Name: factors that shape enzyme function
Uploaded: 2019-01-29T11:04:45.000Z
Duration: 4 min 35 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Life Science

SC.912.L.18

SC.912.L.18.4

Enzyme Activity

ヨーロッパの探検家は十分な知識、技術、設備を持っていましたが、なぜ彼らは15世紀の終わりまで新世界に到達しなかったのでしょうか?この質問に対する答えが、触媒として機能する酵素と呼ばれる小さな生体分子に関連していることを知って驚かれることでしょう。

触媒とは?これは、より少ないエネルギーで反応をより迅速に起こすことを可能にする物質です。触媒を使わない生物学的反応に必要なエネルギーのグラフをプロットすると、次のようになります。この高さは、反応が進行するために必要な最小エネルギー量である活性化エネルギーを表します。酵素は触媒として機能し、より低い活性化エネルギーで代替の反応経路を提供します。

では、酵素は実際にはどのように機能するのでしょうか?ほとんどの酵素はタンパク質です。その構造のうち、触媒する分子と相互作用する部分は活性部位と呼ばれ、特定の基質にのみ親和性を持ち、他の基質とは結合しません。正しい基質が活性部位に入ると、酵素はその形状を変化させ、より高い親和性構成を達成します。この遷移状態は反応を促進し、反応物を生成物に変換します。しかし、この酵素は製品に対する親和性が低いため、製品を放出して元の形状に戻り、同じプロセスを繰り返す準備ができています。これは、単一の基質を分解して複数の生成物を形成するため、異化酵素の例です。これの反対は同化酵素であり、2つの基質を取り、それらを結合してより大きな製品を作ります。

酵素が機能する方法は他にもたくさんあります。例えば、この酵素は単一の基質を新しい形状に変換します。一方、これは、1つの基板の一部を別の基板に移します。一部の酵素は、それ自体で反応を触媒することができず、反応を触媒するために補因子または補酵素を必要とします。

では、これらすべてが15世紀の航海とどのように関連しているのか疑問に思われるかもしれません。当時、船員はコラーゲン合成に不可欠な補酵素であるビタミンCを含む新鮮な農産物を手に入れることができませんでした。そのため、船員たちは壊血病というビタミンC欠乏症を発症し、しばしば命にかかわる結果となりました。彼らは、ビタミンCが豊富な果物や野菜を漬けることでこの問題を解決しました。酸洗いは食品のpHを下げ、食品を腐敗させる原因となる微生物酵素の活性を妨げました。したがって、微生物酵素の破壊と必須補酵素の保存は、長期の遠征の成功に大きな役割を果たしました。

このラボでは、単位時間あたりの反応速度、つまり生成される製品の量を評価することにより、さまざまな条件が酵素機能にどのように影響するかを定量化できます。まず、標準的な室温と中性のpHでベースライン反応速度を測定します。この速度は、すべての酵素分子が基質で完全に飽和するまで、最初は増加します。そして、酵素が結合基質、触媒作用および放出のサイクルを継続するのに忙しいので、触媒作用は安定したレベルに達する。ベースライン反応速度が確立されると、他の条件の基準点として使用できます。このラボで扱う酵素は、カブペルオキシダーゼです。温度とpHのさまざまな値の下でその活性を評価します。

酵素活性

<h4>生体触媒</h4>

すべての生物は、その存在を維持するために、数多くの生化学反応を絶えず行っています。これらの反応のほとんどは、開始するためにエネルギーの入力を必要としますが、これは活性化エネルギーと呼ばれます。触媒は、活性化エネルギーを低下させる化学物質です。触媒は化学反応を促進しますが、それによって消費されるわけではありません。これは、触媒が特定の化学反応を連続して促進し、その反応の速度を増加させることができることを意味します。

