Name: cell chemistry: water and macromolecules
Uploaded: 2020-09-24T15:06:53.000Z
Duration: 2 min 58 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Earth and Space Science

Earth's Systems

3.3.9-12.K

Chemistry of the Cell

細胞は、生物の基本的な構成要素です。それらは主に水、有機分子、および無機イオンで構成されています。
水は細胞の約70%を占めています。細胞質内のこの水性環境は、細胞の構造と細胞内で発生する多くの反応に不可欠です。
水は極性の高い分子であるため、細胞内の他の極性分子やイオンと相互作用しますが、非極性分子とは相互作用しません。
細胞質の親水性環境は、タンパク質の三次元構造の形成を促進し、コアには非極性アミノ酸、表面には極性アミノ酸があります。
膜形成の場合、リン脂質の極性頭部基は水と相互作用します。対照的に、非極性の尾は互いに相互作用し、細胞の外側に対して疎水性の障壁を作り出します。
細胞とそのコンパートメント内の体液のpHは正確に緩衝されます。細胞質のpHは約7.2で、リン酸イオンなどの分子によって調節されています。
対照的に、特殊な細胞コンパートメントであるリソソームのpHは約5です。これは、リソソームには酸性環境下で最適に機能する酵素が含まれているためです。
細胞内の有機分子には、炭水化物、タンパク質、脂質、ヌクレオチドなどがあります。これらのさまざまな高分子は、それぞれにさまざまな役割を持っています。
炭水化物は、さまざまな代謝プロセスを推進する主要なエネルギー源ですが、細胞はタンパク質や脂質を分解して燃料にすることもできます。
タンパク質は、反応を触媒する酵素である場合もあれば、細胞構造に寄与する場合もあります。
脂質は細胞膜の重要な成分です。さらに、これらの高分子は互いに共有結合して、細胞膜によく見られる糖タンパク質や糖脂質などの抱合体を形成することができます。
ヌクレオチドは遺伝物質として機能し、タンパク質と結合して、細胞内のDNAをしっかりとパッケージ化する核タンパク質を形成します。ヌクレオチドATPは、多くの細胞プロセスのエネルギー源でもあります。
細胞機能に重要な無機イオンには、ナトリウム、カリウム、マグネシウム、カルシウム、リン酸塩、塩化物などがあります。これらのイオンは細胞質量の1%未満しか占めていませんが、細胞内ではさまざまな役割を果たしています。
例えば、カルシウムなどのイオンは細胞全体に生物学的シグナルを伝達するために使用され、マグネシウムは多くの酵素の触媒活性に不可欠です。

<ol>
	<li>クーパーGM。細胞:分子的アプローチ。第2版。サンダーランド(MA):シナウアーアソシエイツ;2000. 第 2 章、細胞の化学。以下から入手可能<a href="https://www.ncbi.nlm.nih.gov/books/NBK9884/">https://www.ncbi.nlm.nih.gov/books/NBK9884/</a></li>
	<li>Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 第4版.ニューヨーク:ガーランドサイエンス;2002. 細胞の化学成分。から入手可能: <a href="https://www.ncbi.nlm.nih.gov/books/NBK26883/">https://www.ncbi.nlm.nih.gov/books/NBK26883/</a></li>
	<li>クーパーGM。細胞:分子的アプローチ。第2版。サンダーランド(MA):シナウアーアソシエイツ;2000. 細胞の分子組成。から入手可能: <a href="https://www.ncbi.nlm.nih.gov/books/NBK9879/">https://www.ncbi.nlm.nih.gov/books/NBK9879/</a></li>
</ol>

