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2.3: Chemical Reactions - Biology

2.3: Chemical Reactions - Biology


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2.3: Chemical Reactions

2.3 Chemical Reactions

One characteristic of a living organism is metabolism, which is the sum total of all of the chemical reactions that go on to maintain that organism’s health and life. The bonding processes you have learned thus far are anabolic chemical reactions that is, they form larger molecules from smaller molecules or atoms. But recall that metabolism can proceed in another direction: in catabolic chemical reactions, bonds between components of larger molecules break, releasing smaller molecules or atoms. Both types of reaction involve exchanges not only of matter, but of energy.

The Role of Energy in Chemical Reactions

Chemical reactions require a sufficient amount of energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ones formed. In general, kinetic energy is the form of energy powering any type of matter in motion. Imagine you are building a brick wall. The energy it takes to lift and place one brick atop another is kinetic energy—the energy matter possesses because of its motion. Once the wall is in place, it stores potential energy. Potential energy is the energy of position, or the energy matter possesses because of the positioning or structure of its components. If the brick wall collapses, the stored potential energy is released as kinetic energy as the bricks fall.

In the human body, potential energy is stored in the bonds between atoms and molecules. Chemical energy is the form of potential energy in which energy is stored in chemical bonds. When those bonds are formed, chemical energy is invested, and when they break, chemical energy is released. Notice that chemical energy, like all energy, is neither created nor destroyed rather, it is converted from one form to another. When you eat an energy bar before heading out the door for a hike, the honey, nuts, and other foods the bar contains are broken down and rearranged by your body into molecules that your muscle cells convert to kinetic energy.

Chemical reactions that release more energy than they absorb are characterized as exergonic. The catabolism of the foods in your energy bar is an example. Some of the chemical energy stored in the bar is absorbed into molecules your body uses for fuel, but some of it is released—for example, as heat. In contrast, chemical reactions that absorb more energy than they release are endergonic. These reactions require energy input, and the resulting molecule stores not only the chemical energy in the original components, but also the energy that fueled the reaction. Because energy is neither created nor destroyed, where does the energy needed for endergonic reactions come from? In many cases, it comes from exergonic reactions.

Forms of Energy Important in Human Functioning

You have already learned that chemical energy is absorbed, stored, and released by chemical bonds. In addition to chemical energy, mechanical, radiant, and electrical energy are important in human functioning.

  • Mechanical energy, which is stored in physical systems such as machines, engines, or the human body, directly powers the movement of matter. When you lift a brick into place on a wall, your muscles provide the mechanical energy that moves the brick.
  • Radiant energy is energy emitted and transmitted as waves rather than matter. These waves vary in length from long radio waves and microwaves to short gamma waves emitted from decaying atomic nuclei. The full spectrum of radiant energy is referred to as the electromagnetic spectrum. The body uses the ultraviolet energy of sunlight to convert a compound in skin cells to vitamin D, which is essential to human functioning. The human eye evolved to see the wavelengths that comprise the colors of the rainbow, from red to violet, so that range in the spectrum is called “visible light.”
  • Electrical energy, supplied by electrolytes in cells and body fluids, contributes to the voltage changes that help transmit impulses in nerve and muscle cells.

Characteristics of Chemical Reactions

All chemical reactions begin with a reactant , the general term for the one or more substances that enter into the reaction. Sodium and chloride ions, for example, are the reactants in the production of table salt. The one or more substances produced by a chemical reaction are called the product .

In chemical reactions, the components of the reactants—the elements involved and the number of atoms of each—are all present in the product(s). Similarly, there is nothing present in the products that are not present in the reactants. This is because chemical reactions are governed by the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction.

Just as you can express mathematical calculations in equations such as 2 + 7 = 9, you can use chemical equations to show how reactants become products. As in math, chemical equations proceed from left to right, but instead of an equal sign, they employ an arrow or arrows indicating the direction in which the chemical reaction proceeds. For example, the chemical reaction in which one atom of nitrogen and three atoms of hydrogen produce ammonia would be written as N + 3H → NH 3 N + 3H → NH 3 [email protected]@[email protected]@+=feaagyart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaeOtaiaabccacaqGRaGaaei[email protected][email protected] . Correspondingly, the breakdown of ammonia into its components would be written as NH 3 → N + 3H. NH 3 → N + 3H.