酵素は、生化学反応の速度と効率を高める生物学的触媒です。ほとんどの酵素はタンパク質ですが、特定のリボ核酸分子も触媒特性を持っています。各タイプの酵素は、1つまたは少数の特定の基質にしか結合できないため、非常に多様な酵素があり、すべて異なる機能を持っています。酵素の特異的反応は、その基質の形状と密接に一致する形状を持つ活性部位に依存します。基質が結合すると、酵素はわずかに形状を変化させ、化学反応がより容易に起こりやすくなり、反応の活性化エネルギーが減少します。反応が起こると、酵素は生成物を放出して元の形状に戻り、このプロセスを再び繰り返すことができます。

<h4>触媒分解酵素と同化酵素</h4>

ほとんどの酵素反応は、異化反応と同化反応のいずれかに分類でき、これらは反対の機能を持っています。異化反応を媒介する酵素は、より大きな物質を複数の製品に分解します。よく知られている異化酵素はラクターゼであり、乳製品中の二糖類ラクトースを単糖類のガラクトースとグルコースに分割します。ヒトは出生後、小腸に大量のラクターゼを持っていますが、多くの人は幼児期までにラクターゼの90%以上を失います1。この減少により、乳糖不耐症として知られる加齢依存性で乳糖を消化する能力が低下します2。

同化酵素は、複数の物質を1つの製品にまとめたものです。例えば、DNAポリメラーゼという酵素は、ヌクレオチドを結合させることでDNA分子を合成します。同様に、酵素グリコーゲンシンターゼはグルコース分子を結合してグリコーゲンを生成します。インスリンはグリコーゲン合成酵素の活性を調節するため、インスリンレベルが低いまたはまったくない糖尿病患者は、インスリン治療なしでグリコーゲンを合成できません3。

<h4>環境要因</h4>

酵素の活性部位の形状と電荷は、それが触媒する特定の化学反応に合わせて調整されるため、酵素活性はその活性部位に影響を与える要因の影響を受けます。したがって、酵素が最適なレベルで機能するためには特定の条件が必要であり、その機能と場所によって、これらの条件は大きく異なる可能性があります。これらの要因には、pHと温度が含まれます。例えば、酵素の活性部位はしばしば酸性または塩基性アミノ酸を含む。最適なpHからの逸脱は、活性部位の電荷を変化させ、基質が酵素と相互作用しにくくします。この特性は、何世紀にもわたって、ピクルスによって食品を保存するために使用されてきました。これにより、ピクルス食品のpHが微生物の酵素活性を効果的に阻害するレベルまで低下します。同様に、各酵素は最適な温度範囲で機能します。温度がこの範囲を下回ったり上回ったりすると、活性部位の形状が変化し、基質と効果的に相互作用できなくなります。ほとんどの場合、最適な温度に戻ると酵素の元の形状と機能が回復しますが、温度が高すぎると、酵素の構造が変性したり、不可逆的に損傷したりする可能性があります。繰り返しになりますが、これらの特性は食品の安全性に役立ちます。私たちは、有害なバクテリアの酵素を変性させることで有害なバクテリアを殺すために肉を徹底的に調理し、ほとんどの食品を冷蔵して微生物の酵素活性を遅らせます。

極限環境微生物、つまりほとんどの生命体にとって致命的な極限状態で発見された生物は、その極限状態で機能できる酵素を持っています。例えば、Thermus aquaticusは、温泉や熱水噴出孔で発見される細菌で、ほとんどのタンパク質が変性する温度に達します。Taqポリメラーゼは、T. aquaticusに見られる耐熱性DNAポリメラーゼであり、これにより、迅速なDNA複製のために広く使用されている実験室法であるポリメラーゼ連鎖反応(PCR)の開発が可能になりました。PCRでは、複製するDNA二重らせんの鎖を分離するために高温が必要です。Taqポリメラーゼは、ほとんどの酵素が分解される一方で、これらの高温で安定しています。DNAを一本鎖に分解する高温と、ポリメラーゼが新しい二本鎖DNAを構築できるようにする低温との間のPCRサイクル。

