NUCLEUS

The nucleus is the heart of the cell, containing the cell's DNA. Below are some of the areas related to the nucleus.

CELL DIVISION
All cells, whether single bacterium or cells in a human body, have to grow and make copies of themselves. This process is called cell division. It involved the duplication of every component of the cell, including the DNA in the nucleus. Then, when all is copied, the contents are shared out into two identical ‘daughters’. It is a very tightly controlled process. When this goes wrong, cells can divide without any control, resulting in cancer.

DNA
This is the genetic material which is duplicated before a cell divides and passed to both daughter cells and is the genetic information passed between different generations. It is a thread-like molecule carrying a code which is made up of 4 different chemicals. The order of these chemicals along the thread represents a code which directs the joining up of amino acids into protein chains. Alterations in the DNA chemicals are called mutations. The mutations can be inherited and cause what we call genetic diseases. Sometimes mutations result in altered proteins and this has an effect upon the cell, often detrimental.

CANCER
When cells divide out of control they continue to multiply, resulting in a cancer within our bodies. This results from changes in the DNA which leads to altered proteins being made. These altered proteins lead to differences in the cytoskeleton, receptors or cell signalling processes in the cell. This can allow cells to become more mobile and invade other parts of the body. These cells spread and form tumours. The process of cell death also goes wrong in cancer cells, hence they do not die.

MITOCHONDRIA

Mitochondria, the site of energy production in the cell. Below are some of the issues relating to mitochondria.

CELL DEATH
Most cells in multi-cellular organisms (like humans) are equipped with a set of instructions to kill cells. When something goes wrong with the cell which it cannot repair, this process of cell death is activated. It allows the cell to be digested, allowing all the contents to be recycled by the body.

AGEING PROCESS
As cells age they accumulate debris and damaged components: DNA mutations, proteins which have become non-functional and mitochondria which do not function properly. Whether these contribute to whole body ageing is as yet undetermined.

STEM CELLS

Most cells in multi-cellular organisms (like humans) will divide until they become specialised, like an insulin producing cell in the pancreas or a blood cell. After this they will not divide and will eventually die due to wear and tear. In order to replace these cells, the body has what are called stem cells. These are capable of dividing to replace the lost cells.

CELL MEMBRANE

The outer region of the cell, the membrane determines what substances can leave or enter. It is also responsible for signalling.

SIGNALLING
How a cell relays information from the membrane to its internal components is through the process of signalling. For example, when a skin cell within a human body is being told to divide in order to repair a cut, a signal is received on the membrane by a receptor. This sends a chemical message into the cell which alters many other proteins and eventually leads to cell division. There are many different types of signals.

EXTREMOPHILES

All living organisms on earth exist as cells. The simplest are single cells such as bacterias and yeast, many of which live in very extreme environments such as thermal vents in the oceans or pools of acidic water near volcanoes. These cells are called extremophiles. They have specially adapted components which makes them able to survive in hostile environments.

Content last updated: 26/01/2007

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