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The Central Role of Enzymes as Biological Catalysts - The Cell - NCBI Bookshelf

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A fundamental task of proteins is to act as enzymes-catalysts that increase the rate of virtually all the chemical reactions within cells. Although RNAs are capable of catalyzing some reactions, most biological reactions are catalyzed by proteins.

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Time-saving video description on the mechanistic functions of enzymes. Short Brightstorm video on enzymes, proteins, catalysts and enzyme behavior.

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We have a whole section where we tell you about reactions and the molecules that change in those reactions. Chemical bonds are being created and destroyed over a series of many intermediate reactions. Those changes rarely happen on their own when you look at biological systems.

Will a blob of protein in a Petri dish simply break down into amino acids? No. To break a protein down into its amino acids you will need enzymes. Enzymes are biological molecules (proteins) that act as catalysts and help complex reactions occur everywhere in life. Let's say you ate a piece of meat. Proteases would go to work and help break down the peptide bonds between the amino acids.

Will all enzymes break down all substances? No. Enzymes are very specific catalysts and usually work to complete one task. An enzyme that helps digest proteins will not be useful to break down carbohydrates. Also, you will not find all enzymes everywhere in the body. That would be inefficient. There are unique enzymes in neural cells, intestinal cells, and your saliva.

You all know about cars and the assembly lines where they are made. There are giant robots helping people do specific tasks. Some lift the whole car, some lift doors, and some put bolts on the frames. Enzymes are like those giant robots. They grab one or two pieces, do something to them, and then release them. Once their job is done, they move to the next piece and do the same thing again. They are little protein robots inside your cells.

The robot that was designed to move a car door can't put brakes on the car. The specialized robot arms just can't do the job. Enzymes are the same. They can only work with specific molecules and only do specific tasks. Because they are so specific, their structure is very important. If only one amino acid of the enzyme is messed up, the enzyme might not work. It would be as if someone unplugged one of the cords in a robot.

For example, some herbicides are used to block plant enzyme activity. A tiny herbicide molecule can attach to the active site of an enzyme and stop it from working. Plants have adapted by changing one or two amino acids in their enzymes. They adjust their structure, are able to continue working, and the herbicide can no longer limit the enzyme.

1. The enzyme and the substrate are in the same area. Some situations have more than one substrate molecule that the enzyme will change.

2. The enzyme grabs on to the substrate at a special area called the active site. The combination is called the enzyme/substrate complex. Enzymes are very, very specific and don't just grab on to any molecule. The active site is a specially shaped area of the enzyme that fits around the substrate. The active site is like the grasping claw of the robot on the assembly line. It can only pick up one or two parts.

3. A process called catalysis happens. Catalysis is when the substrate is changed. It could be broken down or combined with another molecule to make something new. It will break or build chemical bonds. When done, you will have the enzyme/products complex.

4. The enzyme releases the product. When the enzyme lets go, it returns to its original shape. It is then ready to work on another molecule of substrate.

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We have a whole section where we tell you about reactions and the molecules that change in those reactions. Chemical bonds are being created and destroyed over a series of many intermediate reactions. Those changes rarely happen on their own when you look at biological systems. Will a blob of protein in a Petri dish simply break down into amino acids?

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At any given moment, all of the work being done inside any cell is being done by enzymes. If you understand enzymes, you understand cells. A bacterium like E. coli has about 1,000 different types of enzymes floating around in the cytoplasm at any given time.

Enzymes have extremely interesting properties that make them little chemical-reaction machines. The purpose of an enzyme in a cell is to allow the cell to carry out chemical reactions very quickly. These reactions allow the cell to build things or take things apart as needed. This is how a cell grows and reproduces. At the most basic level, a cell is really a little bag full of chemical reactions that are made possible by enzymes!

Enzymes are made from amino acids, and they are proteins. When an enzyme is formed, it is made by stringing together between 100 and 1,000 amino acids in a very specific and unique order. The chain of amino acids then folds into a unique shape. That shape allows the enzyme to carry out specific chemical reactions -- an enzyme acts as a very efficient catalyst for a specific chemical reaction. The enzyme speeds that reaction up tremendously.

For example, the sugar maltose is made from two glucose molecules bonded together. The enzyme maltase is shaped in such a way that it can break the bond and free the two glucose pieces. The only thing maltase can do is break maltose molecules, but it can do that very rapidly and efficiently. Other types of enzymes can put atoms and molecules together. Breaking molecules apart and putting molecules together is what enzymes do, and there is a specific enzyme for each chemical reaction needed to make the cell work properly.

You can see in the diagram above the basic action of an enzyme. A maltose molecule floats near and is captured at a specific site on the maltase enzyme. The active site on the enzyme breaks the bond, and then the two glucose molecules float away.

You may have heard of people who are lactose intolerant, or you may suffer from this problem yourself. The problem arises because the sugar in milk -- lactose -- does not get broken into its glucose components. Therefore, it cannot be digested. The intestinal cells of lactose-intolerant people do not produce lactase, the enzyme needed to break down lactose. This problem shows how the lack of just one enzyme in the human body can lead to problems. A person who is lactose intolerant can swallow a drop of lactase prior to drinking milk and the problem is solved. Many enzyme deficiencies are not nearly so easy to fix.

Inside a bacterium there are about 1,000 types of enzymes (lactase being one of them). All of the enzymes float freely in the cytoplasm waiting for the chemical they recognize to float by. There are hundreds or millions of copies of each different type of enzyme, depending on how important a reaction is to a cell and how often the reaction is needed. These enzymes do everything from breaking glucose down for energy to building cell walls, constructing new enzymes and allowing the cell to reproduce. Enzymes do all of the work inside cells.

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At any given moment, all of the work being done inside any cell is being done by enzymes. If you understand enzymes, you understand cells. A bacterium like E. coli has about 1,000 different types of enzymes floating around in the cytoplasm at any given time.

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10 - enzymes as catalysts Flashcards | Quizlet

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Start studying 10 - enzymes as catalysts. Learn vocabulary, terms, and more with flashcards, games, and other study tools.

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SC.912.L.18.11 - Explain the role of enzymes as catalysts that lower the activation energy of biochemical reactions. Identify factors, such as pH and temperature, and their effect on enzyme activity.