Name: cytoplasm and the cell’s internal support
Uploaded: 2023-04-30T10:29:33.000Z
Duration: 1 min 24 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms- Structures and Processes

LS.Bio.1.5

Cytoplasm

בתאים אאוקריוטים, הציטופלסמה היא האזור שבין קרום הפלזמה לבין מעטפת הגרעין.
מכיוון שלתאים פרוקריוטים חסר גרעין, הציטופלסמה מתייחסת לכל מה שסגור בתוך קרום הפלזמה.
בשני סוגי התא, החלל הציטופלזמי מתמלא על ידי מטריצה דמוית ג'ל הנקראת ציטוזול.
הציטוזול הוא תמיסה מימית המכילה יונים מסיסים רבים, מולקולות קטנות ומקרומולקולות.
הציטופלסמה של תאים אאוקריוטים כוללת גם אברונים רבים הקשורים לקרום המבצעים פונקציות תאיות מיוחדות, כגון המיטוכונדריה, הרשתית האנדופלסמית ומנגנון גולג'י.
מסגרת של סיבי חלבון הנמצאים בציטופלסמה – השלד הציטופלזמה, מעניקה לתא את צורתו ומבנהו. זה גם עוזר תחבורה תאית תנועתיות התא.
בנוסף, תפקודים תאיים רבים שאינם אברונים, כגון סינתזת חלבונים, מתרחשים גם בציטופלסמה. האופי המימי של הציטופלסמה מאפשר קיפול חלבונים על ידי דחיית קבוצות לוואי של חומצות אמינו הידרופוביות לתוך ליבת החלבון.
תאים מסוימים גם מאחסנים תוצרים מטבוליים בלתי מסיסים כמו גליקוגן בציטופלסמה שלהם בצורה של תכלילים.

ציטופלזמה

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הציטופלזמה מורכבת מאברונים וממסגרת של שלדי חלבון הנקראים שלד התא (cytoskeleton) התלויים בתמיסה מימית הנקראת הציטוזול. הציטוזול הוא מרק עשיר במים, יונים, מלחים ומגוון מולקולות אורגניות.

קיפול חלבונים ושגיאות בקיפול חלבונים

הציטופלזמה היא המקום שבו מתרחשים מספר תהליכים תאיים, כולל סינתזה וקיפול חלבונים. הטבע המימי של הציטוזול מקדם את קיפול החלבונים כך ששרשרות הצד ההידרופוביות של חומצות האמינו נקברות בליבת החלבון בעוד שהחומצות ההידרופיליות פונות לציטוזול. עם זאת, לחצים תאיים כגון הזדקנות ושינויים ב-pH, טמפרטורה או אוסמולריות יכולים לגרום לשגיאות בקיפול החלבונים. חלבונים מקופלים בצורה לא נכונה עשויים להצטבר בציטופלזמה וליצור צברים בלתי מסיסים של חלבונים. צברים אלו מקושרים להפרעות נוירודגנרטיביות כמו מחלת אלצהיימר ופרקינסון.

הרכב ותפקוד שלד התא

שלד התא האיקריוטי מורכב משלושה סוגים של חלבונים סיביים - מיקרוטובולים, מיקרופילמנטים וסיבי ביניים.

המיקרוטובולים, הסיבים הגדולים ביותר, עשויים מחלבון הנקרא טובולין. הם מבנים דינמיים שיכולים לגדול או להתכווץ על ידי הוספה או הסרה של מולקולות טובולין מקצותיהם. הם מספקים יציבות מבנית לתא ומשמשים כמסילות להובלת חלבונים, וסיקולות ואברונים מסוימים בתוך התא. בנוסף, המיקרוטובולים משחקים תפקיד קריטי בחלוקת התא על ידי יצירת מסגרת שמנחה את הכרומוזומים לקצוות המנוגדים של התא.

מיקרופילמנטים (או סיבי אקטין), הקטנים מבין שלושת הסוגים, עשויים מחלבון הנקרא אקטין. חלבוני אקטין יכולים להתאסף ולהתפרק במהירות ליצירת סיבים. לכן, הם מאפשרים תנועתיות באורגניזמים חד-תאיים כמו אמבות או בנדידת תאי דם לבנים לאתרי זיהום. בתאי שריר שלד, סיבי האקטין מחליקים לאורך סיבי המיוזין כדי לתווך התכווצות שרירים.

