An enzyme is a biomolecule that can be synthesized biologically naturally occurring or through other processes synthetically. Its major function is to act as a catalyst that speeds up a particular chemical reaction without itself being changed in the process. Enzymes are commonly protein molecules with a characteristic sequence of amino acids that fold to produce a specific three-dimensional structure, which gives the molecule unique properties.
Proteins are one of the major biomolecules; the others are carbohydrates especially, polysaccharides , lipids, and nucleic acids. Enzymes that are proteins in nature are composed of polymers of amino acids. The amino acids are joined together by peptide bonds. The type and the sequence of amino acids in an enzyme protein are encoded by the DNA in the cell that produces them.
While not all enzymes are proteins, not all proteins are enzymes as well. Enzymes that are not proteinaceous in nature are exemplified by ribozymes.
A ribozyme is an enzyme made of RNA rather than a protein. An example of a ribozyme is in the ribosome, which is a complex of protein and catalytic RNA units. Enzymes are often globular. They may occur singly or as a subunit in a complex. They are often larger than their substrates. While large relative to their substrates, only a small portion of an enzyme is directly involved in catalysis.
This site involved in catalysis is referred to as the catalytic site. Another site in an enzyme structure is the binding site through which the substrate reacts or binds to. The allosteric site of the enzyme refers to the site where another molecule can bind to causing the enzyme to change its conformation, which then leads to its increase or decrease in its activity. There are two major types of molecules that modulate enzyme activity: 1 inhibitors and 2 activators.
The excess synthesized glucose is often stored as starch that is broken down by other organisms that feed on plants. Galactose part of lactose, or 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 chemically and are known as isomers because of differing arrangements of atoms in the carbon chain.
During this process, the hydroxyl group —OH of one monosaccharide combines with a hydrogen atom of another monosaccharide, releasing a molecule of water H 2 O and forming a covalent bond between atoms in the two sugar molecules.
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 from 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. Polysaccharides may be very large molecules. Starch, glycogen, cellulose, and chitin are examples of polysaccharides. Starch is the stored form of sugars in plants and is made up of amylose and amylopectin both polymers of glucose. Plants are able to synthesize glucose, and the excess glucose is stored as starch in different plant parts, including roots and seeds.
The starch that is consumed by animals is broken down into smaller molecules, such as glucose. The cells can then absorb the glucose. Glycogen is the storage form of glucose in humans and other vertebrates, and 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 glucose levels decrease, glycogen is broken down to release glucose. Cellulose is one of the most abundant natural biopolymers. The cell walls of plants are mostly made of cellulose, which provides structural support to the cell. Wood and paper are mostly cellulosic in nature. Cellulose is made up of glucose monomers that are linked by bonds between particular carbon atoms in the glucose molecule. Every other glucose monomer in cellulose is flipped over and packed tightly as extended long chains.
This gives cellulose its rigidity and high tensile strength—which is so important to plant cells. Cellulose passing through our digestive system is called dietary fiber. While the glucose-glucose bonds in cellulose cannot be broken down by human digestive enzymes, herbivores such as cows, buffalos, and horses are able to digest grass that is rich in cellulose and use it as a food source. In these animals, certain species of bacteria reside in the rumen part of the digestive system of herbivores and secrete the enzyme cellulase.
The appendix also contains bacteria that break down cellulose, giving it an important role in the digestive systems of ruminants. Cellulases can break down cellulose into glucose monomers that can be used as an energy source by the animal. Carbohydrates serve other functions in different animals. Arthropods, such as insects, spiders, and crabs, have an outer skeleton, called the exoskeleton, which protects their internal body parts. This exoskeleton is made of the biological macromolecule chitin , which is a nitrogenous carbohydrate.
It is made of repeating units of a modified sugar containing nitrogen. Thus, through differences in molecular structure, carbohydrates are able to serve the very different functions of energy storage starch and glycogen and structural support and protection cellulose and chitin. Registered Dietitian: Obesity is a worldwide health concern, and many diseases, such as diabetes and heart disease, are becoming more prevalent because of obesity.
This is one of the reasons why registered dietitians are increasingly sought after for advice. Registered dietitians help plan food and nutrition programs for individuals in various settings. They often work with patients in health-care facilities, designing nutrition plans to prevent and treat diseases.
For example, dietitians may teach a patient with diabetes how to manage blood-sugar levels by eating the correct types and amounts of carbohydrates. Dietitians may also work in nursing homes, schools, and private practices. In addition, registered dietitians must complete a supervised internship program and pass a national exam.
Those who pursue careers in dietetics take courses in nutrition, chemistry, biochemistry, biology, microbiology, and human physiology.
Dietitians must become experts in the chemistry and functions of food proteins, carbohydrates, and fats. The underground storage bulb of the camas flower shown below has been an important food source for many of the Indigenous peoples of Vancouver Island and throughout the western area of North America. Camas bulbs are still eaten as a traditional food source and the preparation of the camas bulbs relates to this text section about carbohydrates.
Most often plants create starch as the stored form of carbohydrate. Some plants, like camas create inulin. Inulin is used as dietary fibre however, it is not readily digested by humans. If you were to bite into a raw camas bulb it would taste bitter and has a gummy texture.
The method used by Indigenous peoples to make camas both digestible and tasty is to bake the bulbs slowly for a long period in an underground firepit covered with specific leaves and soil. The heat acts like our pancreatic amylase enzyme and breaks down the long chains of inulin into digestible mono and di-saccharides.
Properly baked, the camas bulbs taste like a combination of baked pear and cooked fig. It is important to note that while the blue camas is a food source, it should not be confused with the white death camas, which is particularly toxic and deadly. The flowers look different, but the bulbs look very similar.
Lipids include a diverse group of compounds that are united by a common feature. This is because they are hydrocarbons that include only nonpolar carbon-carbon or carbon-hydrogen bonds. Lipids perform many different functions in a cell. Cells store energy for long-term use in the form of lipids called fats. Lipids also provide insulation from the environment for plants and animals.
For example, they help keep aquatic birds and mammals dry because of their water-repelling nature. Lipids are also the building blocks of many hormones and are an important constituent of the plasma membrane. Lipids include fats, oils, waxes, phospholipids, and steroids.
A fat molecule, such as a triglyceride, consists of two main components—glycerol and fatty acids. Glycerol is an organic compound with three carbon atoms, five hydrogen atoms, and three hydroxyl —OH groups. In a fat molecule, a fatty acid is attached to each of the three oxygen atoms in the —OH groups of the glycerol molecule with a covalent bond. In the induced-fit model, the active site and substrate don't fit perfectly together; instead, they both alter their shape to connect. Whatever the case, the reactions that occur accelerate greatly — over a millionfold — once the substrates bind to the active site of the enzyme.
The chemical reactions result in a new product or molecule that then separates from the enzyme, which goes on to catalyze other reactions. In the lock and key model , the shape of the active site matches the shape of its substrate molecules.
This makes enzymes highly specific — each type of enzyme can catalyse only one type of reaction or just a few types of reactions. The diagram shows how this works. In this example, the enzyme splits one molecule into two smaller ones, but other enzymes join small molecules together to make a larger one.
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