<h4>酵素活性に影響を与える分子因子</h4>

特定のpHと温度範囲に加えて、一部の酵素は他の分子やイオンの存在下でよりよく機能します。補酵素は、酵素の活性部位に結合し、反応によって消費されることなく触媒作用に関与する生体分子です。補酵素は、多くの場合、電子、特定の原子、官能基を輸送するため、中間キャリアとして機能します。ビタミンB群は、数多くの生化学反応の補酵素として働きます。例えば、パントテン酸の活性型であるコエンザイムA(coA)は、全哺乳類の酵素の4%に必要とされています4。補因子は、酵素機能に必要なイオンなどの無機物質として分類されることがよくあります。例えば、すべてのDNAポリメラーゼ酵素は、DNA複製だけでなく、誤って取り込まれたヌクレオチドの切除にもMg2+またはMn2+を必要とします5。

酵素が機能するために必要ではないが、酵素活性を変化させることができる他の分子もあります。酵素活性を高める物質は活性化剤と呼ばれ、酵素活性を低下させる物質は阻害剤と呼ばれます。これらの分子は、活性部位またはアロステリック部位として知られる酵素上の他の場所で酵素に結合します。これらの分子は、活性部位の正確な位置に基質として結合し、酵素結合をめぐって基質と競合することがあります。他の物質、特にアロステリック部位に結合する物質は、活性部位に結合する基質をブロックせずに酵素機能を変化させることができるため、非競合的です。さらに、阻害剤の結合は可逆的または不可逆的であり得る。相互作用が可逆的である場合、阻害剤が分離すると、酵素はその機能を再開できます。しかし、結合が不可逆的な場合、阻害剤は酵素から決して分離せず、酵素は修復不可能なほど損傷し、交換が必要になります。それにもかかわらず、酵素阻害剤も有用です。例えば、阻害剤は、細菌の増殖を阻害する抗生物質として、また、がん細胞の制御不能な分裂を阻害する化学療法として利用されてきた6。

<h4>酵素機能の測定</h4>

科学者がさまざまな条件が酵素機能に及ぼす影響を研究するために使用する方法の1つは、酵素が反応を触媒する速度である反応速度を定量化することです。したがって、反応速度が高いほど、酵素が反応をより効率的に触媒していることを示し、反応速度が低いほど、酵素の働きが遅くなっていることを意味します。反応速度を決定するために、単位時間あたりに作られる製品の量を測定することにより、反応速度が計算されます。これは、生成物濃度が直線的に増加している反応の開始位置から、酵素が基質で完全に飽和し、触媒作用が定常レベルに達するまで、生成物濃度を測定することによって行われます。ベースライン反応速度が決定されると、さまざまな処理を比較する際の基準点またはコントロールとして使用できます。反応速度は、相対的または絶対的な尺度として評価できます。相対反応速度は、1つの実験での処理など、2つ以上の条件間の違いを示す比較尺度ですが、測定対象の値を示すものではありません。絶対反応速度は、反応の進行の定量的尺度に依存します。相対反応速度と絶対反応速度の違いを理解する簡単な方法は、レースで車の速度を測定することを考えることです。相対的手法は、フィニッシュラインでの車のランキングを評価することで比較しますが、絶対的手法は、個々の車の速度をマイル/時で評価し、比較します。

酵素は非常に広く使用されているため、研究者は、タンパク質工学として知られる、特定のニーズに合わせて酵素を作成および変更する方法を探し始めています。組換えDNAテクノロジーでは、アミノ酸配列を変更して、酵素の形状や活性部位の親和性を変更することができます。これは、さまざまな状態に対する高感度の診断テストを作成するために使用されてきただけでなく、バイオレメディエーションの取り組みや廃棄物管理ツールにも使用されています7。