סיבי ביניים אינם דינמיים כמו המיקרוטובולים או סיבי האקטין, אך כמו הסוגים האחרים, הם מספקים תמיכה מבנית לתא. סיבי ביניים מורכבים מחלבונים שונים בהתאם לסוג התא הספציפי. לדוגמה, סיבי ביניים בשיער ובציפורניים מכילים קרטין, בעוד שבתאי שריר, סיבים אלו עשויים מדסמין.
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הציטופלסמה מורכבת מאברונים וממסגרת של פיגומים חלבוניים הנקראים שלד ציטו-שלד המרחף בתמיסה מימית, הציטוזול. ה...

Education

JoVE Core

Cell Biology

ביולוגיה של התא

Unit 1

יחידה 1

Cells, Genomes, and Evolution

תאים, גנומים ואבולוציה

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

cytoplasm and the cell’s internal support

The cytoplasm is the cell’s internal space that holds organelles and the cytoskeleton. It is suspended in the cytosol, an aqueous fluid made of water, ions, salts, and many organic molecules. This fluid helps keep the cell organized and supports many cellular activities.

The cytoplasm is also where protein synthesis and protein folding take place. The watery cytosol helps proteins fold correctly. In a folded protein, hydrophobic amino acid side chains tend to stay buried in the core, while hydrophilic amino acids face the cytosol.

Cell stress can disrupt this process. Changes in pH, temperature, osmolarity, or aging can cause proteins to misfold. These misfolded proteins may collect in the cytoplasm and form insoluble aggregates. Such aggregates are linked to neurodegenerative disorders like Alzheimer’s and Parkinson’s disease.

The cytoskeleton is the protein framework inside the cytoplasm. It includes three filament types: microtubules, microfilaments, and intermediate filaments. Microtubules are the largest and are built from tubulin. They can grow or shrink by adding or removing tubulin at their ends. They help give the cell structural stability and serve as tracks for moving proteins, vesicles, and some organelles. They also help guide chromosomes to opposite ends of the cell during cell division.

Microfilaments, also called actin filaments, are smaller and are made of actin. They can assemble and disassemble quickly. This rapid change helps amoeba move and helps white blood cells migrate to infection sites. In skeletal muscle cells, actin filaments slide along myosin filaments to drive muscle contraction.

Intermediate filaments are less dynamic than microtubules or actin filaments, but they still provide support. They are made of different proteins depending on the cell type. In hair and nails, intermediate filaments contain keratin. In muscle cells, they are made of desmins.

Cytoplasm and the Cell’s Internal Support

what are cells?

Cells as the Building Blocks of Life

Cells are the basic building blocks of life. A bacterium can be a single cell, while a human is made of trillions of cells. Even with this range, cells share key features that support life. A living cell has a plasma membrane. This is a bilayer of lipids that separates the cytoplasm inside the cell from the outside environment. A cell also carries genetic information in the form of DNA. In prokaryotic cells, DNA is found in a region called the nucleoid. In eukaryotic cells, DNA is enclosed...

the tree of life - bacteria, archaea, and eukaryotes

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Three Domains on the Tree of Life

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prokaryotic cells

How Prokaryotes Survive Without a Nucleus

Prokaryotes are small unicellular organisms that live without a nucleus. They include the domains Archaea and Bacteria. Bacteria include common microbes such as Salmonella and E. coli, while Archaea include extremophiles that live in harsh places like volcanic springs. Prokaryotic cells still share several basic features with eukaryotic cells. They have a plasma membrane, cytoplasm, ribosomes, and genetic material in the form of single, circular DNA. Their cell parts float freely in the...

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How Organelles Keep Cells Working

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eukaryotic evolution

How Eukaryotic Cells Became Complex

Eukaryotic cells became complex through a debated evolutionary path that likely involved endosymbiosis. The most accepted model is the endosymbiont theory, which explains how organelles such as mitochondria and chloroplasts may have entered an ancestral cell. Other ideas include the nucleus-first hypothesis, the mitochondria-first hypothesis, and the eukaryote-first hypothesis. The nucleus-first hypothesis says an ancestral prokaryote first formed a membrane around its DNA, creating the...

animal and plant cell structure

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Plant and animal cells differ in how they divide, organize into tissues, and specialize for different jobs. Both cell types divide by mitosis in non-gametic cells and by meiosis in gametic cells, but the details are not the same. These differences help explain how each cell type supports growth and reproduction. During cell division, animal cells use centrosomes to organize spindle fibers and separate chromosomes. Plant cells do not have centrosomes. Instead, they use a microtubule-organizing...

cytoplasm

The cytoplasm is the cell’s internal space that holds organelles and the cytoskeleton. It is suspended in the cytosol, an aqueous fluid made of water, ions, salts, and many organic molecules. This fluid helps keep the cell organized and supports many cellular activities. The cytoplasm is also where protein synthesis and protein folding take place. The watery cytosol helps proteins fold correctly. In a folded protein, hydrophobic amino acid side chains tend to stay buried in the core, while...

