Practical: Relating Structure to Function (Staining (Nucleus - As the…
Practical: Relating Structure to Function
Four Tenets of Cell Theory
The advancement of generations of life is dependent on cells
The Principle of Complementarity
states that the structure of the cell is related to its function. For example, a smooth muscle cell is fusiform as it has to be able to contract and stretch
The basis of life is dependent on a cellular level.
Cells are the structural and functional unit of life
The actions of an organism depend on the cells work individually as well as together
Essential Functions of Cells
- This is another essential process and cells are able to digest things that enter them, through the processes of lysosomes. These are organelles that are able to allow for the breakdown of contaminants as well as other objects that enter the cell. This means that the entrants can be catabolised into their constituent parts such as proteins and monosaccharides and be recycled by the cell. Lysosomes are present in many cells of the body. An example includes squamous epithelial cells which are able to have macromolecules or even harmful molecules enter the cell through endocytosis and therefore process these in order to break them down and be used for the good of the cell
Generation of energy
- The generation of energy is one of the most important as this is what allows for the cell to actually operate. All cells are able to undergo this function as it is controlled by the important mitochondria. Without the mitochondria, the cell would not be able to exist. Especially pertinent in cells of skeletal muscle as the movement of the human body requires a lot of energy
- Movement can be achieved through the cell's cytoskeleton. The cell can utilise integral proteins
which are able to extend to two faces of the plasma membrane and protrude out of the cell to allow for to have crawling movements. Cells such as spermatozoa are also able to achieve movement as they have flagella that allow them to propel themselves. Cells that are able to move with the assistance of microfilaments include macrophages. This is essential so that they are able to position themselves to phagocytise the pathogenic material
- Growth is also important during the G1 phase of the cell cycle. Growth can be achieved by the plasma membrane increasing in size and therefore the area of the cytoplasm growing as well.
There is increased production of proteins by ribosomes as well.
All cells are able to undergo this phase. It may be however seen more so in liver cells as these cells do not go through the process of mitosis often and therefore they may have either been stuck in the G0 phase or may be in the G1 phase
- Cellular reproduction is able to occur through the process of mitosis. In this process, a parent cell is able to asexually split into two identical daughter cells. All cells somatic cells are able to fulfil this purpose (not gametes). This is especially important with cells of the apical surface of epithelium on the skin as many cells are sloughed off per day and these have to be replaced
- Responsiveness is a key aspect of the operation of all cells. This is because the responsiveness that these cells have to their environment means that they are able to interact with it. This may be though specific receptors on the plasma membrane, specific vesicles, or proteins that protrude from the plasma membrane. Such a feature is present in all cells, however is most important in cells such as those of subcutaneous epithelium which must be responsive to stimuli of the external environment
- This is a very important role of cells as it not only allows for their own protection, but for the clear boundaries of the individual functional units to be set out as well. The cell achieves this through the plasma membrane.
The cytoskeleton is also able to give structure to the cell.
This is especially important for cells of the central nervous system as maintaining boundaries between neurons means that nerve impulses are not scrambled.
Steroid secreting cells will contain many smooth endoplasmic reticula, lipid droplets, Golgi apparatuses, and lysosomes. Mitochondria also do not only produce energy but can synthesise steroids
Size of Cells
The human ovum has to be a large cell as it has to be able accommodate the spermatozoon as well as store the essential mechanisms to start the formation of a zygote
The relatively small size means that many cell bodies are able to pack together into structures such as autonomic ganglia. The long cell body on the other hand is able to maximise the lack of interchanges that are required to send nerve impulses. Thus, the passage of these messages can be quick
Red blood cell
The small size of the red blood cell is essential as the red blood cell has to pass through capillaries in order to access the cell. Sometimes the diameter of the capillary is less than that of the red blood cell and the cell has to fold to pass through. This is further enhances by its biconcave shape (surface area is maximised which is able to ensure that more haemoglobin and oxygen is carried
- As the nucleus is an acidic organelle (as it contains DNA) it will appear purple as it attracts haemotoxylin
- As the plasma membrane contains hydrophobic tails that are a part of the phospholipid bilayer, the stain does not attach
- The Golgi apparatus does not appear on a H&E stain as it is a hydrophobic organelle and thus the stain does not bind
- Lysosomes appear purple as they contain an acidic environment for the digestive enzymes within the cell
- Mitochondria appear to be a pale pink even though they contain genetic material. This is because this genetic material is a very small part of the organelle and it is the proteins that make it eosinophilic
Rough endoplasmic reticulum (rER)
- The rough endoplasmic reticulum stains pink as it contains many proteins which are eosinophilic
- These microvilli will appear pink as they are lined with mucus
- In goblet cells they stain as pink whilst in Leydig cells they are colourless (lipid)
- It will appear purple as it is the border to the acidic environment of the nucleus
Smooth endoplasmic reticulum (sER)
- This structure appears colourless and pink as it synthesises lipids but is surrounded by proteins