Gigantic molecules, called macromolecules, populate a cell and provide it with important functions for life. For example, macromolecules provide structural support, a source of stored fuel, the ability to store and retrieve genetic information, and the ability to speed biochemical reactions. Four major types of macromolecules—proteins, carbohydrates, nucleic acids, and lipids—play these important roles in the life of a cell. In terms of overall structure, all macromolecules except the lipids are considered polymers.
A polymer is a chain of similar subunits, or monomers, that are linked together by covalent bonds. In proteins, the monomers are amino acids; in carbohydrates, the monomers are sugars; and in nucleic acids, the monomers are nucleotides. Lipids are a diverse group of molecules, which come in a variety of nonpolymeric forms. Glucose is a hexose, a sugar composed of six carbon atoms, usually found in ring form.
A starch macromolecule is a polysaccharide composed of thousands of glucose units. In condensation reactions, two molecules covalently bond to each other and release a water molecule. Amylose, or plant starch, is not highly branched. This polysaccharide is stored in animal livers and muscles. Glucose can then be further broken down to release energy that is used in cellular activity. The 20 different amino acids used to make all proteins differ only in their side chains, and the properties of these side chains account for the great diversity of protein structure and function.
One is alpha, the other beta. Starches like amylose and amylopectin link only alpha-type glucose molecules together. With cellulose, it is the beta molecules that link together. Cellulose consists of linear molecules each made up of at least 3, glucose units linked together.
Carbohydrates are compounds of tremendous biological importance since they: provide energy through oxidation supply carbon for the synthesis of cell components serve as a form of stored chemical The foods we eat supply the energy needed by the body to drive its complex chemical, mechanical and electrical systems.
Where does this energy come from, how is it locked into food molecules and Add to collection. To use this interactive, select any of the labelled boxes 1—5 to obtain more information. Transcript Making glucose Green plants manufacture glucose through a process that requires light, known as photosynthesis. This process takes place in the leaf chloroplasts. Glucose structures The molecular formula of glucose is C 6 H 12 O 6. Read more about the editorial team, authors, and our work processes.
Already registered? Your email address will not be published. Lecturio is using cookies to improve your user experience. By continuing use of our service you agree upon our Data Privacy Statement. Are you more of a visual learner? Check out our online video lectures and start your molecular and cell biology course now for free! Structure of beta-D-Lactose. Structure of sucrose saccharose.
Animation of a rotating DNA structure. Fat structural formulae. Skeletal formula of dipalmitoylphosphatidylcholine DPPC. Your path to achieve medical excellence. Study for medical school and boards with Lecturio. Taylor, M. Votes: 28, average: 4. About the Lecturio Medical Online Library Our medical articles are the result of the hard work of our editorial board and our professional authors. Recommended for you. November 9, Lecturio read more. May 19, Lecturio read more. The carbon atom number 1 C1 in one sugar is linked to the fourth carbon atom C4 of the next sugar in an extended array.
All the glucose molecules in cellulose have the beta-configuration at the C1 atom, so all the glycosidic bonds that join the glucose molecules together are also of the beta type. This means that the cellulose molecule is straight, and many such molecules can lay side by side in a parallel series of rows.
Tiny forces called hydrogen bonds hold the glucose molecules together, and the chains in close proximity. Although each hydrogen bond is very, very weak, when thousands or millions of them form between two cellulose molecules the result is a very stable, very strong complex that has enormous strength.
Starch , a word that comes from old English and means to stiffen , is also a polysaccharide made in plants. It is primarily an energy storage molecule, or fuel, for the plant and for its seeds.
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