Name: electron carriers in cellular energy
Uploaded: 2025-05-22T09:05:36.000Z
Duration: 1 min 29 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Life Science

SC.912.L.18

SC.912.L.18.8

Role of Reduced Coenzymes NADH and FADH&#8322;

La nicotinammide adenina dinucleotide o NAD+ e la flavina adenina dinucleotide o FAD sono i due importanti coenzimi che agiscono come trasportatori di elettroni in varie reazioni biochimiche.
Durante una reazione di ossidazione, questi coenzimi assorbono elettroni e si riducono in NADH e FADH2.
Quindi, durante la riduzione, i coenzimi ridotti rilasciano gli elettroni e si riconvertono nella loro forma ossidata.
Nelle cellule eucariotiche, la glicolisi e il ciclo TCA sono due delle principali fonti di coenzimi ridotti.
Nel citosol, la glicolisi ossida il glucosio a piruvato, riducendo il NAD+ a NADH.
Nei mitocondri, il ciclo TCA produce tre molecole di NADH e una molecola di FADH2.
Tuttavia, il NADH prodotto nel citosol non può entrare direttamente nei mitocondri. Pertanto, due vie di trasporto, la navetta malato-aspartato e la navetta glicerolo fosfato, trasferiscono gli elettroni a NAD+ o FAD presenti all'interno dei mitocondri.
Infine, i coenzimi ridotti donano i loro elettroni alla catena di trasporto degli elettroni per generare una forza motrice protonica per la produzione di ATP.

ruolo dei coenzimi ridotti nadh e fadh₂

L'energia rilasciata dalla rottura dei legami chimici all'interno dei nutrienti può essere immagazzinata attraverso la riduzione dei trasportatori di elettroni o nei legami dell'adenosina trifosfato (ATP). Nei sistemi viventi, una piccola classe di composti funziona come trasportatori mobili di elettroni, molecole che si legano e trasportano gli elettroni ad alta energia tra i composti nei percorsi. I principali trasportatori di elettroni che verranno considerati provengono dal gruppo delle vitamine B e sono derivati dei nucleotidi; sono nicotinamide adenina dinucleotide, nicotina adenina dinucleotide fosfato e flavina adenina dinucleotide. Questi composti possono essere facilmente ridotti o ossidati.

La nicotinammide adenina dinucleotide (NAD+/NADH) è il trasportatore di elettroni mobile più comune utilizzato nel catabolismo. NAD+ è la forma ossidata della molecola; NADH è la forma ridotta della molecola. La nicotina adenina dinucleotide fosfato (NADP+), la forma ossidata di una variante NAD+ che contiene un gruppo fosfato extra, è un altro importante trasportatore di elettroni; forma NADPH quando ridotta. La forma ossidata del flavina adenina dinucleotide è FAD e la sua forma ridotta è FADH2. Sia NAD+/NADH che FAD/FADH2 sono ampiamente utilizzati nell'estrazione di energia dagli zuccheri durante il catabolismo nei chemioeterotrofi, mentre NADP+/NADPH svolge un ruolo importante nelle reazioni anaboliche e nella fotosintesi. Collettivamente, FADH2, NADH e NADPH vengono spesso definiti dotati di potere riducente grazie alla loro capacità di donare elettroni a varie reazioni chimiche.

Questo testo è adattato da <a href="https://openstax.org/books/microbiology/pages/8-1-energy-matter-and-enzymes">Openstax, Microbiology, Section 8.1: Energy, Matter and Enzymes</a>

Ruolo dei coenzimi ridotti NADH e FADH₂

L'energia rilasciata dalla rottura dei legami chimici all'interno dei nutrienti può essere immagazzinata sia attraverso la riduzione dei trasportatori di elettroni che ...

Education

Didattica

JoVE Core

Cell Biology

Biologia cellulare

Unit 1

Unità 1

Introduction to Metabolism

Introduzione al metabolismo

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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 adenine dinucleotide. These compounds can switch easily between oxidized and reduced forms.

NAD+ is the oxidized form of nicotinamide adenine dinucleotide, and NADH is its reduced form. NAD+ is the most common mobile electron carrier used in catabolism, the breakdown of molecules for energy. NADP+ is a related carrier with an extra phosphate group, and its reduced form is NADPH. FAD is the oxidized form of flavin adenine dinucleotide, and FADH2 is its reduced form.

NAD+/NADH and FAD/FADH2 are used widely in energy extraction from sugars during catabolism in chemoheterotrophs. NADP+/NADPH has a different main role. It is important in anabolic reactions and in photosynthesis. FADH2, NADH, and NADPH are often called reducing power because they can donate electrons to other chemical reactions.

Electron Carriers in Cellular Energy

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 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.

regulation of metabolism

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,...

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

Learn how NADH, FADH2, and NADPH carry electrons, store energy, and support catabolism, anabolism, and photosynthesis in cells.

Electron Carriers in Cellular Energy | 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.

Macromolecules

Biomolecules
Organisms contain a wide variety of organic molecules with numerous functions which depend on the chemical structures and properties of these ...

Polymers

What are Lipids?

Lipids function as structural components of cellular membranes, in addition to acting as energy reservoirs and signaling molecules. They are thus crucial ...

