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

תאים הם אבני הבניין הבסיסיות של אורגניזמים חיים. הם מורכבים בעיקר ממים, ממולקולות אורגניות ומיונים לא-אורגניים. מים מרכיבים כ-70%מהתא.סביבה מימית זו בציטופלזמה חיונית למבנה התא ולרבות מהתגובות המתרחשות בתוכה. מים הם מולקולה קוטבית ביותר, לכן היא תיצור אינטראקציות עם מולקולות ויונים קוטביים אחרים בתא, אך לא עם מולקולות לא קוטביות. הסביבה ההידרופילית של הציטופלזמה מעודדת את יצירתם של החלבונים מבנים התלת ממדיים, עם חומצות אמינו לא קוטביות בליבה וחומצות אמינו קוטביות על פני השטח.במקרה של יצירת קרום התא, קבוצות ראש קוטביות של פוספוליפידים מקיימות אינטראקציה עם מים. לעומת זאת, הזנבות הלא קוטביים יוצרים אינטראקציה זה עם זה, ויוצרים מחסום הידרופובי לצדו החיצוני של התא. רמת החומציות של נוזלים ביולוגיים בתא ובחלקיו נשמרת באופן מדויק.רמת הpH של הציטופלזמה היא כ-7.2 ונשלטת על ידי מולקולות כגון יוני פוספט. לעומת זאת, רמת הpH בליזוזומים, מחלקות מתמחות בתאים, היא כ-5. זאת מפני שהליזוזומים מכילים אנזימים המתפקדים באופן מיטבי בסביבות חומציות.מולקולות אורגניות בתא כוללות פחמימות, חלבונים, שומנים ונוקליאוטידים. לכל המקרו-מולקולות השונות הללו יש מגוון תפקידים. פחמימות הן מקור האנרגיה הראשוני להנעת תהליכים מטבוליים שונים;יחד עם זאת, התא יכול גם לפרק חלבונים ושומנים כדלק.חלבונים יכולים להיות אנזימים שמזרזים תגובות, והם יכולים לתרום למבנה התא. שומנים הם מרכיב חשוב בקרום התא. בנוסף לכך, מקרו-מולקולות אלה יכולות להיקשר זו לזו בקשר קוולנטי כדי ליצור התלכדויות כגון גליקופרוטאינים וגליקוליפידים, הנמצאות לעיתים קרובות בקרומי תאים.נוקליאוטידים משמשים כחומר גנטי וגם מתחברים לחלבונים ליצירת נוקלאופרוטאינים האורזים באופן הדוק את הדנ"א בתא. נוקלאוטיד ATP הוא גם מקור האנרגיה של תהליכים רבים בתא. יונים לא אורגניים חיוניים לתפקוד התא כוללים נתרן אשלגן, מגנזיום, סידן, פוספט וכלוריד.למרות שיונים אלה מכילים פחות מ-1%ממסת התא, יש להם תפקידים מגוונים בתא. לדוגמה, יונים כגון סידן משמשים להעברת אותות ביולוגיים דרך התא, בעוד שמגנזיום חיוני לפעילות קטליטית של אנזימים רבים.

<ol>
	<li>קופר ג'נרל מנג'ר. התא: גישה מולקולרית. מהדורה שנייה. סנדרלנד (MA): Sinauer Associates; 2000. פרק 2, הכימיה של תאים. זמין מ: <a href="https://www.ncbi.nlm.nih.gov/books/NBK9884/">https://www.ncbi.nlm.nih.gov/books/NBK9884/</a></li>
	<li>אלברטס B, Johnson A, Lewis J, et al. ביולוגיה מולקולרית של התא. מהדורה רביעית. ניו יורק: גרלנד סיינס; 2002. המרכיבים הכימיים של תא. זמין מ: <a href="https://www.ncbi.nlm.nih.gov/books/NBK26883/">https://www.ncbi.nlm.nih.gov/books/NBK26883/</a></li>
	<li>קופר ג'נרל מנג'ר. התא: גישה מולקולרית. מהדורה שנייה. סנדרלנד (MA): Sinauer Associates; 2000. ההרכב המולקולרי של תאים. זמין מ: <a href="https://www.ncbi.nlm.nih.gov/books/NBK9879/">https://www.ncbi.nlm.nih.gov/books/NBK9879/</a></li>
</ol>

כימיה של התא

<div style="direction:rtl">

 התא מורכב כימית ממים, מולקולות אורגניות ויונים אנאורגניים. 

