Name: fermentation pathways without oxygen
Uploaded: 2019-03-11T09:21:11.000Z
Duration: 1 min 29 s
Channel: JoVE

K12 Standards

Tennessee Academic Standards

High School

Biology

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

From Molecules to Organisms: Structures and Processes

BIO1.LS1.9

Fermentation

- [강사] 발효는 산소 없이 설탕을사용하는 혐기성 과정입니다.예를 들어, 젖산 발효 중에 근육이 산소를 소진하면포도당은 당분해 과정을 통해 두 개의피루브산염 분자로 분해되고 두 개의 ATP를 생성하며두 개의 NAD 분자가 NADH로 전환됩니다.그리고 나서 NADH는 피루브산염과 반응하여젖산을 분비하게 되고, 이산화탄소의 방출이 없어더 이상 ATP가 생산되지 않습니다.사실상 유산소 호흡과 같은 양의 ATP를생산하기 위해서, 세포는 훨씬 더 많은 양의설탕을 소비해야 합니다.NADH가 산화된 후 NAD+를 당분해를 위해 재공급되며여기서 포도당의 분해로 ATP가 얻어집니다.인간의 경우 격렬한 운동을 통해산소가 부족해지면 근육 세포는 이 과정에 의해ATP를 생성할 수 있습니다.근육 운동을 통해 과다 분비된 젖산염은혈액에 의해 간으로 운반되고거기서 다시 피루브산염으로 전환됩니다.

발효

대부분의 진핵생물은 생존하고 적절하게 기능하기 위해 산소가 필요합니다. 이러한 유기체는 포도당과 산소를 ​​이산화탄소와 물로 대사하여 유산소(aerobic; 호기성) 호흡을 하며 많은 양의 에너지를 생산합니다. 그러나 대부분의 진핵생물은 산소가 없는 경우에 무산소(anaerobic; 혐기성) 대사를 통해 약간의 에너지를 생성할 수 있습니다.
 
 유산소 호흡은 일련의 산화환원반응(oxidation-reduction reaction)을 통해 진행하고 산소(최종 전자 수용체(final electron acceptor))가 물로 환원되면 종료됩니다. 산소가 없으면 이 반응은 진행되지 않습니다. 그 대신 세포는 피루브산(pyruvate) 같은 유기(organic) 분자를 최종 전자 수용체로 사용해 해당과정(glycolysis)에서 생성되는 NADH를 재생성합니다. 그리고 유기 분자를 사용해 NADH에서 NAD+를 재생성하는 과정을 발효(fermentation)라고 합니다.
 
 발효에는 화학 반응의 최종 생성물에 따라 (1) 유산 발효(lactic acid fermentation)와 (2) 알코올 발효(alcohol fermentation)로 나뉩니다. 포유류에서 유산 발효는 미토콘드리아 부족으로 인해 유산소 호흡을 할 수 없는 적혈구뿐만 아니라 격렬한 운동을 하는 동안 골격근에서도 일어납니다. 유산 발효는 또 요구르트에서 발견되는 것과 같은 특정한 박테리아에서도 일어납니다. 이와 같은 유산 발효에선 피루브산과 NADH가 유산과 NAD+로 변환됩니다.
 
 알코올 발효는 2단계로 이루어집니다. 첫 번째 단계에서는 피루브산이 이산화탄소와 아세트알데하이드(acetaldehyde; 아세트알데히드)로 변환됩니다. 두 번째 단계에서는 아세트알데하이드가 전자 수용체 역할을 해 NADH를 NAD+로 변환하고 그 과정에서 에탄올(ethanol)로 환원됩니다. 전반적으로 알코올 발효는 피루브산과 NADH를 에탄올, 이산화탄소, NAD+로 변환합니다. 효모(yeast)는 알코올 발효를 사용하여 당을 이산화탄소와 에탄올로 변환합니다. 이 과정은 맥주와 와인 같은 술을 생산하기 위해 사용됩니다.

대부분의 진핵생물은 생존하고 적절하게 기능하기 위해 산소가 필요합니다. 이러한 유기체는 호기성 호흡 중에 많은 양의 에너지를 생산합니다.

Education

교육

JoVE Core

생물학

Cellular Processes

세포 과정

Cellular Respiration

세포 호흡

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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.

During glycolysis, NAD+ becomes NADH. Fermentation transfers electrons from NADH to an organic molecule, such as pyruvate. This reaction produces a new organic molecule and restores NAD+.

The two main fermentation types are lactic acid fermentation and alcohol fermentation. Lactic acid fermentation occurs in red blood cells, which lack mitochondria, and in skeletal muscles during strenuous exercise. It also happens in certain bacteria, including those found in yogurt. In this pathway, pyruvate and NADH are converted to lactic acid and NAD+.

Alcohol fermentation happens in two steps. First, pyruvate is changed into carbon dioxide and acetaldehyde. Then acetaldehyde accepts electrons and is reduced to ethanol, while NADH becomes NAD+. Overall, alcohol fermentation turns pyruvate and NADH into ethanol, carbon dioxide, and NAD+.

Yeasts use alcohol fermentation to convert sugars into carbon dioxide and ethanol. People harness this process to produce alcoholic beverages such as beer and wine. Fermentation shows how cells can keep making energy when oxygen is limited.

Fermentation Pathways Without Oxygen

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 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

Explore how fermentation helps cells make energy without oxygen, regenerate NAD+, and produce lactic acid or ethanol in high school biology.

Fermentation Pathways Without Oxygen | JoVE K12

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Virginia  Standards of Learning

HIgh School

Life Science

LS.4

LS.4.b

Next Generation Science Standards

HS-LS1-7

Florida Department of Education

SC.912.L.18

SC.912.L.18.6

Texas Essential Knowledge and Skills

BIO.11

BIO.11.A

new-york-state-science-learning-standards

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

Matter and Energy in Organisms and Ecosystems

HS-LS1-7.

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BIO1.LS1.3

Fermentation Pathways Without Oxygen

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