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

Zellen sind die Grundbausteine lebender Organismen. Sie bestehen hauptsächlich aus Wasser, organischen Molekülen und anorganischen Ionen.
Wasser macht etwa 70 % der Zelle aus. Dieses wässrige Milieu im Zytoplasma ist essentiell für die Struktur der Zelle und für viele der Reaktionen, die in ihr ablaufen.
Wasser ist ein hochpolares Molekül, daher interagiert es mit anderen polaren Molekülen und Ionen in der Zelle, aber nicht mit den unpolaren.
Das hydrophile Milieu des Zytoplasmas fördert die Bildung dreidimensionaler Strukturen von Proteinen, mit unpolaren Aminosäuren im Kern und polaren Aminosäuren an der Oberfläche.
Bei der Membranbildung interagieren polare Kopfgruppen von Phospholipiden mit Wasser. Im Gegensatz dazu interagieren die unpolaren Schwänze miteinander, wodurch eine hydrophobe Barriere nach außen hin entsteht.
Der pH-Wert biologischer Flüssigkeiten in der Zelle und ihren Kompartimenten wird präzise gepuffert. Der pH-Wert des Zytoplasmas liegt bei etwa 7,2 und wird durch Moleküle wie Phosphationen reguliert.
Im Gegensatz dazu liegt der pH-Wert in den Lysosomen, den spezialisierten Zellkompartimenten, bei etwa 5. Denn Lysosomen enthalten Enzyme, die in sauren Umgebungen optimal funktionieren.
Zu den organischen Molekülen in der Zelle gehören Kohlenhydrate, Proteine, Lipide und Nukleotide. All diese verschiedenen Makromoleküle haben eine Vielzahl von Rollen.
Kohlenhydrate sind eine primäre Energiequelle, um verschiedene Stoffwechselprozesse anzutreiben; die Zelle kann jedoch auch Proteine und Lipide als Brennstoff abbauen.
Proteine können Enzyme sein, die Reaktionen katalysieren, oder sie können zur Zellstruktur beitragen.
Lipide sind ein wesentlicher Bestandteil der Zellmembranen. Darüber hinaus können diese Makromoleküle kovalent aneinander binden, um Konjugate wie Glykoproteine und Glykolipide zu bilden, die häufig in Zellmembranen vorkommen.
Nukleotide dienen als genetisches Material und verbinden sich auch mit Proteinen, um Nukleoproteine zu bilden, die die DNA in einer Zelle dicht verpacken. Das Nukleotid ATP ist auch die Energiequelle für viele zelluläre Prozesse.
Zu den anorganischen Ionen, die für die Zellfunktion entscheidend sind, gehören Natrium, Kalium, Magnesium, Kalzium, Phosphat und Chlorid. Obwohl diese Ionen weniger als 1% der Zellmasse ausmachen, haben sie innerhalb der Zelle unterschiedliche Rollen.
So werden beispielsweise Ionen wie Kalzium verwendet, um biologische Signale in einer Zelle weiterzuleiten, während Magnesium für die katalytische Aktivität vieler Enzyme unerlässlich ist.

<ol>
	<li>Cooper GM. Die Zelle: Ein molekularer Ansatz. 2. Auflage. Sunderland (MA): Sinauer Associates; 2000. Kapitel 2, Die Chemie der Zellen. Verfügbar von: <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. Molekularbiologie der Zelle. 4. Auflage. New York: Garland Science; 2002. Die chemischen Bestandteile einer Zelle. Verfügbar von: <a href="https://www.ncbi.nlm.nih.gov/books/NBK26883/">https://www.ncbi.nlm.nih.gov/books/NBK26883/</a></li>
	<li>Cooper GM. Die Zelle: Ein molekularer Ansatz. 2. Auflage. Sunderland (MA): Sinauer Associates; 2000. Die molekulare Zusammensetzung der Zellen. Verfügbar von: <a href="https://www.ncbi.nlm.nih.gov/books/NBK9879/">https://www.ncbi.nlm.nih.gov/books/NBK9879/</a></li>
</ol>

