Function and Purpose of Cell Organelles

FUNCTION AND PURPOSE OF THE CELL ORGANELLES,HOW DO THEY CONTRIBUTE TO THE CELL OVERALL?

What are cell organelles?

The organelles are cellular structures suspended in the cells' cytoplasm, which work together to help the cell perform its necessary functions. Each organelle has a different task to contribute to the cell overall but a highly complex organisational hierarchy ensures that they all perform at maximum potential and efficiency. In Prokaryotic cells, there is little complexity in the organisation of organelles; the cell is divided roughly into areas where certain functional groups can be found. On the other hand, Eukaryotic cells have a much more complex system which allows the organelles to perform more complex tasks in a more reliable and efficient manner. This is the overruling feature which determines how advanced the eukaryotic cell is compared to the prokaryotic cell.

The nucleus is considered the most important organelle in both cells. Much like how the brain is to our bodies, the nucleus is the control centre and decision maker for all activity in the cell. Located in the central area of the Eukaryotic cell, the nucleus is a roughly spherical organelle bounded by a nuclear membrane and contains majority of the cell's genetic material. The membrane itself is a double layer of lipids, with small opening spread throughout to allow the nutrients and materials to pass in and out of the cell. The genetic material (DNA) protected by this membrane is used to instruct the cell how to grow, divide and thrive and is found in the form of chromatin until cell division where it condenses to form distinct chromosomes. More specifically, the DNA found in the nucleus tells the other cell organelles what proteins to make depending on what the cell needs i.e. if the cell needs to grow a little bit more, the DNA will have the instructions to tell the related organelle how to do so. In a different perspective, this organelle is responsible for passing all the genetic information of this certain cell to the next generation.

Aong with its many functions, the nucleus is also responsible for all the chemical processes and metabolism within the cell. From the topic of cell division, we can recall that translation and transcription occurs within the nucleus of the cell; a process that produces enzymes critical to the regulation of chemical reactions and processes that occur in other organelles. There have been many experiments to support the belief that the nucleus is indeed the 'mastermind' behind the perfect functionality of a cell. An example of which involved the removal of the nucleus from the cell to determine if it really had an effect on the function. Results showed that without the nucleus, the cell became disorganised and could not function without proper instruction.

How it contributes to the cell: Without the nucleus, the cell would be completely dysfunctional with chemical reactions occurring under no direction and genetic material being spread throughout the cytoplasm (potentially resulting in the nucleotide found in prokaryotic cells). A dysfunctional cell is of no use in living organisms and can cause a lot of problems; hence the nucleus is important in keeping everything in line.

Microscopic Image of an Animal Cell

Nucleus

Visual Diagram of an Animal Cell

Nucleus

The nucleolus is an organelle made up of RNA and protein, which can found inside the nucleus of a Eukaryotic cell. Its function is to transcribe and process rRNA and assemble ribosomes which is later used in other organelles of the cell. Assembling ribosomes ensures that the cell has plenty to go round whenever it is in need of proteins and it is thanks to the nucleolus that there are enough ribosomes to synthesise for early embryonic development, if possible.

How it contributes to the cell: Without the nucleolus, the cell would not have ribosomes to use, would not be able to undergo protein synthesis (due to inability to transcirbe and process rRNA) which starts a chain reaction of dysfunction in the cell (i.e. no protein synthesis means no amino acids, no amino acids means no proteins can be made and no proteins mean that the cell doesn't have necessary nutrition to function and therefore fails to perform).

Visual Diagram of a Plant Cell

Nucleolus

The Endoplasmic Reticulum is divided into 2 functional groups, each with their own job. These two groups are; smooth ER and rough ER. From their names, it is easy to identify them in the cellular organisation with the rough ER being described as tube-like structures covered in ribosomes and the smooth ER described as smooth membranes compacted together. The Rough ER is found in the cytoplasm from the nuclear envelope to the cell membrane and is interconnected to the smooth ER from there.

