6.4.2 control of blood glucose concentration

factors that influence blood glucose concentration (2)

consumption of carbohydrates - glucose absorbed by blood

rate of respiration of glucose - increases during exercise due to muscle contraction

glycogenesis

converts glucose to glycogen

glycogenolysis

converts glycogen to glucose

gluconeogenesis

converts amino acids and/or glycerol to glucose

what cells detect if blood glucose concentration is too high

beta cells in islets of Langerhans in pancreas

what happens if blood glucose concentration is too high

insulin is secreted

explain the action of insulin in decreasing blood glucose concentration

attaches to specific receptors on cell surface membrane of target cells

1. this causes more glucose channel proteins to join cell surface membrane

• increasing permeability to glucose

• more glucose can enter cell by facilitated diffusion

2. this activates enzymes involved in conversion of glucose to glycogen

• lowering glucose concentration of cells creating a concentration gradient

• so glucose enters cells by facilitated diffusion

what cells detect if blood glucose conc. is too low

alpha cells in islets of Langerhans in pancreas

what happens if blood glucose conc. is too low

glucagon is secreted

explain the action of glucagon in increasing blood glucose concentration

attaches to specific receptors on cell surface membranes of target cells

1. activates enzymes involved in hydrolysis of glycogen to glucose

2. activates enzymes involved in conversion of glycerol/amino acids to glucose

this establishes a concentration gradient - glucose enters blood by facilitated diffusion

what do adrenal galnds do in fear/stress/excercise

secrete adrenaline

explain the role of adrenaline in increasing blood glucose concentration

attaches to specific receptors on cell surface membrane of target cells

activates enzymes involved in hydrolysis of glycogen to glucose

this establishes a concentration gradient - glucose enters blood by facilitated diffusion

describe the second messenger model of adrenaline and glucagon action

adrenaline/glucagon attach to specific receptors on cell membrane which

1. activates enzyme adenylate cyclase

2. which converts ATP to many cyclic AMP

3. cAMP acts as a second messenger - activates protein kinase enzymes

4. protein kinases activate enzymes to break down glycogen to glucose

suggest an advantage of the second messenger model

amplifies signal from hormone

as each hormone can stimulate production of many molecules of second messenger (cAMP)

which can in turn activate many enzymes for rapid increase in glucose

compare the causes of type 1 and 2 diabetes

higher and uncontrolled blood glucose concentration - higher peaks after meals and remains high

type 1 diabetes

beta cells in islets of Langerhans in pancreas produce insufficient insulin

normally develops in childhood due to an autoimmune response destroying beta cells of islets of langerhans

type 2 diabetes

receptor loses responsiveness to insulin

so fewer glucose transport proteins - less uptake of glucose - less conversion of glucose to glycogen

risk factor - obesity

describe how type 1 diabetes can be controlled

injections of insulin

blood glucose concentration monitored with biosensors - dose of insulin matched to glucose intake

eat regularly and control carbohydrate intake to avoid sudden rise in glucose

why can’t insulin be taken as a tablet by mouth

insulin is a protein

would be hydrolysed by endopeptidases/exopeptidases

describe how type 2 diabetes can be controlled

may use drugs which target insulin receptors to increase sensitivity to increase glucose uptake by cells

reduce sugar intake - less absorbed

reduce fat intake - less glycerol converted to glucose

more exercise - uses glucose by increasing respiration

lose weight - increased sensitivity of receptors to insulin

what are health advisers aims when it comes to type 2 diabetes

reduce risk of type 2 diabetes due to health problems

so need to reduce obesity as it is a risk factor

what are food advisors aims when it comes to type 2 diabetes

maximise profit