What do glycogen and polypeptides have in common

Biology Molecular Biology Basics Carbohydrates. Johnny L. Aug 2, Below is the structure of part of a starch molecule the full molecule is too large to show because it can be hundreds of monomers long : Polypeptides are long, unbranched chains of amino acids and can link together to form proteins like hemoglobin.

Related questions What monosaccharides make up starch? What monosaccharides make up lactose? What monosaccharides make up glycogen? What monosaccharides make up cellulose? The chemical makeup of this R group varies from one amino acid to another and gives each amino acid its unique properties.

There are 20 amino acids that are important to humans, and all proteins are made from combinations of these subunits. Chains of amino acids are called peptides. In the poly-peptide chain shown below, can you see the individual amino acids that are strung together in a repeating N-C-C pattern?

When we get to the genetics section of the course, we will study protein synthesis. That's the process by which DNA instructions are transcribed into RNA, which is then translated into the amino acids that are strung together to form long poly-peptide chains.

These chains are then woven together like strands in a rope or like threads in a blanket to form various proteins. When food is consumed, the proteins are broken down into their constituent amino acids and rebuilt into the proteins of the body. However, excess amino acids are not stored for future use, and the body only starts to break down its own proteins during starvation, when the ordinary sources of fuel fats and carbohydrates are not available.

An amino acid forming a peptide bond to a growing poly-peptide chain, releasing H 2 O. Fats are the primary long-term energy storage molecules of the body. Fats are very compact and light weight, so they are an efficient way to store excess energy. A fat is made up of a glycerol, which is attached to 1 to 3 fatty acid chains. Most of the energy from fats comes from the many carbon bonds in these long, fatty acid chains. Fatty acids connect to glycerol in the region where each molecule has an -O-H group.

Two hydrogens and one oxygen are split off, forming H-O-H water and the long carbon chain is attached to the glycerol. Each glycerol can carry up to three fatty acid chains, which would make it a " tri-glyceride. Monosaccharides of four or more carbon atoms are typically more stable when they adopt cyclic, or ring, structures. Glucose, for example, forms a six-membered ring Figure 2. Figure 2. Note in these cyclic structural diagrams, the carbon atoms composing the ring are not explicitly shown.

Two monosaccharide molecules may chemically bond to form a disaccharide. The name given to the covalent bond between the two monosaccharides is a glycosidic bond. Glycosidic bonds form between hydroxyl groups of the two saccharide molecules, an example of the dehydration synthesis described in the previous section of this chapter:.

Common disaccharides are the grain sugar maltose , made of two glucose molecules; the milk sugar lactose , made of a galactose and a glucose molecule; and the table sugar sucrose , made of a glucose and a fructose molecule Figure 3. Polysaccharides, also called glycans , are large polymers composed of hundreds of monosaccharide monomers. Unlike mono- and disaccharides, polysaccharides are not sweet and, in general, they are not soluble in water.

Like disaccharides, the monomeric units of polysaccharides are linked together by glycosidic bonds. Polysaccharides are very diverse in their structure. Three of the most biologically important polysaccharides— starch , glycogen , and cellulose —are all composed of repetitive glucose units, although they differ in their structure Figure 4. Cellulose consists of a linear chain of glucose molecules and is a common structural component of cell walls in plants and other organisms.

Glycogen and starch are branched polymers; glycogen is the primary energy-storage molecule in animals and bacteria, whereas plants primarily store energy in starch. The orientation of the glycosidic linkages in these three polymers is different as well and, as a consequence, linear and branched macromolecules have different properties. Modified glucose molecules can be fundamental components of other structural polysaccharides.

Examples of these types of structural polysaccharides are N-acetyl glucosamine NAG and N-acetyl muramic acid NAM found in bacterial cell wall peptidoglycan. Polymers of NAG form chitin , which is found in fungal cell walls and in the exoskeleton of insects. Figure 4. Starch, glycogen, and cellulose are three of the most important polysaccharides. In the top row, hexagons represent individual glucose molecules.

Micrographs bottom row show wheat starch granules stained with iodine left , glycogen granules G inside the cell of a cyanobacterium middle , and bacterial cellulose fibers right. Chitin is a structural polymer found in cell walls of fungi and exoskeletons of some animals. Skip to main content.