Which monosaccharides make up starch

The structure of amylopectin is similar to that of amylose, but there are numerous branches along the chain. What monosaccharides make up starch?

Biology Molecular Biology Basics Carbohydrates. Ernest Z. Jun 27, Only one monosaccharide makes up starch, and that is glucose. Explanation: Starch exists in two different forms: amylose and amylopectin.

Excess glucose is often stored as starch that is catabolized the breakdown of larger molecules by cells by humans and other animals that feed on plants. Galactose and fructose are other common monosaccharides — galactose is found in milk sugars and fructose is found in fruit sugars. Although glucose, galactose, and fructose all have the same chemical formula C 6 H 12 O 6 , they differ structurally and chemically and are known as isomers because of the different arrangement of functional groups around the asymmetric carbon; all of these monosaccharides have more than one asymmetric carbon Figure 2.

Figure 2. Glucose, galactose, and fructose are all hexoses. They are structural isomers, meaning they have the same chemical formula C6H12O6 but a different arrangement of atoms. Monosaccharides can exist as a linear chain or as ring-shaped molecules; in aqueous solutions they are usually found in ring forms Figure 3.

Figure 3. Five and six carbon monosaccharides exist in equilibrium between linear and ring forms. Fructose and ribose also form rings, although they form five-membered rings as opposed to the six-membered ring of glucose. During this process, the hydroxyl group of one monosaccharide combines with the hydrogen of another monosaccharide, releasing a molecule of water and forming a covalent bond.

A covalent bond formed between a carbohydrate molecule and another molecule in this case, between two monosaccharides is known as a glycosidic bond Figure 4.

Glycosidic bonds also called glycosidic linkages can be of the alpha or the beta type. An alpha bond is formed when the OH group on the carbon-1 of the first glucose is below the ring plane, and a beta bond is formed when the OH group on the carbon-1 is above the ring plane.

Figure 4. Sucrose is formed when a monomer of glucose and a monomer of fructose are joined in a dehydration reaction to form a glycosidic bond.

In the process, a water molecule is lost. By convention, the carbon atoms in a monosaccharide are numbered from the terminal carbon closest to the carbonyl group.

In sucrose, a glycosidic linkage is formed between carbon 1 in glucose and carbon 2 in fructose. Common disaccharides include lactose, maltose, and sucrose Figure 5. Lactose is a disaccharide consisting of the monomers glucose and galactose. It is found naturally in milk.

Maltose, or malt sugar, is a disaccharide formed by a dehydration reaction between two glucose molecules. The most common disaccharide is sucrose, or table sugar, which is composed of the monomers glucose and fructose.

Figure 5. Common disaccharides include maltose grain sugar , lactose milk sugar , and sucrose table sugar. The chain may be branched or unbranched, and it may contain different types of monosaccharides.

The molecular weight may be , daltons or more depending on the number of monomers joined. Starch, glycogen, cellulose, and chitin are primary examples of polysaccharides. Starch is the stored form of sugars in plants and is made up of a mixture of amylose and amylopectin both polymers of glucose.

The starch in the seeds provides food for the embryo as it germinates and can also act as a source of food for humans and animals. The starch that is consumed by humans is broken down by enzymes, such as salivary amylases, into smaller molecules, such as maltose and glucose.

Arthropods have an outer skeleton, the exoskeleton, which protects their internal body parts. This exoskeleton is made of chitin, which is a polysaccharide-containing nitrogen.

Chitin is also a major component of fungal cell walls. Carbohydrates are a major class of biological macromolecules that are an essential part of our diet and provide energy to the body.

Biological macromolecules are large molecules that are necessary for life and are built from smaller organic molecules. One major class of biological macromolecules are carbohydrates, which are further divided into three subtypes: monosaccharides, disaccharides, and polysaccharides.

Carbohydrates are, in fact, an essential part of our diet; grains, fruits, and vegetables are all natural sources of carbohydrates. Importantly, carbohydrates provide energy to the body, particularly through glucose, a simple sugar that is a component of starch and an ingredient in many basic foods. Carbohydrates : Carbohydrates are biological macromolecules that are further divided into three subtypes: monosaccharides, disaccharides, and polysaccharides.

Like all macromolecules, carbohydrates are necessary for life and are built from smaller organic molecules. Carbohydrates have been a controversial topic within the diet world. People trying to lose weight often avoid carbs, and some diets completely forbid carbohydrate consumption, claiming that a low-carb diet helps people to lose weight faster.

Carbohydrates should be supplemented with proteins, vitamins, and fats to be parts of a well-balanced diet. Calorie-wise, a gram of carbohydrate provides 4. Carbohydrates contain soluble and insoluble elements; the insoluble part is known as fiber, which is mostly cellulose. Fiber has many uses; it promotes regular bowel movement by adding bulk, and it regulates the rate of consumption of blood glucose. Fiber also helps to remove excess cholesterol from the body. Fiber binds and attaches to the cholesterol in the small intestine and prevents the cholesterol particles from entering the bloodstream.

Then cholesterol exits the body via the feces. Fiber-rich diets also have a protective role in reducing the occurrence of colon cancer. In addition, a meal containing whole grains and vegetables gives a feeling of fullness. As an immediate source of energy, glucose is broken down during the process of cellular respiration, which produces adenosine triphosphate ATP , the energy currency of the cell. Eliminating carbohydrates from the diet is not the best way to lose weight.

A low-calorie diet that is rich in whole grains, fruits, vegetables, and lean meat, together with plenty of exercise and plenty of water, is the more sensible way to lose weight. Privacy Policy. Skip to main content. Biological Macromolecules. Search for:. Carbohydrate Molecules Carbohydrates are essential macromolecules that are classified into three subtypes: monosaccharides, disaccharides, and polysaccharides.

Learning Objectives Describe the structure of mono-, di-, and poly-saccharides.