Discuss the proposition that plant and animal cells are fundamentally alike

Apart from the nucleus, another important organelle present in a eukaryotic cell is mitochondria.  A mitochondrion is a ‘power plant’ where stored energy from fuel molecules is converted to a more useful form of energy known as ATP to power the cell.  The production of this ATP is identified as cellular respiration.  Along with other organelles, mitochondria are found in the cytosol.  Mitochondria are thought to have derived from bacteria that may have engulfed from an ancestral eukaryotic cell that had survived inside the cell.  They contain their own DNA and reproduce by dividing into two.  

Mitochondria consist of two membranes.  The outer membrane is protective and provides resistance to movement of substances in and out of the cell.  The inner membrane is highly folded to give a much greater surface area known as the cristae.  It contains large protein molecules that are involved in cellular respiration.  Within a mitochondrion is a region known as the mitochondrial matrix.  The matrix contains proteins as well as some ribosomes and DNA that are used to produce proteins for respiration.  

Plant and animal cells also contain networks of tubules, flattened sacs and vesicles known as the endoplasmic reticulum or ER.  There are two types of ER, rough endoplasmic reticulum (RER) which has ribosomes attached to its surface and smooth endoplasmic reticulum (SER).  RER is responsible for isolating newly synthesised proteins from the cytoplasm and transport them to different sites of the cell.  Also to chemically modify proteins as to adjust their function within the cell.  However SER which lacks in ribosomes is the site for hydrolysis of glycogen in animal cells and the site for the synthesis of lipids and steroids.

Also contained within a eukaryotic cell are a series of ‘flattened membranous sacs’ and ‘small membrane-enclosed vesicles’ known as the Golgi apparatus. Golgi apparatus has several roles which includes storing, modifying and packaging proteins before targeting them to their correct destinations within or outside of the cell.

Another organelle which is present in both animal and plant cells are lysosomes.  These are small vesicles that are generated from the Golgi apparatus and contain digestive enzymes.  Lysosomes are the main sites for the hydrolysis of macromolecules, i.e. polysaccharides, proteins, nucleic acids and lipids into their constituent monomers.  They are also the sites for the breakdown of food and foreign bodies that have entered the cell by a process called phagocytosis.  A pocket is formed in the plasma membrane and eventually encloses foreign material.  This breaks off in the form of a vesicle and moves into the cytoplasm as a phagosome.  This fuses with a primary lysosome gradually forming a secondary lysosome where the process of digestion occurs.

Peroxisomes are organelles that are also present in a eukaryotic cell.  They break down toxic peroxides such as hydrogen peroxide found as by-products of chemical reactions.

The ability to provide various types of cellular movement and support for plant and animal cells is an important role of the cytoskeleton. These are sets of long, thin fibres that also maintain the cell shape.  Plant and animal cells depend on their cytoskeleton for separation of their organelles into the two daughter cells during cell division.

All these important organelles are surrounded by a plasma membrane which separates the eukaryotic cell from its environment and because of its feature being partially permeable; it is responsible for the control of material that enters into and out of the cell.

Given the importance of the organelles both present in the animal and plant cell, to name a few, are extremely necessary in order for chemical processes to take place in the body.  Without these organelles, it would be exceptionally difficult to survive.