Name: how cells control metabolic enzymes
Uploaded: 2023-04-30T10:06:39.000Z
Duration: 1 min 19 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Life Sciences

from-molecules-to-organisms-structures-and-processes

From Molecules To Organisms: Structures And Processes

HS-LS1-3

Regulation of Metabolism

Metabolic regulation is the process by which metabolic pathways, are regulated in a cell.
For instance, cellular ATP has a short half-life. Therefore, cells tightly regulate the ATP-producing and utilizing pathways to ensure a continuous supply of ATP for carrying out normal physiological functions.
Metabolism is regulated by controlling the activity and concentration of key enzymes involved in a metabolic pathway, using four major mechanisms.
Allosteric modulation refers to the attachment of small molecules at a site other than the active site of the enzyme, stimulating or inhibiting the enzyme activity.
In covalent modification, the attachment or removal of molecules, such as a phosphate group, activates or inactivates the enzyme.
An enzyme&#39;s activity is also altered by the attachment of a regulatory protein to its active site, which inhibits substrate binding and subsequent product formation.
Regulating the transcription of specific genes coding for metabolic enzymes controls the amount of mRNA produced and the enzyme concentration.

regulation of metabolism

Cellular needs and conditions vary from cell to cell and change within individual cells over time. For example, the required enzymes and energetic demands of stomach cells are different from those of fat storage cells, skin cells, blood cells, and nerve cells. Furthermore, a digestive cell works much harder to process and break down nutrients during the time that closely follows a meal compared with many hours after a meal. As these cellular demands and conditions vary, so do the amounts and functionality of different enzymes.
The rates of biochemical reactions are controlled by activation energy, and enzymes lower the activation energies for chemical reactions. The relative amounts and functioning of the variety of enzymes within a cell ultimately determine which reactions will proceed and at what rates. In certain cellular environments, environmental factors like pH, and temperature partly control enzyme activity. There are other mechanisms through which cells control enzyme activity and determine the rates at which various biochemical reactions will occur.
Metabolic pathways rely on specific enzymatic products expressed by specific genes, which in turn require continuous synthesis of certain metabolites and ATP. So, these two processes must coordinate with one another as cells adapt to the changing conditions. According to the body&#39;s requirement, transcription of the genes is regulated. When there is a need for a specific enzyme to carry out an essential biochemical process, then the concerned gene gets activated and undergoes the process of transcription and translation.
Moreover, enzymes can be regulated in ways that either promote or reduce their activity. There are many different kinds of molecules that inhibit or promote enzyme function, and various mechanisms exist for doing so. For example, in some cases of enzyme inhibition, an inhibitor molecule is similar enough to a substrate that it can bind to the active site and simply block the substrate from binding. When this happens, the enzyme is inhibited through competitive inhibition because an inhibitor molecule competes with the substrate for active site binding. Some inhibitor molecules bind to enzymes in a location where their binding induces a conformational change that reduces the enzyme&#39;s affinity for its substrate. This type of inhibition is an allosteric inhibition.
Catabolic and anabolic hormones in the body also help to regulate metabolic processes. Catabolic hormones stimulate the breakdown of molecules and the production of energy. These include cortisol, glucagon, adrenaline/epinephrine, and cytokines. All of these hormones are mobilized at specific times to meet the needs of the body. Anabolic hormones are required to synthesize molecules and include growth hormone, insulin-like growth factor, insulin, testosterone, and estrogen.
This text is adapted from <a href="https://openstax.org/books/biology-2e/pages/6-5-enzymes">Openstax, Biology 2e, Section 6.5: Enzymes</a>, and <a href="https://openstax.org/books/anatomy-and-physiology-2e/pages/24-1-overview-of-metabolic-reactions">Openstax, Anatomy and physiology 2e, Section 24.1: Overview of metabolic reactions</a>

Cellular needs and conditions vary from cell to cell and change within individual cells over time. For example, the required enzymes and energetic demands ...

Education

JoVE Core

Cell Biology

Unit 1

Introduction to Metabolism

KEY TERMS AND CONCEPTS

how cells control metabolic enzymes

Cells control metabolic enzymes to match changing needs and conditions. Different cells use different enzymes and energy levels, and those needs can also change within the same cell over time. Stomach cells, fat storage cells, skin cells, blood cells, and nerve cells do not all need the same metabolic activity. A digestive cell also works harder soon after a meal than it does many hours later.