細胞の化学

細胞は、化学的には水、有機分子、無機イオンで構成されています。
 水
 水分子は、その極性に起因した水素結合により、生命活動のプロセスと密接に関係しています。生命はもともと水のある環境で進化してきたため、生物の細胞化学や代謝の大部分は細胞質内の水の中で行われています。水の特性としては、熱容量や気化熱が大きいこと、極性分子を溶かすことができること、凝集性や接着性があること、pHの基礎となるイオンに解離することなどが挙げられます。このような水の特性を理解することで、生命維持における水の重要性を理解することができます。
 水の重要な特性の1つは、水が極性分子であることです。水の分子（H2O）内の水素と酸素は極性共有結合を形成しています。水分子は正味の電荷をもたないが、水の極性によって水素にはわずかに正の電荷、酸素にはわずかに負の電荷が生じています。水の極性は、酸素が水素よりも大きな電気陰性度を持つことに起因しています。共有電子は水素原子核よりも酸素原子核に強く引き付けられ、結果として酸素の原子核が相対的に負電荷を帯びるためです。
 水分子は分子内でわずかな正電荷および負電荷（極性）を帯びているため、それぞれの水分子が他の水分子を静電的に引き寄せ、水素結合を形成します。同様に、水は他の極性分子やイオンを引き寄せたり、引き寄せられたりします。水と容易に相互作用したり、水に溶けたりする極性化合物を親水性であるといいます。一方、油や脂肪などの非極性分子は、水との相互作用が弱いです。このような非極性化合物を疎水性であるといいます。
 有機分子
 タンパク質、炭水化物、核酸、脂質は、生命維持に必要な大きな分子であり、小さな有機分子が集まってできた4大生体高分子です。ポリマーは、科学者がモノマーと呼ぶ単一のユニットが共有結合で結合したものです。このポリマーは、個々の構成分子からなる浸透圧よりもはるかに低い浸透圧をもたらすなど、モノマーの総和とは異なる新たな特性を有しています。これは、細胞の浸透圧を維持する上で重要な利点です。モノマーは、水分子の放出によって別のモノマーと結合し、共有結合を形成します。これを脱水反応または縮合反応と呼びます。ポリマーがより小さな単位（モノマー）に分解されるとき、これらの反応によって生まれた結合ごとに水分子が消費されます。このような反応を加水分解反応といいます。脱水反応と加水分解反応はすべての高分子に共通した反応です。脱水反応は、新たな結合形成のためにエネルギーを投入する必要があります。一方で、加水分解反応は、結合の切断によってエネルギーを放出します。
 炭水化物 炭水化物は、細胞の重要なエネルギー源です。植物細胞、菌類、そしてロブスター、カニ、エビ、昆虫、クモなどの節足動物を構造的に支えています。炭水化物は、単糖類、二糖類、多糖類に分類されます。デンプンやグリコーゲンのような高分子の形でブドウ糖を貯蔵すると、代謝にはやや不利になりますが、細胞外に漏れたり、浸透圧が高くなって細胞が過剰に水分を取り込んだりするのを防ぐことができます。
 タンパク質 タンパク質は、細胞内でさまざまな機能を果たす高分子の一種です。酵素、キャリアー、ホルモンなどとして代謝を助けたり、物理的な構造を支える働きがあります。タンパク質の構成要素はアミノ酸です。
 脂質 脂質は、非極性で疎水性の性質を持つ高分子の一種です。主な種類としては、油脂、ワックス、リン脂質、ステロイドなどがあります。油脂はエネルギーの貯蔵庫であり、トリアシルグリセロールまたはトリグリセリドとも呼ばれます。コレステロールはステロイドの一種であり、細胞膜の重要な構成要素であり、膜の流動性を維持する働きがあります。
 Nucleic acids 核酸は、細胞分裂やタンパク質合成などの細胞活動を司るヌクレオチドからなる分子です。核酸には、DNAとRNAの2種類があります。DNAは、細胞の遺伝子の設計図を親から子へと伝えます。RNAは、タンパク質の合成とその制御に関わります。
 無機イオン
 無機イオンは、細胞の質量の1％にも満たないですが、細胞の機能に重要な役割を果たしています。細胞内には、ナトリウム、カリウム、マグネシウム、カルシウム、リン酸、塩化物などの無機イオンが存在します。
 上記の文章は以下から引用しました。<a href="https://openstax.org/details/books/biology-2e">Openstax, Biology 2e, Unit 1: </a><a href="https://openstax.org/details/books/biology-2e">The Chemistry of Life</a>.

