Biology Essay Example: Structure of Eukaryotic Cells

Structure of Eukaryotic Cells and Functions of Membranes

Introduction

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Cells are described to be eukaryotic if they have a membrane surrounding its nucleus. All organisms that have a membrane around their cells are said to be eukaryotic organisms. An organism that does not possess a membrane surrounding the nucleus of their cells is termed to be prokaryotic; science has indicated that there are no organisms that can be prokaryotic and eukaryotic at the same time. Eukaryotic cells have membranes that play key significant purposes that will be later analyzed in this paper (CK-12 Foundation, 2016). The composition of eukaryotic cells includes Mitochondria, Golgi bodies, Lissome, Endoplasmic reticulum and the Vesicles.

Eukaryotic Cells

Eukaryotic cells belong to the kingdom; Plantae, Animalia, Fungi, and Protista. Eukaryotic cells can be distinctively described out of the possession of a nucleus, a plasma membrane, cytosols and ribosomes that make up the cytoplasm composed of the membrane surrounding organelles. The endomembrane in a eukaryotic cell is a system of boundaries or membranes that help in the exchange of materials (Prockop, Phinney, & Bunnell, 2008).

The components found in the cytoplasm of the eukaryotic cells include:

Nucleus

This is the part of the cells that stores all the information that the cell need to grow, function and also for reproduction. The information is stored in long but also thin molecules known as the deoxyribonucleic acid or DNA. The nucleus serves the purpose of protecting the DNA from any damage.

The nucleus also contains the nucleolus that holds the nucleic acids and other proteins. The nucleus wall has membranes that allow communication between the nucleus and other organelles within the cell. The nucleus membrane controls what goes in and what goes out. It is important to understand that the core function of the membranes is to let in nutrients, pass communication and also the extraction of wastes.

Chromosomes are also located in the nucleus, and they are the basic compositions of the DNA. In eukaryotic cells, the DNA material is packaged in condensed forms that include chromatin. Chromosomes are composed of the DNA that contains genes, nucleotides, and proteins; chromatin is a condensed form of chromosomes. Chromatin allows the protection of genetic information that is contained inside the DNA. Histones are large complex forms of proteins which along with the nuclear membrane helps to control message passing for instance DNA to the rest of the cell.

Ribosomes

Ribosomes are composed of proteins and the ribosomal RNA; they are found in prokaryotic and eukaryotic cells. The ribosomes in eukaryotic cells are much bigger and have a slight difference in shape as compared to those in prokaryotic cells. Eukaryotic ribosomes have twice the amount of ribosomal RNA and four to three times the amount of proteins contained in prokaryotic cells (CK-12 Foundation, 2016). The functions of the eukaryotic ribosomes are the same as those of the prokaryotic ribosomes. Ribosomes serve the purpose of translating the RNA into protein forms.

Cytoplasm

The cytoplasm is a gel-like fluid in which all the components of eukaryotic cells are suspended in. The cytoplasm is bound in by a cytoskeleton; the latter is a protein framework that bounds all the components of the cell. The cytoskeleton membrane keeps in proteins, ribosomes, and other organelles (Mathur, 2004).

Eukaryotic Cell Membrane and Function

Plasm membranes are protein structure that surrounds prokaryotic and eukaryotic cells. In eukaryotic cells, plasma membranes are composed of phospholipids. Phospholipids are amphipathic molecules with a hydrophilic phosphate head group and hydrophobic fatty acid. A layer of amphipathic phospholipids are arranged on the outside while the hydrophobic fatty acids remain inside. Some phospholipids contain carbohydrates known as glycolipids attached. Glycolipids play a role of controlling cell to cell communication. The membranes of the cell contain other mobile proteins apart from phospholipids; this indicates that the membrane is fluid and porous, for in and out passage of nutrients and waste, this fluidity is enhanced by the presence of cholesterol (Mathur, 2004).

Functions of the Membrane

All cellular function depend on the communication with the external world; cell must receive oxygen and nutrients for them to function. The maintenance of the osmotic pressure and the removal of waste products such as carbon monoxide wholly depends on the plasma membranes. The plasma membrane is a permeable barrier which can control what goes in and what goes out.

The plasma membrane acts as a barrier that separates the cells cytoplasm from the external environment. The cell cytoplasm is contained within the cell by the plasma membrane this ensures that the cells internal condition is well maintained. The internal conditions remain constant due to the direct control of what can go in and what goes out. The plasma membrane provides a means of communication between the cell and other cells. Cell to cell communication takes place through the use of genetically unique receptors that are present on the surface of the membrane (Prockop, Phinney, & Bunnell, 2008).

Lipids in Membranes

The membranes of eukaryotic cell especially in the kingdom Animalia contain four layers of phospholipids. Phosphatidylcholine is one of the four layers of phospholipids contained in the cell membrane others include; phosphatidylethanolamine, phosphatidylserine, and sphingomyelin. Phospholipids account for over 50% of the cell membrane. There are other components such as Glycolipids that are linked to a polar head that contains carbohydrates which are found exclusively on the outer of the membrane (Prockop, Phinney, & Bunnell, 2008). Cholesterol is another component of the phospholipid membrane; this lipid consists of four hydrocarbon rings which help in maintaining the fluidity of the membrane.

Movements of Substances across the Membrane

Diffusion in the core principle of movement of nutrients to and from the cell with the external cytoplasm. Diffusion occurs based on the concentration gradient inside or outside the cell. Molecules of oxygen can diffuse through the membranes inside the cell; this process is the same as the diffusion of Carbon monoxide from the cells.

Osmosis- this process allows the movement of water inside and outside the cell. The process requires specialized proteins called Aquaporin in the plasma membrane. Aquaporin control the amount of water that is allowed to pass through in and out hence ensuring that the cell’s osmotic pressure is always at a balance.

Active Transport- This process is energy intensive, this involves the transportation of components across the membranes against their concentration gradient. Charged calcium, ions need to be moved out by active transport other ions, for instance, the sodium-potassium pump requires the movement of sodium ions and potassium ions out of the cell.

Membranes play a critical role to the life of a cell through control of the cellular functions and the protection of the organelles inside the cell. Cell membranes are important to maintain the high pressure inside the cell, the balance of the osmotic pressure and osmotic potential all depend on the cell membranes. Cell membranes play a critical role in the life of cells as a leader with perfection and justice.

References

CK-12 Foundation,. (2016). Prokaryotic and Eukaryotic Cells. CK-12 Foundation. Retrieved 12 October 2016, from http://www.ck12.org/biology/Prokaryotic-and-Eukaryotic-Cells/lesson/Prokaryotic-and-Eukaryotic-Cells-BIO/

Mathur, J. (2004). Plant Cytoskeleton: Reinforcing Lines of Division in Plant Cells. Current Biology, 14(7), R287-R289. http://dx.doi.org/10.1016/j.cub.2004.03.027

Prockop, D., Phinney, D., & Bunnell, B. (2008). Mesenchymal stem cells. Totowa, N.J.: Humana Press.