process is essential for the absorption of dietary fats and fat-soluble vitamins.

What are the different types of steroid hormones and their functions?

Steroid hormones are broadly classified into sex hormones and adrenocorticosteroids. Sex hormones include androgens (e.g., testosterone), which regulate male sexual development and muscle growth, estrogens (e.g., estradiol), which control female sexual development, and progestins (e.g., progesterone), which regulate the menstrual cycle and pregnancy. Adrenocorticosteroids include glucocorticoids (e.g., cortisol), which regulate glucose metabolism and reduce inflammation, and mineralocorticoids (e.g., aldosterone), which maintain the balance of sodium and potassium ions in cells and body fluids.

How do steroid hormones function as chemical messengers?

Steroid hormones function as chemical messengers by binding to specific receptors in target cells. Once bound, they can enter the cell nucleus and influence gene expression, leading to changes in protein synthesis. This process allows steroid hormones to regulate various physiological functions, such as metabolism, immune response, and sexual development. Their ability to modulate gene expression makes them powerful regulators of cellular activity and overall body homeostasis.