Name: how cellular respiration makes atp
Uploaded: 2019-08-01T09:24:07.000Z
Duration: 1 min 31 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Life Science

LS.4

LS.4.b

ATP Yield

細胞呼吸では 高分子エネルギーを段階的に生産することで 30〜32個のATPを生産します。解糖でATPを2つとNADHを2つ ピルビン酸酸化でNADHを2つ クエン酸回路でATPを2つ、NADHを6つ FADH2を2つ生産します。そして酸化的リン酸化で 約26〜28個のATPが生産されます。このATPの数が概算である理由は3つあります。まず1つ目の理由は、電子伝達体のNADHとFADH2は 膜間腔に水素イオンを送り込むことで 間接的にATPを生産することから 2.5個と1.5個の理論上端数のATPを それぞれ生産することです。2つ目は、解糖で生産したNADHは ミトコンドリア膜を通過することができず したがって、その高エネルギー電子を ミトコンドリア内の他の電子伝達体にパスする必要があります。そして、細胞の種類によって FADH2またはNADHが生産され それぞれ1.5または2.5個のATPを生産することになります。3つ目の理由は、呼吸で生産されたエネルギーは ピルビン酸がミトコンドリア膜を通過するのに使用され 約30〜32個のATPを生産することです。

atp収量

細胞呼吸では、グルコース1分子あたり30〜32個のATP分子が生成されます。このATPの大部分は酸化的リン酸化と電子伝達系（ETC）によるものですが、あらかじめ4個のATPが得られています（解糖系から2個、クエン酸回路から2個）。
 
 ETCはミトコンドリアの内膜にあり、4つの主要なタンパク質複合体とATP合成酵素から構成されています。NADHとFADH2はこれらの複合体に電子を渡し、複合体はプロトンを膜間に送り込みます。このプロトンの分配により、膜の上に濃度勾配が生じます。この濃度勾配によって、プロトンがATP合成酵素を介してミトコンドリアマトリックスに戻ってきて、ATPが生成されます。
 
 NADHが複合体Iに2個の入力電子を渡すごとに、複合体IとIIIがそれぞれ4個のプロトンを、複合体IVが2個のプロトンを、合計10個のプロトンを送り出します。複合体IIは、NADHによって開始される電子伝達系には関与しません。しかし、FADH2は複合体IIに2個の電子を渡すので、FADH21個あたり、複合体IIIを介して4個、複合体IVを介して2個、合計6個のプロトンが送り出されることになります。
 
 1分子のATPを合成するのに4つのプロトンが必要です。NADH の場合、1分子に対して10個のプロトンが送り込まれるので、NADH1分子あたりで2.5(10/4)分子のATPが得られます。一方FADH2の場合、1個に対して6個のプロトンが送り込まれるので、FADH21分子あたり1.5(6/4)個のATPが得られます。
 
 細胞呼吸では、グルコース1分子あたり最大10個のNADHと2個のFADH2が生成されます。1個のNADHで2.5個のATP、1個のFADH2で1.5個のATPが生成されるので、酸化的リン酸化によって25個のATP+3個のATPが生成されることになります。酸化的リン酸化の前に4つのATPが生成されるので、グルコース1分子あたり最大32分子のATPが得られます。 
 
 重要なことは、解糖は細胞質で行われ、ETCはミトコンドリアにあるということです（真核生物の場合）。ミトコンドリアの膜はNADHに対して透過性がないため、解糖で生成された2個のNADHの電子をミトコンドリア内にシャトルする必要があります。ミトコンドリア内では、電子はNAD+やFADに渡されます。電子伝達体によってATPの収量が異なることを考えると、細胞呼吸の総収量はグルコース1分子あたり30〜32ATPとなります。

ATP収量

細胞呼吸は、グルコース分子あたり30〜32ATPを生成します。ATPの大部分は酸化的リン酸化と電子輸送に起因しますが...

Education

JoVE Core

Biology

生物学

Cellular Processes

細胞プロセス

Cellular Respiration

細胞呼吸

KEY TERMS AND CONCEPTS

主要用語と概念

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 these complexes. As electrons move through the chain, the complexes pump protons into the intermembrane space and build a gradient across the membrane.

That proton gradient powers ATP production. Protons flow back into the mitochondrial matrix through ATP synthase, and this flow drives ATP formation. For every 2 electrons that NADH sends through complex I, 10 protons are pumped in total. Complex I and complex III each pump 4 protons, and complex IV pumps 2 protons. Complex II is not part of the electron chain started by NADH.

FADH2 follows a different path. It passes 2 electrons to complex II, so a total of 6 protons are pumped per FADH2. In this case, complex III pumps 4 protons and complex IV pumps 2 protons. Four protons are needed to make 1 ATP. That means 1 NADH yields 2.5 ATP, and 1 FADH2 yields 1.5 ATP.

Per glucose molecule, cellular respiration can produce up to 10 NADH and 2 FADH2. Since each NADH makes 2.5 ATP and each FADH2 makes 1.5 ATP, oxidative phosphorylation produces 25 ATP from NADH and 3 ATP from FADH2. Adding the 4 ATP made before that stage gives a maximum of 32 ATP per glucose molecule. In eukaryotes, glycolysis happens in the cytosol, and the ETC is in the mitochondria.

The mitochondrial membrane does not let NADH cross. Because of that, the electrons from the 2 NADH made in glycolysis must be shuttled into the mitochondria. Once inside, those electrons may be passed to NAD+ or FAD. Since the shuttle path can change the carrier used, the total ATP yield of cellular respiration is usually 30 to 32 ATP per glucose molecule.

How Cellular Respiration Makes ATP

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 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...

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

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

See how cellular respiration turns glucose into ATP through glycolysis, the citric acid cycle, and the electron transport chain, for a total of 30 to 32 ATP.

How Cellular Respiration Makes ATP | JoVE K12

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Next Generation Science Standards

High School

ecosystems-interactions-energy-and-dynamics

Ecosystems: Interactions, Energy, and Dynamics

HS-LS2-5

Florida Department of Education

SC.912.L.18

SC.912.L.18.5

Texas Essential Knowledge and Skills

BIO.11

BIO.11.A

new-york-state-science-learning-standards

New York State Science Learning Standards

matter-and-energy-in-organisms-and-ecosystems

Matter and Energy in Organisms and Ecosystems

HS-LS1-7.

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

From Molecules to Organisms: Structures and Processes

HS-LS1-7

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LS.4.a

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How Cellular Respiration Makes ATP

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