Name: metabolism, energy, and cell reactions
Uploaded: 2019-03-11T09:21:09.000Z
Duration: 52 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Chemistry

Matter And Its Interactions

HS-PS1-4

What is Metabolism?

Metabolism is the sum of all the chemical reactions taking place in an organism. From the breakdown of macromolecules in food, a catabolic pathway, to the assembly of usable macromolecules from smaller subunits in anabolic pathways.

Protein digestion is a great example of catabolism, very large protein molecules are broken down into smaller polypeptides and then into individual amino acids releasing energy which is stored as ATP.

In reverse, during anabolism the ATP can be used to string together amino acids to form polypeptides, which fold on to one another resulting in a large, complex protein. This process demonstrates the constant interactions that are required for maintaining energy balance.

what is metabolism?

<h4>Overview</h4>

Metabolism represents all of the chemical activity in a cell, including reactions that build molecules (anabolism) and those that break molecules down (catabolism). Anabolic reactions require energy, whereas catabolic reactions provide it. Thus, metabolism describes how cells transform energy through a variety of chemical reactions, which are often made more efficient with the help of enzymes.

<h4>Metabolism Is the Sum of All of the Chemical Reactions That Take Place in an Organism</h4>

Metabolism is the management of energy in cells and provides three key functions:

<ol>
	<li>converting food into energy to run various cellular processes,</li>
	<li>producing energy to build cell components, and</li>
	<li>removing waste products.</li>
</ol>

To produce energy, macromolecules from food must be broken down into smaller molecules&mdash;through a catabolic pathway. This, in turn, provides energy to construct larger molecules from smaller building blocks&mdash;through an anabolic pathway. In other words, the potential energy in food&mdash;comprised of the chemical energy stored in the bonds between atoms&mdash;can be converted into kinetic energy that can be used for cellular reactions. Enzymes are essential molecular tools in metabolic pathways, as they greatly speed up many chemical reactions by reducing the amount of required energy.

<h4>Catabolic Pathways Break Down Molecules and Release Energy</h4>

Catabolism is the breakdown of macromolecules for any purpose. This includes the degradation of food molecules into smaller molecules that can be used as building blocks, a process that releases energy that is transferred to ATP. Protein digestion is an example of catabolism. For the body to utilize the protein we eat, it must be broken down from large protein molecules into smaller polypeptides, and then into individual amino acids.

Excess amino acids that are broken down for removal release, nitrogen-containing ammonia. This ammonia is toxic at high levels, and thus must be converted into a safer form that organisms can handle and dispose of. In humans, ammonia is combined with carbon dioxide and converted into urea before being eliminated from the body in the form of urine. Other organisms use different types of nitrogenous waste, such as uric acid in birds and reptiles. Compared to urea, uric acid requires much less water to be released from the body and therefore has adaptive value certain conditions.

<h4>Anabolic Pathways Synthesize Complex Molecules</h4>

Anabolic pathways construct larger molecules from smaller building block molecules, using energy (in the form of ATP). For example, protein anabolism involves stringing together amino acids to form polypeptides. The synthesized polypeptides then fold into three-dimensional protein structures. Excess amino acids can be used to make triglycerides and stored as fat, or converted into glucose and used to make ATP. Thus, both the anabolic and catabolic pathways are necessary for maintaining energy balance.

Another, less well-known example of anabolism is the production of condensed tannins in seeds. Seeds that are eaten by animals can be protected from digestion if their seed coats contain dark-colored, condensed tannins. Plants produce tannins by linking anthocyanin molecules, using the same dehydration reactions used to build polypeptides.

Overview

Metabolism represents all of the chemical activity in a cell, including reactions that build molecules (anabolism) and those that break ...

Education

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KEY TERMS AND CONCEPTS

metabolism, energy, and cell reactions

Metabolism is the set of chemical reactions that happen in a cell. It includes anabolism, which builds molecules, and catabolism, which breaks them down. These reactions help cells manage energy and keep life processes running.