chemie der zelle

Die Zelle besteht chemisch aus Wasser, organischen Molekülen und anorganischen Ionen. Wasser Die Polarität des Wassermoleküls und die daraus resultierende Wasserstoffbrückenbindung machen Wasser zu einer einzigartigen Substanz mit besonderen Eigenschaften, die eng mit den Prozessen des Lebens verbunden sind. Das Leben entwickelte sich ursprünglich in einer wässrigen Umgebung, und der Großteil der Zellchemie und des Stoffwechsels eines Organismus findet im wässrigen Inhalt des Zytoplasmas der Zelle statt. Besondere Eigenschaften von Wasser sind seine hohe Wärmekapazität und Verdampfungswärme, seine Fähigkeit, polare Moleküle aufzulösen, seine kohäsiven und adhäsiven Eigenschaften sowie seine Dissoziation in Ionen, die zur Festlegung des pH-Wertes führt. Das Verständnis dieser Eigenschaften von Wasser hilft, seine Bedeutung für die Erhaltung des Lebens zu verstehen. Eine der wichtigen Eigenschaften von Wasser ist, dass es ein polares Molekül ist: Wasserstoff und Sauerstoff in Wassermolekülen (H2O) bilden polare kovalente Bindungen. Während ein Wassermolekül keine Nettoladung aufweist, erzeugt die Polarität des Wassers eine leicht positive Ladung bei Wasserstoff und eine leicht negative Ladung bei Sauerstoff, was zu den Anziehungseigenschaften des Wassers beiträgt. Wasser erzeugt Ladungen, weil Sauerstoff elektronegativer ist als Wasserstoff. Dadurch ist es wahrscheinlicher, dass sich ein geteiltes Elektron in der Nähe des Sauerstoffkerns befindet als in der Nähe des Wasserstoffkerns, wodurch die teilweise negative Ladung in der Nähe des Sauerstoffs erzeugt wird. Aufgrund der Polarität des Wassers zieht jedes Wassermolekül aufgrund der entgegengesetzten Ladungen zwischen den Wassermolekülen andere Wassermoleküle an und bildet Wasserstoffbrückenbindungen. Wasser zieht auch andere polare Moleküle und Ionen an oder wird von ihnen angezogen. Eine polare Substanz, die leicht mit Wasser interagiert oder sich darin löst, ist hydrophil. Im Gegensatz dazu interagieren unpolare Moleküle wie Öle und Fette nicht gut mit Wasser. Diese unpolaren Verbindungen sind hydrophob. Organische Moleküle Proteine, Kohlenhydrate, Nukleinsäuren und Lipide sind die vier Hauptklassen biologischer Makromoleküle – große lebensnotwendige Moleküle, die aus kleineren organischen Molekülen aufgebaut sind. Makromoleküle bestehen aus einzelnen Einheiten, die Wissenschaftler Monomere nennen und die durch kovalente Bindungen zu größeren Polymeren verbunden sind. Das Polymer ist mehr als die Summe seiner Teile: Es erhält neue Eigenschaften und führt zu einem osmotischen Druck, der viel geringer ist als der, den seine Inhaltsstoffe bilden. Dies ist ein wichtiger Vorteil bei der Aufrechterhaltung der zellulären osmotischen Bedingungen. Ein Monomer verbindet sich mit einem anderen Monomer unter Freisetzung von Wassermolekülen, was zur Bildung einer kovalenten Bindung führt. Wissenschaftler nennen diese Reaktionen Dehydrierung oder Kondensation. Wenn Polymere in kleinere Einheiten (Monomere) zerfallen, verwenden sie für jede durch diese Reaktionen aufgebrochene Bindung ein Wassermolekül. Solche Reaktionen sind Hydrolysereaktionen. Dehydratisierungs- und Hydrolysereaktionen sind für alle Makromoleküle ähnlich, aber jede Monomer- und Polymerreaktion ist für ihre Klasse spezifisch. Dehydratisierungsreaktionen erfordern typischerweise einen Energieaufwand für die Bildung neuer Bindungen, während Hydrolysereaktionen typischerweise Energie durch das Aufbrechen von Bindungen freisetzen. 

 Kohlenhydrate sind eine Gruppe von Makromolekülen, die eine lebenswichtige Energiequelle für die Zelle darstellen und Pflanzenzellen, Pilzen und allen Arthropoden, zu denen Hummer, Krabben, Garnelen, Insekten und Spinnen gehören, strukturelle Unterstützung bieten. Kohlenhydrate können in Monosaccharide, Disaccharide und Polysaccharide eingeteilt werden. Die Speicherung von Glukose in Form von Polymeren wie Stärke oder Glykogen macht sie für den Stoffwechsel etwas weniger zugänglich; Dies verhindert jedoch, dass es aus der Zelle austritt oder einen hohen osmotischen Druck erzeugt, der dazu führen könnte, dass die Zelle übermäßig viel Wasser aufnimmt. 

 Proteine sind eine Klasse von Makromolekülen, die vielfältige Funktionen für die Zelle erfüllen. Sie unterstützen den Stoffwechsel, indem sie als Enzyme, Träger oder Hormone fungieren und strukturelle Unterstützung bieten. Die Bausteine von Proteinen sind Aminosäuren. 

 Lipide sind eine Klasse von Makromolekülen, die von Natur aus unpolar und hydrophob sind. Zu den Haupttypen gehören Fette und Öle, Wachse, Phospholipide und Steroide. Fette sind eine gespeicherte Energieform und werden auch als Triacylglycerine oder Triglyceride bezeichnet. Cholesterin ist eine Art Steroid und ein wichtiger Bestandteil der Plasmamembran, wo es dazu beiträgt, die flüssige Beschaffenheit der Membran aufrechtzuerhalten. 

 Nukleinsäuren sind Moleküle, die aus Nukleotiden bestehen und zelluläre Aktivitäten wie Zellteilung und Proteinsynthese steuern. Es gibt zwei Arten von Nukleinsäuren: DNA und RNA. Die DNA trägt den genetischen Bauplan der Zelle und gibt ihn von den Eltern an die Nachkommen weiter. RNA ist an der Proteinsynthese und ihrer Regulierung beteiligt. 

 Anorganische Ionen 

 Anorganische Ionen machen weniger als 1 % der Zellmasse aus, sind jedoch für die Zellfunktion von entscheidender Bedeutung. Zu den in einer Zelle vorkommenden Substanzen gehören Natrium, Kalium, Magnesium, Kalzium, Phosphat und Chlorid. Dieser Text wurde angepasst von Openstax, Biology 2e, Unit 1: The Chemistry of Life.

Chemie der Zelle

Die Zelle besteht chemisch aus Wasser, organischen Molekülen und anorganischen Ionen.
Wasser
Die Polarität des Wassermoleküls und des daraus resultierenden Wasserstoffs ...

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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

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3.3.9-12.H

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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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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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3.3.9-12.L

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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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