the nucleus

Nuclear DNA, Chromatin, and Nucleoli

The nucleus is a membrane-bound organelle that stores chromosomal DNA and helps control what proteins a eukaryotic cell makes. It acts as the cell’s control center. DNA in mitochondria and chloroplasts is different because it mainly supports functions specific to those organelles. Inside the nucleus, DNA is wrapped around proteins called histones. This DNA-protein complex is called chromatin. During interphase, when the cell is not dividing, chromatin stays loosely arranged so the DNA is easy...

the dna helix

How DNA Structure Was Discovered

DNA is the genetic material that passes traits from one generation to the next in organisms and most viruses. It is made of two strands of nucleotides that twist into a spring-like double helix. The shape is not perfectly even. It also has repeating grooves called the major groove and the minor groove. The major groove forms where the sugar-phosphate backbones are farther apart. This wider space gives DNA-binding proteins, including transcription factors, better access to the bases. The minor...

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DNA to Protein: RNA’s Role

DNA to protein flow depends on RNA as the link between genetic information and the amino acids that build proteins. Early scientists knew that DNA stores the information for cell functions and that proteins carry out most of those functions. For a long time, they did not know how the code in DNA became a working protein. At first, many people thought one gene was changed directly into its protein. Two findings in eukaryotic cells challenged that idea. Protein production does not happen in the...

mutations

Mutations in DNA and Inherited Disease

Mutations are changes in the DNA sequence. They can happen on their own during DNA copying, or they can be caused by environmental factors. Scientists describe mutations in several ways, including whether they change the amino acid sequence of a protein, how much DNA they affect, and whether they occur in somatic cells or germline cells. Some mutations are point mutations. A point mutation changes a single nucleotide in DNA. Other mutations are chromosomal alterations, which change the number...

genome size and the evolution of new genes

genome-size-and-the-evolution-of-new-genes

Genome Size and Gene Evolution

Genome size and gene evolution are linked through changes in DNA sequence and genome structure. Some genes can arise from parts of the genome that were not coding before, while others come from changes to existing genes. These shifts help explain how new genetic material can appear over time. A genome is the full set of DNA in an organism. Its size can change as DNA is added, removed, or rearranged. The transcript highlights that genome size is not fixed, and that these changes can shape the...

gene families

Shared Origins of Gene Families

Gene families are groups of related genes that share a common origin. They form when genes are copied and then change over time. These related genes can be found within the same genome. The video also connects gene families to homologous genes and orthologous genes. Homologous genes are genes with a shared evolutionary origin. Orthologous genes are homologous genes found in different species. Gene families help show how these relationships are used to study evolution and related gene functions.

gene evolution - fast or slow?

Gene Evolution Rates and Selection

Gene evolution can happen at different rates, and natural selection helps shape those changes. Some genes change slowly because important DNA changes are removed over time. Other genes can change more quickly when different mutations are kept in a population. The rate of evolution depends on how a gene is used and how strongly it is affected by selection. Genes with essential jobs often stay more similar across species. Genes under weaker pressure may show more variation and may evolve faster.<br...

types of genetic transfer between organisms

types-of-genetic-transfer-between-organisms

Vertical and Horizontal Gene Transfer

Genetic transfer between organisms happens in two main ways: vertical gene transfer and horizontal gene transfer. These two routes explain how hereditary material moves from one generation to the next or between organisms that are not parent and offspring. Vertical gene transfer passes genes from parent to offspring during reproduction. This is the usual way genetic information is inherited in living things. Horizontal gene transfer moves genetic material between organisms outside of...

key terms and concepts

Learn how the cytoplasm, cytosol, and cytoskeleton support cell structure, protein folding, transport, cell division, movement, and muscle contraction.

Cytoplasm and the Cell’s Internal Support | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Louisiana Student Standards for Science

High School

Life Sciences

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance And Variation Of Traits

HS-LS3-1

Compounds Essential to Human Function

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Biomolecules
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Globular Proteins

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Fibrous Proteins

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Protein Denaturation

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Role of Proteins in the Human Body

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ATP Energy Storage and Release

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LS.Bio.1.2

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The Nucleus

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Ribosomes

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Golgi Apparatus

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Lysosomes

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The Extracellular Matrix

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Tissues

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Plasmodesmata

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Construct explanations to compare prokaryotic and eukaryotic cells in terms of structures and degree of complexity.

LS.Bio.1.4

The DNA Helix

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Construct an explanation to summarize how DNA and RNA direct the synthesis of proteins.

Analyze how the relationship between structure and function supports life processes within organisms.

Cytoplasm and the Cell’s Internal Support

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