As cell needs change, the amount and activity of enzymes change too. Enzymes lower activation energy, which is the energy needed for a reaction to start. The mix of enzymes in a cell helps decide which biochemical reactions happen and how fast they proceed. In some cell environments, pH and temperature also affect enzyme activity.

Cells use more than one way to control enzyme function. Metabolic pathways depend on enzymes made from genes, and those genes must be expressed to keep supplying needed metabolites and ATP. When the body needs a specific enzyme, the related gene can be activated for transcription and translation. This links gene control with changing cellular demands.

Enzymes can also be turned down or blocked by other molecules. In competitive inhibition, an inhibitor is similar to the substrate and binds to the active site, so the substrate cannot bind. In allosteric inhibition, an inhibitor binds somewhere else on the enzyme and causes a shape change that lowers the enzyme’s affinity for its substrate. Hormones also help regulate metabolism.

Catabolic hormones support the breakdown of molecules and the release of energy. Examples include cortisol, glucagon, adrenaline, also called epinephrine, and cytokines. Anabolic hormones support the building of molecules. These include growth hormone, insulin-like growth factor, insulin, testosterone, and estrogen. Together, these controls help cells respond to the body’s needs.

How Cells Control Metabolic Enzymes

overview of metabolism

Metabolism in Plants, Animals, and Microbes

Metabolism is the set of chemical reactions that keep living cells working. These reactions are linked through many pathways. Together, they support the normal function of cells in plants, animals, and microbes. In plants, sunlight is the main energy source. Chlorophyll pigments in the leaves absorb this light. The plant then uses that energy for photosynthesis. During photosynthesis, water is oxidized to oxygen and carbon dioxide is reduced to glucose. Glucose then serves as a starting...

carbohydrate metabolism

Carbohydrates, Digestion, and Blood Sugar

Carbohydrates are an important source of energy and a key part of human nutrition. They are made of carbon, hydrogen, and oxygen. One gram of carbohydrate provides four kilo-calories of energy, so carbohydrates are the body’s most efficient instant fuel. Starch makes up about 60% of the carbohydrates people eat. It is broken down by amylase enzymes, but amylase cannot work in the stomach’s acidic environment. That is why starch digestion happens in the mouth and the small intestine. Simple...

glycolysis: preparatory phase

Glycolysis: Energy Investment Steps

Glycolysis begins with energy investment steps in the cytoplasm of both prokaryotic and eukaryotic cells. It is the first step in cellular metabolism, which is the complete breakdown of glucose to extract energy. In heterotrophic cells, glucose enters by secondary active transport or through GLUT proteins, which are glucose transporter proteins that help glucose diffuse into the cell. The pathway starts with one six-carbon, ring-shaped glucose molecule and ends with two three-carbon molecules...

glycolysis: pay-off phase

Glycolysis: ATP and NADH Output

The pay-off phase of glycolysis turns the two three-carbon sugar molecules into ATP, NADH, and pyruvate. By this stage, the cell has already spent two ATP molecules. The remaining reactions recover that investment and add two more ATP molecules and two high-energy NADH molecules. The sixth step oxidizes glyceraldehyde 3-phosphate, a three-carbon sugar made earlier in glycolysis. High-energy electrons are transferred to NAD+, which becomes NADH. A second phosphate group is then added to form...

fates of pyruvate

Pyruvate Pathways in Fermentation

Pyruvate is a key product of glycolysis and can follow different pathways depending on oxygen availability. During glycolysis, glucose is oxidized to pyruvate, NAD+ is reduced to NADH, and two ATP are made by substrate-level phosphorylation. In aerobic organisms, pyruvate then enters the citric acid cycle, which helps produce the reduced coenzymes NADH and FADH2. These coenzymes are later oxidized in the electron transport chain to make ATP and regenerate NAD+ and FAD. When oxygen is absent,...

role of reduced coenzymes nadh and fadh&#8322;

Electron Carriers in Cellular Energy

Electron carriers help store and move energy during nutrient breakdown. Cells can save released energy by reducing these carriers or by making ATP, the cell’s main energy molecule. These mobile electron carriers bind high-energy electrons and shuttle them between compounds in metabolic pathways. The main carriers discussed here come from the B vitamin group and are nucleotide derivatives. They include nicotinamide adenine dinucleotide, nicotinamide adenine dinucleotide phosphate, and flavin...

