Intro to Carbohydrates - Online Tutor, Practice Problems & Exam Prep

Intro to Carbohydrates Concept 1

Now carbohydrates are sugars or saccharides composed of carbon, hydrogen, and oxygen. They're also rich in hydroxyl groups. Remember, when we say hydroxyl groups, we're talking about OH groups. Here we're going to say that they're the primary source of energy for living organisms, and monosaccharides represent the simplest carbohydrates with the general formula of CH2On. And here, this would be n, n here is going to be a number that's equal to or greater than 3. The structure of CH2On, kind of gives away why we call it a carbohydrate. Carb because of carbon, and remember when we hydrate something we're adding water to it. N is just telling us that these monosaccharides are 3 carbons are larger, at least the ones that we're going to pay attention to. And we're going to say, it can be straight chains or rings.

Now, here we have two examples of monosaccharides. The first one has an aldehyde group, which remember is a carbonyl group connected to an H. We'd say that its sugar form is called an aldose. All because of the aldehyde, o's because of the sugar. Here we have a ketone. Remember, a ketone is a carbonyl and it has a carbon on each side. Now here, if an aldehyde sugar is called an aldose, what is a ketone sugar called? A ketose. So ket for ketone and ose because it is a sugar. So here we have an Aldose sugar and a Ketose sugar.

Intro to Carbohydrates Example 1

Which of the following chemical formulas represents that of a simple carbohydrate? Remember, simple carbohydrates follow a formula of CH₂O, and then n. If we take a look here, which one has that type of ratio? The ratio is we're going to have twice as many hydrogens as we do carbons or oxygens. If we took a look at all our options, a doesn't work because the number of hydrogens is not double the amount of carbons or oxygen. Same here for c. Same here for d. The answer here would be b, because in b, we have C₆H₁₂O₆. We have twice as many hydrogens than we do carbons or oxygens. So again, this represents the basic formula for a simple monosaccharide or simple carbohydrate, n here would be equal to or greater than 3. So again, for this particular question, the answer is option b.

Monosaccharide Generic Names Concept 2

Now when it comes to monosaccharides and naming them, we're going to say they use both generic names and specific names. Think of glucose. In this example, it says, "provide a generic name for the following monosaccharide." So, step 1 is we're going to start with Aldo or Keto depending on the functional group present. If it's an aldehyde sugar, we start with Aldo. If it's a ketone sugar, we start with Keto. We can see we have a carbonyl here with a carbon on each side, so it's a ketone sugar. So, we're going to start with Keto. Step 2, we count the number of carbons, and we use prefixes, numerical prefixes: Tri for 3, Tetra for 4, Pent for 5, Hex for 6, and Hept for 7. Here, we'd number from the end closest to the carbonyl carbon, so we'd start numbering up here: 1, 2, 3, 4, 5. Five carbons. So, that would be Pent. And then finally, step 3, because it is a sugar or a carbohydrate, we end it with 'ose,' like glucose. So here, the ending would be 'ose.' So the generic name for the following monosaccharide will be a Ketopentose sugar. Right? So Ketopentose would be its generic name. We know it's Keto since it's a Ketone Sugar, Pent since there are 5 carbons, and Ose because it is a monosaccharide or a Sugar.