The Rough Endoplasmic Reticulum is the site of protein and membrane synthesis. This is partly the reason it is located so close to the cell membrane and the nuclear envelope, as it collects the amino acids produced from the ribosomes made by the nucleolus and bounds them together to form long chains, commonly known as proteins. These proteins, with some having carbohydrates attached to them (glycoproteins), have the potential to be used as cell membrane receptors, hence it is known as the site of membrane synthesis also.

The Smooth Endoplasmic Reticulum is not bound with ribosomes like it's rough counterpart, but is instead just another membrane in the cytoplasm (as mentioned earlier). This organelle is also referred to as the Production Line of the Cell as it has the task of arranging and packaging enzymes in an order that is highly efficient for the transportation of proteins and lipids throughout the cell.

How it contributes to the cell: Both Endoplasmic Reticulum types are so important in keeping the cell healthy and functioning through the production of necessary proteins, upholding of the membrane and ensuring that the cell functions efficiently for transportation of necessary proteins and lipids to other organelles (to continue the next step). Without these organelles, the flow of function in the cell would be disrupted and the cell would be dysfunctional.

Endoplasmic Reticulum

Often located near the cell membrane in form of layers of membrane packed together, the Golgi Body is trusted with the task of synthesising, packaging and secreting materials. The Golgi Body takes the proteins produced by the ribosomes in the Rough ER and arranges them to form more complex and larger proteins for later use either inside or outside the cell. Like a factory, the Golgi Body synthesises these proteins to form proteins for more complex tasks such as strengthening up the cell membrane or the cell itself. The Golgi Body is also in control as to where these proteins are sent to in the cell.

Scientists had found the Golgi Body long before they knew what it's function was. It was only in the recent 20th century that technology at that time was able to confirm their suspicions and broaden their depth of knowledge.

How it contributes to the cell: The Golgi Body plays a large role in efficiency of cell functionality. If the Golgi Body did not exist in the cell, there would only be simple proteins floating around (there might be some complex ones but not purposefully arranged, more like co-incidence) and the cell would not be able to produce the complex sub-nutrients it needs to perform high-level tasks.

Found encompassing the contents of the cell itself, the cell membrane is the boundary between the cell itself and its surrounding environment. In saying this, the membrane itself does not isolate the cell completely from it's environment as the cell needs to be in constant presence of necessary nutrients and resources to function. The cell membrane controls which substances can and/or cannot enter the cell. It can also be related to the boundaries of countrie, which regulate who passes into or out of the country. Homeostasis, Diffusion and Osmosis are dependant on the cell membrane regulating the concentrations and amounts of fluid brought into or taken out of the cell. Made up of lipid bilayers with proteins placed in-between, the cell membrane is also capable for using these proteins to make carbohydrates that it can release outside of the cell.

How it contributes to the cell: Without the cell membrane, the cell would have no control as to what substances or compounds make it into the cell, whether they be necessary or harmful to the cell. The cell membrane keeps the balance between the two worlds and ensures that the cell receives all it needs without threat from harmful substances.

Golgi Body

Cell Membrane

Cell Wall

Cell Membrane

Visual Diagram of Golgi

Body

Micrograph of the Golgi Body

Micrograph of Cell Wall

Visual Diagram

The cell wall is only found in plant cells in terms of Eukaryotes, and provides support to the cell. Made out of cellulose which is a polysaccharides (many chains of monosaccharaides), the cell wall is a membrane found outside the usual plasma membrane. In addition to providing support to the cell, the cell wall gives the cell extra structure, protects the contents /organelles inside the cell and increases strength, especially in multicellular organisms. Plants in particular rely on the the cell wall for each cell to tessellate well and support each other for the structure to be strong enough to survive.

How it contributes to the cell: The cell wall ensures that the cell is stronger to have better chances of survive while protecting the inside contents. Without it, the plant cell would not nearly be as strong physically.

