Active Transport: Endocytosis, Exocytosis, and Protein Pumps


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My AP Biology Thoughts

Unit 2 Cell Structure and Function

Welcome to My AP Biology Thoughts podcast, my name is Morgan Bernstein and I am your host for episode #59 Unit 2: Active Transport: Endocytosis, Exocytosis, and Protein Pumps.

Segment 1: Introduction to Active Transport

First, we have to know that within any cell, things are always moving. Proteins need to get places, waste has to be excreted, and food is consumed.

  • Two umbrella terms of movement- Passive Transport and Active Transport
  • Passive Transport=no energy required, almost like a habit
  • Active transport = within a vesicle, does require energy

Active transport is what we will be discussing in this episode, but be sure to check out episode 58 to learn about passive transport as well!

Why does active transport require energy?

  • Goes against the concentration gradient
  • Things are moving from low concentration to high concentration (disrupts equilibrium and requires extra energy)
  • Can happen across a cell membrane or within the cell itself

Segment 2: Examples of Active Transport: Endo/Exocytosis and Pumps

The first type of active transport is one that does cross a cell-membrane barrier, and it is known as the sodium-potassium pump.

  • Two potassium ions into the cell and takes three sodium ions out
  • Works because of the protein pump in the plasma membrane.
  • Three sodium ions bind to the carrier protein pump inside the cell, and are transported out using the energy available from ATP.
  • Protein then changes shape to allow for the potassium ions to bind to it as well, and pumps those inside of the cell membrane where they are transported for use in the cell before the process repeats.
  • Higher concentration of potassium ions inside the cell than outside, and a higher concentration of sodium ions outside the cell, so this sodium-potassium pump is going against the concentration gradient and is therefore a form of ACTIVE transport
  • Requires energy.

Another form of active transport comes in endocytosis and exocytosis

  • First, cytosis means cell, which is present in all three terms
  • Endo = enter, + cytosis = cell, so endocytosis = into the cell
  • Exo = exit, + cytosis = cell, so exocytosis = exiting the cell.


  • Things brought into the cell across the membrane, but not through a pump
  • Requires energy
  • Happens inside a vesicle (small cellular bubble that holds and transports other molecules and ions)
  • Molecules or ions outside of the cell are enclosed by a part of the plasma membrane, forming the vesicle, and vesicle brings the contents through the membrane into the cell for transport


  • export proteins or excrete waste products
  • Requires energy

Necessary protein or waste products inside of a transport vesicle, vesicle connects with plasma membrane and contents released into outside environment.

Segment 3: Connection to the Course

Active transport has many connections to our Unit 2 about Cells and to biology in general.

  • Goes against the rules used for any other cellular movement ex. osmosis or diffusion.
  • Usually moving from high concentrated areas to low concentrated areas, active transport is OPPOSITE and requires energy.

These processes are all due to the selective permeability of the plasma membrane of cells.

  • Membrane structure of phospholipids and proteins (w/0 = everything or nothing would be able to enter and exit a cell)
  • No active transport without transport vesicles and protein pumps
  • Potassium is charged- could not enter phospholipid bilayer
  • Important to remember the characteristics and functions of the cell membrane and organelles when studying types of cellular movement such as active transport.

We can also connect active transport to the most basic of everyday activities; eating and drinking

  • phagocytosis and pinocytosis- cellular eating and cellular drinking
  • Without this, cells would be unable to get essential nutrients needed to function (humans hungry/dehydrated)

Lastly, I want to touch on one more type of cellular transport that requires energy, which is transcytosis. movement across a cell, also takes place in a vesicle

  • Transport vesicles move proteins to various regions of the cell to perform necessary processes

Connects to central dogma through the making of proteins (ribosomes to Endoplasmic Reticulum and Golgi Apparatus, DNA translation, RNA transcription, protein synthesis)

Thank you for listening to this episode of My AP Biology Thoughts. For more student-ran podcasts and digital content, make sure that you visit See you next time!

Music Credits:

  • “Ice Flow” Kevin MacLeod (
  • Licensed under Creative Commons: By Attribution 4.0 License

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