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Biology - Hormones (AQA Syllabus A)

In GCSE Science, how organisms use nerves and hormones is one subject that is looked at. This is the third of five quizzes on that topic and it looks in particular at hormones, where they are produced, the effects that they have and their possible uses.

Hormones are chemical messengers in the form of protein molecules that are produced in endocrine glands. These enter the bloodstream and can therefore reach every cell in the body. Hormones cause effects to occur in certain cells, but not every cell reacts to every hormone.

In order for a hormone to have effects on cells, those cells must have the right receptor molecules on the surface of their cell membrane. The hormone (protein) molecules will only bind to those cells that have the correct receptor molecules. When this happens, the hormone affects enzymes within the cell, affecting its function.

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Hormones have a widespread and long lasting effect on the body, unlike nerves, whose action is rapid. One of the most important of the endocrine glands is the pituitary gland. This is situated at the base of the brain and has an effect on many other organs, including other glands. As these other glands are stimulated, they in turn can affect other glands. For example, the pituitary gland releases FSH (follicle stimulation hormone) which causes eggs in the ovaries to mature. FSH stimulates the ovaries to start producing higher oestrogen levels. As oestrogen levels increase in the bloodstream, this causes the pituitary gland to stop producing FSH and to produce LH (luteinising hormone) instead. This causes the egg to be released into the uterus.

There are many more examples of organs and glands working together like this, creating feedback to control how your body works.

Hormones can now be produced artificially. Insulin, for example, used to come only from the pancreas of animals but is now made on a grand scale by genetically engineered bacteria. There are also uses for hormones outside of the body - in garden nurseries for example, where they are used to stimulate root growth, or on farms where their ability to delay fruit from ripening can extend the shelf life of a crop.

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  1. Which of the following glands is found in the brain?
    This gland is extremely important and forms the link between the nervous system and the endocrine (hormone) system
  2. In the Nineteenth Century, pineapples were really rare and expensive. Why are exotic fruits much more widely available nowadays?
    This means that they will not ripen until they are in the shops wheras in the past, the fruits ripened on the journey and most of them were too ripe to sell when they reached the shops. Exotic fruits are usually grown a long way from Britain and face a long journey to get here
  3. Which hormone is likely to be used in fertility treatments?
    FSH stimulates the egg cells to mature which can then be used for IVF
  4. How are hormones transported round the body?
    Glands secrete hormones into the bloodstream
  5. What are hormones?
    Hormones control many aspects of your body. They regulate the amount of water in your blood and your blood sugar for example. They also have a huge role in puberty and fertility
  6. Which hormone is used to treat diabetes?
    Most insulin is now made from genetically engineered bacteria
  7. Where is oestrogen produced?
    Oestrogen is the hormone responsible for the regulation and development of the female reproductive system and secondary sexual characteristics. In books and articles from the USA, you will see it spelt 'Estrogen' - it is the same hormone, just spelt differently
  8. The first birth-control pills contained higher amounts of oestrogen than the pills taken today. Modern birth-control pills contain much less oestrogen. Some only contain progesterone. Why has this changed?
    The original high oestrogen pills caused significant side effects in women, such as changes in weight, mood and blood pressure
  9. Which of the following uses hormones?
    Hormones in selective weedkillers make the weeds grow too fast so that they collapse and die
  10. Why would a gardener use rooting powder?
    Not all cuttings will succeed. Rooting powders (and liquids) contain hormones that stimulate root growth so dipping a cutting into rooting compounds increases the chances of success

Author: Kev Woodward

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