What kind of organic molecule is an enzyme

Covering: up to Cofactor-dependent enzymes which need small organic molecule cofactors to accomplish enzymatic activity are widespread. You have access to this article. Please wait while we load your content Something went wrong. Try again? Cited by. Download options Please wait Article type Review Article.

Submitted 21 May First published 12 Aug Download Citation. Request permissions. For more information, the Mayo Clinic has a detailed website that outlines the risks and potential benefits of alcohol consumption. It has a high vapor pressure, and its rapid evaporation from the skin produces a cooling effect. It is toxic when ingested but, compared to methanol, is less readily absorbed through the skin and can thus be used topically for muscle soreness. Overall, the processes of oxidation and reduction are critical for life.

This is because the oxidation of our food molecules provides enough energy for the cells in our body to recycle the major source of energy for cellular metabolism and other energetic reactions required for life, adenosine triphosphate ATP Figure 7. This is also a major building block for RNA biosynthesis. When the phosphate bonds are hydrolyzed to produce ADP and water, there is a large release of energy. The ability of the ATP phosphoester bonds to undergo hydrolysis is the reason it is such a great energy source!

The average human will typically use their body weight in ATP every day kg!! This means that each ATP molecule must be recycled between times each day! ATP is the main energy source within the body. Cleavage of the high energy phosphate bonds releases large amounts of energy that are used for neuron function, muscle contraction, and other metabolic processes in the body. In fact, so much energy is needed to run the human body that each ATP molecule must be recycled an average of times per day.

Thought question 1: If there is 0. If each of these molecules is recycled times on a particularly active day , how many chemical reactions take place just to regenerate this energy source? Thought question 2: If there is 0.

The bulk of the ATP molecules are recycled inside the mitochondria. Mitochondria are small organelles within the cell that are thought to have originated as a bacterial symbiont within the cell Figure 7. Mitochondria have a double membrane, with the innermembrane being highly convoluted and folded, providing a lot of surface area for embedded membrane proteins. Mitochondria also contain their own circular DNA which is reminiscent of their bacterial origin.

The mitochondria are commonly known as the powerhouse of the cell, as this is the primary site where ADP is recycled into ATP. As food is ingested, the large macromolecules proteins, carbohydrates, and lipids are digested into their monomer units. This regeneration process is called oxidative phosphorylation.

The term oxidative is used because the food molecules are fully oxidized to carbon dioxide CO 2 during the process to release energy.

Phosphorylation is the process of adding a phosphate group to a molecule. In this case, the energy that is harvested from the oxidation of the food molecules, specifically the electrons and protons, is being used to phosphorylate ADP back into an ATP Figure 7. Most of the oxidation reactions in the breakdown of food molecules take place in the interior of the mitochondria, called the matrix. Once they reach the innermembrane, the electrons are delivered to a series of proton pump proteins.

The intermembrane space is the area beetween the two membranes of the mitochondria the innermembrane and the outermembrane. As the intermembrane space becomes full of protons, this creates a gradient potential. You can think of a gradient potential in a similar way that humans will use the power of water in a dam to generate electricity. The dammed water holds potential energy when there is high water in the dam. When the dam is opened in a controlled way to allow water to flow out, the power of the dammed water moving from an area of high concentration to an area of low concentration is used to turn turbines that can generate electricity.

Similarly, in the mitochondria, the protons that are concentrated in the intermembrane space also have potential energy. The electrons that have been used to generate the proton gradient end up reducing molecular oxygen O 2 into water H 2 O. The oxygen supplied for this process is the oxygen that we breath in through our lungs.

Thus, the oxidative phosphorylation process is also known as cellular respiration. This is, in fact, why breathing is crucial for our survival. Without a steady supply of oxygen to accept the electrons moving through the electron transport chain of proton pumps, the electrons would back up and get stuck inside the proton pumps like a traffic jam, blocking the further movement of protons into the intermembrane space.

Without the proton gradient, the production of ATP would no longer be possible. The first organ to run out of ATP during a lack of oxygen is the brain. If you block the passage of oxygen-carrying blood to the brain, a person will pass out in as little as 5 — 10 seconds! A summary of the oxidative phosphorylation process is shown in Figure 7. Note that the protons also came from the food molecules during the oxidation process — hydrogens and electrons often move together during oxidation!