Cells use metabolism to turn food into energy, make cell parts, and remove waste products. Food stores potential energy in the bonds between atoms. Catabolic pathways break large food molecules into smaller ones and release that energy. Anabolic pathways use that energy to build larger molecules from smaller building blocks. Enzymes help many of these reactions happen faster by lowering the energy needed to start them.

Catabolism is the breakdown of macromolecules for a purpose. One example is protein digestion, where large proteins are broken into polypeptides and then into individual amino acids. When extra amino acids are broken down, they release ammonia, a nitrogen-containing waste that can be toxic at high levels. In humans, ammonia combines with carbon dioxide to form urea, which leaves the body in urine. Other organisms produce different nitrogenous wastes, such as uric acid in birds and reptiles. Uric acid uses much less water for removal, which can be helpful in some environments.

Anabolic pathways build complex molecules and require energy in the form of ATP. Protein anabolism joins amino acids into polypeptides, and those polypeptides then fold into three-dimensional proteins. Extra amino acids can also be turned into triglycerides for fat storage or converted into glucose and used to make ATP. Both anabolic and catabolic pathways are needed to keep energy balance in cells. A less familiar example of anabolism is the making of condensed tannins in seeds. Some plants link anthocyanin molecules to form tannins, and these dark seed coats can help protect seeds from digestion.

Metabolism, Energy, and Cell Reactions

Metabolism is the set of chemical reactions that happen in a cell. It includes anabolism, which builds molecules, and catabolism, which breaks them down. These reactions help cells manage energy and keep life processes running. Cells use metabolism to turn food into energy, make cell parts, and remove waste products. Food stores potential energy in the bonds between atoms. Catabolic pathways break large food molecules into smaller ones and release that energy. Anabolic pathways use that energy...

first law of thermodynamics

Energy Flow in a Food Web

Energy flow in a food web shows the First Law of Thermodynamics in action. Energy cannot be created or destroyed. It can only change form as it moves through living things and the environment. Sunlight is the starting point. Plants capture radiant energy from the sun during photosynthesis and turn it into chemical energy stored in complex carbohydrates. At the same time, oxygen is released into the atmosphere. Herbivores eat the plants and use those sugars during digestion. The energy is...

second law of thermodynamics

Entropy in Food Web Energy Flow

The Second Law of Thermodynamics explains why entropy increases as energy moves through a system. Entropy means the amount of disorder in a system. Each time energy is transferred or transformed, some energy is lost as unusable heat. That heat can raise the motion of nearby molecules for a short time and make the surroundings less ordered and more random. This idea also appears in a food web. Primary producers, such as plants, take in energy from the sun and make food. During this process,...

kinetic energy

Motion as a Source of Energy

Kinetic energy is the energy of motion. It appears when an object is moving and can do work or cause change. A waterfall is one clear example. Water behind a dam has potential energy, but when it rushes downward, that moving water has kinetic energy. When the water reaches the bottom and stops moving, its energy can become potential energy again. Kinetic energy also shows up in living systems. Plants absorb light particles, called photons, which move very fast and help create chemical energy...

potential energy

Stored Energy in Motion and Bonds

Stored energy in motion and bonds is called potential energy. It depends on the structure of an object or the position of matter in space. Raising a kettlebell changes its location and increases its potential energy. A stretched rubber band also stores potential energy, which can later change into kinetic energy. Chemical bonds between atoms hold another form of stored energy called chemical energy. These bonds involve attractive forces, and that energy can change into other forms during a...

free energy

Gibbs Free Energy in Chemical Reactions

Gibbs free energy is a measure of useful energy that can be taken from a chemical reaction to do work. It is written as G and named for scientist Gibbs, who discovered it. This energy is what remains after entropy is considered. A reaction can either take in energy or release it. Reactions that absorb energy are called endergonic reactions. Reactions that release energy are called exergonic reactions. The direction of energy flow helps show which type of reaction is happening. Plants carry...

activation energy

How Catalysts Lower Reaction Barriers

Activation energy is the minimum energy a chemical reaction needs to keep going. When the activation energy is higher, the reaction usually happens more slowly. Adding heat can speed the reaction because molecules move faster and collide more often. As reactants collide, bonds break and the reaction moves through an uphill phase. That step creates the transition state, which is an unstable, high-energy state of the reactants. After that, new bonds form, products appear, and free energy is...

