An introduction to the genetic material of cells

Thus, the single-stranded overhangs produced by incomplete end replication in humans are fairly long, and the chromosome shortens significantly with each round of cell division. Telomeres need to be protected from a cell's DNA repair systems because they have single-stranded overhangs, which "look like" damaged DNA. The overhang at the lagging strand end of the chromosome is due to incomplete end replication see figure above. Proteins associated with the telomere ends also help protect them and prevent them from triggering DNA repair pathways.

An introduction to the genetic material of cells

Insulin Insulin Insulin is an essential hormone produced by the pancreas. Its main role is to control glucose levels in our bodies. A person with diabetes being injected with insulin to regulate their blood sugar levels. Insulin is a hormone made by an organ located behind the stomach called the pancreas.

There are specialised areas within the pancreas called islets of Langerhans the term insulin comes from the Latin insula that means island. The islets of Langerhans are made up of different type of cells that make hormones, the commonest ones are the beta cells, which produce insulin.

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Insulin is then released from the pancreas into the bloodstream so that it can reach different parts of the body. Insulin has many effects but mainly it controls how the body uses carbohydrates found in certain types of food.

Glucose is the main energy source used by cells. Insulin allows cells in the muscles, liver and fat adipose tissue to take up this glucose and use it as a source of energy so they can function properly.

Without insulin, cells are unable to use glucose as fuel and they will start malfunctioning. Extra glucose that is not used by the cells will be converted and stored as fat so it can be used to provide energy when glucose levels are too low.

In addition, insulin has several other metabolic effects such as stopping the breakdown of protein and fat. How is insulin controlled?

The main actions that insulin has are to allow glucose to enter cells to be used as energy and to maintain the amount of glucose found in the bloodstream within normal levels.

The release of insulin is tightly regulated in healthy people in order to balance food intake and the metabolic needs of the body. This is a complex process and other hormones found in the gut and pancreas also contribute to this blood glucose regulation.

When we eat food, glucose is absorbed from our gut into the bloodstream, raising blood glucose levels. This rise in blood glucose causes insulin to be released from the pancreas so glucose can move inside the cells and be used.

As glucose moves inside the cells, the amount of glucose in the bloodstream returns to normal and insulin release slows down. Proteins in food and other hormones produced by the gut in response to food also stimulate insulin release.

Hormones released in times of acute stress, such as adrenalinestop the release of insulin, leading to higher blood glucose levels to help cope with the stressful event.

Insulin works in tandem with glucagonanother hormone produced by the pancreas. While insulin's role is to lower blood sugar levels if needed, glucagon's role is to raise blood sugar levels if they fall too low.

Using this system, the body ensures that the blood glucose levels remain within set limits, which allows the body to function properly.

What is insulin?

What happens if I have too much insulin? If a person accidentally injects more insulin than required, e. This leads to abnormally low blood glucose levels called hypoglycaemia. The body reacts to hypoglycaemia by releasing stored glucose from the liver in an attempt to bring the levels back to normal.

Low glucose levels in the blood can make a person feel ill.

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The body mounts an initial 'fight back' response to hypoglycaemia through a specialised set of of nerves called the sympathetic nervous system.

This causes palpitations, sweating, hunger, anxiety, tremor and pale complexion that usually warn the person about the low blood glucose level so this can be treated. However, if the initial blood glucose level is too low or if it is not treated promptly and continues to drop, the brain will be affected too because it depends almost entirely on glucose as a source of energy to function properly.

This can cause dizziness, confusion, fits and even coma in severe cases. Some drugs used for people with type 2 diabetesincluding sulphonylureas e.

DNA replication

The body responds in the same way as if excess insulin has been given by injection. Furthermore, there is a rare tumour called an insulinoma that occurs with an incidence of per million population.Bacteria consist of single are much smaller than animal or plant cells.

These cells have several similarities with cells of (green) plants and animals, but lots of differences, which is why they are put into a kingdom of their own. On the outside of the cell is a cell wall, but it is not usually made of cellulose.

Inside this is a membrane enclosing the cytoplasm. Telomeres as protective "caps" on the tips of eukaryotic chromosomes. How telomerase extends telomeres. An introduction to genetics that takes covers basic components of genetics such as DNA, genes, chromosomes and genetic inheritance.

An introduction to the genetic material of cells

Haploid cells fuse and combine genetic material to create a diploid cell with paired chromosomes. Diploid organisms form haploids by dividing, without replicating their DNA, to create daughter cells that randomly inherit one of each pair of chromosomes.

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