Name: glycolysis: how cells break down glucose
Uploaded: 2019-03-11T09:21:10.000Z
Duration: 56 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Biology

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

From Molecules to Organisms- Structures and Processes

LS.Bio.3.3

What is Glycolysis?

- [Eğitici] Glikoliz, enerji üretmek için şekerin parçalandığı metabolik süreçtir.
 Glikoz önce hücrenin sitoplazmasına girer ve iki ana evrede dönüşüme uğrar.
 İlk evrede, glikoz molekülünü içeriye hapsetmek ve bunu birkaç adımda değiştirmek için ATP formunda enerji gereklidir.
İkinci evrede elektronlardan enerji alınır ve bu enerji kullanılarak, yüksek enerjili NADH'ye ve daha fazla ATP molekülüne dönüştürülür.
 Birden fazla enzimatik adımdan sonra, 2 üç-karbonlu şeker, piruvat üretilir ve sitrik asit döngüsüne girmek üzere mitokondriye taşınmaya hazırdır.

glikoliz nedir?

<h4>Genel Bakış </h4>

Hücreler makromolekülleri parçalayarak enerji üretir. Hücresel solunum, gıda enerjisini (makromoleküllerin kimyasal bağlarından) adenosin trifosfat (ATP) şeklinde kimyasal enerjiye dönüştüren biyokimyasal bir süreçtir. Bu sıkı düzenlenmiş ve karmaşık sürecin ilk adımı glikolizdir. Glikoliz kelimesi Latince gliko (şeker) ve lizis (parçalama)' dan gelmektedir. Glikoliz iki ana hücre içi fonksiyona hizmet eder: diğer yolaklra beslenmek için ATP ve ara metabolitler üretir. Glikolitik yol, bir heksozu (glikoz gibi altı karbonlu karbonhidrat), piruvat gibi iki trioz molekülüne (üç karbonlu karbonhidrat) ve iki ATP molekülünden (dört üretilen, iki tüketilen) ve iki nikotinamid adenin dinükleotid molekülüne (NADH) dönüştürür.

<h4>Glikolizin Keşfi</h4>

Glikolizin keşfedilen ilk biyokimyasal yolak olduğunu biliyor muydunuz? 1800'lerin ortalarında Louis Pasteur, mikroorganizmaların oksijen yokluğunda (fermantasyon) glikozun parçalanmasına neden olduğunu belirledi. 1897'de Eduard Buchner, fermantasyon reaksiyonlarının, hücreyi kırarak ve çözünür molekülleri ve organelleri içeren sitoplazmayı toplayarak elde edilen hücre içermeyen maya ekstraktlarında hala gerçekleştirilebileceğini buldu. (Pi)) ve NAD gibi düşük moleküler ağırlıklı (inorganik iyonları ısıya dayanıklı kısmını, ATP, ADP ve koenzim) inorganik fosfat ilavesi olmadan fermantasyon hızı azalttığı ve fermantasyondan sonra enzimlerin hem bir dizi içerecek şekilde tespit hem de bir ısı varlığı duyarlı bileşeni (gerektiren 1905'te kısa bir süre olduğunu keşfetti (Arthur Harden ve William Young bu keşifte rol oynadı). 1940 yılına gelindiğinde, birçok insanın çabasıyla, glikolizin tam yolu Gustav Embden, Otto Meyerhof, Jakub Karol Parnas, ve diğerleritarafından kuruldu. Aslında, glikoliz şimdi EMP yolu olarak bilinir.

<H4> Glikozun Kaderi</h4>

Glikoz hücrelere iki şekilde girebilir: glikozu sitizol içine sokan GLUT (glikoz taşıyıcı) proteinleri adı verilen bir grup integral protein aracılığıyla kolaylaştırılmış difüzyon şeklinde. GLUT protein ailesinin üyeleri, insan vücudundaki belirli dokularda bulunur. Alternatif olarak, ikincil aktif taşıma, glikozu bir transmembran simporter proteini yoluyla konsantrasyon gradyanına karşı hareket ettirir. Simporter, bir iyonu pompalarken elektrokimyasal enerjiyi kullanır. Örnekler, ince bağırsakta, kalpte, beyinde ve böbreklerde sodyum-glukoz bağlantılı taşıyıcılardır.

Hem aerobik (O2 zengin) hem de anaerobik (O2 eksik) koşullar altında, glikoz bir hücrenin sitozolüne girdiğinde glikoliz başlayabilir. Glikolizin iki ana aşaması vardır. İlk aşama enerji gerektirir ve bir hazırlık aşaması olarak kabul edilir, hücredeki glikozu yakalar ve altı karbonlu omurgayı verimli bir şekilde bölünebilecek şekilde yeniden yapılandırır. İkinci aşama, enerjiyi serbest bırakan ve piruvat üreten geri ödeme aşamasıdır.

