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

细胞是活生物体的基本组成部分。它们主要由水、有机分子 和无机离子组成。水约占细胞的 70％细胞质中的这种水性环境 对于细胞的结构细胞内发生的 许多反应至关重要。水是一种高极性分子，它会与细胞中的其他极性分子和离子相互作用，但不会与非极性分子和离子相互作用。细胞质的亲水环境促进了 蛋白质的三维结构的形成，非极性氨基酸位于核心，极性氨基酸位于表面。在膜形成的情况下，磷脂的极性头基团 与水相互作用。相反，非极性尾部相互作用，对细胞外部形成一个 疏水屏障。精确缓冲了细胞和细胞腔室中 生物体液的 pH 值。细胞质的 pH 值约为 7.2，由磷酸根离子等分子调节。相反，特殊的细胞区室，溶酶体的 pH 值约为 5。这是因为溶酶体所含的酶 最适宜在酸性环境中发挥作用。细胞中的有机分子包括 碳水化合物、蛋白质、脂质和核苷酸。所有这些不同的大分子 都具有不同的作用。碳水化合物是驱动各种代谢过程 的主要能量来源；然而，细胞也可以 分解蛋白质和脂质作为燃料。蛋白质可以是催化反应的酶，也可以对细胞结构做出贡献。脂质是细胞膜的重要组成部分。另外，这些大分子能够以共价键彼此结合 形成共轭物，例如糖蛋白和糖脂，通常出现在细胞膜中。核苷酸不仅是遗传物质，还与蛋白质结合，形成核蛋白，将 DNA 紧紧地包裹在细胞中。核苷酸三磷酸腺苷 还是 许多细胞过程的能量来源。对细胞功能至关重要的无机离子 包括钠、钾、镁、钙、磷酸盐 和氯化物。尽管这些离子只占细胞质量的不到 1％但它们在细胞内具有不同的作用。例如，诸如钙之类的离子用于在整个细胞中 传递生物信号，而镁 对许多酶的催化活性 必不可少。

<ol>
	<li>库珀 GM。细胞:分子方法。第 2 版。桑德兰（马萨诸塞州）:Sinauer Associates;2000. 第 2 章，细胞的化学。可从以下位置获得:<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. 细胞分子生物学。第 4 版。纽约:Garland Science;2002. 细胞的化学成分。可从以下位置获得:<a href="https://www.ncbi.nlm.nih.gov/books/NBK26883/>https://www.ncbi.nlm.nih.gov/books/NBK26883/</a></li>
	<li>库珀 GM。细胞:分子方法。第 2 版。桑德兰（马萨诸塞州）:Sinauer Associates;2000. 细胞的分子组成。可从以下位置获得:<a href="https://www.ncbi.nlm.nih.gov/books/NBK9879/>https://www.ncbi.nlm.nih.gov/books/NBK9879/</a></li>
</ol>

细胞化学

该细胞由水，有机分子和无机离子化学组成。 
 水 
 水分子的极性及其产生的氢键使水成为一种与生命过程密切相关的具有特殊性质的独特物质。 生命最初是在水环境中进化的，生物体的细胞化学和代谢大多发生在细胞细胞胞质的水含量内。 特惠的水性质是其高热容量和汽化热，其对溶解极性分子，凝聚和附着性质的能力以及对可导致 pH 值基准的离子的离解。 了解这些水的特性有助于阐明水在维持生命方面的重要性。 
 水的重要性质之一是它是一个极分子：水分子 (H2O) 中的氢氧形成极性共价键。 虽然水分子没有净电荷，但水的极性会在氢气上产生轻微的正电荷，而在氧上产生轻微的负电荷，从而导致水的吸引力性质。 水会产生电荷，因为氧气的电化程度比氢强，这使得共用电子更有可能靠近氧核而不是氢核，从而在氧附近产生部分负电荷。 
 由于水极性的影响，每个水分子都会吸引其他水分子，因为水分子之间的电荷正好相反，形成氢键。 水也会吸引或吸引其他极性分子和离子。 容易与水发生相互作用或溶解的极性物质是亲水性物质。 相反，非极分子 (如油和脂肪) 与水的相互作用不大。 这些非极化合物具有疏水性。 
 有机分子 
 蛋白质，碳水化合物，核酸和脂质是生物巨分子的四大类—由较小的有机分子制造的生命所需的大分子。 巨分子由科学家称之为单体的单个单位组成，这些单体由共价键联合形成更大的聚合物。 聚合物不仅仅是其零件的总和：它获得了新的特性，并导致渗透压比其成分形成的要低得多。 这是保持细胞渗透条件的一个重要优势。 一个单体与另一个具有水分子释放的单体结合，形成共价键。 科学家称这些脱水或凝结反应。 当聚合物分解成更小的单位 (单体) 时，它们会通过这些反应为每个键破损使用水分子。 这些反应是水解反应。 所有巨分子的脱水和水解反应都相似，但每种单体和聚合物反应都是其类别特有的。 脱水反应通常需要投资于能量以形成新的键，而水解反应通常通过分解键释放能量。 
 碳水化合物碳水化合物是一组巨分子，它们是细胞的重要能量来源，为植物细胞，真菌和所有节肢动物 (包括龙虾、螃蟹、虾、昆虫和蜘蛛) 提供结构支持。 碳水化合物可以分为单糖，双糖和多糖。 葡萄糖以淀粉或糖原等聚合物的形式储存，使其代谢的可访问性稍低；但这可防止其从细胞中泄漏或产生高渗透压，从而导致细胞摄入过多水。 
 蛋白质是一类为细胞执行多种功能的大型分子。 它们通过充当酶，载体或激素来帮助代谢，并提供结构支持。 蛋白质的组成部分是氨基酸。 
 脂质脂类是一类宏观分子，其性质为非极性和疏水性。 主要类型包括脂肪和油，蜡，磷脂和类固醇。 脂肪是能量的一种储存形式，也称为三乙基甘油或甘油三酯。 胆固醇是一种类类固醇，是等离子体膜的重要组成部分，有助于保持膜片的流体性质。 
 核酸核酸是由可指导细胞分裂和蛋白质合成等细胞活性的核苷酸组成的分子。 核酸有两种类型： 脱氧核糖核酸（DNA） 和 RNA。 脱氧核糖核酸（DNA） 携带着细胞的基因蓝图，并将其从父母传给后代。 RNA 涉及蛋白质合成及其调节。 
 无机离子 
 无机离子构成细胞质量的小于 1% ，但对细胞功能至关重要。 在细胞中发现的物质包括钠、钾、镁、钙、磷酸盐和氯化物。 
 本文改编自<a href="https://openstax.org/details/books/biology-2e"> Openstax, 生物学 2e, 第1单元：</a><a href="https://openstax.org/details/books/biology-2e"> 生命化学</a>。

细胞在化学上由水、有机分子和无机离子组成。  
水  
水分子的极性及其所形成的氢键……

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Chemistry

化学

Biochemistry

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KEY TERMS AND CONCEPTS

关键术语与概念

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 化学通过简单明了且通俗易懂的动画视频课程，将普通化学概念带入到现实生活当中。此外，在科学家行动视频中，我们演示了在实验室中进行的经典和原始研究实验。

Florida Department of Education

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Life Science

SC.912.L.14

SC.912.L.14.1

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Biology

BIO.5

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3.3.9-12.H

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Conditions on Early Earth

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Radioactive Decay and Radiometric Dating

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Types of Radioactivity

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Isotopes and Radioisotopes

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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

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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

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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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3.3.9-12.L

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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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