With the potential to reach up to 10 micrometers in length, the mitochondria are found floating around in the cytoplasm of the cell. With a reputation of being the cell's powerhouse, the mitochondria are the site of the later stages of aerobic respiration. This is crucial to the function of the cell as aerobic respiration releases large amount of energy in which the cell uses to perform other activities. Through the cross section of the mitochondria, it is easy to identify the inner folded membranes which are named cristae. This increases the surface area of the mitochondria itself so that chemical reactions can occur on a larger plane. Each tissue or organ in your body has varying cells with different mitochondria numbers. For example, the muscle cells in your body will have a significantly higher number of mitochondria in their cells as they require a lot of perform tasks. Therefore, the higher your number of mitochondria in your cells, the more energy you produce and thus the more energy your cell has to perform.

It is believed that the mitochondria began as individual prokaryotic bacteria who were absorbed into the bodies of other prokaryotes through process of endosymbiosis (refer to page 'How did Life Begin on Earth?'). They also have the ability to divide independently which is evidence to support this belief but regardless, this little organelle does not go underappreciated.

How it contributes to the cell: Without the mitochondria, our cells would not have the energy it needs to function (refer to page 'Survival Tips from a Cell') and therefore would not be able to perform. No performing cells would mean we- as multicellular organisms- would not be able to exist like we do today.

Found in plant cells in parts where light exposure is high (and also in single-celled organisms as well), the chloroplast is a dented oval shaped organelle tasked with the duty to convert inorganic material to organic molecules. It is a type of plastid containing chlorophyll (a pigment with the ability to capture light energy) and consists of two outer membranes. On the inside of the chloroplasts, a system of pigment filled circular discs/ flattened sacs called thylakoids forms small stacks and work together to aid the process of photosynthesis. Each stack is called grana and is surrounded by a fluid named stroma. The first stages of photosynthesis occur in the grana before moving to the stroma for the last few stages. These chloroplasts are important as they are the first response or step in cell energy rejuvenation. It is here that the energy the plant needs to survive (well, energy by means of light) begins its way to the cell itself.

How it contributes to the cell: There is no doubt that the chloroplast contributes much to the cell, especially with it providing one of the many sources of energy the cell needs to survive.

Mitochondria

Chloroplasts

Micrograph of a mitochondrion in a plant cell

Micrograph of a chloroplast in a plant cell

Visual Diagram of a chloroplast

The vacuole is one the key differences between the plant and animal cell, as discussed earlier. In plant cells, the vacuole takes up majority of the space while in animal cells, there are multiple that are significantly small compared to the plant vacuole.

Found in the cytoplasm, the vacuole stores solutes and maintains balance of water and salts in plants while storing waste products for excretion later on. It is often referred to as the storage container of the cell, with it holding so many solutions at once for so many different purposes. The vacuoles are filled with sap made up of solutes such as slats in form of ions, simple sugars, amino acids and even pigments. So when the plant cells have enough energy to suck water into the vacuole, it gets big enough to provide addition support to the cell (in conjunction with the already existing cell wall, cytoskeleton and membrane). Evidence has supported the belief that the more mature the cell is, the larger the central vacuole and this detail has become a widely used method in determining how well functioning a ell is for its age. The vacuole in plant cells takes up so much space that the cytoplasm and nucleus are squeezed between the vacuole itself and the cell wall.

On the other hand, animal cells have smaller vacuoles that branch out into 2 functional groups. Firstly, the food vacuole is used when a cell engulfs a particle by process of phagocytosis. The other is the contractile vacuole, which is involved in removing excess water that diffuses into the cell as a result of osmosis (keeping the balance).

How it contributes to the cell: Vacuoles hold all the necessary nutrients or even unwanted nutrients for the cell while the cell works out the perfect time for it to use these nutrients/excrete these nutrients. Without these cellular storage tanks, the cell would constantly be in a state of unbalance and would not have the extra support (plant cells) that it needs to survive for extended periods of time.

