6.4.1 - Principles of homeostasis and negative feedback

Question 1

Define the term homeostasis. (1)

Answer 1

• Maintaining/keeping the internal conditions/environment (relatively) constant

Question 2

One of the systems involved with homeostasis is the endocrine system. Explain how the endocrine system functions to bring about responses in the body. (3)

Answer 2

• The release of hormones from (endocrine) glands
• The transport of hormones in the blood
• The binding of hormones to complementary/specific receptors (on target organs)

Question 3

Homeostatic mechanisms work to regulate body temperature in mammals. Explain why the regulation of body temperature is important. (2)

Answer 3

• At temperatures below this, there is less kinetic energy and reactions take place too slowly / molecules move around more slowly / successful collisions are less frequent / collisions take place with less energy
• At temperatures above this the enzymes denature due to bonds breaking / loss of tertiary structure / alteration of the active site structure

Question 4

Body temperature is regulated by a mechanism known as negative feedback. State how a negative feedback mechanism works. (2)

Answer 4

• Receptors monitor/detect any changes in normal (internal) conditions
• A corrective mechanism acts / the body responds and returns conditions to normal / to within a normal range / reverses the effects of the change

Question 5

Explain how the maintenance of a constant body temperature in humans allows for metabolic reactions within cells to proceed at maximum efficiency. (5)

Answer 5

• The body temperature / 37 °C is the optimum temperature for enzyme activity
• Excess/extreme heat denatures enzymes / excess/extreme heat alters the tertiary structure of enzyme / excess/extreme heat alters the shape of active site
• So the reactions stop / slow down
• Too little heat reduces the kinetic energy of molecules / molecules move more slowly in colder temperatures
• So there are fewer collisions / fewer ES complexes are formed