細胞は、水、有機分子、無機イオンから化学的に構成されています。
水
水分子の極性とその結果生じる水素...

Education

JoVE Core

Chemistry

化学

Biochemistry

生化学

KEY TERMS AND CONCEPTS

主要用語と概念

cell chemistry: water and macromolecules

Cell chemistry includes water, organic molecules, and inorganic ions. These materials shape how cells store energy, build structures, and carry out life processes. Most cellular chemistry and metabolism happen in the watery cytoplasm.

Water is a key part of the cell because it has special properties tied to its polarity. In a water molecule, hydrogen and oxygen form polar covalent bonds, so the molecule has no net charge but does have a slightly positive end and a slightly negative end. Oxygen is more electronegative than hydrogen, so shared electrons spend more time near oxygen. This polarity lets water molecules attract each other and form hydrogen bonds.

Water also interacts with other substances in important ways. It can dissolve polar molecules and attract ions. A substance that mixes well with water is hydrophilic, while nonpolar substances such as oils and fats are hydrophobic. Water also has high heat capacity and a high heat of vaporization, and it shows cohesive and adhesive behavior. When water dissociates into ions, it helps form the basis of pH.

The cell also contains the four major classes of biological macromolecules: proteins, carbohydrates, nucleic acids, and lipids. Macromolecules are large molecules built from smaller monomers that join by covalent bonds to make polymers. Polymers have properties that are different from their building blocks, including lower osmotic pressure than the parts would create alone. Monomers join in dehydration, or condensation, reactions, which release water. Polymers break apart in hydrolysis reactions, which use water. Dehydration usually needs energy, while hydrolysis usually releases energy.

Carbohydrates provide energy and structural support. They can be monosaccharides, disaccharides, or polysaccharides. Cells store glucose in polymers such as starch or glycogen. This storage form is less available for metabolism, but it helps keep glucose from leaking out and helps prevent high osmotic pressure that could draw too much water into the cell.

Proteins have many jobs in the cell. They can act as enzymes, carriers, or hormones, and they also provide structural support. Their building blocks are amino acids. Lipids are nonpolar and hydrophobic. Major lipid types include fats and oils, waxes, phospholipids, and steroids. Fats, also called triacylglycerols or triglycerides, store energy. Cholesterol is a steroid that helps maintain the fluid nature of the plasma membrane.

Nucleic acids are made of nucleotides and direct cell activities such as cell division and protein synthesis. DNA stores the genetic blueprint and passes it from parents to offspring. RNA helps with protein synthesis and its control. Inorganic ions make up less than 1% of cell mass, but they are still essential. Important ions include sodium, potassium, magnesium, calcium, phosphate, and chloride.

Cell Chemistry: Water and Macromolecules

functional groups

Functional Groups in Organic Chemistry

Functional groups in organic chemistry are groups of atoms that give molecules specific properties. When these groups attach to a carbon skeleton, they can change how the molecule behaves. Some functional groups make a molecule hydrophilic, or water-attracting. Others make it hydrophobic, or water-repelling. Functional groups are a key part of organic chemistry and are also found in major biological molecules. They appear in carbohydrates, proteins, lipids, and nucleic acids. Each functional...

structure of lipids

Lipids, Fats, and Cell Membranes

Lipids are nonpolar molecules that do not mix well with water. They are hydrophobic, which means “water fearing,” because they contain mostly nonpolar carbon-carbon and carbon-hydrogen bonds. In cells, lipids store long-term energy as fats, help insulate plants and animals, and form protective water-repellent layers on feathers and fur. They are also part of cell membranes and serve as building blocks for many hormones. Common lipids include fats, oils, waxes, phospholipids, and steroids. A...

