Biology B4

1. What is the definition of Homeostasis?

2. Name 4 things that Homeostasis applies to....

3. Name what the receptor, processing centre, and effector do and give an example....

4. What is negative feedback?

5. What are antagonistic effectors and what are advantages of antagonistic pairs??

Homeostasis is the body's method of keeping conditions in your body constant. e.g correct levels of salt and water

Any 4 of 5 : Constant body temperature, Correct levels of water and salt, Amounts of Nutrients e.g glucose, Enough Oxygen for respiration, Getting rid of toxic waste e.g urea and CO2.

Receptor- detects stimuli (change in environment) Processing centre- receives information from receptors and send siganls to effectors Effectors- act on information received from processing centre and produce a response e.g Receptor (Incubator sensor senses fall in temperature) Processing Centre (Thermostat receives information from Senser and sends signals to heater) Effector (heater switches on)

Negative Feedback is a type of control that acts in opposite ways to the situation it is in e.g temperature fall- heater switched on temperature gain- heater off

Antagonistic Effectors are things that work in pairs producing opposite effects e.g brake and accelerator. They work well because a control system with antagonistic pairs is more sensitive than a system with only one effector.

6. What are enzymes?

7. What are they made up of?

8. How do enzymes work?

9. How does the active site work and what model is used to explain it?

10. Why do we need enzymes?

6. Enzymes are catalysts that speed up chemical reactions.

7. They are made up of long chains of amino acids.

8. Some enzymes break down large molecules into smaller ones and others join small molecules together,

9. The active site is where the reactions take place. Only the correct molecule can fit into the active site and scientists explain it as a lock and key model. After the reaction the enzyme can be used again for further reactions,

10. We need ezymes because with our body temperature at 37 degrees chemical reactions would happen too slowly to keep you alive. Enzymes increase reaction speed by 1000s!

11. What happens if your body temperature becomes too high?

12. Why does increasing temperature speed up reactions?

13. How does temperature affect enzymes and what is denaturing and the optimum temperature?

14. What else can affect enzymes and how?

15. What does amylase do?

11. If your body temperature becomes too high your cells are damaged and eventually you die. You would also need a lot more food to fuel respiration.

12. Increasing temperature speeds up chemical reactions because the rate at which molecules are travelling increases. They have more energy and collide more often with easier reactions.

13. Above a certain point temp. the reaction stops. Enzymes are proteins therefore temp. can change the shape of them if they get too warm. This means reactions can stop in the active site. This is called denaturing. If the temp. is too low in an ezyme reactions slow down and occur less producing less of a result. The optimum temperature is the temp. at which an ezyme works most efficiently without being too hot to denature. Optimum temp in humans is around 37 degrees.

14. pH can also affect the active site of an enzyme. Enzymes also have an optimum pH value at which they work best.

15. Amylase is an ezymes that changes starch to maltose(sugar). Amylase is found in our saliva.

16. What two things must be balanced to keep body temperature constant?

17. What is the hypothalamus and what does it control?

18. Name the two main ways of cooling down and warming up.

19. What scientific terms are they given?

20. How do these two body processes controlling body temperature work?

16. Body heat loss and Body heat gained must be balanced to ensure your temperature stays constant.

17. The hypothalamus is the processing centre in the brain and controls sleep, water, balance, body temperature, appeitite, and other functions.

18. The two main ways of cooling down and warming up are sweating and shivering.

19.Sweating is produced by vasodilation and Shivering if produced by vasoconstriction.

20. Vasodilation is when the blood vessels near the surface of the skin dilate and the blood is travels closer to the skin therefore more heat being lost to the environment. Vasoconstriction is when the blood vessels constrict and get smaller so less blood flows near the skin and less energy is lost to the environment.

21. Desribe the process of Diffusion....

22. What type of process is it and what dos that mean?

23. Why do we need diffusion in our body?

24. What are partially permeable membranes?

25. Name 3 chemicals that move in and out of cells by diffusion....

21. The process of Diffusion the movement of molecules from a high concentration to a low concentration e.g tea bag in hot water. Eventually there is an equal amount of molecules overall.

22. Diffusion is a passive process which means it requires no energy.

23. We need diffusion in our bodies because our cells need raw materials for chemical reactions so waste products must be removed from the cells. Molecules move in and out.