<H4> Piruvatın Kaderi</h4>

Oksijen seviyesine ve mitokondrinin varlığına bağlı olarak, piruvat iki olası kaderden birine sahip olabilir. Aerobik koşullar altında, mitokondri mevcut olduğunda, piruvat mitokondriye girer, sitrik asit döngüsünden geçer ve elektron taşıma zinciri (ETC) CO2, H2O ve hatta daha fazla ATP’ye oksitlenir. Buna karşılık, anaerobik koşullar altında (yani, çalışan kaslar) veya mitokondri eksikliği (yani, prokaryotlar), piruvat laktat fermantasyonuna uğrar (yani, anaerobik koşullarda laktata indirgenir). İlginç bir şekilde, maya ve anaerobik koşullar altındaki bazı bakteriler, alkol fermantasyonu olarak bilinen bir işlemle piruvatı etanol'e dönüştürebilir.

<h4>Glikolizin Düzenlenmesi</h4>

Glikoliz gibi enzim aracılı metabolik yolların sıkı kontrolü ve düzenlenmesi, bir organizmanın düzgün çalışması için kritik öneme sahiptir. Kontrol, substrat sınırlaması veya enzime bağlı düzenleme ile gerçekleştirilir. Substrat sınırlaması, hücredeki substrat ve ürünlerin konsantrasyonu dengeye yakın olduğunda ortaya çıkar. Sonuç olarak, substratın mevcudiyeti reaksiyonun hızını belirler. Enzime bağlı düzenlemede, substrat ve ürünlerin konsantrasyonu dengeden uzaktır. Enzimin aktivitesi, genel yolun akışını kontrol eden reaksiyon hızını belirler. Glikolizde, üç düzenleyici enzim heksokinaz, fosfofruktokinaz ve piruvat kinazdır.

Glikoliz Nedir?

Genel bakış
Hücreler makromolekülleri parçalayarak enerji üretirler. Hücresel solunum, "gıda enerjisini" dönüştüren biyokimyasal süreçtir (...

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TEMEL TERİMLER VE KAVRAMLAR

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 are used. It also generates two molecules of NADH, a carrier used in later energy reactions.

The history of glycolysis began with studies of fermentation. In the mid-1800s, Louis Pasteur showed that microorganisms break down glucose without oxygen. In 1897, Eduard Buchner found that fermentation could still happen in cell-free yeast extracts, which showed that the cytoplasm contains the needed soluble components.

Later, Arthur Harden and William Young found that fermentation slows without inorganic phosphate. They also showed that the process needs both a heat-sensitive part, later linked to enzymes, and a heat-stable part with small molecules such as inorganic ions, ATP, ADP, and coenzymes like NAD. By 1940, Gustav Embden, Otto Meyerhof, Jakub Karol Parnas, and others had established the full pathway, which is now also called the EMP pathway.

Glucose can enter cells in two main ways before glycolysis begins. GLUT proteins move glucose into the cytosol by facilitated diffusion. Transmembrane symporter proteins can also bring glucose in against its concentration gradient by secondary active transport, using energy from ion pumping. Sodium-glucose-linked transporters are examples found in the small intestine, heart, brain, and kidneys.

Glycolysis can begin after glucose enters the cytosol under both aerobic and anaerobic conditions. The pathway has two main phases. The first is an energy-requiring preparatory phase that traps glucose in the cell and rearranges its six-carbon backbone so it can be split efficiently. The second phase releases energy and forms pyruvate.

Pyruvate can follow different paths depending on oxygen and mitochondria. Under aerobic conditions with mitochondria, pyruvate enters the mitochondria and continues through the citric acid cycle and the electron transport chain, where it is oxidized to carbon dioxide, water, and more ATP. Under anaerobic conditions, such as in working muscles, or in cells without mitochondria, such as prokaryotes, pyruvate undergoes lactate fermentation. Yeast and some bacteria can instead convert pyruvate to ethanol through alcohol fermentation.

Glycolysis is tightly regulated because metabolic pathways must be controlled for proper cell function. Regulation can depend on substrate limitation, which occurs when substrate and product levels are near equilibrium and the available substrate sets the reaction rate. It can also depend on enzyme-linked regulation, where the pathway is controlled by key enzymes. Hexokinase, phosphofructokinase, and pyruvate kinase are three enzymes that help determine the overall flux of glycolysis.

Glycolysis: How Cells Break Down Glucose

what is glycolysis?

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

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 glycolysis breaks down glucose, produces ATP and NADH, and connects to pyruvate fate, fermentation, and pathway regulation in cells.

Glycolysis: How Cells Break Down Glucose | JoVE K12

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JoVE Core serisi, biyolojinin ana konseptlerini açıklayan 300 adet kısa ve kolay anlaşılabilir olan video dersleriyle ve günümüz laboratuvarlarında yürütülen gerçek araştırmaları gösteren 150'den fazla \"bilim insanları iş başında\" videolarıyla biyolojiye hayat vermektedir.

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Glycolysis: How Cells Break Down Glucose

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