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

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Earth and Space Science

Earth's Systems

3.3.9-12.K

Chemistry of the Cell

Les cellules sont les éléments de base des organismes vivants. Ils sont composés majoritairement d'eau, de molécules organiques, et les ions inorganiques. L'eau constitue environ 70%de la cellule.Cet environnement aqueux dans le cytoplasme est essentiel à la structure de la cellule et pour de nombreuses réactions qui se produisent en son sein. L'eau est une molécule hautement polaire, il interagira donc avec d'autres molécules polaires et les ions dans la cellule mais pas avec les non polaires. L'environnement hydrophile du cytoplasme favorise la formation des structures tridimensionnelles des protéines, avec des acides aminés non polaires au centre et polaires à la surface.En cas de formation de membrane, groupes de tête polaire de phospholipides interagissent avec l'eau. En revanche, les queues non polaires interagissent les uns avec les autres créant une barrière hydrophobe à l'extérieur de la cellule. Le pH des fluides biologiques dans la cellule et ses compartiments est précisément tamponné.Le pH du cytoplasme est d'environ 7, 2 et il est régulé par des molécules telles que les ions phosphate. En revanche, le pH dans les lysosomes, des compartiments cellulaires spécialisés, est d'environ 5. C'est parce que les lysosomes contiennent des enzymes qui fonctionnent de manière optimale dans des environnements acides.Les molécules organiques de la cellule comprennent glucides, protéines, lipides et nucléotides. Toutes ces différentes macromolécules ont une variété de rôles. Les glucides sont une principale source d'énergie pour alimenter divers processus métaboliques;cependant, la cellule peut décomposer les protéines et les lipides pour le carburant aussi bien.Les protéines peuvent être des enzymes qui catalysent les réactions, ou ils peuvent contribuer à la structure cellulaire. Les lipides sont un composant important des membranes cellulaires. De plus, ces macromolécules peuvent se lier de manière covalente pour former des conjugués tels que les glycoprotéines et les glycolipides, souvent retrouvés dans les membranes cellulaires.Les nucléotides servent de matériel génétique et s'associent également aux protéines pour former les nucléoprotéines qui emballent étroitement l'ADN dans une cellule. Le nucléotide ATP est également la source d'énergie pour de nombreux processus cellulaires. Les ions inorganiques essentiels à la fonction cellulaire comprennent le sodium, le potassium, le magnésium, le calcium, le phosphate, et le chlorure.Bien que ces ions constituent moins de 1%de la masse cellulaire, ils ont des rôles divers au sein de la cellule. Par exemple, des ions tels que le calcium sont utilisés pour relayer des signaux biologiques à travers une cellule, tandis que le magnésium est essentiel pour l'activité catalytique de nombreuses enzymes.

<ol>
	<li>Cooper GM. La cellule : une approche moléculaire. 2ème édition. Sunderland (MA) : Sinauer Associates ; 2000. Chapitre 2, La chimie des cellules. Disponible à partir de : <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. Biologie moléculaire de la cellule. 4e édition. New York : Garland Science ; 2002. Les composants chimiques d’une cellule. Disponible à partir de : <a href="https://www.ncbi.nlm.nih.gov/books/NBK26883/">https://www.ncbi.nlm.nih.gov/books/NBK26883/</a></li>
	<li>Cooper GM. La cellule : une approche moléculaire. 2ème édition. Sunderland (MA) : Sinauer Associates ; 2000. La composition moléculaire des cellules. Disponible à partir de : <a href="https://www.ncbi.nlm.nih.gov/books/NBK9879/">https://www.ncbi.nlm.nih.gov/books/NBK9879/</a></li>
</ol>