Then they are used in combination with protons, to reduce oxygen O 2 into water H 2 O. This Figure was adapted from: Geraldine Adele Lewis. In the previous sections, you have learned an important key takeaway about chemical reactions: In all types of chemical reactions, bonds are broken and reassembled into new products. You have also learned that energy is stored in chemical bonds. This is the energy of attraction between the atoms involved in the chemical bond and is called the bond energy.

Thus, to break a chemical bond requires energy ie the attraction of the atoms for each other has to be overcome in order to pull them apart. Similarly, when new bonds are formed, energy is released as the formation of the bond creates a more stable situation for each of the atoms involved in the bonds. It is also of note, that not all chemical bonds are created equally.

We have learned in previous chapters that some atoms tend to form ionic bonds where they will fully donate or accept electrons between the atoms involved in the bond. Others form covalent bonds where they share electrons between the atoms and sometimes this sharing is unequal creating a polar covalent bond. Thus, for each type of chemical bond, the bond energy will be different. Each molecule will have its own characteristic bond energies.

Other factors that influence the overall energy required for reactions are the physical state of the reactants and products ie solid, liquid, or gaseous , the temperature of the reaction, and the amounts of reactants and products present.

Thus, when assessing whether or not a reaction will proceed spontaneously , it is necessary to determine which side of the equation energy will either be required or released. If the reaction requires more energy to break the bonds on the reactant side than is formed on the product side the reaction is said to be endergonic and will require an input of energy. This type of reaction will not be spontaneous. If the reaction produced by the formation of new bonds on the product side is more that the energy required to break the chemical bonds on the reactant side of the equation, the reaction will release energy and is said to be exergonic.

Exergonic reactions will happen spontaneously. Note that reaction spontaneity does not depend on the presence or absence of an enzyme ie.

Figure provided by The Khan Academy. The single most important property of enzymes is the ability to increase the rate chemical reactions occurring in living organisms, a property known as catalytic activity. Enzymes speed up the rate of reactions because they lower energy required to get to the transition state of the reaction.

The transition state of the reaction is an unstable intermediate structure formed during the reaction process. For example, in Figure 7. When enzymes or catalysts are present, the transition state energy is lowered which in turn has an exponential effect on the reaction rate Figure 7. Thus, enzymes can increase the reaction rate by many orders of magnitude.

The reaction energy of an uncatalyzed reaction is shown in red. Note that the transition state of the reaction is the most unstable part of the reaction and thus, is the position on the graph with the highest free energy. In the presence of an enzyme blue line The activation energy is lowered which causes an exponential increase in the reaction rate.

Note that the presence of the enzyme does not change the Gibbs Free Energy of the reactants or of the products. Figure is adapted from Fvasconcellos. Because most enzymes are proteins, their activity is affected by factors that disrupt protein structure, as well as by factors that affect catalysts in general. Factors that disrupt or denature protein structure include temperature and pH; factors that affect catalysts in general include reactant substrate concentration and enzyme concentration.

The activity of an enzyme can be measured by monitoring either the rate at which a substrate disappears or the rate at which a product forms. In the presence of a given amount of enzyme, the rate of an enzymatic reaction increases as the substrate concentration increases until a limiting rate is reached, after which further increase in the substrate concentration produces no significant change in the reaction rate part a of Figure 7.

At this point, so much substrate is present that essentially all of the enzyme active sites have substrate bound to them. In other words, the enzyme molecules are saturated with substrate. The excess substrate molecules cannot react until the substrate already bound to the enzymes has reacted and been released or been released without reacting. Note that in biological systems that the enzyme concentration is much smaller than the amount of substrate present.

Thus, enzyme concentration increases will never reach the saturation point in biological systems. Ten taxis enzyme molecules are waiting at a taxi stand to take people substrate on a minute trip to a concert hall, one passenger at a time.

If only 5 people are present at the stand, the rate of their arrival at the concert hall is 5 people in 10 minutes. If the number of people at the stand is increased to 10, the rate increases to 10 arrivals in 10 minutes.

With 20 people at the stand, the rate would still be 10 arrivals in 10 minutes. The rate would simply be higher 20 or 30 people in 10 minutes before it leveled off. When the concentration of the enzyme is significantly lower than the concentration of the substrate as occurs in biological systems , the rate of an enzyme-catalyzed reaction is directly dependent on the enzyme concentration [part b of Figure 7.