Notice that, in the first example, a nitrogen (N) atom and three hydrogen (H) atoms bond to form a compound. This anabolic reaction requires energy, which is then stored within the compound’s bonds. Such reactions are referred to as synthesis reactions. A synthesis reaction is a chemical reaction that results in the synthesis (joining) of components that were formerly separate (Figure 2.12a). 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. A + B → AB. [email protected]@[email protected]@+=feaagyart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaqc[email protected][email protected]

In the second example, ammonia is catabolized into its smaller components, and the potential energy that had been stored in its bonds is released. Such reactions are referred to as decomposition reactions. A decomposition reaction is a chemical reaction that breaks down or “de-composes” something larger into its constituent parts (see Figure 2.12b). The general equation for a decomposition reaction is: AB → A + B AB → A + B [email protected]@[email protected]@+=feaagyart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqa[email protected][email protected] .

Factors Influencing the Rate of Chemical Reactions

If you pour vinegar into baking soda, the reaction is instantaneous the concoction will bubble and fizz. But many chemical reactions take time. A variety of factors influence the rate of chemical reactions. This section, however, will consider only the most important in human functioning.

Properties of the Reactants

If chemical reactions are to occur quickly, the atoms in the reactants have to have easy access to one another. Thus, the greater the surface area of the reactants, the more readily they will interact. When you pop a cube of cheese into your mouth, you chew it before you swallow it. Among other things, chewing increases the surface area of the food so that digestive chemicals can more easily get at it. As a general rule, gases tend to react faster than liquids or solids, again because it takes energy to separate particles of a substance, and gases by definition already have space between their particles. Similarly, the larger the molecule, the greater the number of total bonds, so reactions involving smaller molecules, with fewer total bonds, would be expected to proceed faster.

In addition, recall that some elements are more reactive than others. Reactions that involve highly reactive elements like hydrogen proceed more quickly than reactions that involve less reactive elements. Reactions involving stable elements like helium are not likely to happen at all.

Temperature

Nearly all chemical reactions occur at a faster rate at higher temperatures. Recall that kinetic energy is the energy of matter in motion. The kinetic energy of subatomic particles increases in response to increases in thermal energy. The higher the temperature, the faster the particles move, and the more likely they are to come in contact and react.

Concentration and Pressure

If just a few people are dancing at a club, they are unlikely to step on each other’s toes. But as more and more people get up to dance—especially if the music is fast—collisions are likely to occur. It is the same with chemical reactions: the more particles present within a given space, the more likely those particles are to bump into one another. This means that chemists can speed up chemical reactions not only by increasing the concentration of particles—the number of particles in the space—but also by decreasing the volume of the space, which would correspondingly increase the pressure. If there were 100 dancers in that club, and the manager abruptly moved the party to a room half the size, the concentration of the dancers would double in the new space, and the likelihood of collisions would increase accordingly.

Enzymes and Other Catalysts

For two chemicals in nature to react with each other they first have to come into contact, and this occurs through random collisions. Because heat helps increase the kinetic energy of atoms, ions, and molecules, it promotes their collision. But in the body, extremely high heat—such as a very high fever—can damage body cells and be life-threatening. On the other hand, normal body temperature is not high enough to promote the chemical reactions that sustain life. That is where catalysts come in.

In chemistry, a catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any change. You can think of a catalyst as a chemical change agent. They help increase the rate and force at which atoms, ions, and molecules collide, thereby increasing the probability that their valence shell electrons will interact.

The most important catalysts in the human body are enzymes. An enzyme is a catalyst composed of protein or ribonucleic acid (RNA), both of which will be discussed later in this chapter. Like all catalysts, enzymes work by lowering the level of energy that needs to be invested in a chemical reaction. 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 2.13).

