Cells and organisms (article) | Khan Academy (2024)

Review your understanding of cells and organisms in this free article aligned to NGSS standards.

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  • ctepe

    2 years agoPosted 2 years ago. Direct link to ctepe's post “So I have 2 questions. 1 ...”

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    So I have 2 questions. 1 is last year we learned that atoms are the smallest things but this year we learned that cells are the smallest things so which is it. And number 2 if you have 2 unicellular things and they combine would that make it a multicellular

    (89 votes)

    • Johanna

      2 years agoPosted 2 years ago. Direct link to Johanna's post “The cell is the smallest ...”

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      The cell is the smallest unit of life, and the atom is the smallest unit of a chemical element. Cells are much bigger, and they’re made up of many, many atoms.

      Atoms aren’t even the smallest thing, though! They are made of tiny particles including protons, neutrons, and electrons. Protons and neutrons are made of even smaller things called quarks!

      Two individual cells can be together to make something multicellular. If you take any two random cells, though, they won’t necessarily make a multicellular organism.

      (198 votes)

  • YasserS

    8 months agoPosted 8 months ago. Direct link to YasserS's post “so i learned that cells c...”

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    so i learned that cells can sometimes split called "cell division" but what i wonder is why do they split, and how do they split?

    (51 votes)

    • lauren

      8 months agoPosted 8 months ago. Direct link to lauren's post “There are two types of ce...”

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      There are two types of cell division: mitosis and meiosis. Most of the time, when someone refers to “cell division,” they mean mitosis, the process of making new body cells. [[Meiosis is the type of cell division that creates egg and sperm cells.]]

      Cell division happens when a parent cell divides into two or more cells called daughter cells. But your question is why and how. So, let me answer your questions.

      **Why do cells split?**

      Cells divide, or split, for multicellular organisms to grow and renew themselves. It is also important for cells to divide so that old or damaged cells can be replaced.

      **How do cells split?**

      During mitosis, a cell duplicates all of its contents, including its chromosomes, and splits to form two identical daughter cells. Cell division usually occurs as part of a larger cell cycle. This process is carefully done by your genes, because if done incorrectly, health problems can result.

      Hope this helps!

  • sgh07

    2 years agoPosted 2 years ago. Direct link to sgh07's post “Are all bacterias unicell...”

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    Are all bacterias unicellular or just some?

    (70 votes)

  • kaden.rogers

    2 years agoPosted 2 years ago. Direct link to kaden.rogers's post “How long do cells live? A...”

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    How long do cells live? And if they do not live very long how are we alive? And if it is because they multiply, how do we die?

    (33 votes)

    • kyle_klaver

      2 years agoPosted 2 years ago. Direct link to kyle_klaver's post “Cells in your body are co...”

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      Cells in your body are constantly dying, but also constantly reproducing, so you live a much longer life than your cells. We die not when our cells die, but when they stop preforming the functions they are supposed to.

      (57 votes)

  • Mahi more

    2 years agoPosted 2 years ago. Direct link to Mahi more's post “is a cell smaller than a ...”

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    is a cell smaller than a atom or Atoms the smallest thing ever

    (13 votes)

    • Johanna

      2 years agoPosted 2 years ago. Direct link to Johanna's post “Cells are made up of many...”

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      Cells are made up of many, many, many atoms, so they are definitely bigger than atoms.

      Atoms are very small (brooklyn.cuny.edu says “ a row of 10^8 (or 100,000,000) atoms would stretch a centimeter, about the size of your fingernail. ”). However, there are things even smaller than atoms! Atoms are actually made up of some combination of protons, neutrons, and electrons. The protons and neutrons make up the nucleus at the center. Just for scale, if the whole atom were the size of an American football stadium, the nucleus would be the size of a golf ball inside of it!

      I hope this helps!

      (36 votes)

  • dominhvu1310

    a year agoPosted a year ago. Direct link to dominhvu1310's post “How many cells are there ...”

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    How many cells are there in a human body?

    (9 votes)

    • emma

      a year agoPosted a year ago. Direct link to emma's post “The average human has abo...”

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      The average human has about 37.2 trillion cells!

      (22 votes)

  • kikigalilei

    2 years agoPosted 2 years ago. Direct link to kikigalilei's post “what are cell divisions”

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    what are cell divisions

    (8 votes)

    • benjaminb24

      2 years agoPosted 2 years ago. Direct link to benjaminb24's post “Cell divisions may sound ...”

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      Cell divisions may sound like different groups, but it is a process of a cell splitting into two to make more cells

      (24 votes)

  • Sena

    9 months agoPosted 9 months ago. Direct link to Sena's post “If we got cells and our p...”

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    If we got cells and our parents got cells and our grandparents got cells and our ancestors got cells where did the first cell come from?

    (12 votes)

    • Player3

      9 months agoPosted 9 months ago. Direct link to Player3's post “To add on, here is a pass...”

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      To add on, here is a passage from the University of Washington: "First cells on ancient Earth may have emerged because building blocks of proteins stabilized membranes. Life on Earth arose about 4 billion years ago when the first cells formed within a primordial soup of complex, carbon-rich chemical compounds..."
      Hope this helped.

      (5 votes)

  • EmmaK

    9 months agoPosted 9 months ago. Direct link to EmmaK's post “are there cells in human ...”

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    are there cells in human skin?

    (7 votes)

    • Aeternum

      9 months agoPosted 9 months ago. Direct link to Aeternum's post “Yes. Each inch of your sk...”

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      Yes. Each inch of your skin has approximately 19 million skin cells.

      (16 votes)

  • william.surdi

    2 years agoPosted 2 years ago. Direct link to william.surdi's post “What is that red blood ce...”

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    What is that red blood cell

    (10 votes)

    • leungosegaetsho

      a year agoPosted a year ago. Direct link to leungosegaetsho's post “this is a cell, which has...”

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      this is a cell, which has protein called hemoglobin, that transports oxygen the lungs to the rest of the body.
      imagine this, the hemoglobin is a car that transports the oxygen to and from somewhere, just like a taxi. then it drops the the oxygen off to its destination for example different types of organs.

      (9 votes)

Cells and organisms (article) | Khan Academy (2024)
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