This is true for any catalyst; the reaction rate increases as the concentration of the catalyst is increased. To some extent, this rule holds for all enzymatic reactions. After a certain point, however, an increase in temperature causes a decrease in the reaction rate, due to denaturation of the protein structure and disruption of the active site [part a of Figure 7.

Note that human body maintains a constant temperature of 37 o C. Thus, most proteins have evolved to have maximal activity around this temperature. At high temperatures, the enzymes will melt and denature causing a loss of function, whereas at lower temperatures, the protein cannot kinetically move as fast to mediate the reaction.

Other species, such as those found at deep sea thermal vents, will have enzymes specialized for those environments and have different optimal temperature ranges. This fact has several practical applications. We sterilize objects by placing them in boiling water, which denatures the enzymes of any bacteria that may be in or on them. We preserve our food by refrigerating or freezing it, which slows enzyme activity.

Ionizable side groups located in the active site must have a certain charge for the enzyme to bind its substrate. An enzyme exhibits maximum activity over the narrow pH range in which a molecule exists in its properly charged form.

The median value of this pH range is called the optimum pH of the enzyme [part b of Figure 7. With the notable exception of gastric juice the fluids secreted in the stomach , most body fluids have pH values between 6 and 8. Not surprisingly, most enzymes exhibit optimal activity in this pH range. However, a few enzymes have optimum pH values outside this range. For example, the optimum pH for pepsin, an enzyme that is active in the stomach, is 2.

Pharmacology is the branch of medicine concerned with the uses, modes and mechanisms of action of drug molecules. The term mechanism of action MOA refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect.

A mechanism of action usually includes mention of the specific molecular targets to which the drug binds, such as an enzyme or receptor. Receptor sites have specific affinities for drugs based on the chemical structure of the drug, as well as the specific action that occurs there. Drugs that do not bind to receptors produce their corresponding therapeutic effect by simply interacting with chemical or physical properties in the body.

Common examples of drugs that work in this way are antacids and laxatives. In comparison, a mode of action MoA describes functional or anatomical changes, at the cellular level, resulting from the exposure of a living organism to a substance. This section will focus primarily on common drug MOAs. Drugs can act on molecular targets from any of the major macromolecule groups or from mixtures of the different groups. DNA and RNA often form complexes with proteins and many cellular receptors are modified with carbohydrate structures forming both glycoproteins and glycolipids.

Drugs can have effects through the binding of molecular targets are very specified locations in the cell as depicted in Figure 7. Drug molecules can bind many different types of cellular targets to mediate their effects. Several are indicated in the diagram above. The figure is adapted from: The National Science Foundation. Drugs mediate their effects by acting either as agonists or antagonists. 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.

During this covalent bond formation, three water molecules are released. The three fatty acids in the fat may be similar or dissimilar.

These fats are also called triglycerides because they have three fatty acids. Some fatty acids have common names that specify their origin. For example, palmitic acid, a saturated fatty acid, is derived from the palm tree. Arachidic acid is derived from Arachis hypogaea , the scientific name for peanuts.

Fatty acids may be saturated or unsaturated. In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is saturated. Saturated fatty acids are saturated with hydrogen; in other words, the number of hydrogen atoms attached to the carbon skeleton is maximized.

When the hydrocarbon chain contains a double bond, the fatty acid is an unsaturated fatty acid. Most unsaturated fats are liquid at room temperature and are called oils. If there is one double bond in the molecule, then it is known as a monounsaturated fat e. Saturated fats tend to get packed tightly and are solid at room temperature. Animal fats with stearic acid and palmitic acid contained in meat, and the fat with butyric acid contained in butter, are examples of saturated fats.

Mammals store fats in specialized cells called adipocytes, where globules of fat occupy most of the cell. In plants, fat or oil is stored in seeds and is used as a source of energy during embryonic development. Unsaturated fats or oils are usually of plant origin and contain unsaturated fatty acids.

Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats. Unsaturated fats help to improve blood cholesterol levels, whereas saturated fats contribute to plaque formation in the arteries, which increases the risk of a heart attack.

In the food industry, oils are artificially hydrogenated to make them semi-solid, leading to less spoilage and increased shelf life. Simply speaking, hydrogen gas is bubbled through oils to solidify them. During this hydrogenation process, double bonds of the cis -conformation in the hydrocarbon chain may be converted to double bonds in the trans -conformation.