Enzymes are critical to the body’s healthy functioning. They assist, for example, with the breakdown of food and its conversion to energy. In fact, most of the chemical reactions in the body are facilitated by enzymes.


The Role of Energy in Chemical Reactions

Chemical reactions require a sufficient amount of energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ones formed. In general, kinetic energy is the form of energy powering any type of matter in motion. Imagine you are building a brick wall. The energy it takes to lift and place one brick atop another is kinetic energy&mdashthe energy matter possesses because of its motion. Once the wall is in place, it stores potential energy. Potential energy is the energy of position, or the energy matter possesses because of the positioning or structure of its components. If the brick wall collapses, the stored potential energy is released as kinetic energy as the bricks fall.

In the human body, potential energy is stored in the bonds between atoms and molecules. Chemical energy is the form of potential energy in which energy is stored in chemical bonds. When those bonds are formed, chemical energy is invested, and when they break, chemical energy is released. Notice that chemical energy, like all energy, is neither created nor destroyed rather, it is converted from one form to another. When you eat an energy bar before heading out the door for a hike, the honey, nuts, and other foods the bar contains are broken down and rearranged by your body into molecules that your muscle cells convert to kinetic energy.

Chemical reactions that release more energy than they absorb are characterized as exergonic. The catabolism of the foods in your energy bar is an example. Some of the chemical energy stored in the bar is absorbed into molecules your body uses for fuel, but some of it is released&mdashfor example, as heat. In contrast, chemical reactions that absorb more energy than they release are endergonic. These reactions require energy input, and the resulting molecule stores not only the chemical energy in the original components, but also the energy that fueled the reaction. Because energy is neither created nor destroyed, where does the energy needed for endergonic reactions come from? In many cases, it comes from exergonic reactions.


Forms of Energy Important in Human Functioning

You have already learned that chemical energy is absorbed, stored, and released by chemical bonds. In addition to chemical energy, mechanical, radiant, and electrical energy are important in human functioning.

  • Mechanical energy, which is stored in physical systems such as machines, engines, or the human body, directly powers the movement of matter. When you lift a brick into place on a wall, your muscles provide the mechanical energy that moves the brick.
  • Radiant energy is energy emitted and transmitted as waves rather than matter. These waves vary in length from long radio waves and microwaves to short gamma waves emitted from decaying atomic nuclei. The full spectrum of radiant energy is referred to as the electromagnetic spectrum. The body uses the ultraviolet energy of sunlight to convert a compound in skin cells to vitamin D, which is essential to human functioning. The human eye evolved to see the wavelengths that comprise the colors of the rainbow, from red to violet, so that range in the spectrum is called “visible light.”
  • Electrical energy, supplied by electrolytes in cells and body fluids, contributes to the voltage changes that help transmit impulses in nerve and muscle cells.

What happens in a chemical reaction?

Q: are these found in eukaryotes, prokaryotes or both? 1. nucleus 2. cell membrane 3. inclusion bodie.

A: There are a variety of forms of life that exist in nature. All the organisms of different species ar.

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A: Soil matric potential is the measure of water potential of the soil and indicates how easy or diffic.

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A: According to the question, we have to explain that cauliflower is amphidiploid or not. So, let us ha.

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A: Osmosis occurs by the movement of the solvent to a higher concentration. Solutions can be hypotonic.

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A: Blood supplies nutrients, oxygen, and other molecules such as hormones to the cells and takes away c.

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A: The brain is one of the primary organs of the central nervous system. The brain comprises many parts.

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A: The disease is the state that is caused due to the deviation from the normal. The disease is caused .

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A: Bacteria are the most important microorganisms to the food processor. Some bacteria are beneficial a.

Q: Answer each questions for 5-6 sentences: 1. What is the composition or normal semen? 2. What chemica.

A: Male accessory glands consists of paired seminal vesicles, a prostate gland and a paired bulbourethr.


Proteins

Proteins are one of the most abundant organic molecules in living organisms and are much more diverse in structure and function than other classes of macromolecules. A single cell can contain thousands of proteins, each with a unique function. Although their structures and functions vary widely, all proteins are made up of one or more chains of amino acids.

