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Biology - Hormones (AQA)
In the Nineteenth Century, pineapples were really rare and expensive. Today, thanks to hormones which delay ripening, they are much cheaper and more common.

Biology - Hormones (AQA)

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.

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.

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?
Because progesterone reduces the side effects
Because progesterone is much more effective
Because progesterone is a lot cheaper
Because progesterone is easier to swallow
The original high oestrogen pills caused significant side effects in women, such as changes in weight, mood and blood pressure
Which of the following uses hormones?
Selective weedkiller
Rooting powder
Neither of the above
Both of the above
Hormones in selective weedkillers make the weeds grow too fast so that they collapse and die
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
Which hormone is used to treat diabetes?
Most insulin is now made from genetically engineered bacteria
Which hormone is likely to be used in fertility treatments?
FSH stimulates the egg cells to mature which can then be used for IVF
In the Nineteenth Century, pineapples were really rare and expensive. Why are exotic fruits much more widely available nowadays?
Because more different fruits grow
Because fruit growers use hormones to make their exotic fruits grow bigger and faster
Because feeding the fruit trees with growth hormone makes them produce a lot more fruit
Because the exotic fruits are sprayed with hormones that delay ripening
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
How are hormones transported round the body?
Via the nervous system
Via the lymphatic system
Via the circulatory system
Via the respiratory system
Glands secrete hormones into the bloodstream
Where is oestrogen produced?
In the ears
In the adrenal glands
In the large intestine
In the ovaries
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
What are hormones?
Proteins secreted by endocrine glands
Proteins secreted by the main organs of the body
Proteins that carry information betweeen nerve cells
Proteins that carry messages from your brain to your muscles
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
Why would a gardener use rooting powder?
It is cheaper than buying compost
They can produce many plants from cuttings more easily
It gives vegetables a bigger root system
It slows down the growth rate of plants
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
You can find more about this topic by visiting BBC Bitesize - Hormones in human reproduction - AQA

Author:  Kev Woodward

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