chimie de la cellule

La cellule est chimiquement composée d'eau, de molécules organiques et d'ions inorganiques. 
 L’eau 
 La polarité de la molécule d'eau et des liaisons hydrogène qui en résultent font de l'eau une substance unique aux propriétés spéciales qui sont intimement liées aux processus de la vie. À l’origine, la vie a évolué dans un environnement aqueux, et la majeure partie de la chimie et du métabolisme d’un organisme cellulaire se trouve à l’intérieur du contenu aqueux du cytoplasme de la cellule. Les propriétés spéciales de l'eau sont sa capacité thermique élevée et sa chaleur de vaporisation, sa capacité à dissoudre les molécules polaires, ses propriétés cohésives et adhésives, et sa dissociation en ions qui est à la base du pH. Comprendre ces caractéristiques de l'eau aide à élucider son importance dans le maintien de la vie. 
 L’une des propriétés importantes de l’eau est que c'est une molécule polaire : l’hydrogène et l’oxygène dans les molécules d’eau (H2O) forment des liaisons covalentes polarisées. Bien qu'il n'y ait pas de charge nette sur une molécule d'eau, la polarité de l'eau crée une charge légèrement positive sur l'hydrogène et une charge légèrement négative sur l'oxygène, contribuant ainsi aux propriétés d'attraction de l'eau. L'eau génère des charges parce que l'oxygène est plus électronégatif que l'hydrogène, ce qui fait qu'il est probable qu'un électron commun soit plus près du noyau de l'oxygène que du noyau de l'hydrogène, générant ainsi la charge partielle négative près de l'oxygène. 
 En raison de la polarité de l'eau, chaque molécule d'eau attire d'autres molécules d'eau à cause des charges opposées entre les molécules d'eau, formant des liaisons hydrogène. De plus, l'eau attire ou est attirée par d'autres molécules polaires et ions. Une substance polaire qui interagit facilement avec l'eau ou se dissout dans l'eau est hydrophile. En revanche, les molécules apolaires telles que les huiles et les graisses n'interagissent pas bien avec l'eau. Ces composés apolaires sont hydrophobes. 
 Molécules organiques 
 Les protéines, les glucides, les acides nucléiques et les lipides sont les quatre principales classes de macromolécules biologiques, les grandes molécules nécessaires à la vie, qui sont fabriquées à partir de molécules organiques plus petites. Les macromolécules sont composées d'unités uniques que les scientifiques appellent des monomères qui sont joints par des liaisons covalentes pour former des polymères plus grands. Le polymère est plus que la somme de ses parties : il acquiert de nouvelles caractéristiques et conduit à une pression osmotique beaucoup plus faible que celle formée par ses ingrédients. C'est un avantage important dans le maintien des conditions osmotiques cellulaires. Un monomère se joint à un autre monomère avec la libération d'une molécule d'eau, ce qui conduit à la formation d'une liaison covalente. Les scientifiques appellent cela des réactions de déshydratation ou de condensation. Lorsque les polymères se décomposent en unités plus petites (monomères), ils utilisent une molécule d'eau pour chaque liaison rompue par ces réactions. De telles réactions sont des réactions d'hydrolyse. Les réactions de déshydratation et d'hydrolyse sont similaires pour toutes les macromolécules, mais chaque réaction de monomère et de polymère est spécifique à sa catégorie. Les réactions de déshydratation nécessitent généralement un investissement d'énergie pour la formation de nouvelles liaisons, tandis que les réactions d'hydrolyse libèrent généralement de l'énergie en cassant les liaisons. 
 Glucides Les glucides sont un groupe de macromolécules qui sont une source d'énergie vitale pour la cellule et fournissent un soutien structurel aux cellules végétales, aux champignons et à tous les arthropodes parmi lesquels sont compris les homards, les crabes, les crevettes, les insectes et les araignées. Les glucides peuvent être classés en monosaccharides, disaccharides et polysaccharides. Le stockage du glucose, sous forme de polymères comme l'amidon ou le glycogène, le rend légèrement moins accessible pour le métabolisme ; cependant, cela l'empêche de s'échapper de la cellule ou de créer une pression osmotique élevée qui pourrait entrainer la cellule à absorber une quantité excessive d'eau. 
 Protéines Les protéines sont une classe de macromolécules qui remplissent diverses fonctions pour la cellule. Elles aident au métabolisme en agissant comme enzymes, porteurs ou hormones et fournissent un soutien structurel. Les éléments constitutifs des protéines sont les acides aminés. 
 Lipides Les lipides sont une catégorie de macromolécules de nature non polaire et hydrophobe. Les principaux types comprennent les graisses et les huiles, les cires, les phospholipides et les stéroïdes. Les graisses sont une forme stockée d'énergie et sont également connues sous le nom de triacylglycérols ou triglycérides. Le cholestérol est un type de stéroïde et c'est un constituant important de la membrane plasmatique, où il aide à maintenir la nature fluide de la membrane. 
 Acides nucléiques les acides nucléiques sont des molécules composées de nucléotides qui dirigent les activités cellulaires telles que la division cellulaire et la synthèse des protéines. Il existe deux types d'acides nucléiques : l'ADN et l'ARN. L'ADN porte le plan génétique de la cellule et le transmet des parents à la progéniture. L'ARN est impliqué dans la synthèse des protéines et sa régulation. 
 Ions inorganiques 
 Les ions inorganiques représentent moins de 1 % de la masse de la cellule, mais ils sont essentiels à la fonction cellulaire. Ceux qui se trouvent dans une cellule comprennent le sodium, le potassium, le magnésium, le calcium, le phosphate et le chlorure. 
 Ce texte a été adapté de<a href="https://openstax.org/details/books/biology-2e"> Openstax, Biologie 2e, unité 1 :</a><a href="https://openstax.org/details/books/biology-2e"> La chimie de la vie</a>.

Chimie de la cellule

La cellule est chimiquement composée d’eau, de molécules organiques et d’ions inorganiques.
Eau
La polarité de la molécule d’eau et l’hydrogène qui en résulte ...

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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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What is Climate?

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Mechanisms of Heat Transfer II

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3.3.9-12.H

Igneous Intrusive Rock

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Igneous Volcanic Rock

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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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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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determining-spatial-orientation-rock-layers-with-brunton

Determining Spatial Orientation of Rock Layers with the Brunton Compass

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Dynamics of Structures

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Sound Waves and Doppler Shift

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Reflection of Waves

When a wave travels from one medium to another, it gets reflected at the boundary of the second medium. A common example of this is when a person yells at ...

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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States of Water

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The Water Cycle

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Cohesion

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physical-and-chemical-properties-of-matter

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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Water: A Bronsted-Lowry Acid and Base

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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:

What are Biogeochemical Cycles?

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The Carbon Cycle

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What is Photosynthesis?

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Carbon-dioxide Fixation

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The Calvin Cycle

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Oxygenic Photosynthesis

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3.3.9-12.L

What is Evolutionary History?

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The Evidence for Evolution

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What is an Ecosystem?

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Species Distribution and Biogeography

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The Soil Ecosystem

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Extinction

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The Colonization of Land

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Ecological Succession

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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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