In this video, we're going to begin our lesson on prokaryotic ribosomes. A ribosome is a cell component found inside all cells, regardless of their type. These ribosomes consist of a large and a small ribosomal subunit. The large and small ribosomal subunits will associate with each other to form the complete ribosome. This complete ribosome will be able to perform protein synthesis or build proteins. Ribosomes are also referred to as the site of protein synthesis. Although all cells have ribosomes, they are not always identical in different cells. Prokaryotic ribosomes will differ from eukaryotic ribosomes. We'll be able to talk more about that as we move forward in our course. The large and small ribosomal subunits that come together to make up the full ribosome consist of multiple proteins, along with ribosomal RNA, or rRNA for short. The ribosome itself is really just a big mixture of proteins and ribosomal RNA. We will talk more about this idea as we move forward. In this set of videos, we're mainly going to be focusing on prokaryotic ribosomes. We'll discuss the prokaryotic ribosome structure in our next video. So, I'll see you all there.
Prokaryotic Ribosomes - Online Tutor, Practice Problems & Exam Prep
Prokaryotic Ribosomes
Video transcript
Structure of Prokaryotic Ribosomes
Video transcript
In this video, we're going to talk more about the structure of prokaryotic ribosomes. In order to better understand the structure of prokaryotic ribosomes, it's first helpful to address what the sedimentation coefficient is. This sedimentation coefficient is measured in units called Svedberg units, named after the scientist who helped discover them. Svedberg units are abbreviated with the capital letter s. What you're going to see is that the ribosomal subunits and the ribosomes themselves are basically named using the Svedberg units; thus, you'll see this 's' throughout this lesson. What is this sedimentation coefficient, anyway? It's a value that characterizes the rate of sedimentation and the particles' behavior in an instrument known as a centrifuge, which spins really fast and is commonly used to help separate materials using centrifugal forces. What you should know is that the greater the s value, the faster the molecule will centrifuge. By labeling these ribosomal components with the s value, you can get a sense of the size of the subunit.
It's important to note that prokaryotic organisms have 70S ribosomes. The "70S" refers to the sedimentation coefficient for that ribosome. These 70S ribosomes have two ribosomal subunits: a large 50S ribosomal subunit and a small 30S ribosomal subunit. The large 50S ribosomal subunit and the small 30S ribosomal subunit come together to create the 70S ribosome, and this is only the case in prokaryotic organisms. In eukaryotic organisms, the ribosomes are different. We'll talk more about the eukaryotic ribosomes later in a different video in our course. For now, one thing to note is that 50 + 30 does not equal 70. Students often have the tendency to try to simply add the Svedberg units, but that is not how they work. You cannot just simply add them. Instead, the 50S large ribosomal subunit, when it complexes with the small 30S ribosomal subunit, forms the 70S ribosome, as we'll be able to see down below in our image.
The large 50S ribosomal subunit contains two ribosomal RNAs, a 23S ribosomal RNA, and a 5S ribosomal RNA. The 30S small ribosomal subunit has a 16S ribosomal RNA. We'll be able to see this below in our image, focusing on the prokaryotic ribosome structure. Notice that the 70S ribosome consists of a large subunit and a small subunit. The large subunit contains two ribosomal RNAs highlighted in yellow: the larger one being the 23S ribosomal RNA, and the smaller one being the 5S ribosomal RNA. In the small ribosomal subunit, there is also a ribosomal RNA highlighted in yellow, the 16S ribosomal RNA. Note that there are three compartments in the middle of the ribosome. These three compartments are the active site of the ribosome.
One thing to also note is that archaea, although they are prokaryotes along with bacteria, the ribosomes are not identical. Archaeal and bacterial ribosomes are the same in size, so they're both 70S ribosomes. However, they differ in two important ways. The first way is that the sequences of the ribosomal RNAs are different. The 23S rRNA, the 5S rRNA, and the 16S rRNA all have different sequences in archaea compared to bacteria. The second way archaeal ribosomes differ from bacterial ribosomes is that archaeal ribosomes have a greater number of proteins in each subunit, reflecting their differences. Because archaeal ribosomes are not identical to bacterial ones, this is why archaea are unaffected by antibiotics that target protein synthesis in bacteria. These ribosomes are crucial for protein synthesis, and antibiotics that specifically target bacterial ribosomes may not work on those in archaea due to these differences. This concludes our lesson on the structure of prokaryotic ribosomes, and we'll be able to apply these concepts as we move forward in our course. I'll see you all in our next video.
Which of the following statements about ribosomes is FALSE?
Prokaryotic 70S ribosomes are composed of which of the following subunits?
Svedbergs are a measurement of the size and sedimentation rate of cellular structures such as ribosomes.
How are prokaryotic and archaeal ribosomes different from one another?
Do you want more practice?
Your Microbiology tutor
- Match the structures in column A to their functions in column B.<IMAGE>
- Which of the following pairs is mismatched?a. metachromatic granules—stored phosphatesb. polysaccharide granul...
- Which of the following characteristics regarding prokaryotic ribosomes supports the endosymbiotic theory?a. Pr...
- Indicate the true statements about prokaryotic cells, and then reword the false statements so that they are tr...
- Which of the following is true of Svedbergs?a. They are not exact but are useful for comparisons.b. They are a...