This forms a trans -fat from a cis -fat. The orientation of the double bonds affects the chemical properties of the fat. Margarine, some types of peanut butter, and shortening are examples of artificially hydrogenated trans -fats. Many fast food restaurants have recently eliminated the use of trans -fats, and U. Essential fatty acids are fatty acids that are required but not synthesized by the human body.

Consequently, they must be supplemented through the diet. Omega-3 fatty acids fall into this category and are one of only two known essential fatty acids for humans the other being omega-6 fatty acids.

They are a type of polyunsaturated fat and are called omega-3 fatty acids because the third carbon from the end of the fatty acid participates in a double bond. Salmon, trout, and tuna are good sources of omega-3 fatty acids. Omega-3 fatty acids are important in brain function and normal growth and development. They may also prevent heart disease and reduce the risk of cancer. Like carbohydrates, fats have received a lot of bad publicity. However, fats do have important functions.

Fats serve as long-term energy storage. They also provide insulation for the body. Phospholipids are the major constituent of the plasma membrane. Like fats, they are composed of fatty acid chains attached to a glycerol or similar backbone. Instead of three fatty acids attached, however, there are two fatty acids and the third carbon of the glycerol backbone is bound to a phosphate group.

The phosphate group is modified by the addition of an alcohol. A phospholipid has both hydrophobic and hydrophilic regions. The fatty acid chains are hydrophobic and exclude themselves from water, whereas the phosphate is hydrophilic and interacts with water. Cells are surrounded by a membrane, which has a bilayer of phospholipids. The fatty acids of phospholipids face inside, away from water, whereas the phosphate group can face either the outside environment or the inside of the cell, which are both aqueous.

Because fat is the most calorie dense food and having a storable, high calorie compact energy source would be important to survival. The nature of its fat also made it an important trade good.

Like salmon, ooligan returns to its birth stream after years at sea. Its arrival in the early spring made it the first fresh food of the year. As you learned above all fats are hydrophobic water hating. To isolate the fat, the fish is boiled and the floating fat skimmed off.

Importantly it is a solid grease at room temperature. Because it is low in polyunsaturated fats which oxidize and spoil quickly it can be stored for later use and used as a trade item.

Its composition is said to make it as healthy as olive oil, or better as it has omega 3 fatty acids that reduce risk for diabetes and stroke. It also is rich in three fat soluble vitamins A, E and K.

Unlike the phospholipids and fats discussed earlier, steroids have a ring structure. Although they do not resemble other lipids, they are grouped with them because they are also hydrophobic.

All steroids have four, linked carbon rings and several of them, like cholesterol, have a short tail. Cholesterol is a steroid. Cholesterol is mainly synthesized in the liver and is the precursor of many steroid hormones, such as testosterone and estradiol.

It is also the precursor of vitamins E and K. Cholesterol is the precursor of bile salts, which help in the breakdown of fats and their subsequent absorption by cells. Although cholesterol is often spoken of in negative terms, it is necessary for the proper functioning of the body. It is a key component of the plasma membranes of animal cells. Waxes are made up of a hydrocarbon chain with an alcohol —OH group and a fatty acid.

Examples of animal waxes include beeswax and lanolin. Plants also have waxes, such as the coating on their leaves, that helps prevent them from drying out.

Proteins are one of the most abundant organic molecules in living systems and have the most diverse range of functions of all macromolecules. Proteins may be structural, regulatory, contractile, or protective; they may serve in transport, storage, or membranes; or they may be toxins or enzymes.

Each cell in a living system may contain thousands of different proteins, each with a unique function. Their structures, like their functions, vary greatly. They are all, however, polymers of amino acids, arranged in a linear sequence. The functions of proteins are very diverse because there are 20 different chemically distinct amino acids that form long chains, and the amino acids can be in any order.

For example, proteins can function as enzymes or hormones. Enzymes , which are produced by living cells, are catalysts in biochemical reactions like digestion and are usually proteins. Each enzyme is specific for the substrate a reactant that binds to an enzyme upon which it acts. Enzymes can function to break molecular bonds, to rearrange bonds, or to form new bonds. An example of an enzyme is salivary amylase, which breaks down amylose, a component of starch.

Hormones are chemical signaling molecules, usually proteins or steroids, secreted by an endocrine gland or group of endocrine cells that act to control or regulate specific physiological processes, including growth, development, metabolism, and reproduction. For example, insulin is a protein hormone that maintains blood glucose levels. Proteins have different shapes and molecular weights; some proteins are globular in shape whereas others are fibrous in nature.