VIRUSES lesson 5: How Viruses Enter Cells


This lesson is divided into two parts.  In part (a) we see how viruses enter cells by using receptors on the cell’s surface, then using a fusion protein to either poke a hole in the membrane or fuse with it.  In part (b) we focus on just the influenza virus and take a closer look at how it enters.  Influenza is one of the most studied viruses and its method of entry is considered a “classic” in the world of virology.



This video runs 50 minutes, with an optional intermission at about the 30 minute mark.

Download and print this template page before you begin watching the video for part (a):

Template page for Virology 5a

You might also want to print this info page for part (a).  It gives a written description of what we learn in this lesson.

Info page for Virology 5a

If you need to see the final drawing, here is the one I did on camera:

Sample of final drawing Virology 5a


LESSON 5(b):  How Influenza Enters Cells

This video runs 47 minutes, with a natural break halfway through, after finishing the top half.


Download and print this template page before you begin watching the video for part (b):

Template page for virus 5(b)

You might also want to print this info page for part (b).  It gives a written description of what we learn in this lesson.

Info page for Virus 5b

Here is a sample of the final drawing.  Your influenza virus drawing may look different from mine.  Whatever you draw will be just fine.

Final sample of drawing Viruses 5b

This animation will be helpful, also.  It shows the influenza virus being taken into a cell using the HA receptor on the cell surface.



ACTIVITY IDEAS for part(a):

Activity 5.1:  LAB ACTIVITY:  Simulation of membranes and endosomes

You will need a plate or shallow dish, water, oil, (food coloring optional), plus a few spoons, or sticks, whatever you have lying around the kitchen.

Pour some water in the bottom of the dish– just enough to cover it, NOT very deep.  You can leave it clear or add food coloring.  Pour a small pool of oil on one side.  This will represent a cell.  Pour a smaller blob in another part of the dish.  This will be the enveloped virus.  Now experiment with bringing the virus over to the cell to see the membranes merge.  You will likely see that the two can sit side by side and not merge.  There is the tiniest bit of water between them, but you can’t see it.  Rub some oil on the end of a stick or spoon and use it as your fusion protein.  As soon as the fusion protein touches, the two immediately merge.

Try making some endosomes by pulling in a bubble of water, into the oil area, and sealing it off.  Perhaps you could even float a tiny object to represent a virus inside.  (I used a teeny snip of dehydrated garlic.  Anything that floats, and is not greasy, will work.    Then try some experiments of your own and get a feel for how polar substances (water) interact with polar (oily) substances.

If you want to see my quickie video demo, click on the link below.



ACTIVITY IDEAS for part(b):

Activity 5.2:  Triskelions in history  (a 6-minute info video)

Activity 5.3:  Memory Match Word Game

When scientists write articles for research journals, there are certain words they tend to avoid.  They don’t like some of the simple, everyday words we use all the time.  They prefer to use synonyms (same or similar meaning) that sound more difficult.  For example, they never say “cut,” but instead say “cleave.”  Both words mean the same thing, but “cleave” sounds more difficult.  Instead of “new” they say “novel.”  Instead of “make” they say “synthesize.”  Just for fun, while I’ve been reading lots of research articles about viruses, I kept a list of words that scientists like, or don’t like, to use.  I chose 15 of them to put into this activity.

Here are 15 words that scientists don’t like to use, and the words they replace them with.  First comes the word they don’t like, followed by the word they prefer.    1) cut/cleave   2) make/synthesize    3) new/novel    4) control/mediate    5) area/domain    6) clump/agglutinate   7) weaken/attenuate   8) copy/replicate   9) start/initiate    10) help/facilitate    11) use/utilize    12) explain/elucidate    13) shape/conformation    14) effectiveness/efficacy    15) everywhere/ubiquitous  (We already learned ubiquitous, in lesson 2.)

Here is a Memory-Match word puzzle where you match the simple word with its more difficult synonym.




Here are the Amoeba Sisters to talk about receptors and how they are normally used by cells.  At the end of the video they mention HIV virus and how it uses a receptor called CD4 to get inside T cells.  As you watch, see this from a virus’s point of view– each part of the signaling process can be a target for take over.




This video has several great animations.  DON’T WORRY ABOUT ALL THE DIFFICULT WORDS!  All you have to do is notice these points.

1) Notice the 3-armed clatherin triskelion proteins.

2) Notice that many smaller molecules are involved in this process, starting and stopping it, so clathrins don’t start clumping in places they shouldn’t.  Don’t worry about all their names, just notice that many small molecules are needed to control this process.

3) Notice the bullet-shaped thing being taken into the cell.  That has to be a rabies virus, don’t you think?

4) Enjoy the last animation.  (The music is a piece called “Flight of the Bumblebee” by Rimsky-Korsakov.)


Here is a video that shows the “hair-pinning we tried to draw.  Again, don’t worry about difficult words you don’t recognize!  What I want you to do is realize how much you DO understand.  You’ll see many of the things we talked about while drawing.  At the end of this video she will explain how one anti-viral drug works.  You will see how this molecule sticks to the HA glycoprotein and prevents it from unfolding and hair-pinning.  No hair-pinning means no fusion, and no fusion means that the virus is stuck inside the endosome.  The endosome will then merge with a lysosome which is a digesting machine, and the virus will be destroyed.


This video clips shows a motor protein dragging its cargo as it “walks” down a microtubule.


Ready to take the quiz?  (Not required)

(If the online quiz isn’t working, try turning off your ad blocker.  I’ve heard that can fix the problem.)

If you need a printed copy, here is both the quiz and the answer key:

Virology quiz lesson 5

Back to: Intro to VIROLOGY