 מים 

 הקוטביות של מולקולת המים וקשירת המימן הנובעת ממנה הופכת את המים לחומר ייחודי בעל תכונות מיוחדות הקשורות באופן הדוק לתהליכי החיים. החיים התפתחו במקור בסביבה מימית, ורוב הכימיה התאית ומטבוליזם של האורגניזם מתרחשים בתוך התוכן המימי של הציטופלזמה של התא. תכונות מיוחדות של מים הן קיבולת החום הגבוהה וחום האידוי, יכולתם להמיס מולקולות קוטביות, תכונות הלכידות והדביקות שלהם ופירוקם ליונים המוביל לבסיס ה-pH. הבנת מאפיינים אלו של מים עוזרת להבהיר את חשיבותם בשמירה על החיים. 

 אחת התכונות החשובות של המים היא היותם מולקולה קוטבית: המימן והחמצן בתוך מולקולות המים (H2O) יוצרים קשרים קוולנטיים קוטביים. בעוד שאין מטען נטו למולקולת מים, הקוטביות של המים יוצרת מטען מעט חיובי על מימן ומטען מעט שלילי על חמצן, מה שתורם לתכונות המשיכה של המים. מים מייצרים מטענים מכיוון שחמצן הוא אלקטרושלילי יותר ממימן, מה שהופך את הסבירות לכך שאלקטרון משותף יהיה ליד גרעין החמצן מאשר גרעין המימן, ובכך יוצר את המטען השלילי החלקי ליד החמצן. 

 כתוצאה מקוטביות המים, כל מולקולת מים מושכת מולקולות מים אחרות בגלל המטענים ההפוכים בין מולקולות המים, ויוצרות קשרי מימן. מים גם מושכים או נמשכים למולקולות ויונים קוטביים אחרים. חומר קוטבי שמקיים אינטראקציה קלה עם מים או מתמוסס במים הוא הידרופילי. לעומת זאת, מולקולות לא קוטביות כגון שמנים ושומנים אינן מקיימות אינטראקציה טובה עם מים. תרכובות לא קוטביות אלו הינן הידרופוביות. 

 מולקולות אורגניות 

 חלבונים, פחמימות, חומצות גרעין ושומנים הם ארבעת המחלקות העיקריות של מקרומולקולות ביולוגיות - מולקולות גדולות הנחוצות לחיים הבנויות ממולקולות אורגניות קטנות יותר. מקרומולקולות מורכבות מיחידות בודדות שמדענים מכנים מונומרים המחוברים בקשרים קוולנטיים ליצירת פולימרים גדולים יותר. הפולימר הוא יותר מסך חלקיו: הוא מקבל מאפיינים חדשים ומוביל ללחץ אוסמוטי נמוך בהרבה מזה שנוצר על ידי מרכיביו. זהו יתרון חשוב בשמירה על תנאים אוסמוטיים תאיים. מונומר מצטרף עם מונומר אחר עם שחרור מולקולת מים, מה שמוביל ליצירת קשר קוולנטי. מדענים קוראים לזה תגובות התייבשות או עיבוי. כאשר פולימרים מתפרקים ליחידות קטנות יותר (מונומרים), הם משתמשים במולקולת מים עבור כל קשר שנשבר על ידי תגובות אלה. תגובות כאלה הן תגובות הידרוליזה. תגובות התייבשות והידרוליזה דומות עבור כל המקרומולקולות, אך כל תגובה מונומר ופולימר היא ספציפית למעמד שלה. תגובות התייבשות דורשות בדרך כלל השקעת אנרגיה ליצירת קשרים חדשים, בעוד שתגובות הידרוליזה בדרך כלל משחררות אנרגיה על ידי שבירת קשרים. 

 פחמימותפחמימות הן קבוצה של מקרומולקולות המהוות מקור אנרגיה חיוני לתא ומספקות תמיכה מבנית לתאי הצמח, לפטריות ולכל פרוקי הרגליים הכוללים לובסטרים, סרטנים, שרימפס, חרקים ועכבישים. ניתן לסווג פחמימות לחד-סוכרים, דו-סוכרים ופולי-סוכרים. אחסון גלוקוז, בצורה של פולימרים כמו עמילן או גליקוגן, הופך אותו מעט פחות נגיש למטבוליזם; עם זאת, הדבר מונע ממנו לדלוף החוצה מהתא או ליצור לחץ אוסמוטי גבוה שעלול לגרום לתא לספוג עודף מים.

 חלבוניםחלבונים הם סוג של מקרומולקולות המבצעות מגוון רחב של פונקציות עבור התא. הם עוזרים בחילוף החומרים על ידי פעולתם כאנזימים, נשאים או הורמונים ומספקים תמיכה מבנית. אבני הבניין של חלבונים הן חומצות אמינו.

 ליפידים ליפידים הם מחלקה של מקרומולקולות שאינן קוטביות והידרופוביות בטבען. הסוגים העיקריים כוללים שומנים ושמנים, שעווה, פוספוליפידים וסטרואידים. שומנים הם צורה מאוחסנת של אנרגיה ומוכרים גם כטריאצילגליצרולים או טריגליצרידים. כולסטרול הוא סוג של סטרואידים ומהווה מרכיב חשוב בממברנת הפלזמה, שם הוא עוזר לשמור על אופי הנוזל של הממברנה. 

