Cell Structure and Function

Cell Structure and Function

The structure of the cell or an organelle will always determine how a cell or an organelle will function. The paper explores the various functions of cell organelles the narrow down to show how structure relates to the functioning of a cell organelle by using the mitochondrion and the chloroplast as the case study (Darnell, 2015). The cell is well known as the basic structural, functional, and biological unit that supports life. Inside the cell, we have small compound parts called organelles. The cell is made up of the cell wall which is only found in plant cells, the cell membrane, the cytoplasm, and internal cell organelles structures made of smaller parts called organelle.  The diagram below shows an illustration of the internal part of the cell.

(Source: Darnell, 2015)

The outer part of the cell is composed of the cell wall and the cell membrane. The cell wall theoretically is not part of the living cell since it is outside the membrane. It provides rigid structural support in the plant, fungi, some algae, and prokaryotic cells. Each organism has different chemical composition and thickness. However, the cell membrane forms a physical obstacle and a blockade between the cell and the exterior environment as it permits only selected binding molecules to go through and also the same time prevents entry of unwanted, unnecessary substances. It is semi-permeable hence allowing only small-sized molecules to pass through while hindering large-sized molecules (Darnel et al., 2015). Water and small elements can slip through the phospholipid bilayer while bigger and more complex constituents must pass through one of the protein passages implanted in the membrane. Therefore the primary function of the cell membrane is to selectively filter materials entering and leaving the cell.

The inner part of the cell is composed of a fluid medium called the cytoplasm, the nucleus, and internal organelles. The cytoplasm is a fluid matrix of the cell that contains dissolved ions and other materials. The two primary functions of the cytoplasm are to allow the movement of materials within the cell and enable the movement of organelles during cyclosis (Ingber, 2016). Whereas the nucleus is termed as the control unit of the cell because it is where the DNA is stored, the DNA is the set of information for the cell to function, not only for reproduction but also enzymes and other functions.

The cell also has the plastids which are found only in autotrophs. There are two types of plastids: chloroplast and leucoplast. The chloroplast is the site of photosynthesis while the function of the leucoplast is to store starch. The other cell organelle that is more highly used in plants than in animal cells is the cell vacuole these membranous sacs have many functions (Pospescu et al., 2014). The material can be conveyed within the cell, from one organelle to another, Vacuoles can take materials to the membrane for expulsion and also can be formed of the membrane and transport materials into the cell. Metabolic waste and water are stored in plants and eukaryotic algae that have a large central vacuole.  But the number and types can vary.

All cells that need a lot of energy to perform their function have mitochondrion. For instance, the sperm cell needs a lot of energy to swim toward the egg cell. The mitochondrion is the powerhouse of the cell, the site of aerobic respiration. All eukaryotic cells have mitochondria (Ingber, 2016). Also, we have the Golgi bodies which are a stack of membranes within the cell. The package materials and form vesicles for transport out of the cell and are mainly found in Eukaryotic cells.

The Endoplasmic reticulum is an organelle that extends throughout the cell. It is of two types: the Smooth Endoplasmic Reticulum that luck ribosomes on it and the Rough Endoplasmic Reticulum that has ribosomes on it. The Smooth Endoplasmic Reticulum synthesise, package, and transports lipids while the Rough Endoplasmic Reticulum packages and transports proteins. They are found in eukaryotic cells. On the other hand, Ribosomes are not part of the organelles, but structures of the cell. They are in the cytoplasm, on Rough Endoplasmic Reticulum, and in the nucleus. One of the key roles of ribosomes is that they are the site of protein synthesis (Cooper, 2010). All cells possess ribosomes.

The cytoskeleton has many different functions in the cell. One, they are responsible for maintaining the internal shape of the cell, acting as a framework for all the other parts (Leowey, 2013). ‘The cytoskeleton assists in the movement of organelles and materials in cyclosis, and they also form the spindle structure during cell division.’ They are mainly made of three different structures microtubules, microfilaments, and intermediate filaments (Pospescu et al., 2014). The cytoskeleton is present in all cells.

To bring about the relation between the cell structure and there, I Focused on the Mitochondria and the chloroplast. These organelles are mainly membranes within membranes with space in between. We have already seen that the main function of the mitochondria is to convert glucose to a usable form of energy for the cell through the process of respiration. This important role is largely possible because of the unusual structure of the mitochondrial membranes, which allow an intermembrane space to form where protons accumulate and a matrix to which the protons flow (Cooper, 2010). In the absence of the inner mitochondrial membrane, there would be no barrier to holding protons back and forcing them to flow through the ATP synthase rotor. More so, the inner membrane is folded into structures called cristae, which increases the surface area hence paving the way for millions of ATP synthase complexes to jam into a single mitochondrion (Lehninger, 2015). Without the exceptional folded structure of cristae, cells would need millions of mitochondria to produce the same amount of energy manufactured by just a few with cristae. This solely shows that structure dictates function.

For chloroplasts, without the thylakoid membranes splitting the stroma from the lumen, there would be no space for protons to amass and flow back. In the absence of the products produced by the thylakoid.

References

Cooper, g. M., & Hausman, R. E. (2010). The cell (pp. 725-730). Sunderland: Sinauer Associates.

Darnell, J. E, Lodish, H., & Baltimore, D. (2015). Molecular Cell Biology.(Vol. 2). New York: Scientific American Books.

Ingber, D. E. (2016). Tensegrity I. Cell Structure and Hierarchical Systems biology. Journal of cell science. 116(7), 1157-1173.

Lehninger, A. L. (2015). Biochemistry: THE MOLECULAR BASIS OF CELL STRUCTURE AND FUNCTION (NO. Qp514. 2. L431972.).

Leowey, A. G., & Siekevitz, P. (2013). Cell Structure and Function: An integrated approach.

Pospescu, G., Ikeda, T., Dasari, R. R., & Field, M. S. (2014). Diffraction Phase Microscopy for quantifying cell structure and dynamics. Optics Letters, 31(6), 775-777.