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A synthesis reaction is a chemical reaction that results in the synthesis (joining) of components that were formerly separate (Figure 2.3.1 a). Again, nitrogen and hydrogen are reactants in a synthesis reaction that yields ammonia as the product. The general equation for a synthesis reaction is A + B→AB.
- Lindsay M. Biga, Sierra Dawson, Amy Harwell, Robin Hopkins, Joel Kaufmann, Mike LeMaster, Philip Mat...
- 2019
7.7 Chapter Summary. Metabolism is the set of life-sustaining chemical reactions in organisms. Metabolic reactions may be categorized as catabolic – the breaking down of compounds, or anabolic – the building up (synthesis) of compounds. Most metabolic reactions in the body require the activity of an enzyme catalyst.
- Overview
- The basics
- What do enzymes do?
- How enzymes work
- The perfect conditions
- Cofactors
- Inhibition
- Examples of specific enzymes
- Summary
Enzymes help with specific functions that are vital to the operation and overall health of the body. They help speed up chemical reactions in the human body. They are essential for respiration, digesting food, muscle and nerve function, and more.
Each cell in the human body contains thousands of enzymes. Enzymes provide help with facilitating chemical reactions within each cell.
Since they are not destroyed during the process, a cell can reuse each enzyme repeatedly.
This article reviews what enzymes are and the roles they play in various parts of the body.
The majority of enzymes are proteins, though some are Ribonucleic acid (RNA) molecules. RNA molecules translate information from DNA and create proteins.
Each cell contains thousands of enzymes, providing specific help throughout the body.
Enzymes help with the chemical reactions that keep a person alive and well. For example, they perform a necessary function for metabolism, the process of breaking down food and drink into energy.
Enzymes speed up (catalyze) chemical reactions in cells. More specifically, they lower the threshold necessary to start the intended reaction. They do this by binding to another substance known as a substrate.
Enzymes provide support for many important processes within the body. Some examples include:
•The digestive system: Enzymes help the body break down larger complex molecules into smaller molecules, such as glucose, so that the body can use them as fuel.
•DNA replication: Each cell in the body contains DNA. Each time a cell divides, the cell needs to copy its DNA. Enzymes help in this process by unwinding the DNA coils.
•Liver enzymes: The liver breaks down toxins in the body. To do this, it uses a range of enzymes the facilitate the process of destroying the toxins.
Other activities enzymes help with include:
•hormone production
The “lock and key” model was first proposed in 1894. In this model, an enzyme’s active site is a specific shape, and only the substrate will fit into it, like a lock and key.
A newer model, the induced-fit model, helps to account for reactions between substrates and active sites that are not exact fits.
Enzymes can only work in certain conditions. Most enzymes in the human body work best at around 98.6-degrees Fahrenheit (F) (37°C), which is the body’s typical temperature. At lower temperatures, they may still work but much more slowly.
If the temperature is too high or if the environment is too acidic or alkaline, the enzyme changes shape; this alters the shape of the active site so that substrates cannot bind to it. This is denaturing.
Some enzymes cannot function unless they attach to a specific non-protein molecule, known as cofactors. There are two types of cofactors, ions and coenzymes.
Ions are inorganic molecules that loosely bond to the enzyme to ensure it can function. By contrast, coenzymes are organic molecules that also loosely bond with and allow an enzyme to do its job.
To ensure that the body’s systems work correctly, it is sometimes necessary to slow down enzyme function. For instance, if an enzyme makes too much of a product, then the body needs a way to reduce or stop the production.
Several factors can limit enzyme activity levels, including:
•Competitive inhibitors: This inhibitor molecule blocks the active site so that the substrate has to compete with the inhibitor to attach to the enzyme.
•Non-competitive inhibitors: This molecule binds to an enzyme somewhere other than the active site and reduces how effectively it works.
•Uncompetitive inhibitors: This inhibitor binds to the enzyme and substrate. The products leave the active site less easily, which slows the reaction.
•Irreversible inhibitors: This is an irreversible inhibitor, which binds to an enzyme and permanently inactivates it.
Thousands of enzymes in the human body exist to perform around 5,000 different functions. A few examples include:
•Lipases: This group of enzymes help digest fats in the gut.
•Amylase: In the saliva, amylase helps change starches into sugars.
•Maltase: This also occurs in the saliva, and breaks the sugar maltose into glucose.
•Trypsin: These enzymes break proteins down into amino acids in the small intestine.
•Lactase: Lactase breaks lactose, the sugar in milk, into glucose and galactose.
Enzymes play a large part in the day-to-day running of the human body. Enzymes work by combining with molecules to start a chemical reaction. They work best at certain pH levels and temperatures.
They play a vital role in the proper functioning of the digestive system, the nervous system, muscles, and more.
Figure 2.12 The Three Fundamental Chemical Reactions The atoms and molecules involved in the three fundamental chemical reactions can be imagined as words. In the second example, ammonia is catabolized into its smaller components, and the potential energy that had been stored in its bonds is released.
3.10 Summary. Biochemical reactions are chemical reactions that take place inside of living things. The sum of all of the biochemical reactions in an organism is called metabolism. Metabolism includes catabolic reactions, which are energy-releasing (exothermic) reactions, as well as anabolic reactions, which are energy-absorbing (endothermic ...
- Christine Miller
- 2020
A chemical reaction’s activation energy is the “threshold” level of energy needed to break the bonds in the reactants. Once those bonds are broken, new arrangements can form. Without an enzyme to act as a catalyst, a much larger investment of energy is needed to ignite a chemical reaction (Figure 2.3.2 2.3. 2).
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Lesson 5: Cellular respiration. Cellular respiration introduction. Introduction to cellular respiration and redox. Steps of cellular respiration. Overview of cellular respiration. Oxidative phosphorylation and the electron transport chain. Oxidative phosphorylation. Fermentation and anaerobic respiration. ATP synthase.
