CONTROL OF BLOOD GLUCOSE Flashcards
why does blood glucose need to be controlled
all cells need energy to work
glucose is a respiratory substrate
what is the rough conc of blood glucose in blood
around 90mg per 100cm3
when does blood glucose conc rise
after eating
when does blood glucose conc fall
after exercise
what 2 hormones control blood glucose conc
insulin and glucagon
how do insulin and glucagon work
They travel in the blood to their target cells (effectors)
They’re secreted by clusters of cells in the pancreas called ISLETS OF LANGERHANS
What cells secrete insulin into the blood
beta cells
what cells secrete glucagon into the blood
alpha cells
what is the role of insulin
insulin lowers blood glucose conc when its too high
It binds to specific receptors on cell membrane of liver cells and muscle cells
Increases the permeability of muscle cell membranes to glucose
Cell takes up more glucose
This involves increasing the number of channel proteins in the cell membrane
Insulin also activates enzymes in liver and muscle cells which convert glucose to glycogen
Can then store glycogen in cytoplasm as energy source
what is the role of glucagon
glucagon raises blood glucose conc when its too low
Binds to specific receptors on cell membrane of liver cells
Activates enzymes in liver cells that break down glycogen to glucose (glycogenolysis)
Activates enzymes involved in the formation of glucose from glycerol and amino acids
what is glycogenesis
the process of forming glycogen from glucose
what is glycogenolysis
the process of breaking down glycogen to glucose
What is gluconeogensis
the process of forming glucose from non carbohydrates
why is hormone transmission slower than nerve impulse transmission
hormones travel in the blood and are therefore slower
However hormones are not broken down as quickly/ easily as nerve impulses and therefore their effects last for longer
what is GLUT4
a glucose transporter
a channel protein that transports glucose
what happens to GLUT4 when insulin levels are low
GLUT4 is stored in vesicles of the cytoplasm
what happens to GLUT4 when insulin binds to receptors
when the insulin binds to receptors on the CSM it triggers the movement of of GLUT4 to the membrane
Glucose can be transported into the cell through the GLUT4 protein by facilitated diffusion
what does adrenaline do to blood glucose concentration
alike to glucagon adrenaline increases blood glucose concentration
how does adrenaline increase blood glucose concentration
Adrenaline is secreted when there is a low conc of glucose in blood, when your stressed and when your exercising
It binds to the receptors in the cell membrane of liver cells
Activates glycogenolysis (glycogen to glucose)
Inhibits glycogenesis (glucose to glycogen)
It also activates glucagon secretion and inhibits insulin secretion which increases glucose conc which gets body ready for exercise as more glucose (respiratory substrate)
How do adrenaline and glucagon act
Via a second messenger
what is a second messenger and give an example
the chemical signal created by the conversion of ATP cyclic AMP (cAMP)
How do adrenaline and glucagon act inside the cell when they attach to receptors on the outside
The receptors have specific tertiary structures
Adrenaline and glucagon bind and activate an enzyme called adenylate cyclase
Activated adenylate cyclase converts ATP to a chemical signal (second messenger) called cAMP
cAMP activates an enzyme called protein kinase A
Protein kinase A activates a cascade of reactions that breaks down glycogen into glucose (glycogenolysis)
what is diabetes
a condition where blood glucose can’t be controlled properly
type 1 and type 2
what is type 1 diabetes
Immune system attacks B cells in the islets of Langerhans
They then can’t produce any insulin
After eating, blood glucose level rises and stays high (hyperglycaemia)
Can result in death if not treated
Kidneys can not re absorb all of this glucose so some of it is excreted as urine
what is type 2 diabetes
It occurs when B cells don’t produce enough insulin or when the body cells don’t respond properly to insulin
The cells don’t respond properly because their receptors on their membranes don’t work properly so the cells don’t take up enough glucose
Resulting in blood glucose levels being higher than normal
How is type 1 diabetes treated
Insulin therapy
Most people need regular insulin injections throughout day
Some people use a regular insulin pump continually
Insulin therapy has to be monitored carefully as too much insulin can result in a dangerous drop in blood glucose levels (hypoglycaemia)
when and why may you get type 2 diabetes
Usually acquired later in life
Often linked with obesity
More often associated within families
Other risk factors include lack of exercise, age and poor diet
how is type 2 diabetes treated
eating healthy
balanced diet
losing weight
regular exercise
glucose lowering medication can be taken
insulin injections may be needed
what have food companies done in response to criticism
found sugar alternatives to sweeten food/ drink
reduced the sugar/ fat/ salt content of products
in the quantitative benedicts test describe how colour varies with conc of glucose
as glucose conc increases the blue colour of the Benedictus gets paler
use colorimeter to measure
