6.4.1

Question 1

What is homeostasis

Answer 1

Internal environment is maintained within set limits around an optimum

Question 2

Why is it important that core temperature remains stable?

Answer 2

-Maintains stable rate of enzyme-controlled reactions and prevent damage to membranes.
-Temperature too low = enzyme and substrate molecules have insufficient kinetic energy
-Temperature too high = enzymes denature

Question 3

Why is it important that blood pH remains stable

Answer 3

Maintain stable rate of enzyme-controlled reactions (& optimum conditions for other proteins)
Acidic pH = H+ ions interact with H-bonds and ionic bonds in tertiary structure of enzymes so shape of active site changes so no ES complexes form

Question 4

Why is it important that blood glucose concentration remains stable

Answer 4

-maintain constant blood water potential: prevent osmotic lysis/ crenation of cells
-Maintain constant concentration of respiratory substrate: organism maintains constant level of activity regardless of environmental conditions

Question 5

Define negative and positive feedback

Answer 5

Negative feedback: self-regulatory mechanisms return internal environment to optimum when there is a fluctuation

Positive feedback: a fluctuation triggers changes that result in an even greater deviation from the normal level

Question 6

Outline the general stages involved in negative feedback

Answer 6

Receptors detect deviation -> coordinator -> corrective mechanism by effector -> receptors detect that conditions have returned to normal

Question 7

Suggest why separate negative feedback mechanisms control fluctuations in different directions

Answer 7

Provides more control, especially in case of ‘overcorrection’ which would lead to a deviation in the opposite direction from the original one

Question 8

Suggest why coordinators analyse inputs from several receptors before sending an impulse to effectors

Answer 8

-receptors may send conflicting information
-optimum response may require multiple types of effector

Question 10

Why is there a time lag between hormone production and response by an effector?

Answer 10

It takes time to:
-produce hormone
-transport hormone in the blood
-cause required change to the target protein