Control of blood glucose conc Flashcards
How is glucose used and the importance of it
Small molecule, easily moves put of the blood capillaries into tissue fluid
Enters cells by fac diff using glucose transport proteins
In healthy people, conc of glucose in blood is maintained at around 900mg/dm3
Many cells need constant supply of glucose as respiratory substance
Importance of blood glucose conc
Brain cells are very sensitive to any change in blood glucose levels
Hypoglycaemia, below 600mg, brain cells do not get enough glucose for respiration
Hyperglycaemia, affect water potential, water will move out of the body cells by osmosis
How can the glucose conc be increased
Digestion of carbohydrate rich food into monosaccharides
Glycogenolysis
Gluconeogenesis
How can the glucose conc be decreased
Uptake by cells as main respiratory substrate
Conversion of glycogen for storage, liver and muscle
Converted to fat for storage
Insulin and glucagon
Produced by the Islet of Langherhans
Insulin released by beta cells
Glucagon released by alpha cells
Role and structure of insulin
Globular protein made up of 51 AA
Beta cells detect rise in blood glucose conc and secrete insulin
Exert its effect by binding to glycoprotein receptors in the cell surface membranes of target cells
Almost all body cells except RBC have insulin receptors
How does insulin reduce blood glucose concs
Glucose transport protein channels change shape and open, allow more glucose into cells
Insulin causes more glucose transport proteins to move into membrane from vesicles in cytoplasm
Effects of insulin on rates
Increases rate of absorption of glucose by respiring cells
Increases rate at which glucose is used in respiration especially in muscle cells
Increases rate of conversion of glucose to fat in adipose tissue
Increases rate at which glucose is converted by glycogenesis into the liver and muscles
Glycogenesis also increases uptake of glucose from blood as the conc of glucose in the cells decreases, steeper conc grad formed
If blood glucose falls
Detected by beta cells, stop secreting insulin
Detected by alpha cells, start secreting glucagon
Glucagon arrives at liver cells
Binds with cell surface glycoprotein receptor
Effects of glucagon
Activates enzymes which causes glycogenolysis
Speeds up rate of gluconeogenesis
Reduces rate of respiration
Characteristic of T1D
Body is unable to produce insulin
Normally begins in childhood, adults can develop it
May be the result of an autoimmune response, immune system attacks beta cells of the Islet of Langherhans
Develops quickly, usually over a few weeks, symptoms can be severe
Characteristics of T2D
Normally due to glycoprotein receptors on cells losing their sensitivity to insulin or being lost
May also be due to an inadequate supply of insulin from the pancreas
Generally developed in people over the age of 40, although with increasing levels of obesity and poor diet, can be diagnosed in young people
Develops slowly, symptoms are less severe than T1
Overweight people are likely to develop T2, 90% have T2
Adrenaline and the second messenger model
Receptor is a transmembrane protein
When adrenaline/ glucagon (first messenger) binds to the receptor
Transmembrane protein changes shape and changes the shape of adenyl cyclase
Converts ATP to cyclic AMP
cAMP changes shape and activates kinase enzyme
Kinase catalyses conversion of glycogen to glucose
Role of adrenaline in regulating blood glucose conc
Released from medulla of adrenal glands
Adrenal glands lie on the kidneys
Medulla, secretes adrenaline
Cortex, role to secret other hormones like cortisol
Released very rapidly as nerve impulses are sent from hypothalamus to adrenal medulla
Advantages of adrenaline release in response to stress
Increase blood glucose conc, glycogen hydrolyses to glucose
Muscles have more glucose, more aerobic respiration to run
Vasoconstriction of blood vessels in stomach and intestines, vasodilation of blood vessels in muscles
