Key Area 5
(a) The cytoskeleton and cell division
In this section, we will learn about the role of the cytoskeleton in the process of cell division. We aim to understand how progression through the cell cycle is controlled and what happens when damage is detected.
Understanding control of the cell cycle and pathways involved in cell death are fundamental themes within Cancer research. At the Beatson Institute in Glasgow, many research teams are involved in just this, including Professor Stephen Tait's team who focus on understanding "how mitochondria control cell death and address how this is deregulated in cancer". The aim of these research teams is to ultimately improve existing therapies for patients and develop new approaches to win the fight against cancer.
Before you start on this section, you should aim to be secure in these areas:
Mitosis is required for growth and repair
The sequence of events of mitosis, being comfortable with your understanding of terms such as chromatids, chromosomes, spindle fibres and equator.
Diploid cells have 2 matching sets of chromosomes (e.g. human cells have 46 chromosomes or 23 PAIRS of chromosomes). These chromosomes are replicated during cell division.
Before we begin, let's take a couple of minutes to watch these wonderful fluorescent microscopy videos of cell division.
The Cytoskeleton
Watch the video about the cytoskeleton (left) and then read the article below by clicking on the white button.
Task 71
It was the beginning of another Monday in school. The new post-lockdown timetable for school for "interesting" and the AH class were finding the triple period with Dr M a wee bitty "intense".
"Miss, a hink we cud all dae wi a wee break", yawned Big Davie from the back of the room. Dr McRobbie could just about see the top of his head but most of him had seemingly caved in on himself under the table.
"Aye, it's certainly no easy putting up wi you lot for 3 periods in a row", laughed Dr M (half-joking), "Let's work a bit together - we will watch this video (above) and read the article. Then, use Google docs to collaborate, as a class, to make your own notes about the role of the cytoskeleton and the key protein molecules that form the cytoskeleton".
Big Davie took a big stretch and whispered something to wee Jonny, a suspicious smirk on his face.
"Remember", warned Dr McRobbie, "I can track who has contributed what on the Google Doc..." she left it hanging.
You should do the same. Suggested answers are available here.
The eukaryotic cell is a 3D structure. It has a network of proteins extending throughout the cytoplasm, known as the cytoskeleton. The cytoskeleton gives mechanical support and shape to cells.
The cytoskeleton consists of different proteins structures, which are found in all eukaryotic cells. These protein structures include:
Microfilaments - these are the smallest components of the cytoskeleton and include the protein actin.
Intermediate filaments
Microtubules (shown in green in the image opposite) - these are hollow, straight cylinders composed of globular proteins called tublins (see image below). These proteins control the movement of membrane-bound organelles, including segments of the ER, the Golgi apparatus, secretory vesicles and lysosomes (see Key Area 2b) and chromosomes.
Task 72
Dr McRobbie was explaining, "The cytoskeleton is made up of different types of structures". She set the task of trying to state the three types of structures and for everyone to sketch a diagram of a microtubule, labeling the protein it is composed of.
Complete this task in your notes within box 72. Suggested answers are available here.
Microtubules may occur at essentially any location in the nucleus or cytoplasm. There are some specialised sites of microtubule assembly called microtubule organising centres (MTOCs). For microtubules, the MTOC is the centrosome, from which cytoskeletal microtubules originate and extend.
Microtubules grow from the MTOCs with their minus ends anchored in the sense matter of the MTOC and their plus ends directed outward. These microtubule structures form the spindle fibres that are active during cell division.
Cell division require remodelling of the cytoskeleton. This might involve formation and breakdown of microtubules, which requires polymerisation (build up) or depolymerisation (break down) of tubulin.
Task 73
"Miss, I'm gonnae have a seriously dour-face by the end o this period if you don't explain what polymerisation means. That word has just been thrown in there". Dr McRobbie couldn't help but agree and suggested the class work in small groups to learn.
"Read through this article ("Microtubule polymerisation: one step at a time") and then we will watch this video" (accessed via the pink button).
You can now do the same. Use a highlighter (if printed) or add sections into your notes to show parts of the text that help you understanding what is meant by “polymerization of tubulin” during the cell cycle. How would you cite and reference the article using Harvard referencing system?
Suggested answers are here.
Copy of Microtubule polymerisation article.pdfClick here for a Quizlet on Topic 1, Key Area 5a.
Now go to SCHOLAR "5.1 The cytoskeleton and cell division" for consolidation.