chemistry of the cell

Cell chemistry includes water, organic molecules, and inorganic ions. These materials shape how cells store energy, build structures, and carry out life processes. Most cellular chemistry and metabolism happen in the watery cytoplasm. Water is a key part of the cell because it has special properties tied to its polarity. In a water molecule, hydrogen and oxygen form polar covalent bonds, so the molecule has no net charge but does have a slightly positive end and a slightly negative end. Oxygen...

dna base pairing

Chargaff’s Rules and DNA Pairing

Chargaff’s rules and DNA base pairing explain how DNA strands match up. In double-stranded DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). Chargaff also found that A equals T, G equals C, and the total amount of purines (A and G) equals the total amount of pyrimidines (C and T). Watson and Crick later showed why these matches matter. A forms two hydrogen bonds with T, while G forms three hydrogen bonds with C. These pairings keep the DNA double helix a...

chemistry of carbohydrates

Carbohydrates as Energy and Storage Molecules

Carbohydrates are important energy sources in human and animal diets. Grains, fruits, and vegetables are natural sources of carbohydrates. They help provide energy to the body, especially through glucose, a simple sugar found in starch and many staple foods. Carbohydrates are identified by the stoichiometric formula (CH2O)n, where n is the number of carbons in the molecule. This means the ratio of carbon to hydrogen to oxygen is usually 1:2:1. The name carbohydrate comes from this pattern,...

protein and protein structure

How Protein Shape Controls Function

Proteins are a major class of organic molecules in living systems, and their shape helps determine what they do. They can act as structural, regulatory, contractile, or protective molecules. They also take part in transport, storage, membranes, toxins, and enzymes. All proteins are polymers of amino acids arranged in a linear sequence. A protein’s function depends on its three-dimensional form. For example, an enzyme works when its active site can bind a specific substrate. If local changes or...

amino acids

Amino Acids and Protein Building

Amino acids are the building blocks of proteins. Each amino acid has the same basic structure. A central carbon atom, called the alpha carbon, is bonded to an amino group, a carboxyl group, and a hydrogen atom. Each amino acid also has an R group, or side chain, attached to the central carbon. The R group is different for every amino acid. It helps determine whether an amino acid is acidic, basic, polar, or nonpolar. Scientists call these molecules amino acids because they contain both amino...

peptide bonds

Peptide Bond Formation and Shape

Peptide bonds join amino acids into peptides and polypeptides. They form when the carboxyl group of one amino acid reacts with the amino group of another. This dehydration reaction releases a water molecule and creates a covalent link. As more amino acids are added, the chain becomes a polypeptide. Each polypeptide has a free amino group at one end. This end is the N-terminal, or amino-terminal. The other end has a free carboxyl group. This end is the C-terminal, or carboxyl-terminal. The...

nucleic acids

DNA and RNA: Genetic Instructions

DNA and RNA are the nucleic acids that store genetic information and help direct cell activity. These macromolecules carry the cell’s genetic blueprint and the instructions it uses to function. DNA is the genetic material in all living organisms, from single-celled bacteria to multicellular mammals. In eukaryotic cells, DNA is found in the nucleus and also in organelles such as chloroplasts and mitochondria. In prokaryotes, DNA is not enclosed in a membrane. The full genetic content of a cell...

dna replication

DNA Copying: Leading and Lagging Strands

DNA replication copies genetic material before a cell divides. Each original DNA strand serves as a template for a new complementary strand. The result is semiconservative replication, which means each new DNA molecule contains one old strand and one new strand. The two daughter cells then receive DNA with the same sequence. Replication starts when helicase separates the two strands of the double helix. This creates a Y-shaped replication fork. Primase then adds short RNA primers that give DNA...

from dna to protein

The Genetic Code and Codons

The genetic code and codons explain how cells turn DNA information into proteins. Genes first direct the sequence of mRNA, and mRNA then directs the sequence of amino acids that make up proteins. Specific proteins and RNAs carry out this decoding. Cells copy DNA into mRNA so the original DNA stays protected while the cell uses the message for protein synthesis. Copying DNA to RNA is relatively simple. One nucleotide is added to the mRNA strand for every nucleotide read on the DNA strand.

