Name: electron carriers in cellular respiration
Uploaded: 2019-03-11T09:21:11.000Z
Duration: 1 min 24 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Life Science

LS.4

LS.4.b

Electron Carriers

נשאי אלקטרונים הם תרכובות המעבירות אלקטרונים בעלי אנרגיה גבוהה, יכולת התא להפיק אנרגיה הניתנת לצריכה באמצעות תגובות חמצון-חיזור, תוך תאום מצבים של חמצון וחיזור, מסירה וקליטה בהתאמה של חלקיקים אלו בעלי מטען שלילי. למשל, תרכובת עיקרית אחת היא ניקוטינאמיד אדנין דינוקלאוטיד, או NAD, המכונה כך כי טבעת ריבוז אחת היא בעלת בסיס אדנין, בעוד לשניה יש ניקוטינאמיד המחובר לאטומי הפחמן הראשונים. בעמדת הפחמן החמישי, שני נוקלאוטידים אלה מקושרים על-ידי שתי קבוצות פוספט.במהלך המטבוליזם, NAD, כקואנזים, נקשר לאנזים שבתורו מזרז את התגובות ופועל כמחמצן על-די הסרת שני אטומי מימן יחד עם זוג אלקטרונים מהמגיב, כמו סוכר. האלקטרונים מועברים לאחר מכן לחנקן הנושא מטען חיובי, ואטום מימן מתחבר אל הפחמן הנגדי ומייצר NADH. בסופו של דבר, פרוטונים עודפים של מימן נשארים בציטופלזמה, ו-NADH מעביר את האלקטרונים אל הקרום המיטוכונדרי, שבו הם נכנסים ל‫שרשרת מעבר האלקטרונים, והנשאים יכולים להמשיך לעבור תגובות חמצון-חיזור.

נושאי אלקטרונים

<div style="direction:rtl">אפשר לחשוב על נושאי אלקטרונים כמעבורות אלקטרונים. תרכובות אלו יכולות בקלות לקבל אלקטרונים (כלומר, להיות מופחתות) או לאבד אותם (כלומר, להתחמצן). הם ממלאים תפקיד חיוני בייצור אנרגיה מכיוון שהנשימה התאית מותנית בזרימת האלקטרונים. במהלך השלבים הרבים של הנשימה התאית, גלוקוז מתפרק לפחמן דו חמצני ומים. נושאי אלקטרונים קולטים אלקטרונים שאבדו על ידי גלוקוז בתגובות אלו, אוגרים אותם באופן זמני ומשחררים אותם לשרשרת העברת האלקטרונים. שני נושאי אלקטרונים כאלה הם NAD+ ו-FAD, שניהם מופקים מויטמיני B. הצורות המופחתות של NAD+ ו-FAD, NADH ו-FADH2, בהתאמה, מיוצרות בשלבים מוקדמים יותר של הנשימה התאית (גליקוליזה, חמצון פירובטים ומחזור חומצת הלימון). נושאי האלקטרונים המופחתים NADH ו-FADH2 מעבירים אלקטרונים לקומפלקסים I ו-II של שרשרת העברת האלקטרונים, בהתאמה. בתהליך, הם מתחמצנים ליצירת NAD+ ו-FAD. נשאי אלקטרונים נוספים בשרשרת העברת האלקטרונים הם פלבופרוטאינים, צבירי ברזל-גופרית, קינונים וציטוכרומים. בסיוע אנזימים, נושאי אלקטרונים אלו מעבירים בסופו של דבר את האלקטרונים למולקולות חמצן. נושאי האלקטרונים מתחמצנים כשהם תורמים אלקטרונים ומוחזרים כשהם מקבלים אותם, וכך מתחמצנים בין צורותיהם המחומצנות והמוחזרות. נושאי אלקטרונים מספקים זרימה מבוקרת של אלקטרונים המאפשרת ייצור ATP. בלעדיהם, התא יפסיק לתפקד.</div>

ניתן לחשוב על נשאי אלקטרונים כעל מעבורות אלקטרונים. תרכובות אלה יכולות בקלות לקבל אלקטרונים (כלומר, להיות מופחתות) או לאבד אותם (כלומר, להיות מחומצן). ...

Education

JoVE Core

Biology

ביולוגיה

Cellular Processes

תהליכים תאיים

Cellular Respiration

נשימה תאית

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

electron carriers in cellular respiration

Electron carriers help move electrons through cellular respiration. They act like shuttles that can accept electrons, which means they are reduced, or give electrons away, which means they are oxidized. This changing between oxidized and reduced forms is essential for energy production.