Enzymes: Enzymes act as catalysts in biochemical reactions (that is, they accelerate them). Each enzyme recognizes one or more substrates, the molecules that serve as the starting material for the reaction it catalyzes. Different enzymes participate in different types of reactions and can break down, bind, or rearrange their substrates.
An example of an enzyme found in your body is salivary amylase, which breaks down amylose in food into smaller sugars. Amylose does not taste very sweet, but the smaller sugars do. That&aposs why starchy foods are sweeter if you chew them longer, you&aposre giving salivary amylase time to do its job.

Hormones: Hormones are long-distance chemical signals released by endocrine cells that control specific physiological processes, such as growth, development, metabolism, and reproduction. While some hormones are steroid-based, meaning they are lipids, others are proteins. These protein-based hormones are called peptide hormones.
For example, insulin is an important peptide hormone that helps regulate blood glucose levels, it is produced by the pancreatic beta cells, which travel throught the organism to allow the cells absorb glucose. This process allows blood glucose to return to normal levels at rest.


Conditions of equilibrium state

The four conditions that apply to all systems at equilibrium state:

2. The observable (macroscopic) properties of a system at equilibrium are constant.

At equilibrium, there is no overall change in the properties that depend on the total quantity of matter in the system.

Examples of these properties include colour, pressure, concentration, and pH.

3. Equilibrium can only be reached in a closed system.

For this reason, a system can be at equilibrium only if it is at constant temperature.

Small changes to the components of a system are sometimes negligible. Thus, equilibrium principles can be applied if a system is not physically closed.

4. The equilibrium state of a chemical system can be approached from either direction, both from the side of forward and reverse reactions.

For a closed chemical equilibrium system in constant environmental conditions, the same equilibrium concentrations are reached regardless of the direction by which equilibrium was reached.


The substance that can be added to the reaction mixture to maintain a high activity of the enzyme, with the reason for the same. Introduction: The acidic or basic character is expressed in terms of pH (potential of hydrogen). It is a negative logarithm of the concentration of H + . A solution is neutral if its pH is 7, basic if it is greater than 7, and acidic if it is less than 7. The maintenance of pH is critical to living organisms because changes in pH bring about changes in the ionic states of biomolecules.

The substance that can be added to the reaction mixture to maintain a high activity of the enzyme, with the reason for the same.

Introduction:

The acidic or basic character is expressed in terms of pH (potential of hydrogen). It is a negative logarithm of the concentration of H + . A solution is neutral if its pH is 7, basic if it is greater than 7, and acidic if it is less than 7. The maintenance of pH is critical to living organisms because changes in pH bring about changes in the ionic states of biomolecules.


Iron reacts with oxygen

When iron rusts, it is because the iron metal reacts with oxygen in the air to form iron oxide.

An old car with rust on the bonnet. http://www.flickr.com/photos/dok1/3513263469/

A closeup photo of a rusted barrel. http://www.flickr.com/photos/jeua/7217824700/

The word equation is the following:

iron + oxygen→ iron oxide

The chemical equation is the following:

Is the equation balanced? Draw a submicroscopic picture to help you decide.

Learner's diagram should look like this. They may find it difficult to convert the equations into diagrams. Help them to interpret the formulae in the following way: Fe on its own means there is just one atom of iron (Fe). O2 means there must be two atoms of O, linked up to form a molecule. Fe2O3 means two Fe atoms and three O atoms are clustered together.

The colours are not important, as long as all the atoms of the same element are the same colour. The arrangement of the atoms in the Fe2O3 'cluster' is also not important. Since Fe2O3 is an ionic compound, we would not ordinarily speak of a 'molecule' of Fe2O3. Like all other ionic compounds, it consists of large clusters of Fe3+ and O2- ions in a regular crystalline packing that extends in three dimensions, much like the ionic lattice of NaCl in the picture below (shown in Chapter 1 also).

It is not recommended that you mention this information here, as it more likely to confuse learners at this point than add to their understanding of balancing equations.


Watch the video: BIO 137: Chemical reactions and Macromolecules (June 2022).