polymers

Polymer Chains and How They Form

Polymers are long chains of molecules made from repeating units called monomers. The word polymer comes from the Greek words "poly," meaning many, and "mer," meaning parts. Polymers can be found in nature, such as DNA and proteins, or made synthetically, such as plastics. A polymer’s shape helps define its properties. Some polymers form linear chains, while others are branched or arranged in complex networks. Functional groups on a polymer also affect how it behaves. The repeating units in a...

key terms and concepts

Explore how water, macromolecules, and inorganic ions shape cell function. Learn about polarity, pH, carbohydrates, proteins, lipids, DNA, and RNA.

Cell Chemistry: Water and Macromolecules | JoVE K12

chemistry

JoVE Core 化学は、簡潔で理解しやすいアニメーションビデオレッスンを使用して、一般的な化学の概念を生き生きとしたものにします。さらに、活動する科学者のビデオでは、現在世界中の実験室で行われている古典的そして独創的な研究・実験をお見せします。

Florida Department of Education

High School

Life Science

SC.912.L.14

SC.912.L.14.1

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Biology

BIO.5

BIO.5.A

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Students who demonstrate understanding can analyze geoscience data to make the claim that one change to Earth's surface can create feedback that causes changes to other Earth systems.  Clarification Statement: Examples should include climate feedbacks, such as how an increase in greenhouse gases causes a rise in global temperatures that melts glacial ice, which reduces the amount of sunlight reflected from Earth's surface, increasing surface temperatures and further reducing the amount of ice.  Examples could also be taken from other system interactions, such as how the loss of ground vegetation causes an increase in water runoff and soil erosion;  how dammed rivers increase groundwater recharge, decrease sediment transport, and increase coastal erosion;  or how the loss of wetlands causes a decrease in local humidity that further reduces the wetland extent.  Assessment Boundary:

3.3.9-12.H

Igneous Intrusive Rock

Source: Laboratory of Alan Lester - University of Colorado Boulder
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Igneous Volcanic Rock

Source: Laboratory of Alan Lester - University of Colorado Boulder
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Source: Laboratory of Jeff Salacup&#160;- University of Massachusetts Amherst
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Making a Geologic Cross Section

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Conditions on Early Earth

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Radioactivity and Nuclear Equations

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Radioactive Decay and Radiometric Dating

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Types of Radioactivity

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Nuclear Power

Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by ...

Isotopes and Radioisotopes

In the early 1900s, English chemist Frederick Soddy realized that an element could have atoms with different masses that were chemically ...

Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process ...

Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with ...

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Determining Spatial Orientation of Rock Layers with the Brunton Compass

Source: Laboratory of Alan Lester - University of Colorado Boulder
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Dynamics of Structures

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
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Sound Waves and Doppler Shift

Source: Arianna Brown,&#160;Asantha Cooray, PhD, Department of Physics &#38; Astronomy, School of Physical Sciences, University of California, Irvine, CA
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Students who demonstrate understanding can develop a model based on evidence of Earth's interior to describe the cycling of matter by thermal convection.  Clarification Statement: Emphasis is on both a one-dimensional model of Earth, with radial layers determined by density, and a three-dimensional model, which is controlled by mantle convection and the resulting plate tectonics.  Examples of evidence include maps of Earth's three-dimensional structure obtained from seismic waves, records of the rate of change of Earth's magnetic field (as constraints on convection in the outer core), and identification of the composition of Earth's layers from high-pressure laboratory experiments.  Assessment Boundary:

3.3.9-12.I

Role of Water in Human Biology

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physical-and-chemical-properties-of-matter

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Physical Properties of Matter

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The cell is chemically composed of water, organic molecules and inorganic ions.
Water
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The potential of hydrogen (pH) is a measure of the acidity or basicity of a water-based solution determined by the concentration of hydronium ions (H3O+). ...