As glucose breaks down into carbon dioxide and water, it loses electrons at several stages. Electron carriers pick up those electrons and store them temporarily. They then release the electrons into the electron transport chain, where the cell can use them to make ATP.

NAD+ and FAD are two important electron carriers. Both come from B vitamins. Their reduced forms, NADH and FADH2, are made during glycolysis, pyruvate oxidation, and the citric acid cycle. NADH donates electrons to complex I of the electron transport chain, while FADH2 donates electrons to complex II.

Other electron carriers also work in the electron transport chain. These include flavoproteins, iron-sulfur clusters, quinones, and cytochromes. With help from enzymes, they pass electrons along until oxygen receives them. This controlled flow of electrons keeps ATP production going, and without it, the cell would stop working.

Electron Carriers in Cellular Respiration

electron-carriers-in-cellular-respiration

what is glycolysis?

Glycolysis: How Cells Break Down Glucose

Glycolysis is the first stage of cellular respiration and a key way cells break down glucose to make energy. Cellular respiration converts food energy from macromolecules into ATP, the cell’s main energy currency. Glycolysis also creates intermediate molecules that can feed into other pathways. In this pathway, one six-carbon sugar such as glucose is split into two three-carbon molecules, including pyruvate. The process produces a net gain of two ATP molecules, since four ATP are made and two...

energy-requiring steps of glycolysis

Glycolysis: Glucose Trapping and Splitting

Glycolysis begins in the cytosol, where glucose is prepared for use as energy. This process has two phases: an energy-requiring phase and an energy-releasing phase. The first phase changes glucose into a more reactive, unstable form before it can move into later steps. In the first step, glucose is phosphorylated, which means a phosphate group is added from ATP. This produces glucose 6-phosphate. The added phosphate is negatively charged, so it cannot cross the hydrophobic cell membrane. As a...

energy-releasing steps of glycolysis

Glycolysis: ATP and NADH Formation

Glycolysis produces ATP and NADH during its energy-releasing phase. These reactions are the last steps of glycolysis and convert glyceraldehyde-3-phosphate, or G3P, into pyruvate. The phase is often described as steps 6 to 10, and it happens twice because two 3-carbon sugars are made earlier in glycolysis. The sixth step begins with two linked events. G3P is oxidized, which means it loses hydrogen, and it is phosphorylated, which means a phosphate group is added. NAD+ acts as the electron...

pyruvate oxidation

How Pyruvate Becomes Acetyl CoA

Pyruvate is prepared for the next stage of cellular respiration inside the mitochondria. After glycolysis, the charged pyruvate molecules enter the mitochondria by active transport. There, they go through three enzymatic reactions so the energy stored in pyruvate can be used by the cell. First, pyruvate dehydrogenase removes the carboxyl group from pyruvate. This step releases carbon dioxide. Next, the stripped molecule is oxidized, and the electrons are picked up by NAD+ to make NADH. The...

the citric acid cycle

Citric Acid Cycle Energy and Products

The citric acid cycle is a key energy-making pathway in cells. It is also called the Krebs cycle or the TCA cycle. In eukaryotic cells, it takes place in the matrix of mitochondria. In prokaryotic cells, it occurs in the cytoplasm. The cycle starts with acetyl CoA, which enters the pathway after pyruvate oxidation. That earlier step makes two acetyl CoA molecules per glucose molecule. For that reason, the citric acid cycle runs twice for each glucose molecule. The pathway includes eight...

electron transport chains

ATP Production by the Electron Transport Chain

ATP production in the electron transport chain is the final stage of cellular respiration. This stage is part of oxidative phosphorylation, which has two steps: the electron transport chain and chemiosmosis. In eukaryotic cells, the electron transport chain sits in the inner mitochondrial membrane. Its main job is to build a proton gradient. That gradient is then used during chemiosmosis to make ATP. The process also regenerates the electron carriers NAD+ and FAD, which are needed again in...

chemiosmosis

ATP Production by Chemiosmosis

ATP production by chemiosmosis is part of oxidative phosphorylation, the efficient stage of cellular respiration that makes most of the cell’s ATP. Oxidative phosphorylation includes two linked processes: the electron transport chain and chemiosmosis. Together, they help generate adenosine triphosphate, or ATP, the main energy molecule used by cells. The electron transport chain is a series of protein complexes in the inner mitochondrial membrane. These complexes pass electrons through a set...

electron carriers

Electron carriers help move electrons through cellular respiration. They act like shuttles that can accept electrons, which means they are reduced, or give electrons away, which means they are oxidized. This changing between oxidized and reduced forms is essential for energy production. As glucose breaks down into carbon dioxide and water, it loses electrons at several stages. Electron carriers pick up those electrons and store them temporarily. They then release the electrons into the...

