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(6.4) Control of Blood Glucose Concentration - Coggle Diagram
(6.4) Control of Blood Glucose Concentration
changing the concentration of blood glucose
blood glucose conc must be controlled as all cells need constant energy supply to work
normal conc of blood glucose = 90mg per 100cm^3
monitored by cells in the pancreas
blood glucose conc
rises
after eating containing carbohydrates
blood glucose conc
falls
after exercise as more glucose is used in respiration to release energy
insulin
an effector secreted by beta cells in the islets of Langerhans (pancreas)
lowers blood glucose conc when it's too high
binds to receptors on membrane of hepatocytes (liver cells) & muscle cells
increases permeability of cell membranes to glucose, so the cells take up more glucose (less in blood), involves increasing no. of channel proteins
activates enzymes in liver/muscle cells that convert glucose -> glycogen, cells store glycogen in their cytoplasm as energy source
glycogenesis
= glycogen -> glucose
increases rate of respiration of glucose, especially in muscle cells
GLUT4
channel protein in skeletal & cardiac muscle cells
glucose transporter
insulin binds to receptors on CSM, triggers movement of GLUT4 to the membrane -> glucose can be transported into cell via GLUT4 protein (facilitated diffusion)
glucagon
raises blood glucose conc when its too low
binds to specific receptors on cell membranes of liver cells
activates enzymes in liver cells that break down glycogen -> glucose
glycogenolysis
= glycogen -> glucose
an effector secreted by alpha cells in the islets of Langherhans (pancreas)
gluconeogenesis
= glucagon activates enzymes that are involved in formation of glucose from glycerol & amino acids
decreases rate of respiration of glucose in cells
can act via a
second messenger
to activate glycogenolysis inside a cell even though it binds to receptors outside the cell
adrenaline
hormone secreted from
adrenal glands
it's secreted when there is a low conc of glucose in the blood, when stressed, or exercising
binds to receptors in the cell membrane of liver cells
activates
glycogenolysis
(breakdown of glycogen -> glucose)
inhibits
glycogenesis
(synthesis of glycogen from glucose)
activates glucagon secretion & inhibits insulin secretion (increasing glucose conc)
gets the body ready for action by making more glucose available for muscles to respire
acts via a
second messenger
second messenger
1.receptors for
adrenaline
&
glucagon
have specific tertiary structures that make them complementary to respective hormones
2.adrenaline & glucagon bind to their receptors & activate
adenylate cyclase
3.activated adenylate cyclase converts ATP into a chemical signal called as second messenger
4.
second messenger = cyclic AMP (cAMP)
5.cAMP activates
protein kinase A
(enzyme), cascade is activated that leads to glycogenolysis (glycogen -> glucose)
diabetes
condition where blood glucose conc cant be controlled
type 1 diabetes
immune system attacks beta cells in islets of Langerhans so they don't produce insulin
after eating, blood glucose conc rises & stays high (
hyperglycaemia
)
kidneys cant absorb extra glucose and is excreted in urine -> can result in death
treated with
insulin therapy
, regular insulin injections throughout the day but some use an
insulin pump
to deliver insulin continuously
insulin levels have to be carefully monitored as too much insulin can cause a deadly drop in blood glucose levels (
hypoglycaemia
)
eating regularly & controlling simple carb intake helps to avoid a sudden rise in glucose
some people may have a genetic predisposition or viral infection that can induce diabetes
type 2 diabetes
usually acquired later in life
linked to obesity & lifestyle, age, & family history
occurs when beta cells don't produce enough insulin or when body cells receptors don't respond properly to insulin
insulin receptors don't work properly, so cells don't take up enough glucose -> blood glucose conc higher than normal
can be treated by eating a healthy, balanced diet, losing weight & regular exercise
glucose-lowering medication can be taken if diet & exercise cant control it, insulin injections may be needed
growing health problem in the UK
can cause additional health issues like, visual impairment & renal failure
in response to the problem, food companies have attempted to make products more healthy -> sugar alternatives & reducing sugar, fat, salt content of products
determining the concentration of a glucose solution
normally glucose conc in urine is very low (0-0.8mM)
higher than usual conc can be a sign of diabetes
1.
quantitative Benedict's reagent
is different to normal Benedict's reagent -> when heated with glucose, initial blue colour is lost but brick-red precipitate isn't formed
a colorimeter can measure the light absorbance of a solution after the quantitative Benedict's test has been carried out
the higher the conc of glucose, the more blue colour will be lost = decreasing the absorbance of the solution