Hi, I'm Cathy with Level Up RN. In this video, I'm going to begin my coverage of prokaryotic cells, including a discussion of cell shapes and the arrangement of cells. At the end of the video, I'm going to give you guys a quiz to test your understanding of some of the key points I'll be covering. So definitely stay tuned for that. And if you have our Level Up RN microbiology flashcards, go ahead and pull out your flashcards on cell shapes and arrangements so you can follow along with me.
Let's first go over some common prokaryotic cell shapes. So a coccus is spherical, whereas a bacillus is rod-shaped. And then a coccobacillus is kind of in between a coccus and bacillus. So it will have an oval shape. Spiral bacteria come in three forms, including a vibrio, a spirillum, and a spirochete. A vibrio looks like a curved or comma-shaped rod. A spirillum has a rigid corkscrew shape, whereas a spirochete has a more flexible corkscrew shape. Another key difference between spirilla and spirochetes is that spirilla move using flagella, whereas spirochetes move using axial filaments, which are kind of like internal flagella.
Let's now discuss the different arrangements of prokaryotic cells, starting with cocci arrangements. So as a reminder, when we are talking about one cell, then we call that a coccus, and when we're talking about two or more cells, that is referred to as cocci. So when we have a pair of two cocci, we refer to that as diplococci. When we have a chain of cocci, that is called streptococci. When we have a group of four cocci that is referred to as a tetrad. When we have a group of eight cocci that resembles a cube, this is called sarcinae. And then when we have a grape-like cluster of cocci, this is referred to as staphylococci.
Let's now talk about bacilli arrangements. When we have a single rod-shaped cell, that is a bacillus. When we have multiple rod-shaped cells, then we refer to that as bacilli. So bacilli arrangements include a pair of bacilli, which is referred to as diplobacilli. If we have a chain of bacilli, that is referred to as streptobacilli. And then when we have the fence-like arrangement of bacilli, where they are side by side, that is called palisades.
All right. It's quiz time. And in this particular quiz, I want you to name that cell shape or the configuration of cells. Are you guys ready? Number one, name this shape. The answer is coccus. Number two, name this configuration of cells. The answer is staphylococci. Number three, name this shape. The answer is bacillus. Number four, name this configuration of cells. The answer is streptobacilli. Number five, name this shape. The answer is coccobacillus. Number six, name this configuration of cells. The answer is tetrad.
All right. I hope you did great with that quiz, and I hope you found this video to be helpful. Take care, and thank you so much for watching.
