Plants synthesize glucose using carbon dioxide and water, and glucose, in turn, is used for energy requirements for the plant. Galactose a milk sugar and fructose found in fruit are other common monosaccharides. Although glucose, galactose, and fructose all have the same chemical formula C 6 H 12 O 6 , they differ structurally and stereochemically.
This makes them different molecules despite sharing the same atoms in the same proportions, and they are all isomers of one another, or isomeric monosaccharides. Glucose and galactose are aldoses, and fructose is a ketose.
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. Glycosidic bonds also called glycosidic linkages can be of the alpha or the beta type. Disaccharides : 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. 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. The chain may be branched or unbranched, and it may contain different types of monosaccharides. Starch, glycogen, cellulose, and chitin are primary examples of polysaccharides.
Plants are able to synthesize glucose, and the excess glucose is stored as starch in different plant parts, including roots and seeds. The starch in the seeds provides food for the embryo as it germinates while the starch that is consumed by humans is broken down by enzymes into smaller molecules, such as maltose and glucose.
The cells can then absorb the glucose. Glycogen is the storage form of glucose in humans and other vertebrates. It is made up of monomers of glucose. Glycogen is the animal equivalent of starch and is a highly branched molecule usually stored in liver and muscle cells. Whenever blood glucose levels decrease, glycogen is broken down to release glucose in a process known as glycogenolysis. Cellulose is the most abundant natural biopolymer.
The cell wall of plants is mostly made of cellulose and provides structural support to the cell. Every other glucose monomer in cellulose is flipped over, and the monomers are packed tightly as extended long chains. This gives cellulose its rigidity and high tensile strength—which is so important to plant cells. Because of the way the glucose subunits are joined, every glucose monomer is flipped relative to the next one resulting in a linear, fibrous structure.
Carbohydrates serve various functions in different animals. 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. Examples: fructose, lactose, maltose, sucrose, glucose, galactose, ribose. Complex Carbohydrates: Three or more sugars oligosaccharides or polysaccharides bonded together in a more complex chemical structure.
These take longer to digest and therefore have a more gradual effect on the increase in blood sugar. Examples: cellobiose, rutinulose, amylose, cellulose, dextrin. Starches: Complex carbohydrates contain a large number of glucose molecules. Plants produce these polysaccharides. Examples include potatoes, chickpeas, pasta, and wheat. Fiber: Non-digestible complex carbohydrates that encourage healthy bacterial growth in the colon and act as a bulking agent, easing defecation.
The main components include cellulose, hemicellulose, and pectin. Insoluble: Absorbs water in the intestines, thereby softening and bulking stool. Benefits include regularity of bowel movements and a decreased risk of diverticulosis. Soluble: Helps decrease blood cholesterol and LDL levels, reduces straining with defecation, and blunts postprandial blood glucose levels.
Excerpt Carbohydrates are one of the three macronutrients in the human diet, along with protein and fat. Structures Monosaccharide : The most basic, fundamental unit of a carbohydrate. Examples: glucose, galactose, fructose Disaccharide: Compound sugars containing two monosaccharides with the elimination of a water molecule with the general chemical structure C12H22O11 Examples: sucrose, lactose Oligosaccharide: The polymer contains three to ten monosaccharides Examples: maltodextrins, raffinose Polysaccharides: Polymers containing long chains of monosaccharides connected through glycosidic bonds Examples: amylose, cellulose Types Simple Carbohydrates: One or two sugars monosaccharides or disaccharides combined in a simple chemical structure.
Examples: fructose, lactose, maltose, sucrose, glucose, galactose, ribose Foods: candy, carbonated beverages, corn syrup, fruit juice, honey, table sugar Complex Carbohydrates: Three or more sugars oligosaccharides or polysaccharides bonded together in a more complex chemical structure. Examples: cellobiose, rutinulose, amylose, cellulose, dextrin Foods: apples, broccoli, lentils, spinach, unrefined whole grains, brown rice Starches: Complex carbohydrates contain a large number of glucose molecules.
Examples: brans, seeds, vegetables, brown rice, potato skins. Examples are fleshy fruit, oats, broccoli, and dried beans.
0コメント