How many of the following statements regarding transport across the cell membrane are correct? endocytosis and exocytosis

General
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how many of the following statements regarding transport across the cell membrane are correct? endocytosis and exocytosis are active transport and use energy. atp is always used in active transport. all cells carry out the three types of endocytosis. in the processes of endocytosis and exocytosis, small molecules cannot cross the membrane.

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How many of the following statements regarding transport across the cell membrane are correct?

LectureNotes made several statements about transport across the cell membrane and asked how many of them are correct. Let’s go through each statement one by one:

  1. “Endocytosis and exocytosis are active transport and use energy.” – This statement is correct. Endocytosis and exocytosis are both active transport processes that require energy expenditure by the cell. Endocytosis involves the engulfment of particles or molecules into the cell by the formation of vesicles, while exocytosis involves the release of molecules or waste materials from the cell by fusion of vesicles with the plasma membrane.

  2. “ATP is always used in active transport.” – This statement is also correct. ATP (adenosine triphosphate) is the primary energy source used by cells for various energy-requiring processes, including active transport. Active transport mechanisms, such as the sodium-potassium pump, utilize ATP to move molecules or ions against their concentration gradient.

  3. “All cells carry out the three types of endocytosis.” – This statement is incorrect. While endocytosis is a fundamental process in many cell types, not all cells carry out all three types of endocytosis. The three types of endocytosis are phagocytosis (engulfment of large particles or microorganisms), pinocytosis (engulfment of fluid and dissolved substances), and receptor-mediated endocytosis (specific uptake of ligands bound to receptors). Each cell may predominantly rely on one or more specific types of endocytosis depending on its function and needs.

  4. “In the processes of endocytosis and exocytosis, small molecules cannot cross the membrane.” – This statement is incorrect. In fact, small molecules can cross the membrane through these processes. In endocytosis, small molecules dissolved in the extracellular fluid can be taken up by the cell along with the engulfed vesicles. Similarly, in exocytosis, small molecules can be released from the cell along with the secretory vesicles.

In conclusion, the correct statements out of the four given statements are:

  • Endocytosis and exocytosis are active transport and use energy.
  • ATP is always used in active transport.

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