24. Partially permeable membranes let some molecules through but not others. e.g some membranes let water through but not glucose.

25. 3 chemicals that move in and out of cells by diffusion are Carbon Dioxide, Oxygen and Glucose during respiration.

26. Describe Osmosis....

27. Does Osmosis use energy?

28. If the molecules cannot be transported which process do cells sometimes use and how does this process work?

29. Where does the energy come from that is used in active transport?

30. Name one chemical that is transported by active transport?

26. Osmosis is the process where many water molecules move away from an area of high concentration of water molecules. Almost diffusion of water. Flow across a partially permeable membrane.

27. Osmosis is a passive process. No energy required.

28. If the molecules cannot be transported through diffusion the process cells use to move molecules (in higher concentration outside the cell) is active transport. This

29. The energy used in active transport is gained from respiration.

30. A chemical that is transported by active transport is glucose.

31. Why do freshwater animals have problems with water concentration in their cells unlike seawater animals?

32. What do land animals have problems with when it comes to maintaining levels of water?

33. What would happen if red blood cells were placed in freshwater?

34. What do some single celled organisms have that helps with water balance?

35. What organ helps with controlling water balance?

31. Freshwater animals have problems with water concentration in their cells unlike seawater animals because the concentration of dissolved chemicals in their body is much higher in freshwater than in seawater animals. Water constantly enters the body by osmosis and these animals have to constantly pump water out of their body.In sea animals the balance of water entering and water leaving is at the same rate.

32. Land animals have problems with when it comes to maintaining levels of water but it is the opposite problem to water animals. They lose too much water through excretion and respiration and other life proccesses so they have to find ways of replacing the water lost otherwise their cells do not work properly.

33. If red blood cells were placed in freshwater they would burst.

34. Some single celled organisms have a contractile vacuole that helps with water balance by bursting over and over to get rid of water. Otherwise the cell would swell and burst.

35. The kidney helps with controlling water balance.

36. What two processes do your kidneys primarily control and how do they do this?

37. What is Urea made from?

38. How do Kidneys work?

39. Why are some chemicals reabsorbed and which ones?

40.What do kidney's do when you are hydrated or dehydrated?

36. Two processes that your kidneys primarily control are excretion and water balance (water homeostasis).

37.Urea is made from amino acids that have been broken down by the Liver.

38. Kidneys work by acting as sieves. Small molecules are filtered out of the blood as it passes through your kidneys. These are water, sugar(glucose) and urea and ions of salt. Blood cells and proteins are too big so they stay in the blood.

39.The chemicals that are reabsorbed are all of the sugar (glucose), as much salt as the body needs, and as much water as it needs. The rest of the filtered chemicals go to your bladder and make up urine.

40.When you are well hydrated the kidneys produce large volumes of dilute urine in order to get rid of some of the water and when you are de-hydrated you produce small volumes of concentrated urine as you are losing water through sweating etc.

41. List a few ways the salt concentration in your blood can increase....

42. How do Caffeine and Alcohol and Ecstasy affect your water balance?

43. What is water balance/salt concentration change detected by and what control system is this part of?

44. Where is ADH released from and what does this hormone do?

45. How do Drugs, Caffeine and Alcohol affect ADH?

41. The salt concentration in your blood can increase due to excess sweating, de-hydration, and too much salt intake.

42. Caffeine in tea causes a large volume of dilute urine to be produced. Alcohol has the same effect but even more so. Ecstasy has the opposite effect by reducing the volume of urine a person makes. Overheating causes more water to be drunk and therefore makes the brain swell with too much water.

43. Our water balance/salt concentration change is detected by the hypothalamus in our brains. The hypothalamus is the processing centre and this is part of a negative feedback control system.

44. The hormone ADH is released when the hypothalamus detects the salt concentration is too high.ADH is released from the pituitary gland also in the brain. It travels in the blood to the kidney tubules which are the effectors and affects the amount of water that can be reabsorbed. ADH is not released when the salt levels are low.

45. Drugs, Caffeine and Alcohol also affect ADH again by affecting the amount of urine produced. e.g Alcohol suppresses ADH production and so less water is reabsorbed and more urine is made.