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

Cellen zijn de basisbouwstenen van levende organismen. Ze zijn voornamelijk samengesteld uit water, organische moleculen en anorganische ionen. Water maakt ongeveer 70%van de cel uit.Deze waterige omgeving in het cytoplasma is essentieel voor de celstructuur en voor veel van de reacties die daarin plaatsvinden. Water is een sterk polair molecuul, dus het zal een wisselwerking hebben met andere polaire moleculen en ionen in de cel, maar niet met de niet-polaire. De hydrofiele omgeving van het cytoplasma bevordert de vorming van de driedimensionale structuren van eiwitten, met niet-polaire aminozuren in de kern en polaire aminozuren aan het oppervlak.In het geval van membraanvorming interageren polaire kopgroepen van fosfolipiden met water. De niet-polaire staarten daarentegen werken met elkaar samen en creëren een hydrofobe barrière naar de buitenkant van de cel. De pH van biologische vloeistoffen in de cel en zijn compartimenten wordt nauwkeurig gebufferd.De pH van het cytoplasma is ongeveer 7, 2 en wordt gereguleerd door moleculen zoals fosfaationen. Daarentegen is de pH in de lysosomen, gespecialiseerde cellulaire compartimenten, ongeveer 5. Dit komt doordat lysosomen enzymen bevatten die optimaal functioneren in zure omgevingen.Organische moleculen in de cel zijn onder meer koolhydraten, eiwitten, lipiden en nucleotiden. Al deze verschillende macromoleculen hebben verschillende rollen. Koolhydraten zijn een primaire energiebron voor verschillende stofwisselingsprocessen;de cel kan echter ook eiwitten en lipiden afbreken als brandstof.Eiwitten kunnen enzymen zijn die reacties katalyseren, of ze kunnen bijdragen aan de celstructuur. Lipiden zijn een belangrijk onderdeel van celmembranen. Bovendien kunnen deze macromoleculen covalent aan elkaar binden om conjugaten te vormen zoals glycoproteïnen en glycolipiden, die vaak in celmembranen worden aangetroffen.Nucleotiden dienen als het genetisch materiaal en associëren zich ook met eiwitten om nucleoproteïnen te vormen die het DNA stevig in een cel verpakken. Het nucleotide ATP is ook de energiebron voor veel cellulaire processen. Anorganische ionen die cruciaal zijn voor de celfunctie zijn onder meer natrium, kalium, magnesium, calcium, fosfaat en chloride.Hoewel deze ionen minder dan 1%van de celmassa uitmaken, hebben ze verschillende rollen binnen de cel. Zo worden ionen zoals calcium gebruikt om biologische signalen door een cel te sturen, terwijl magnesium essentieel is voor de katalytische activiteit van veel enzymen.

chemie van de cel

De cel is chemisch samengesteld uit water, organische moleculen en anorganische ionen. 
 Water 
 De polariteit van het watermolecuul en de daaruit voortvloeiende waterstofbinding maken water tot een unieke stof met bijzondere eigenschappen die nauw verbonden zijn met de processen van het leven. Het leven is oorspronkelijk geëvolueerd in een waterige omgeving, en het grootste deel van de cellulaire chemie en het metabolisme van een organisme vindt plaats in de waterige inhoud van het cytoplasma van de cel. Speciale eigenschappen van water zijn de hoge warmtecapaciteit en verdampingswarmte, het vermogen om polaire moleculen op te lossen, de cohesieve en hechtende eigenschappen, en de dissociatie in ionen die leidt tot de basis van de pH. Het begrijpen van deze kenmerken van water helpt om het belang ervan voor het in stand houden van het leven te verduidelijken.

 Een van de belangrijke eigenschappen van water is dat het een polair molecuul is: de waterstof en zuurstof in watermoleculen (H2O) vormen polaire covalente bindingen. Hoewel er geen netto lading is voor een watermolecuul, creëert de polariteit van water een licht positieve lading op waterstof en een licht negatieve lading op zuurstof, wat bijdraagt aan de aantrekkingskracht van water. Water genereert ladingen omdat zuurstof elektronegatiever is dan waterstof, waardoor het waarschijnlijker is dat een gedeeld elektron zich in de buurt van de zuurstofkern bevindt dan de waterstofkern, waardoor de gedeeltelijke negatieve lading in de buurt van de zuurstof wordt gegenereerd. Als gevolg van de polariteit van water trekt elk watermolecuul andere watermoleculen aan vanwege de tegengestelde ladingen tussen watermoleculen, waardoor waterstofbruggen worden gevormd. Water trekt ook andere polaire moleculen en ionen aan of wordt erdoor aangetrokken. Een polaire stof die gemakkelijk interageert met of oplost in water is hydrofiel. Daarentegen hebben niet-polaire moleculen zoals oliën en vetten geen goede interactie met water. Deze niet-polaire verbindingen zijn hydrofoob. 
 Organische moleculen 

