When you think of carbohydrates do potatoes, pasta and bread come to mind? Carbohydrates, carbs for short, are a class of organic compounds. Pasta potatoes, and breads, are foods that contain a high percentage of carbohydrate molecules. Text 32- 33 show the chemical formulas and structural formulas for various carbs. Obviously if you’re eating carbs you’re eating lots of carbon, hydrogen, and oxygen atoms. Theses three carbohydrate categories distinguish different carbohydrate molecules by their relative size. The suffix, saccharide, is a reference to sugar. Monosaccharide means we have a simple, or one sugar. These sugar molecules have names such as glucose and fructose. Disaccharides, two sugars, or two monomers bonded together. These molecules are also called sugar molecules, but note they have different molecular names and different formulas. This is sucrose, lactose, two monomers bonded together. Polysaccharides- Poly means many, and usually these are huge molecules thousands of monomers (simple sugars) are bonded together. The names of some specific polysaccharide molecules are starch, cellulose, and glycogen. So let’s take a look at some of these carbohydrate molecules. The chemical formula for glucose is C6H12O6 and here is a ring structure showing us how those twenty-four atoms are arranged. Remember we talked about the covalent bonds. Just like you can be a son, a brother, a father, a worker, a student; you have many different jobs and names that can be applied to you- Molecules are the same; sometimes it’s a bit confusing because all of these terms can be related to this molecule. Spend a little bit of time looking at these terms and how they relate to glucose. if you have any questions or don’t understand how these terms relate to this molecule be sure to ask for help. Glucose is very important to humans. Glucose is blood sugar -the sugar that travels in your blood. Here’s a blood vessel- this could be an artery, a capillary, or a vein, and as this molecule goes to your cells -it provides something for yourselves and you’re gonna see the term energy here energy. Glucose is an energy molecule. what it does is and we’re going to talk about the process and how it provides energy to your cells later in this module. In addition, if you don’t have an immediate need in that cell for energy your body has the ability to do some other things with glucose molecules. Glucose can be taken up by your liver and your skeletal muscles cells and make another carbohydrate called glycogen. Glycogen is going be for short term energy you know for something you’re gonna use pretty quickly, like maybe going to the gym or going for a walk with your dog or playing with your kids. Iit can also be used for a little bit more long-term energy. Glucose can actually be converted into fat -for long-term storage. So regardless of its eventual use, glucose is an energy molecule. This says, “energy not needed”, it means immediately. Glucose has many hidden talents- Here we see glucose and here we see it combining with other molecules (other monomers); monosaccharides;. These simple single sugars look a lot alike- these are ring structures. They look a lot like glucose. Cells have the ability to combine these two monomers together to make a brand new type of sugar. Here are two examples of disaccharides that are formed from the combination of two monosaccharides. Let’s talk about sucrose first. In nature sucrose molecules are found in plants; they travel through their vascular or vessel system similar to glucose in our bodies (it travels in our blood vessels). Humans collect sucrose from plants like sugarcane and sugar beets and it is processed into white crystals that we call table sugar. Sucrose can also be processed into syrup- For example-maple syrup from maple trees. The purpose of sucrose in plants is to distribute the carbohydrate molecules for the energy needs of the plant. Here is another disaccharide, lactose, also called milk sugar. This sugar is only produced in special mammary gland cells of mammals. It enables a lactating female to nourish her young with energy, carbohydrate energy. Plants are really experts at carbohydrate utilization. Starch is another carbohydrate and it’s a polysaccharide- which means that many sugars comprise it. This diagram is actually only a partial illustration of starch. Starch is actually made up of thousands of glucose molecules. Each one of these glucose monomers bond. What we see here was made through a dehydration synthesis reaction. Whereas humans store excess energy as fat molecules, plants accomplish that function with starch molecules. Starch can be found – where do plants store this excess energy? They can store it in their stems, their roots, and their seeds. That is why we eat wheat grains, or rice, or potatoes because they’re full of starch, full of energy. So we’re stealing the energy from the plant to eat ourselves. Another important plant carbohydrate molecule is cellulose. it is a polysaccharide. It is also made up of thousands of individual glucose molecules – so this is only showing a portion of the molecule. Plants use cellulose