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Homeostasis
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Living Environment Regents January 2008 Question 12 |
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Tuesday, 21 April 2009 10:36 |
Option 2 – The gene insulin has a different sequence of molecular bases than the gene for testosterone.
Insulin is produced exclusively by pancreatic beta cells. This endocrine hormone has a compact three-dimensional structure consisting of three short helices and three invariant disulfide bridges. Its quaternary conformation can adopt a therapeutically-significant "R" or "T" state. A single molecule of insulin acts as a bivalent ligand to the insulin receptor, by way of two binding surfaces. Circulating, and biologically active, insulin is monomeric. It is composed of two polypeptide chains: chain A has 21 amino acids and chain B has 30 amino acids (in humans).
Testosterone is a steroid hormone from the androgen group. Testosterone is secreted in the testes of men and the ovaries of women. It is the principal male sex hormone. In both males and females, it plays key roles in health and well-being. Testosterone is derived from cholesterol just like other steroid hormones. The largest amounts of testosterone are produced by the testes in men, but it is also synthesized in smaller quantities in women by the theca cells of the ovaries, by the placenta.
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Living Environment Regents January 2008 Question 22 |
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Tuesday, 21 April 2009 11:17 |
Option 4 – Boiling deactivates the enzyme responsible for converting sugar to starch.
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Last Updated on Tuesday, 21 April 2009 11:24 |
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Living Environment Regents January 2008 Question 43 |
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Wednesday, 22 April 2009 05:41 |
- Increased insulin results in a decrease in blood sugar levels.
- As the CO2 level in the blood increases, the breathing rate increases.
- When the guard cells close openings in leaves, the rate of water loss decreases.
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Living Environment Regents January 2008 Question 46 |
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Wednesday, 22 April 2009 05:51 |
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Option 3 – Eat salty foods
Water, Chocolate or Canberry juice cannot increase the level of sodium in blood. Sodium is present in salt and eating salty foods is the best way to reduce symptoms of hyponatremia.
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Living Environment Regents January 2008 Question 47 |
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Wednesday, 22 April 2009 05:54 |
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- Reduces loss of sodium
- Cools the body
- Decreases perspiration
- Decreases water loss
- Reduces the chances of hyponatremia
Homeostasis is the mechanism of the body to handle change and water poured on the body by runners helps them to cool down the body and reduce loss of water from the body helping the runner to reasonably maintain the balance of water in the body.
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Living Environment Regents January 2008 Question 48 |
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Wednesday, 22 April 2009 05:57 |
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• Less urine would be produced because a large amount of water is being lost as sweat.
• Less urine will be produced because the feedback mechanisms in the kidneys regulate water in the blood.
• The runner would sweat more, decreasing water levels in the blood. This decrease would slow urine production because there is less water in the blood to be filtered.
• Urine would be more concentrated because it would contain less water.
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Living Environment Regents January 2008 Question 49 |
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Wednesday, 22 April 2009 06:06 |
- It could raise their blood pressure.
- It could cause them to retain water.
- It could decrease urine production.
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Living Environment Regents January 2008 Question 56 |
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Wednesday, 22 April 2009 07:17 |
 
The substance in a vaccine that makes the vaccine effective is a weakened virus.
The white blood cells produce antibodies in response to the vaccine.
Antibodies have specific shapes and each antibody shape is complementary to one shape of the virus.
Vaccine can be made for any disease caused by a specific virus. But, common cold is caused by many different types of viruses. Hence, the vaccine for common cold would have to contain all the viruses causing this.
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Last Updated on Wednesday, 22 April 2009 07:25 |
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Living Environment Regents January 2008 Question 58 |
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Wednesday, 22 April 2009 07:25 |
As the number of decomposers increases, they use more oxygen for respiration.
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Living Environment Regents January 2008 Question 71 |
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Wednesday, 22 April 2009 08:21 |
- heart: increased blood flow supplies more oxygen and/or nutrients
- skeletal muscle: greatly increased supply of blood, providing additional oxygen and/ornutrients
- skeletal muscle: removes more waste during exercise
- digestive organs: a reduction in blood flow, diverting blood to other parts of the body
- where use of oxygen has increased
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Last Updated on Monday, 30 November 2009 15:54 |
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