Hormonal Communication

Question 1

Describe how negative feedback is able to control the blood glucose concentration

Answer 1

• Beta cells detect the increased blood glucose concentration.
• Beta cells release insulin
• This causes an increased uptake of glucose by liver cells. (glycogenes)
• Alpha cells detect a decreased blood glucose concentration.
• Alpha cells release glucagon
• Glycogen is converted to glucose (gluconeogenesis)
• Glucose leaves liver cells by facilitated diffusion and enters the bloodstream

Question 2

Describe the role of ATP

Answer 2

• Releases energy in suitable quantities.
• Energy is released for metabolism
• ADP can attach to a phosphate during photosynthesis

Question 3

Describe how a pregnancy test works

Answer 3

• hCG molecules are carried up a test in urine
• hCG molecules bind to mobile antibodies to form a hCG/antibody complex
• hCG/mobile antibody complex bind to immobilised antibodies to form a coloured line if a woman is pregnant.
• Excess mobile antibodies bind to immobilised antibodies to form a coloured line whether a woman is pregnant or not.

Question 4

Describe the depolarisation of beta cells

Answer 4

• When blood glucose levels are high, more glucose enters the beta cells by facilitated diffusion.
• More glucose in a beta cell causes the rate of respiration to increase, making more ATP.
• The rise in ATP triggers the potassium ion channels in the beta cell plasma membrane to close.
• This means that Potassium ions can’t get through the membrane, so they build up inside the cell.
• This makes the inside of the beta cell less negative because there are more positively charged potassium ions inside the cell. This causes the plasma membrane of the beta cell to become depolarised.
• Depolarisation triggers calcium ion channels to open, so calcium ions diffuse inside the beta cell.
• This causes the vesicles to fuse with the beta cell plasma membrane, releasing insulin via exocytosis.