Thursday, September 30, 2021

Active Cellular Transport

Biology Index

Where are we going with this? The information on this page should increase understanding related to this standard:  Evaluate comparative models of various cell type…Evaluate eukaryotic and prokaryotic cells.

Article includes ideas, images, and content from Troy Smigielski (2021-09)

Active Cellular Transport
(Are we talking about phones yet?)

Whereas passive cellular transport occurs without the expenditure of energy (because concentrations of stuff are moving from high levels to low), active cellular transport occurs only when the cell uses energy to move something.

You will recall that in passive transport, substances moved through the concentration gradient from high to low.

But, sometimes your cells need a material that requires it move against the concentration gradient. This means that the cells need materials to go from an area of low concentration to an area of high concentration. 

A classic example of this (
substances moving from low concentration to high) is seen in the sodium-potassium pump.

The Na+/K+ pump helps keep the sodium concentration high outside the cell and the potassium concentration high inside the cell. This is crucial in allowing your muscles to contract.

For this process to take place requires active cellular transport.

Active transport is transport of molecules from a low concentration to a high concentration.

Active transport requires two things: 
  • energy 
  • a transport protein (integral protein).
These things are needed because active transport moves against the concentration gradient, which does not happen naturally.

Think of it like this… Naturally, substances move from high concentration to low. This is like things flowing in water running downstream. Active transport is like swimming upstream; swimming against the current.

There are two (2) main types of active transport.

Both require the use of vesicles that are used to package the material being transported.

These vesicles do not require a transport protein to enter or exit the cell.

Hey! Now's a really good time to learn some more prefixes. Endo- and Exo- pop up in science all over the place! What do they mean?

Endo- kinda sounds like "enter" and that's what it (as a general concept) means. Endothermic means energy in the form of heat going in.

Exo- sounds a lot like exit. And… yeah, that's what it means. Exothermic means energy is given off; energy exits the… whatever.
Okay, back to our cellular transport discussion!


Endocytosis occurs when materials enter the cell via vesicles

Phagocytosis: ingesting solid materials
Pinocytosis: ingesting liquid materials

Endocytosis is the first step in lysosomes breaking down a molecule.


Exocytosis occurs when materials exit the cell via vesicles


We've previously established that…

Active transport requires two things: 
  • energy 
  • a transport protein (integral protein).
Also, we said that active transport can move things from low concentration to high.

Well… well… well…

Endocytosis and exocytosis don’t always move from low to high. AND, they don’t need a transport protein, but they do require energy.

Both types of active transport can work together:


How about a cool graphic to sum things up?

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