<h4>参照</h4>

<ol class="references">
	<li>スウェーガティDLジュニア、ウォーリングAD、クラインRM。乳糖不耐症。アムファムの医師。 2002年、第65巻、9:1845-50。</li>
	<li>Lomer MC、Parkes GC、Sanderson JD。総説:臨床診療における乳糖不耐症--神話と現実。Aliment Pharmacol Ther. 2008年、第27巻、2:93-103。</li>
	<li>AR、サルティエル。2型糖尿病の分子病因と治療に関する新たな視点。セル。 2001年、第104巻、4:517-29。</li>
	<li>やれ、ケネディ。ビタミンB群と脳:メカニズム、用量、有効性-レビュー。栄養素。 2016年、第8巻、2:68 doi:10.3390/nu8020068。</li>
	<li>Vashishtha AK、Wang J、Konigsberg WH.異なる二価カチオンは、DNAポリメラーゼの動態と忠実度を変化させます。J Biol Chem. 2016年、第291巻、40:20869-20875。</li>
	<li>ワトソンID、スチュワートMJ、プラットDJ。抗菌化学療法における酵素阻害剤の臨床薬物動態。クリンファーマコキネット。 1988年、第15巻、3:133-64。</li>
	<li>Ahuja SK、Ferreira、GM、モレイラAR。環境アプリケーションのための酵素の利用。Crit Rev Biotechの壁紙 2004年、第2-3巻、125-54。</li>
</ol>

生体触媒

すべての生物は、その存在を維持するために、数多くの生化学反応を絶えず行っています。これらの反応のほとんどは...

Education

JoVE Lab Manual

Biology

生物学

Cellular Processes

細胞プロセス

factors that shape enzyme function

Enzymes are biological catalysts that help living things run biochemical reactions faster. They lower activation energy, which is the energy needed to start a reaction. Enzymes are not used up in the process, so they can keep working again and again. Most enzymes are proteins, although some ribonucleic acid molecules also have catalytic activity.

Each enzyme usually binds only one or a few specific substrates. This selectivity depends on the enzyme’s active site, which fits its substrate like a matching shape. When the substrate binds, the enzyme changes shape slightly and makes the reaction easier. After the products form, the enzyme releases them and returns to its original shape.

Enzyme reactions are often grouped as catabolic or anabolic. Catabolic enzymes break larger molecules into smaller products. Lactase is a catabolic enzyme that splits lactose in dairy products into galactose and glucose. Many people lose most of their lactase by early childhood, which can lead to lactose intolerance. Anabolic enzymes build larger molecules from smaller parts. DNA polymerase joins nucleotides to make DNA, and glycogen synthase links glucose molecules to form glycogen. Insulin helps regulate glycogen synthase, so people with little or no insulin may need treatment to make glycogen normally.

Enzyme activity depends on conditions such as pH and temperature. Many active sites contain acidic or basic amino acids, so changes in pH can alter charge and make substrate binding harder. Pickling uses this idea by lowering pH and slowing microbial enzyme activity. Temperature also matters because each enzyme has an optimal range. Low or moderate shifts may slow the enzyme, but high temperatures can denature it and cause lasting damage. Cooking meat and refrigerating food both reduce harmful microbial activity in this way. Extremophiles live in harsh environments and have enzymes that still work there. Thermus aquaticus is one example, and its Taq polymerase stays stable in the high heat used for PCR, a method that copies DNA by cycling between hot and cooler temperatures.

Some enzymes also need coenzymes or cofactors. Coenzymes are biomolecules that help the reaction and are not consumed. They often carry electrons, atoms, or functional groups, and many B vitamins serve this role. Coenzyme A, the active form of pantothenic acid, is needed by many mammalian enzymes. Cofactors are usually inorganic substances, such as ions. DNA polymerase, for example, requires Mg2+ or Mn2+ for DNA replication and for correcting some mistakes.