overview of nitrogen metabolism

Nitrogen Cycle in Soil and Plants

Nitrogen moves through soil, plants, animals, and microbes in a cycle that keeps this macronutrient available for life. It is a major part of proteins and nucleic acids, so cells need it to build both amino acids and nucleotides. In nature, nitrogen is recycled from organic compounds and stored in several forms, including ammonia, ammonium ions, nitrate, nitrite, and nitrogen gas. Many of the key steps in this cycle are carried out only by prokaryotes. The largest nitrogen pool in terrestrial...

overview of fatty acid metabolism

Fatty Acids: Energy, Membranes, and Cholesterol

Fatty acids help cells store and use energy, and they also support important cell structures. Lipids are nonpolar and hydrophobic, so they do not mix well with water. Major lipid types include fats and oils, waxes, phospholipids, and steroids. Cells break down fatty acids by beta-oxidation. This process happens in the matrix of the mitochondria and cuts fatty acid chains into two-carbon acetyl groups. CoA picks up these groups to form acetyl CoA, which then enters the citric acid cycle. Extra...

sugars as energy storage molecules

Glucose Storage in Plants and Animals

Glucose storage in plants and animals helps cells manage energy for metabolism. Sugar is a simple carbohydrate, and cells use it because a lot of energy is stored in its bonds. Consumed carbohydrates often come from photosynthesizing organisms, especially plants. Plants make glucose during photosynthesis by using sunlight to convert carbon dioxide into sugar molecules. Because this builds a larger, energy-storing molecule, the process needs an energy input. Glucose can then be stored for later...

fats as energy storage molecules

How Triglycerides Fuel ATP Production

Triglycerides store long-term energy in fats. A triglyceride is built from glycerol and three fatty acids. When the body needs energy, these molecules are broken down first. This breakdown is called lipolysis, and it happens in the cytoplasm by hydrolysis. Lipolysis splits triglycerides into fatty acids and glycerol. The glycerol then enters glycolysis as DHAP, which connects fat breakdown to the cell’s main energy pathway. The fatty acids are then oxidized by beta-oxidation into acetyl-CoA.

Cells control metabolic enzymes to match changing needs and conditions. Different cells use different enzymes and energy levels, and those needs can also change within the same cell over time. Stomach cells, fat storage cells, skin cells, blood cells, and nerve cells do not all need the same metabolic activity. A digestive cell also works harder soon after a meal than it does many hours later. As cell needs change, the amount and activity of enzymes change too. Enzymes lower activation energy,...

positive and negative feedback loops

Homeostasis and Body Feedback Control

Homeostasis keeps body conditions in a steady range through feedback control. Animal organs and organ systems constantly adjust to internal and external changes. This balance is called a dynamic equilibrium because the body keeps adapting while still staying within specific ranges. The goal of homeostasis is to stay near a set point, which is the value the body tries to maintain. A change in the internal or external environment is a stimulus. A receptor detects that change and sends a signal...

key terms and concepts

Explore how cells regulate metabolic enzymes through gene expression, inhibition, pH, temperature, and hormones that support breakdown or building of molecules.

How Cells Control Metabolic Enzymes | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Next Generation Science Standards

Life Science

From Molecules to Organisms: Structures and Processes

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Transcription

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Translation

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structure-and-organization-of-smooth-muscles

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chromatin-position-affects-gene-expression

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Organization of Genes

Chromosome Structure

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HS-LS1-1

Characteristics of Life

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https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10647.jpg

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Taxonomy

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Phylogeny

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HS-LS1-2

Overview of Metabolism

Living cells constantly carry out various chemical reactions which are necessary for their proper functioning. These reactions are interlinked to one ...

Positive and Negative Feedback Loops

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Functions of Life

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Requirements for Human Life

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What is Homeostasis?

Maintaining homeostasis requires that the body continuously maintain its internal conditions. Each physiological condition has a particular set point, ...

Negative and Positive Feedback

Homeostatic Imbalance

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pH Homeostasis

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homeostatic-imbalances-in-body-temperature

Homeostatic Imbalances in Body Temperature

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...

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Positive Regulator Molecules

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Replicative Cell Senescence

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Cells Coordinate Growth and Proliferation

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Chromosome Duplication

Cohesins

Condensins

The Mitotic Spindle

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Spindle Assembly

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HS-LS1-4

How Cells Control Metabolic Enzymes

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