for structural purposes. It comprises their cell walls walls. Some plants have thin walls. You can easily chew the cell walls of most fruits and veggies. Other plant parts have really thick cellulose walls and you can’t really chew them- things like wood, and the hulls of nuts and seeds. Regardless if the walls are thick or thin your body cannot hydrolyze, cannot break that bond, we don’t have the enzyme that will allow us to do that. So what happens to all these cellulose molecules that we eat every time we eat plants? They provide fiber in your diet to keep your regular and they comprise the bulk of healthy fecal material. Another carb is glycogen. Notice it is synthesized in animals. It is a polysaccharide -so again a huge molecule made up of thousands of glucose monomers. But this molecule is going to be synthesized in the liver and skeletal muscle cells of animals. This runner is going to be using glycogen for her muscles to work. Notice it says that it can be used for about 24 hours. So our skeletal muscles store enough energy to allow us maybe like to run for quite a long time. Most marathons are completed in a couple of hours so 24 hours is a long time. Glycogen stores will be depleted if you are continually exercising for a long period of time. So again glycogen is an animal carbohydrate molecule. Are there good and bad carbs? Let’s look at this issue in more detail- look into carbohydrates and their relative health. Whole grains are natural- here’s an example of a whole grain. also called a seed. Seeds have three distinct distinct layers; bran, endosperm, and germ layers. The bran is a protective outer layer; it’s going to protect the seed. The germ is the embryo, it is going to become the future plant- once it breaks out or germinates from the seed. The starch, or endosperm, is going to provide the energy for this germinating embryo- enable it to grow through the ground so it can get above the soil level where it can start doing photosynthesis. So this is the packet that we call a seed or a whole grain. Let’s use wheat grains as an example of a whole grain- Whole grain means that the seed is intact. Processing separates the seed’s components- isolating the bran, the endosperm, and the germ. This is done through processing and isolating these things. You can go to the store and buy wheat bran, or you can buy just wheat flour, we call that starch, or we can buy wheat germ. You can also buy white bread- which is primarily all starch, very little bran or germ. Whole wheat bread is starch but it does have some bran and some germ, depending on the brand of whole wheat bread. Whole grain bread actually utilizes the whole grains in the bread itself- but then to make it somewhat palatable it also has all these components- that are somewhat processed. So it has a combination of all of these. So what does this have to do with good and bad carbs? Really the issue is blood glucose levels- How they respond to the food we ingest. Some food causes rapid spikes- So over here we have a graph. We actually have a graph – so let’s take a look at this. Text 252 has this graph- it shows normal blood glucose levels. They change (fluctuate) a little bit but they stay around 90 to 100. That’s a normal healthy blood glucose level. In this illustration, the red line is showing what a spike in blood glucose level looks like. So it would be like this after after an individual has eaten. We would expect to see a response. So if we take a look over here we see that fructose which is a sugar that is naturally found in a lot of fruit (it is irrelevant whether or not the sugar is coming from a natural source or from a processed source like a candy bar) it still has the same effect of causing a rapid spike in blood sugar. Whereas if you’re eating something more whole-grain – this example is oatmeal. Oats are also a grain. You’ll notice that yes we still have an increase in blood glucose levels but it’s more gradual. Why this matters is because we have something called insulin. Insulin is a hormone that tells your cells to take in glucose from your blood. If cells do not take in glucose, glucose remains in the blood and excess blood glucose can actually damage cells. So what happens is if you have a diet that is composed primarily of foods that spike your blood sugar- it’s also spiking your insulin levels as well. This can lead to something called Type 2 Diabetes. How can you mitigate this scenario? I’m not saying don’t eat oranges or other fruit – what this indicates is that if you’re going to eat this, maybe eat this with a handful of nuts or something else that will reduce or eliminate those rapid spikes. If you think about this historically, the diets of humans have really not included large amounts of processed foods or a lot of sugary foods. Normal blood glucose levels can be maintained therefore by just making wise dietary choices. Things like whole grains, minimal processed foods, or combining foods that will not cause those spikes in blood sugar. This concludes our carbohydrate discussion and again you’ll be doing some work in lab using these terms. The next ppt will be on lipids.