Ribosomes are mainly found on the walls of the Rough ER but can also be found floating around in the cytoplasm. These organelles contain RNA and are involved in the process of translation in protein synthesis. Together, the ribosomes work with other organelles, specifically the rough ER, to efficiently pass on the amino acids and proteins they make. The ribosomes collect their amino acids from translation and transcription of DNA which is passed on from the nucleus. Being attached to the Rough ER, the ribosomes can efficiently collect these amino acids, compile them to form the proteins and send them off using the function of the Rough ER. This is a very efficient process, which is good because cells like efficiency, and shows how two organelles work together to help the cell receive its' necessary nutrients more efficiently.

Cytoplasm is the mainly aqueous solution found everywhere within the cell itself. The aqueous component of the cytoplasm is thanks to a substance known as cytosol, one of the many solutes and substances that make up the cytoplasm. In Eukaryotic cells, the cytoplasm supports and contains organelles for the cell to function while in prokaryotic cells, the cytoplasm is only the liquid the nucleotide is suspended in.

How it contributes to the cell: The cytoplasm upholds the organelles and makes it easier for cellular movement while protecting the organelles themselves from damage. The cytoplasm also stores molecules for cellular processes needed later on.

Lysosomes are found in the Endoplasmic Reticulum also and filled with enzymes that are strong enough (concentrated enough) to break down other cellular structures. Lysosomes partially digest the food absorbed taken by the cell using its enzymes before sending off the nutrients back through the membrane to be used by the cell. It is also important as it gets rid of non-efficient structures as the cell ages and recycles these material to make new and improved structures for the cell (the newer the structure, the better running the system is). In the case that the lysosome becomes damaged and breaks within the cell, the enzymes inside will escape and destroy the rest of the cell by digesting it.

How it contributes to the cell: Lysosomes help the cell by recycling old materials to make new structures that the cell can use ot perform better with as it ages. Without them, the cell would be stuck with lots of unwanted material from dying structures without new ones being built, meaning that they will die of from inability to function without proper organelles.

Vacuole

Ribosomes

Cytoplasm

Lysosomes

Cytoplasm

Micrograph of the vauole in a plant cell

Visual Diagram of Ribosome

Micrograph of Ribosomes with their proteins

Diagram of the Vacuole

With so many things going on at once in a cell, it's hard to keep control as to which organelle does what and where things go. This is why a high level of organisation and structure is so important to the cell function as it ensures the cell is working at full efficiency and potential without any delays.

Cells are grouped in accordance to their purpose/function to form tissues. Each cell group produces a different type of tissue. These tissues then work together to form organs, which are then responsible for upkeeping the systems of your body.In turn, these sytems work together so that your body can function well and with proper co-ordination. Without this heirarchy, there would be no organisationa dn we would not be able to function as we do today. The flow of function would be delayed and broken so that the entire system would be dysfunctional. This is why it is critical that we keep our cells healthy and well, so that the chain chain reaction will be positive.

Image Bibliography

https://upload.wikimedia.org/wikipedia/commons/0/06/Blausen_0212_CellNucleus.png

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http://www.getmededu.com/uploads/1/9/9/5/19952889/3014999_orig.jpg

http://www.lifesci.sussex.ac.uk/home/Julian_Thorpe/tem29.jpg

http://academic.brooklyn.cuny.edu/biology/bio4fv/page/rough.gif

http://liquidbio.pbworks.com/f/1194817600/endoplasmic%20reticulum.jpg

http://cache3.asset-cache.net/xt/128619942.jpg?v=1&g=fs1%7C0%7CPRC%7C19%7C942&s=1

http://medicaltreasure.com/wp-content/uploads/2013/08/golgi-apparatus.png

https://upload.wikimedia.org/wikipedia/commons/7/7b/Annular_Gap_Junction_Vesicle.jpg

https://www.ru.ac.za/media/rhodesuniversity/content/emu/images/Plant%20cell.jpg

https://micro.magnet.fsu.edu/cells/mitochondria/images/mitochondriafigure1.jpg