Other molecules can change enzyme activity without being required for the reaction. Activators increase activity, while inhibitors decrease it. These molecules may bind at the active site or at allosteric sites, which are different locations on the enzyme. Some inhibitors compete with the substrate for the active site, while others act in a non-competitive way by binding elsewhere. Inhibitor binding can also be reversible or irreversible. Reversible inhibitors can detach and let the enzyme work again, but irreversible inhibitors permanently damage the enzyme. Scientists use enzyme inhibitors as antibiotics and as chemotherapeutic agents to limit cancer cell division.

Scientists measure enzyme function by looking at reaction rate, or how fast product is made. A faster rate means the enzyme is working more efficiently. Reaction velocity is measured by tracking product concentration over time, usually from the start of the reaction until the enzyme becomes saturated with substrate and the rate levels off. Researchers use that baseline as a control when comparing different treatments. Reaction rates can be reported as relative or absolute values. Relative rates compare conditions, while absolute rates give a direct quantitative measure, much like comparing race rankings versus miles per hour.

Because enzymes are so useful, researchers also engineer them for special tasks. Protein engineering uses recombinant DNA technology to change amino acid sequences and adjust enzyme shape or active site binding. This approach has helped create sensitive diagnostic tests, as well as tools for bioremediation and waste management.

Factors That Shape Enzyme Function

photosynthesis

Photosynthesis: Light, Sugars, and Carbon

Photosynthesis turns sunlight into chemical energy in the form of glucose. This process powers most life on Earth by helping autotrophs, or primary producers, make food. The glucose they make can provide quick energy or be stored as starch for later use. Consumers depend on these producers for energy. Photosynthesis happens in many kinds of organisms. Cyanobacteria, some protists such as algae, and plants can all carry out this process. In eukaryotic cells, it takes place in the chloroplast.

cellular respiration

Cellular Energy From Glucose Breakdown

Cellular respiration is the process cells use to release usable energy from biomolecules such as sugars and lipids. Living things need a steady energy supply for growth, repair, movement, defense, and reproduction. Cells use that energy mainly by converting adenosine diphosphate (ADP) to adenosine triphosphate (ATP). Autotrophs and heterotrophs get the molecules for respiration in different ways. Autotrophs, such as plants, algae, and photosynthetic and chemosynthetic bacteria, build...

cell division

Cell Cycle, Mitosis, and Meiosis

Cell division is essential for growth, repair, and reproduction in living organisms. It lets single-celled organisms create a new organism and helps multicellular organisms make new cells for development and for replacing damaged cells. In multicellular species, cell division also makes reproductive cells needed for reproduction. Before a cell divides, it must copy its genetic material and split it into two daughter cells. This process is called the cell cycle. Although the timing can vary...

transpiration

Water Movement in Plants

Water movement in plants depends on transpiration and the vascular system. Plants must move water and dissolved nutrients from the roots to the leaves. They also exchange materials with the environment as part of normal life processes. Vascular plants use bundles of tissues that run from the roots to the tips of the plant. Root hairs absorb water and nutrients, and osmosis moves water into the xylem, the main water-conducting tissue. Water then travels to the tallest parts of the plant and...

enzyme activity

Enzymes are biological catalysts that help living things run biochemical reactions faster. They lower activation energy, which is the energy needed to start a reaction. Enzymes are not used up in the process, so they can keep working again and again. Most enzymes are proteins, although some ribonucleic acid molecules also have catalytic activity. Each enzyme usually binds only one or a few specific substrates. This selectivity depends on the enzyme’s active site, which fits its substrate like...

cellular processes

Explore how pH, temperature, inhibitors, cofactors, and substrates affect enzyme function, plus examples like lactase, Taq polymerase, and PCR.

Factors That Shape Enzyme Function | JoVE K12

SC.912.L.18.11

酵素活性 を教える準備を、この 2 分間の教員向けガイドで行いましょう。JoVE Lab Manual の Biology ラボの主要な準備手順を解説します。

Biology の 酵素活性 教員準備 - 7.1K+ 回の視聴 | JoVE Lab Manual

この 9 分間の学生プロトコル動画で、酵素活性 の手順をステップごとに学びましょう。JoVE Lab Manual の Biology コレクションの一部です。

Biology の 酵素活性 学生プロトコル - 34K+ 回の視聴 | JoVE Lab Manual

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

Fats and lipids are crucial components in the human body. Some lipid-derived compounds, such as fat-soluble vitamins, eicosanoids, lipoproteins, and ...

