Hormones and the regulation of blood glucose concentration

What are the features of hormones?

produced in glands - secrete hormone directly into the blood

carried in the blood plasma to the target cells - have specific receptors on their cell-surface membrane that are complementary to a specific hormone

effective in low concentration but have widespread and long-lasting effects

What is the second messenger model?

adrenaline binds to a transmembrane proteins receptor within the cell-surface membrane of a liver cell

binding of adrenaline causes the protein to change shape

protein changing shape activates adenyl cyclase - converts ATP to cyclic AMP

cAMP acts as as second messenger that binds to kinase, changing its shape and activating it

activated kinase catalyses the conversion of glycogen to glucose

How does the glucose move into the blood?

moves out of the liver cell by facilitation diffusion and into the blood through channel proteins

The pancreas is made up of groups of hormone-producing cells which are known as what?

islets of Langerhans

What are the cells of the islets of Langerhand?

Alpha cells - larger cells that produce glucAgon

beta cells - smaller and produce insulin

What 3 processes that regulate blood sugar take place in the liver?

glycogenesis

glycogenolysis

gluconeogensis

What is glycogenesis?

glucose → glycogen

(when blood glucose is higher than normal)

What is glycogenolysis?

glycogen → glucose

(when blood glucose concentration is lower)

What is gluconeogensis?

the production of glucose from sources other than carbohydrates (e.g glycerol and amino acids)

(when glycogen supply is exhausted)

Why is regulating blood glucose concentration important?

glucose is a substrate for respiration - source of energy

if too low, cells will be deprived of energy and die

if too high, lowers the water potential of the blood which can lead to dehydration

Blood glucose comes from where?

diet

hydrolysis in the small intestine of glycogen (glycogenolysis)

gluconeogenesis

What happens when blood glucose concentration rises above normal?

receptors on b cells detect increase and secrete insulin directly into the blood plasma

What are found on almost all body cells, except red blood cells?

glycoprotein receptors on their cell-surface membranes that bind specifically with insulin molecules

Blood glucose concentration is lowered in what ways?

increased cellular respiration

ACTIVATION OF ENZYMES THAT CAUSE THE:

conversion of glucose to glycogen

conversion of glucose to fat

absorption of glucose into cells

How is a fall in blood glucose concentration detected?

by the alpha cells of the islets of Langerhans - which secretes glucagon directly into the blood plasma

How does glucagon increase blood glucose concentration?

attaching to specific protein receptors on the cell-surface membrane of liver cells

activating enzymes that convert glycogen to glucose

activating enzymes involved in to the conversion of amino acids and glycerol into glucose (gluconeogenesis)

How does adrenaline increase blood glucose concentration?

attaching to protein receptors on the cell-surface membrane of target cells

activating enzymes that cause the breakdown of glycogen to glucose in the liver

What is a summary of the regulation of blood glucose concentration?

Why is there high glucose concentration in the urine of those with diabetes?

high glucose concentration in the blood/ filtrate

so not all glucose is reabsorbed at the proximal convoluted tubule

as all the carrier proteins are saturate / working at the maximum rate

What role does glucagon play in gluconeogenesis?

Attaches to receptors on target cells and activates/stimulates enzymes

so glycerol/amino acids are converted to glucose