 חומצות גרעיןחומצות גרעין הן מולקולות המורכבות מנוקלאוטידים המכוונים את הפעילויות התאיות כגון חלוקת תאים וסינתזת חלבון. ישנם שני סוגים של חומצות גרעין: DNA ו-RNA. ה-DNA נושא את השרטוט הגנטי של התא ומעביר אותו מההורים לצאצאים. RNA מעורב בסינתזת חלבון ובוויסות שלו.

 יונים אנאורגניים 

 יונים אנאורגניים מהווים פחות מ-1% ממסת התא אך הם קריטיים לתפקוד התא. אלו המצויים בתא כוללים נתרן, אשלגן, מגנזיום, סידן, פוספט וכלוריד. 

 טקסט זה מותאם מ<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>.</div>

התא מורכב כימית ממים, מולקולות אורגניות ויונים אנאורגניים.
מים
הקוטביות של מולקולת המים והמימן המתקבל ממנה ...

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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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The radiation pressure applied by an electromagnetic wave on a perfectly absorbing surface equals the energy density of the wave. The wave&#39;s momentum ...

The Electromagnetic Spectrum

The electromagnetic spectrum consists of all the types of electromagnetic radiation arranged according to their frequency and wavelength. Each of the ...

What is Weather?

Overview

Weather refers to the current state of atmospheric conditions at a specific time and place. Weather is temporary and is influenced by the ...

The Wave Nature of Light

The nature of light has been a subject of inquiry since antiquity. In the seventeenth century, Isaac Newton performed experiments with lenses and prisms ...

Mechanisms of Heat Transfer I

Just as interesting as the effects of heat transfer on a system are the methods by which the heat transfer occur. Whenever there is a temperature ...

Mechanisms of Heat Transfer II

In convection, thermal energy is carried by the large-scale flow of matter. Ocean currents and large-scale atmospheric circulation, which result from the ...

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
Igneous rocks are products of the cooling and crystallization of high temperature ...

Igneous Volcanic Rock

Source: Laboratory of Alan Lester - University of Colorado Boulder
Igneous rocks are the products of cooling and crystallization of magma. Volcanic rocks ...

an-overview-of-alkenone-biomarker-analysis-for-paleothermometry

An Overview of Alkenone Biomarker Analysis for Paleothermometry

Source: Laboratory of Jeff Salacup&#160;- University of Massachusetts Amherst
Throughout this series of videos, natural samples were extracted and ...

Making a Geologic Cross Section

Source: Laboratory of Alan Lester - University of Colorado Boulder
Geologic maps were first made and utilized in Europe, in the mid-to-late 18th century. ...

Conditions on Early Earth

Nuclear Stability

Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10&#8722;15 meters, a nucleus is ...

Radioactivity and Nuclear Equations

Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for ...

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Types of Radioactivity

The most common types of radioactivity are &#945; decay, &#946; decay, &#947; decay, neutron emission, and electron capture.
Alpha (&#945;) decay is the ...

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 ...

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

Determining Spatial Orientation of Rock Layers with the Brunton Compass

Source: Laboratory of Alan Lester - University of Colorado Boulder
Most rock units exhibit some form of planar surfaces or linear features. Examples ...

Dynamics of Structures

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
It is rare nowadays that a whole year goes by ...

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
...

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

Water is the one of the most significant components of the human body; it plays a crucial role in several physiological activities because of its unique ...

States of Water

Water exists in any one of the three classical states: solid (ice), liquid (water), and gas (steam or water vapor). The state of water depends on i) the ...

The Water Cycle

The Earth&rsquo;s hydrosphere includes all of the areas where the storage and movement of water occurs. Since water is the basis of all living processes, ...

Cohesion

Cohesion is the attraction between molecules of the same type, such as water molecules. Water molecules have an overall neutral charge but are polar ...

physical-and-chemical-properties-of-matter

Physical and Chemical Properties of Matter

The characteristics that enable us to distinguish one substance from another are called properties.

Physical Properties of Matter

A physical property is ...

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

Water: A Bronsted-Lowry Acid and Base

The reaction between a Br&#248;nsted-Lowry acid and water is called acid ionization. For example, when hydrogen fluoride dissolves in water and ionizes, ...

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

A solvent is a substance, most often a liquid, that can dissolve other substances. Here, the substance being dissolved is called a solute. When a solvent ...

Adhesion

Adhesion occurs when one type of molecule is attracted to a different molecule. Water exhibits adhesive properties in the presence of polar surfaces, such ...

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?

The most common elements in organic molecules, carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus, are only available in the ecosystem in limited ...

The Carbon Cycle

Carbon is the basis of all organic matter on Earth, and is recycled through the ecosystem in two primary processes: one in which carbon is exchanged among ...

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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