Solvents

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Adhesion

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Students who demonstrate understanding can plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes. [cite: 44] Clarification Statement: Emphasis is on mechanical and chemical investigations with water and a variety of solid materials to provide the evidence for connections between the hydrologic cycle and system interactions commonly known as the rock cycle. [cite: 45] Examples of mechanical investigations include stream transportation and deposition using a stream table, erosion using variations in soil moisture content, or frost wedging by the expansion of water as it freezes. [cite: 46] Examples of chemical investigations include chemical weathering and recrystallization (by testing the solubility of different materials) or melt generation (by examining how water lowers the melting temperature of most solids). [cite: 47] Assessment Boundary:

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The Carbon Cycle

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What is Photosynthesis?

Photosynthesis is a multipart, biochemical process that occurs in plants as well as in some bacteria. It captures carbon dioxide and solar energy to ...

Carbon-dioxide Fixation

Carbon dioxide fixation in prokaryotes enables the assimilation of inorganic carbon into organic molecules, supporting biosynthetic pathways, sustaining ...

The Calvin Cycle

Overview

Oxygenic photosynthesis converts approximately 200 billion tons of carbon dioxide (CO2) annually to organic compounds and produces approximately ...

Oxygenic Photosynthesis

Oxygenic photosynthesis is a fundamental process in which light energy is harnessed to drive the oxidation of water, leading to the production of ...

Students who demonstrate understanding can develop a quantitative model to describe the cycling of carbon among the hydrosphere, atmosphere, geosphere, and biosphere. [cite: 154] Clarification Statement: Emphasis is on modeling biogeochemical cycles that include the cycling of carbon through the ocean, atmosphere, soil, and biosphere (including humans), providing the foundation for living organisms. [cite: 155] Assessment Boundary:

3.3.9-12.L

What is Evolutionary History?

Scientists record evolutionary history by analyzing fossil, morphological, and genetic data. The fossil record documents the history of life on Earth and ...

The Evidence for Evolution

Genetic variations accumulating within populations over generations give rise to biological evolution. Evolutionary changes can result in the formation of ...

What is an Ecosystem?

Overview

An ecosystem is the interaction between all abiotic and biotic factors in an environment and can be classified as terrestrial or aquatic. ...

Species Distribution and Biogeography

Species Distribution

Biogeography is the study of species distribution across geographic space and the processes that shape these distributions. This ...

The Soil Ecosystem

Plants obtain inorganic minerals and water from the soil, which acts as a natural medium for land plants. The composition and quality of soil depend not ...

Extinction

The History of Life on Earth
Fossils of organisms that were different from anything alive today had been documented as early as the 17th century, but it ...

The Colonization of Land

Changes in the environment of the early Earth drove the evolution of organisms. As prokaryotic organisms in the oceans began to photosynthesize, they ...

Ecological Succession

Ecological succession is influenced by the processes of facilitation, inhibition, and toleration. Facilitation occurs when early successional species ...

Energy Dynamics

The Food Chain
Energy is one of the most important abiotic factors in an ecosystem and organisms in an ecosystem are connected by the flow of energy and ...

Students who demonstrate understanding can construct an argument based on evidence about the simultaneous coevolution of Earth's systems and life on Earth. [cite: 59] Clarification Statement: Emphasis is on the dynamic causes, effects, and feedbacks between the biosphere and Earth's other systems, whereby geoscience factors control the evolution of life, which in turn continuously alters Earth's surface. [cite: 60] Examples include how photosynthetic life altered the atmosphere through the production of oxygen, which in turn increased weathering rates and allowed for the evolution of animal life; [cite: 61] how microbial life on land increased the formation of soil, which in turn allowed for the evolution of land plants; [cite: 62] or how the evolution of corals created reefs that altered patterns of erosion and deposition along coastlines and provided habitats for the evolution of new life forms. [cite: 63] Assessment Boundary: Assessment does not include a comprehensive understanding of the mechanisms of how the biosphere interacts with all of Earth's other systems. [cite: 64]

3.3.9-12.N

Cell Chemistry: Water and Macromolecules

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