Structure of Lipids

lipid-derived-compounds-in-the-human-body

Lipid-derived Compounds in the Human Body

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Peptide Bonds

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Protein and Protein Structures

Protein Organization

Globular Proteins

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Fibrous Proteins

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Protein Denaturation

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Mechanical Protein Function

Structural Protein Function

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Chemistry of Carbohydrates

Sugars as Energy Storage Molecules

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Nucleic Acid Structure

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The DNA Helix

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RNA Structure

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Types of RNA

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Noncovalent Attractions in Biomolecules

Describe the basic molecular structures and primary functions of the four major categories of biological macromolecules.

SC.912.L.18.1

Cellulose and Pectic Polysaccharides

&#160;Every plant cell has a cell wall that protects the cell, provides structural support, and gives the cell shape. Cellulose, the main structural ...

Membrane Carbohydrates

The plasma membrane is a dynamic barrier composed of lipids, proteins, and carbohydrates. It is the epicenter of many cellular processes required for cell ...

Describe the important structural characteristics of monosaccharides, disaccharides, and polysaccharides and explain the functions of carbohydrates in living things.

SC.912.L.18.2

Overview of Fatty Acid Metabolism

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What are Membranes?

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Membrane Fluidity

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Fluid Mosaic Model

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Membrane Lipids

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Asymmetric Lipid Bilayer

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Lipids as Anchors

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The Significance of Membrane Transport

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Describe the structures of fatty acids, triglycerides, phospholipids, and steroids. Explain the functions of lipids in living organisms. Identify some reactions that fatty acids undergo. Relate the structure and function of cell membranes.

SC.912.L.18.3

Ligand Binding Sites

Cofactors and Coenzymes

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Introduction to Enzymes

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Enzymes and Activation Energy

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Introduction to Enzyme Kinetics

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Turnover Number and Catalytic Efficiency

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Catalytically Perfect Enzymes

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introduction-to-mechanisms-of-enzyme-catalysis

Introduction to Mechanisms of Enzyme Catalysis

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Ligand Binding and Linkage

Cooperative Allosteric Transitions

Ribozymes

Enzyme Activity

Biological Catalysts

All living organisms continuously perform numerous biochemical reactions to sustain their presence. Most of these reactions require ...

Describe the structures of proteins and amino acids. Explain the functions of proteins in living organisms. Identify some reactions that amino acids undergo. Relate the structure and function of enzymes.

SC.912.L.18.4

Chemiosmosis

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electron-transport-chain-complex-i-and-ii

Electron Transport Chain: Complex I and II

The mitochondrial electron transport chain (ETC) is the main energy generation system in the eukaryotic cells. However, mitochondria also produce ...

electron-transport-chain-complex-iii-and-iv

Electron Transport Chain: Complex III and IV

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The Electron Transport Chain

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the-supercomplexes-in-the-crista-membrane

The Supercomplexes in the Crista Membrane

The mitochondrial cristae membrane is the primary site for the oxidative phosphorylation (OXPHOS) process of energy conversion mediated through ...

ATP Synthase: Structure

ATP synthase or ATPase is among the most conserved proteins found in bacteria, mammals, and plants. This enzyme can catalyze a forward reaction in ...

ATP Synthase: Mechanism

In animals, the mitochondrial F1F0 ATP synthase is the key protein that synthesizes ATP molecules through a complex catalytic mechanism. While the nuclear ...

The ADP/ATP Carrier Protein

ADP/ATP carrier or AAC protein is the most abundant carrier protein in the inner mitochondrial membrane. It transports large quantities of ADP and ATP, ...

ATP Yield

Cellular respiration produces 30 - 32 ATP per glucose molecule. Although most of the ATP results from oxidative phosphorylation and the electron transport ...

Discuss the use of chemiosmotic gradients for ATP production in chloroplasts and mitochondria.

SC.912.L.18.5

Fermentation

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Biofuels: Producing Ethanol from Cellulosic Material

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University
In this experiment, cellulosic material (such as corn stalks, leaves, ...

Discuss the role of anaerobic respiration in living things and in human society.

SC.912.L.18.6

Photosynthesis

Autotrophs

Almost all living organisms on Earth depend on photosynthesis, which is the process that converts sunlight energy into a simple sugar called ...

What is Photosynthesis?

All living organisms on Earth are directly or indirectly dependent on photosynthesis. It is the only biological process that can capture energy from ...

The Anatomy of Chloroplasts

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Photosystems

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The Photochemical Reaction Center

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The Antenna Complex

Plants and other photosynthetic organisms comprise pigments capable of absorption of direct sunlight. These pigments are present in the reaction center - ...

the-z-scheme-of-electron-transport-in-photosynthesis

The Z-Scheme of Electron Transport in Photosynthesis

The light reactions of photosynthesis assume a linear flow of electrons from water to NADP+. During this process, light energy drives the splitting of ...

Identify the reactants, products, and basic functions of photosynthesis.

SC.912.L.18.7

A. All living things are composed of four basic categories of macromolecules and share the same basic needs for life.

B. Living organisms acquire the energy they need for life processes through various metabolic pathways (primarily photosynthesis and cellular respiration).

C. Chemical reactions in living things follow basic rules of chemistry and are usually regulated by enzymes.

D. The unique chemical properties of carbon and water make life on Earth possible.

Electron Carriers in Cellular Energy

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