Chemical control in mammalsEdexcel A-Level Biology B: Subtopic test

1. 1
   The adrenal glands, the thyroid gland and the pancreas are endocrine glands. A hormone released from an adrenal gland is carried in the blood to every tissue in the body, but only some tissues respond to it.

   (a)

   Which statement describes an endocrine gland?

   [1 mark]

   • AIt secretes enzymes through a duct into the gut
   • BIt secretes substances through a duct onto the body surface
   • CIt detects changes in the environment and sends nerve impulses
   • DIt has no duct and secretes hormones directly into the blood

   (b)

   Why do only target cells respond to a particular hormone?

   [1 mark]

   • AThe hormone is only carried to the target cells
   • BTarget cells have receptors with a shape complementary to the hormone
   • COnly target cells have DNA
   • DThe hormone is destroyed in all non-target cells

   (c)

   Explain why adrenaline causes a response in liver cells but not in every cell it reaches.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Adrenaline is secreted by the adrenal glands during a stress response. In a liver cell, adrenaline binds to a receptor on the cell surface membrane. This activates an enzyme, adenylyl cyclase, which converts ATP to cyclic AMP (cAMP). The cAMP then activates other enzymes in the cell, which break down glycogen to glucose.

   (a)

   What is the role of cAMP in this response?

   [1 mark]

   • AIt is a second messenger that activates enzymes inside the cell
   • BIt is the first messenger that is carried in the blood
   • CIt is the receptor on the surface membrane
   • DIt is the substrate that is broken down to glucose

   (b)

   Why does adrenaline bind to a receptor on the cell surface membrane instead of entering the cell?

   [1 mark]

   • AIt is lipid-soluble and is blocked by the membrane proteins
   • BIt is too large to be carried in the blood
   • CIt cannot pass through the phospholipid bilayer because it is not lipid-soluble
   • DIt is broken down as soon as it reaches the liver

   (c)

   Explain how the use of a second messenger allows a small amount of adrenaline to cause a large response.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Oestrogen is a steroid hormone secreted by the ovaries. It is lipid-soluble. It stimulates cells in the lining of the uterus to grow and to produce new proteins.

   (a)

   Describe how oestrogen causes a target cell to produce a new protein.

   [3 marks]

   (b)

   Compare the way that oestrogen and adrenaline act on target cells.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Researchers studied two types of target cell. Liver cells respond to adrenaline within seconds, but cells of the uterus lining respond to oestrogen only after several hours. When the production of cAMP was blocked in each cell type, the liver cells no longer responded to adrenaline, but the uterus cells still responded to oestrogen.

   (a)

   Explain the results of this investigation.

   [6 marks]

   (b)

   Describe the principles of mammalian hormone production by an endocrine gland and explain how the effects of a hormone are limited to its target cells.

   [6 marks]

   Total for question 4: 12 marks

End of questions