 Eiwitten, koolhydraten, nucleïnezuren en lipiden zijn de vier belangrijkste klassen van biologische macromoleculen: grote moleculen die nodig zijn voor het leven en die zijn opgebouwd uit kleinere organische moleculen. Macromoleculen zijn samengesteld uit afzonderlijke eenheden die wetenschappers monomeren noemen en die door covalente bindingen met elkaar zijn verbonden om grotere polymeren te vormen. Het polymeer is meer dan de som der delen: het krijgt nieuwe eigenschappen en leidt tot een osmotische druk die veel lager is dan die gevormd door de ingrediënten. Dit is een belangrijk voordeel bij het handhaven van cellulaire osmotische omstandigheden. Een monomeer verbindt zich met een ander monomeer waarbij watermoleculen vrijkomen, wat leidt tot de vorming van een covalente binding. Wetenschappers noemen dit uitdrogings- of condensatiereacties. Wanneer polymeren uiteenvallen in kleinere eenheden (monomeren), gebruiken ze een watermolecuul voor elke binding die door deze reacties wordt verbroken. Dergelijke reacties zijn hydrolysereacties. Dehydratie- en hydrolysereacties zijn voor alle macromoleculen vergelijkbaar, maar elke monomeer- en polymeerreactie is specifiek voor zijn klasse. Uitdrogingsreacties vereisen doorgaans een energie-investering voor de vorming van nieuwe bindingen, terwijl hydrolysereacties doorgaans energie vrijmaken door bindingen te verbreken. 
 Koolhydraten Koolhydraten zijn een groep macromoleculen die een vitale energiebron voor de cel zijn en structurele ondersteuning bieden aan plantencellen, schimmels en alle geleedpotigen, waaronder kreeften, krabben, garnalen, insecten en spinnen. Koolhydraten kunnen worden ingedeeld in monosachariden, disachariden en polysachariden. Glucoseopslag, in de vorm van polymeren zoals zetmeel of glycogeen, maakt het iets minder toegankelijk voor de stofwisseling; Dit voorkomt echter dat het uit de cel lekt of een hoge osmotische druk veroorzaakt waardoor de cel overmatig water kan opnemen. 
 Eiwitten Eiwitten zijn een klasse macromoleculen die een breed scala aan functies voor de cel vervullen. Ze helpen bij de stofwisseling door te fungeren als enzymen, dragers of hormonen en bieden structurele ondersteuning. De bouwstenen van eiwitten zijn aminozuren. 

 Lipiden Lipiden zijn een klasse macromoleculen die niet-polair en hydrofoob van aard zijn. De belangrijkste soorten zijn onder meer vetten en oliën, wassen, fosfolipiden en steroïden. Vetten zijn een opgeslagen vorm van energie en worden ook wel triacylglycerolen of triglyceriden genoemd. Cholesterol is een soort steroïde en is een belangrijk bestanddeel van het plasmamembraan, waar het helpt de vloeibare aard van het membraan te behouden. 

 Nucleïnezuren Nucleïnezuren zijn moleculen die zijn samengesteld uit nucleotiden die cellulaire activiteiten zoals celdeling en eiwitsynthese aansturen. Er zijn twee soorten nucleïnezuren: DNA en RNA. DNA draagt de genetische blauwdruk van de cel en geeft deze door van ouders op nakomelingen. RNA is betrokken bij de eiwitsynthese en de regulatie ervan. 

 Anorganische ionen Anorganische ionen vormen minder dan 1% van de celmassa, maar zijn cruciaal voor de celfunctie. De stoffen die in een cel worden aangetroffen, zijn onder meer natrium, kalium, magnesium, calcium, fosfaat en chloride. Deze tekst is aangepast van <a href="https://openstax.org/details/books/biology-2e">Openstax, Biologie 2e, Eenheid 1: </a><a href="https://openstax.org/details/books/biology-2e">De chemie van het leven</a>.

Chemie van de cel

The cell is chemically composed of water, organic molecules and inorganic ions.
Water
The polarity of the water molecule and its resulting hydrogen ...

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KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

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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Florida Department of Education

High School

Life Science

SC.912.L.14

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Biology

BIO.5

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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

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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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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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