What is Homeostasis?

Homeostasis is involved in keeping the body's internal environment constant (like the thermostat of a central heating system). Homeostasis keeps the body's temperature at a certain level (36.5oC) and it keeps the pH of the body at a certain level so that enzymes don't denature. Blood glucose is kept constant, CO2 levels and O2 levels are monitored to ensure that enough oxygen and not too much carbon dioxide are in the blood. The overall concentration and volume of blood is also monitored homeostatically. The term Homeostasis was first used by Cannon in the late 1920s. Homeostasis is very important to animals because it allows them to rely on the external environment. A constant internal environment allows a considerable degree of independence and allows animals to live in areas from the arctic to the tropics. Many of the mechanisms involved rely on negative feedback. A movement from the set level (e.g. a rise or fall in body temperature) is detected by receptors. These receptors then send information to the control centre in the brain which reacts by returning to the original value. For example, the temperature control mechanism. Humans maintain body temperature within 1oC of 36.5. If the temperature rises too high, the resulting increase in blood temperature is detected by receptors in the hypothalamus in the brain. The heat loss centre also in the hypothalamus sends

  • Word count: 1604
  • Level: AS and A Level
  • Subject: Science
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What do You Understand by Recombinant DNA Technology?

What do You Understand by Recombinant DNA Technology? Discuss the Moral, Ethical, Social, Economic and Environmental Issues Associated with the Technology, giving your views. There are two essential substances found inside bacterial cells required before the process can begin. Present in the cytoplasm of a bacterial cell are a number of small circular pieces of DNA known as plasmids. Also present within the bacterial cell are restriction enzymes which cut DNA molecules at specific sites. By selecting the correct restriction enzyme, DNA molecules from different organisms can be cut at predictable sites to extract specific genes from lengths of DNAi. The first task in the process is to isolate the required gene. This can be done in three different ways; working backwards from the protein, using messenger RNA, or using DNA probes. Once the gene has been isolated, the next step is to cut the gene from its DNA chain. This is done using the restriction enzymes (restriction endonucleases). Now we have the required gene the next stage is to insert it into a vector which will be used to produce the required protein. This is where the plasmids described earlier come in (this could also be done using a virus as a vector). The plasmid is cut using the same restriction enzyme as was used to cut the gene out. In a process called ligation (controlled by the ligase enzyme) the ends of the

  • Word count: 1708
  • Level: AS and A Level
  • Subject: Science
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Why does the colour leak out of cooked beetroot?

Why does the colour leak out of cooked beetroot? Aim: To investigate the effect of temperature on membrane structure Introduction: I will be measuring the amount of light absorbed by the pigment in the beetroot, which will tell me how much dye has been released from the beetroot. My null hypothesis (H?) is: no matter what the temperature increase, the amount of dye being released from the beetroot will remain the same. My alternate hypothesis (H1) is: an increase in temperature will cause an increase in the amount of dye being released from the beetroot. Beetroot cells, like any other cells with membranes, have many types of cells with special functions. Some of these organelles are bounded by a single membrane, eg. vacuole, and some are bounded by two membranes e.g. nucleus, mitochondrion. Beetroot appears as a dark red/ purple colour and this is caused by the betalain pigment, which is contained within the vacuole of the beetroot cells. In order for the betalain to leave the cell it needs to pass through two different membranes; the membrane bounding the vacuole and the membrane enclosing the cell. An increase in temperature will damage and denature the membranes and cause the betalain to leak out. Variables: My independent variable is the temperature at which I am heating the beetroot, whilst my dependant variable is the amount of light absorbed by the pigment. I

  • Word count: 1921
  • Level: AS and A Level
  • Subject: Science
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