3.3.5 A-A* Substance Ex & Digestion

Question 1

Describe the role of brown adipose

Answer 1

Brown adipose serves as a mechanism of heat generation to help babies regulate their body
temperature.

Question 2

Describe the changes from babies to adults

Answer 2

Babies have a very high surface area to volume ratio. As humans grow up, their volume increases much more than the surface area of their skin. This means adults have a smaller surface area to volume ratio.

Question 3

Why does the stomach have a low pH?

Answer 3

Enzyme activity: pepsin has optimal activity at a low pH. This means that it catalyses the break down of proteins best when in acidic conditions. The stomach, therefore, has ideal conditions for breakdown using pepsin.

Killing bacteria: low pH denatures many proteins which are not evolved to function in acidic conditions. The low pH of the stomach is a mechanism to kill any bacteria which are present in the food in order to protect the body from infection.

Question 4

Describe the effect on insulin production

Answer 4

The fast absorption of sugars from juice creates a spike in blood glucose levels. This stimulates the pancreas to secrete more insulin to counteract this effect. Because the rise in sugar levels is faster with fruit juice, more insulin must be produced and more stress is put on the body to carry out homeostasis.

Question 5

What cell type is the site of gas exchange in dicotyledonous plants?

Answer 5

Mesophyll cells