fermentation

Fermentation Pathways Without Oxygen

Fermentation is a metabolic pathway that lets cells make energy without oxygen. It begins after glucose is split into two pyruvate molecules during glycolysis. Glycolysis is the same first step used in aerobic respiration. When oxygen is unavailable, pyruvate does not enter aerobic respiration. Instead, cells convert pyruvate into other organic molecules through pathways that depend on the organism. A key purpose of fermentation is to regenerate NAD+ from NADH so glycolysis can keep running. <br...

dietary connections

How Food Becomes ATP

Food becomes ATP through connected steps in cellular respiration. Carbohydrates, proteins, and lipids all feed into these pathways. The body can use foods such as apples, cheese, and guacamole as sources of energy. Carbohydrate digestion starts with enzymes that break complex carbohydrates into simple sugars. Glucose can enter glycolysis directly. Fructose and galactose must first be converted into sugars that are intermediates of the glycolytic pathway. Proteins are digested into amino acids.

introduction to cellular respiration

Cellular Respiration: ATP Production Steps

Cellular respiration is the process cells use to turn energy from food into ATP. ATP, or adenosine triphosphate, stores energy in chemical bonds that can be released quickly when cells need it. Much of the energy released during respiration becomes heat, but some of it is captured to make ATP. This process depends on oxidation-reduction, or redox, reactions. In these reactions, oxidation means electron loss and reduction means electron gain. The electron carriers NAD+ and FAD, along with their...

products of the citric acid cycle

Citric Acid Cycle Output in Cellular Respiration

The citric acid cycle is a key stage of aerobic respiration in cells. It is also called the Krebs cycle or the tricarboxylic acid (TCA) cycle. Plants and animals use this oxygen-requiring pathway as part of cellular respiration. This cycle happens after glycolysis and pyruvate oxidation. Glycolysis makes two pyruvate molecules from each glucose molecule. During pyruvate oxidation, each pyruvate becomes acetyl-CoA, which is the input for the citric acid cycle. That means one glucose molecule...

outcomes of glycolysis

Glycolysis Products in Cellular Respiration

Glycolysis is the first step of cellular respiration and breaks glucose into smaller molecules. Cells use this process to pull energy from glucose over a series of chemical reactions. Cellular respiration can happen with oxygen or without oxygen. In both aerobic and anaerobic cellular respiration, glycolysis makes a net gain of two pyruvate molecules, two NADH molecules, and two ATP molecules. Four ATP molecules are produced, but two ATP molecules are used earlier in the pathway. Glycolysis...

atp yield

How Cellular Respiration Makes ATP

Cellular respiration makes ATP from glucose in several stages. The process usually produces 30 to 32 ATP per glucose molecule. Most of that ATP comes from oxidative phosphorylation and the electron transport chain, while 4 ATP are made earlier, with 2 from glycolysis and 2 from the citric acid cycle. The electron transport chain, or ETC, sits in the inner mitochondrial membrane. It has four main protein complexes and ATP synthase, the enzyme that makes ATP. NADH and FADH2 deliver electrons to...

key terms and concepts

Learn how NADH, FADH2, and other electron carriers move electrons through cellular respiration to support ATP production in high school biology.

Electron Carriers in Cellular Respiration | 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.

biology

Next Generation Science Standards

High School

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

From Molecules to Organisms: Structures and Processes

HS-LS1-7

Texas Essential Knowledge and Skills

BIO.11

BIO.11.A

myJoVE Corporation

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LS.4.a

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What is Glycolysis?

Overview
Cells make energy by breaking down macromolecules. Cellular respiration is the biochemical process that converts &#34;food energy&#34; (from the ...

Energy-requiring Steps of Glycolysis

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Energy-releasing Steps of Glycolysis

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Outcomes of Glycolysis

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Pyruvate Oxidation

After glycolysis, the charged pyruvate molecules enter the mitochondria via active transport and undergo three enzymatic reactions. These reactions ensure ...

The Citric Acid Cycle

The citric acid cycle, also known as the Krebs cycle or TCA cycle, consists of several energy-generating reactions that yield one ATP molecule, three NADH ...

Products of the Citric Acid Cycle

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Electron Transport Chains

The final stage of cellular respiration is oxidative phosphorylation that consists of two steps: the electron transport chain and chemiosmosis. The ...

Chemiosmosis

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ATP Yield

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Fermentation

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Phosphorylation

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The student will investigate and understand that there are chemical processes of energy transfer which are important for life. Key ideas include photosynthesis and cellular respiration support life processes.

Electron Carriers in Cellular Respiration

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