hydrolysis of atp

ATP Breakdown and Energy Release

ATP breakdown releases energy for cell work. Adenosine triphosphate, or ATP, can lose one or two phosphate groups when water is added. This hydrolysis reaction is exergonic, which means it releases energy that the cell can use. When one phosphate group is removed, ATP becomes ADP, or adenosine diphosphate. Inorganic phosphate is also released. ADP can then be hydrolyzed again to form AMP, or adenosine monophosphate, after a second phosphate group is removed. ATP has a clear structure. It is...

phosphorylation

Phosphorylation and Protein Control

Phosphorylation helps control how proteins work in cells. It is the addition or removal of phosphate groups, and it is the most common chemical change that regulates cellular processes. These changes can alter a protein’s structure, activity, stability, location inside the cell, and interactions with other proteins. During phosphorylation, protein kinases move the terminal phosphate group from ATP to a specific amino acid side chain on a target protein. The amino acids most often...

induced-fit model

How Enzymes Adjust to Their Substrates

Enzymes speed up many chemical reactions in cells. They are biological catalysts, so they increase reaction speed without being consumed or permanently changed. They do this by lowering the activation energy needed to turn reactants into products. Enzymes are proteins that usually work by binding to a substrate, which is the reactant molecule they act on. They show substrate specificity, meaning they bind only certain substrates. This specificity depends mainly on the shape and chemical...

enzyme kinetics

Substrate Effects on Enzyme Rates

Enzyme kinetics examines how enzymes change the rate of a reaction. Enzymes speed reactions by lowering the activation energy of the reactants. The reaction rate is the speed at which an enzyme turns reactants into products, and it can be affected by several factors, including the number of available reactants. Scientists often study enzyme kinetics in a test tube with a fixed amount of enzyme. When more substrate, or reactant, is added, the reaction rate increases because the enzyme can make...

enzyme inhibition

Competitive vs Noncompetitive Inhibitors

Enzyme inhibitors are molecules that reduce enzyme activity by binding to enzymes. Cells use these inhibitors to help regulate normal enzyme function. Drugs and toxins can also block enzymes and change how they work. Some inhibitors bind at the active site, which is the part of the enzyme where the substrate normally fits. Competitive inhibitors do this by occupying the active site and preventing the substrate from binding. If the substrate concentration becomes high enough, it can outcompete...

feedback inhibition

How Cells Control Product Buildup

Cells use enzymes to run biochemical reactions and make the products they need. These reactions are happening constantly, and enzymes speed them up so they happen fast enough to matter. Enzyme activity also has to be regulated. Cells need the right amounts of starting materials, intermediate metabolites, and final products. If these substances build up too much or drop too low, the cell can be harmed. That is why cells use control systems to keep metabolic levels balanced. One important...

allosteric regulation

Allosteric Control of Enzyme Speed

Allosteric control changes enzyme speed when a molecule binds to a site other than the active site. That alternate binding spot is called an allosteric site. An enzyme can have more than one allosteric site. This type of control can raise or lower enzyme activity. Many enzymes with allosteric control are metabolic enzymes. They help with the breakdown or the building of specific molecules in cells. In allosteric inhibition, the effector molecule causes a shape change that lowers the enzyme's...

cofactors and coenzymes

Enzyme Helpers: Metals, Vitamins, and More

Enzyme helpers are needed for many enzymes to work properly. These helpers fall into two groups: cofactors and coenzymes. Cofactors are metallic ions, while coenzymes are non-protein organic molecules. Both can be tightly bound to an enzyme or attach only when the substrate binds. Cofactors are common in mature proteins, appearing in about 30% of them. They are often added as the enzyme folds and help with catalytic activity. Magnesium is one important cofactor, and it is needed by more than...

key terms and concepts

Learn how metabolism uses catabolic and anabolic pathways, ATP, enzymes, and waste removal to manage energy in cells and build molecules.

Metabolism, Energy, and Cell Reactions | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

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Metabolism, Energy, and Cell Reactions

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