Eukaryotic Cells - A Closer Look

Keywords

Human cells, organelle, nucleus, ribosome, mitochondria, cell membrane, cytoplasm, Golgi apparatus, lysosome, vacuole, vesicle, functions, DNA, genetics, eukaryotes.

Introduction

All of our cells have the same basic makeup. They all have their own function, and each cell has a set of organelles that enable your cells to have function. Humans, animals and plant cells are all very similar, but sometimes they have different functions.

What is an Organelle?

An organelle is a specialised structure within a cell that has a specific purpose. Like a job.

Let's take a look at a typical workplace. Each person at a workplace has his or her own function. Therefore, for further example a school has a series of teachers. They each have a specialised role - they generally teach one or two subjects at most. Then, you have heads of year, a deputy head teacher, and a head teacher.

But that's not it, there are then support staff - a series of Learning Support Staff who help children with special needs - and also other members of staff such as cooks, lunchtime assistants, cleaners, and so on.

Everyone Has a Job

So, as a school has many people, so do eukaryotic cells. And each part, called an organelle, has it's own job. There are several organelles in a eukaroytic cell, including:

• Nucleus
• Mitochondria
• Ribosome
• Endoplasmic Reticulum
• Cell membrane
• Cytoplasm
• Golgi apparatus
• Lysosome
• Vacuole
• Vesicle

Interesting fact: all the cells in our body replicate over 11 months. So, the term "new year, new me" can be taken quite literally, as your body's cells will all be new.

Take a Closer Look

So let's have a closer look at each organelle:

Nucleus

The nucleus is the most important part of a cell. It holds our chromosomes and DNA information. Without this, we would not have any features. The name nucleus is derived from a Latin word that means 'kernel of a nut'.

Functions

Although holding our genetic information is one of the most important parts of the nucleus' function, it does have other functions.

• It helps with cell growth and reproduction. It can send out signals to the rest of the cell to enable the creation of extra organelles.
• Because of the DNA housed within the nucleus, it is able to replicate itself to create a copy.
• It is also able to create strands of RNA to create a 'page' style transcription. This means they can copy sections of DNA, turn them into RNA for a specific reason, which is then able to be read by the rest of the cell.

Mitochondria

This organelle creates most of the chemical energy needed for the cell's biochemical reactions. This chemical energy is stored in a small molecule called Adenosine Triphosphate (ATP). This process uses aerobic respiration, as it also uses oxygen. Mitochondria are only received from the mother parent, as they contain their own small chromosomes.

Functions

Other functions of mitochondria include:

• Depending on the size and function of the cell depends on the amount of mitochondria included within it. This is because some cells require more energy.
• If there are not enough mitochondria organelles in a certain type of cell, like muscles, the liver or the brain, a defect can result in diseases.

Ribosome

A ribosome creates a protein within a cell. Not only that, they use this protein to connect and translate genetic information from the nucleus and they use messenger RNA to translate this information.

A ribosome is made up of RNA and protein, and there are many of them within a cell. They are each made of two subunits. Each ribosome is located around the RNA, and allow for the addition of a specific amino acid. Once the ribosome has created the protein, it breaks up.

Endoplasmic Reticulum

A large organelle in the cell, the endoplasmic reticulum is made of sheets of membrane and tubes that begin near the nucleus. They often extrude through the cell, and they create, package and secrete many of the cell's products. They work alongside ribosomes, creating protein.

When you look at it under a microscope, you can compare it to isobar lines on a weather map, but it would be a massive low pressure system heading in from the North, creating cold weather. This is not a weather report.

Cell Membrane

This is the outer wall of the cell. When a cell duplicates itself through mitosis or meiosis, the cell membrane expands. Essentially, it keeps all the other organelles together in the same place and protects them from the outside areas.

The cell membrane is semipermeable, which means it allows transport of material entering and exiting the cell. This doesn't mean all the other organelles can come and go though, they are instead held in.

Cytoplasm

Cytoplasm is the jelly-like fluid within the cell that surrounds all the other organelles within the membrane to further protect them all. It also allows for fluidity within the cell. It is made up of water, salts, and other organic molecules.

If you split the word up, it basically means "cell stuff", with cyto meaning cell, and plasm meaning stuff.

So, it holds all the other organelles within the cell inside, and provides a little bit of rigid structure to the cell itself.

Golgi Apparatus

The golgi apparatus processes proteins and lipids (fats) into small molecules called vesicles, which are sent to three places - within the cell to other organelles, the plasma membrane and the outside of the cell.

The golgi apparatus has other names - golgi body, or just golgi. This was named after the scientist that discovered it - Camillo Golgi. It's appearance looks like a series of stacked membranes.

The golgi works with the endoplasmic reticulum, which processes protein. The golgi will then further process the protein. They are both situated directly underneath the nucleus in every cell - often referred to a perinuclear.

Lysosome

A cell has areas that stop working. When they do, it is the job of the lysosome to break these parts down. It also helps with destroying unwanted viruses and bacteria that enter the cell.

Another interesting function is the death of the entire cell. A process called apoptosis, where the lysosome will help with the self-destruction of the whole cell if it is damaged beyond repair.

Because the lysosome is an acidic enzyme, it is housed in it's own compartment.

Vacuole

This organelle removes waste products from the cells and is one of the larger parts of the cell. It can also remove any harmful toxins from the cell. It works differently in humans than it does in plants.

The vacuole will grow in size within the cell, taking in waste product, and then removing it. It works with the inside of the cell and the outside of the cell to do this.

Vesicle

Once the golgi apparatus has processed the protein and fats, it can become a vesicle. These are small parcels that can be ejected out of the cell by exocytosis, or held within to be used by the cell.

The vesicle itself has a membrane, and is considered an organelle. There can be different types of vesicle in cells, which are used for food storage, energy, excretion and other uses.