3.6.4.1 Principles of homeostasis and negative feedback ( 3.6 Organisms respond to changes in their internal and external environments )

Question 1

describe homeostasis in mammals

Answer 1

• maintenance of a stable internal environment with restricted limits
• by physiological control systems

Question 2

explain the importance of maintaining stable core temperature

Answer 2

• if temperature too high
  • hydrogen bonds in tertiary structure of enzymes break
  • enzymes denature , active sites change shapes so substrates can’t bind
  • so fewer enzyme substrates complexes
• if temperature is too low :
  • not enough kinetic energy so fewer enzyme substrate complexes

Question 3

explain the importance of maintaining a stable blood pH

Answer 3

• above or below optimal pH , ionic : hydrogen bonds in tertiary structure break
• enzymes denature , active sites change shape and substrates cant bind
• so fewer enzyme substrate complexes

Question 4

Explain the importance of maintaining stable blood glucose concentration

Answer 4

too low :
- not enough glucose for respiration
- so less ATP produced
- active transport can’t happen so cell death

too high :
- water potential of blood decreases
- water lost from tissues to blood via osmosis
- kidneys can’t absorb all glucose - more water lost in urine causing dehydration

Question 5

describe the role of negative feedback in homeostasis

Answer 5

1) receptors detect change from optimum
2) effectors response to counteract change
3) returning levels to optimum / normal

Question 6

explain the importance of conditions being controlled by separate mechanisms involving negative feedback

Answer 6

• departures in different directions from the original state can all be controlled / reversed
• giving a greater degree of control

Question 7

describe positive feedback

Answer 7

1) receptors detect change from normal
2) effectors respond to amplify change
3) producing a greater deviation from normal