Fats as Energy Storage Molecules

Amino acids

Amino acids are the monomers that comprise proteins. Each amino acid has the same fundamental structure, which consists of a central carbon atom, or the ...

Peptide Bonds

A peptide bond covalently attaches amino acids through a dehydration reaction. One amino acid&#39;s carboxyl group and another amino acid&#39;s amino ...

What are Proteins?

Protein and Protein Structures

Protein Organization

Globular Proteins

In organisms, proteins are the most abundant macromolecules. They act as the building blocks of life and play various crucial roles in the body. Proteins ...

Fibrous Proteins

Fibrous proteins are either long and narrow proteins or assemble to form long and thin structures. They contain repetitive units and usually consist of ...

Protein Denaturation

The function of proteins depends on their native three-dimensional structure, which is dictated by the amino acid sequence of the specific protein. ...

Role of Proteins in the Human Body

Proteins are the building block of life. They are also&#160; the most abundant macromolecules with as many diverse roles in the body. They are part of ...

Mechanical Protein Function

Structural Protein Function

Introduction to Carbohydrates

Carbohydrates, proteins, and fats are the primary macronutrients in the human diet. However, carbohydrates are the most favored source of energy in the ...

Chemistry of Carbohydrates

Sugars as Energy Storage Molecules

Nucleic Acids and Nucleotides

Nucleic acids are the most important macromolecules for the continuity of life. They carry the cell&#39;s genetic blueprint and have instructions for its ...

Nucleic Acid Structure

The pentose sugar in DNA is deoxyribose, while in RNA the pentose sugar is ribose. The difference between the sugars is the presence of the hydroxyl group ...

The DNA Helix

Deoxyribonucleic acid, or DNA, is the genetic material responsible for passing traits from generation to generation in all organisms and most viruses. DNA ...

RNA Structure

The basic structure of RNA consists of a string of ribonucleotides attached by phosphodiester bonds. Although most RNA is single-stranded, it can form ...

Types of RNA

Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs perform diverse ...

Noncovalent Attractions in Biomolecules

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

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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.

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Overview of Fatty Acid Metabolism

Lipids also are sources of energy that power cellular processes. Like carbohydrates, lipids are composed of carbon, hydrogen, and oxygen, but these atoms ...

What are Membranes?

A cell&#39;s plasma membrane demarcates the cell&#39;s borders and determines the nature of its interaction with the environment. Cells exclude certain ...

Membrane Fluidity

Membrane fluidity is explained by the fluid mosaic model of the cell membrane, which describes the plasma membrane structure as a mosaic of ...

Fluid Mosaic Model

Scientists identified the plasma membrane in the 1890s and its principal chemical components (lipids and proteins) by 1915. The model for plasma membrane ...

Membrane Lipids

Lipids are an essential component of all biological membranes. The average lipid content in mammalian membranes is 50%, though it can be as low as 20% in ...

Asymmetric Lipid Bilayer

Biological membranes show uneven distribution of different types of lipids in the inner and outer layers, resulting in transverse asymmetric membranes. ...

Lipids as Anchors

In the plasma membrane, the lipids forming the bilayer can also act as an anchor to tether proteins to the membrane. The three main types of lipid anchors ...

The Significance of Membrane Transport

The transport of solutes across the cell membrane is essential for metabolic processes, like maintaining cell size and volume, generating the action ...

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.

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Ligand Binding Sites

Cofactors and Coenzymes

Enzymes are proteins made of amino acids. The functional group of each constituent amino acid catalyzes a wide variety of chemical reactions via ionic ...

