Homeostatsis Flashcards
Define homeostasis
maintaining a constant internal environment within restricted limits
Explain the importance of maintaining a body temperature close to normal in relation to enzyme activity
If body temperature is too high;
- hydrogen bonds break within enzymes, changes their tertiary structure and the shape of the active site. Less enzyme-substrate complexes form
If body temperature is too low;
- Enzymes have too low kinetic energy, less enzyme-substrate complexes, so metabolic rate is reduced
Explain the importance of maintaining blood pH close to normal in relation to enzyme activity
If blood pH is too high;
- hydrogen bonds break within proteins, changing their tertiary structure
If blood pH is too low;
- Hydrogen bonds break within proteins, changing their tertiary structure
Explain the importance of maintaining blood glucose close to normal in relation to water potential of blood and availability of glucose for respiration
If blood glucose is too high;
- Blood has a lower water potential than cells, water leaves cells into blood by osmosis. Cells lack water for metabolic reactions such as hydrolysis and as a solvent
If blood glucose is too low;
- Glucose is not provided to cells fast enough for a high enough rate of respiration
Define negative feedback and give an example in biology
Negative feedback reverses the direction of change back to its original level
e.g. When body temperature is above 37 degrees C, the body responds to decrease it back to original
In negative feedback, why is it important to have separate mechanisms for increasing and decreasing the factor?
Separate mechanisms are used to increase and decrease the factor, as this gives a greater degree of control
What are hormones? Where are they secreted from? How do they travel in the body? Where do they act? How long does their effect last?
- Hormones are chemical messengers, secreted by glands which are transported by the blood stream
- They only act at target cells which have complementary receptors
- Their effect is widespread and long lasting
In which cells are insulin and glucagon produced?
- Insulin is produced in Beta cells in Islets of Langerhans
- Glucagon is produced in alpha cells in Islets of Langerhans
Define positive feedback and give an example in biology
Positive feedback is where the change in one direction is amplified i.e. an increase leads to a further increase
e.g. VG Na+ channels open which causes depolarisation which causes more VG Na+ channels to open
Explain the importance of maintaining blood water potential close to normal in relation to blood pressure and metabolic reactions
If blood water potential is too high;
- Water enters cells by osmosis. Too much can cause cell lysis. Lots of water in blood causes high blood pressure
If blood water potential is too low;
- water leaves cells by osmosis. Cells lack water for metabolic reactions like hydrolysis and as a solvent
Explain how insulin lowers blood glucose when it binds a receptor
- Inserting more glucose channel proteins into the cell membrane so more glucose enters cell by facilitated diffusion
- Activating enzymes to convert glucose to glycogen for storage (glycogenesis)
What are the target cells for insulin?
Liver and muscle cells
Explain how glucagon increases blood glucose when it binds to receptor?
- Activating enzymes to hydrolyse glycogen to glucose (glycogenolysis)
- Activating enzymes to convert glycerol/amino acids to glucose (gluconeogenesis)
What are the target cells for glucagon?
Liver cells
How does adrenaline increase blood glucose?
- Adrenaline is released from adrenal gland
- It binds receptors on liver cells
- Enzymes are activated which hydrolyse glycogen to glucose (glycogenolysis)