Introduction to Enzymes

The use of enzymes by humans dates to 7000 BCE. Humans first used enzymes to ferment sugars and produce alcohol without knowing that this was an ...

Enzymes and Activation Energy

The activation energy (or free energy of activation), abbreviated as Ea, is the small amount of energy input necessary for all chemical reactions to ...

Introduction to Enzyme Kinetics

Enzyme kinetics studies the rates of biochemical reactions. Scientists monitor the reaction rates for a particular enzymatic reaction at various substrate ...

Turnover Number and Catalytic Efficiency

The turnover number of an enzyme is the maximum number of substrate molecules it can transform per unit time. Turnover numbers for most enzymes range from ...

Catalytically Perfect Enzymes

The theory of catalytically perfect enzymes was first proposed by W.J. Albery and J. R. Knowles in 1976. These enzymes catalyze biochemical reactions at ...

introduction-to-mechanisms-of-enzyme-catalysis

Introduction to Mechanisms of Enzyme Catalysis

For many years, scientists thought that enzyme-substrate binding took place in a simple &#34;lock-and-key&#34; fashion. This model stated that the enzyme ...

Ligand Binding and Linkage

Cooperative Allosteric Transitions

Ribozymes

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.

Chemiosmosis

Oxidative phosphorylation is a highly efficient process that generates large amounts of adenosine triphosphate (ATP), the basic unit of energy that drives ...

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

During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then ...

The Electron Transport Chain

The electron transport chain or oxidative phosphorylation is an exothermic process in which free energy released during electron transfer reactions is ...

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.

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Fermentation

Most eukaryotic organisms require oxygen to survive and function adequately. Such organisms produce large amounts of energy during aerobic respiration by ...

biofuels-producing-ethanol-from-cellulosic-material

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.

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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

Green algae and plants, including green stems and unripe fruit, harbor specialized organelles called chloroplasts to carry out photosynthesis. They ...

Photosystems

Photosystems are multiprotein complexes that form the functional units of photosynthesis in plants, algae, and cyanobacteria. They are found embedded in ...

The Photochemical Reaction Center

Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center ...

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 ...

The Calvin Benson Cycle

Ribulose 1,5- bisphosphate carboxylase/oxygenase (RuBisCo) is a critical enzyme that catalyzes carbon dioxide assimilation during photosynthesis. However, ...

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

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Introduction to Cellular Respiration

Organisms harvest energy from food, but this energy cannot be directly used by cells. Cells convert the energy stored in nutrients into a more usable ...

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 ...

Glycolysis: Preparatory Phase

In cellular metabolism (the complete breakdown of glucose to extract energy),&#160; glycolysis is the first step. Glycolysis takes place in the cytoplasm ...

Glycolysis: Pay-off Phase

So far, glycolysis has cost the cell two ATP molecules and produced two small, three-carbon sugar molecules. These molecules will proceed through the ...

Fates of Pyruvate

Pyruvate is the end product of glycolysis, where glucose is oxidized to pyruvate, simultaneously reducing NAD+ to NADH. Two molecules of ATP are also ...

Role of Reduced Coenzymes NADH and FADH&#8322;

The energy released from the breakdown of the chemical bonds within nutrients can be stored either through the reduction of electron carriers or in the ...

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 ...

The Citric Acid Cycle: Overview

In aerobic organisms, the citric acid cycle is the second stage of cellular respiration wherein molecules derived from the breakdown of carbohydrates, ...

The Citric Acid Cycle: Output

The citric acid cycle is termed an amphibolic pathway as it operates both anabolically and catabolically. The cyclic reactions balance the flux of the ...

Products of the Citric Acid Cycle

The cells of most organisms&#8212;including plants and animals&#8212;obtain usable energy through aerobic respiration, the oxygen-requiring version of ...

Identify the reactants, products, and basic functions of aerobic and anaerobic cellular respiration.

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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.

Factors That Shape Enzyme Function

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