3.4.7 Hormones and the Control of Blood Glucose Concentration Flashcards Preview

A-level Biology Oxford AQA > 3.4.7 Hormones and the Control of Blood Glucose Concentration > Flashcards

Flashcards in 3.4.7 Hormones and the Control of Blood Glucose Concentration Deck (39)
Loading flashcards...

What organ monitors blood glucose concentration?



 When blood glucose levels are too low, why is the brain most vulnerable?

∵ only respire glucose 


Name 4 factors that affect glucose concentration

  • Rate of activity
  • Diet
    • Starch is hydrolysed
    • Hydrolysis of lactose and sucrose
  • Hydrolysis of glycogen 
  • Making glucose from non-carbohydrates sources, amino acids + glycerol


Where is insulin and glucagon secreted from?

 islets of Langerhans

(clusters of cells in pancreas)


Which cells secrete insulin into the blood?

β cells


Which cells secrete glucagon into the blood?

α cells


Describe how insulin lowers blood glucose conc. when it's too high

  1. Insulin binds to specific receptors on cell membranes of liver & muscle cells
    • Increases permeability of muscle-cell membranes to glucose
      • Allows cells to take up more glucose
  2. Insulin activates enzymes in liver and muscle cells that convert glucose to glycogen (glycogenesis)
    • Cells able to store glycogen in their cytoplasm as an energy source
  3. Insulin increases rate of respiration of glucose (especially in muscle cells)


How does insulin increase the permeability of muscle-cell membranes to glucose?

Changes the tertiary structure of glucose transport protein channels


What is GLUT4?

Glucose transporter

(channel protein)


Where is GLUT4 found?

Skeletal and cardiac muscle cells


Describe what happens to GLUT4 when insulin levels are low

GLUT4 is stored in vesicles in the cytoplasm of cells


What happens to GLUT4 when insulin levels are high and what does this allow?

  • When insulin binds to receptors on cell-surface membrane, it triggers the movement of GLUT4 to membrane
  • Glucose can be transported into cell through GLUT4 protein by facilitated diffusion


Describe how glucagon raises blood glucose concentration when it's too low

  1. Glucagon binds to specific receptors on cell membranes of liver cells
  2. Glucagon actives enzymes in liver cells that break down glycogen into glucose (glycogenolysis)
  3. Glucagon activates enzymes that form glucose from glycerol and amino acids
    • Known as gluconeogenesis
  4. Glucagon decreases rate of respiration of glucose in cells


Where is adrenaline secreted from?

Adrenal glands


When is adrenaline secreted?

When there's low conc. of glucose in your blood, when you're stressed and when you're exercising


Describe how adrenaline increases blood glucose concentration

  1. Adrenaline binds to receptors in cell membrane of liver cells
  2. Activates glycogenolysis 
  3. Inhibits glycogenesis 
  4. Activates glucagon secretion and inhibits insulin secretion


How does adrenaline get the body ready for action?

Makes more glucose available for muscles to respire


What can adrenaline and glucagon both do & how?

  • Both can activate glycogenolysis inside cell even though they bind to receptors on outside of the cell
  • Act via a second messenger


Describe how adrenaline and glucagon act via a second messenger

  1. Adrenaline and glucagon bind to receptors and activate enzyme = adenylate cyclase (aka adenylyl cyclase)
  2. Adenylate cyclase converts ATP into cAMP (second messenger)
  3. cAMP activates protein kinase A (enzyme)
  4. Protein kinase A activates a cascade (chain of reactions)
    • = catalyses glycogenolysis 


Describe what occurs in type 1 diabetes

Immune system attacks β cells ≠ produce insulin


How is type 1 diabetes caused?

  • Think disease triggered by viral infection
  • Some people have genetic predisposition for it


What is it called when blood glucose is very high?



What is it called when blood glucose is very low?



For diabetic people, why is glucose found in their urine?

Kidneys can't reabsorb all glucose ∴ some excreted in urine


How is type 1 diabetes treated?

Treated with insulin therapy

  • Take regular insulin injections throughout day
  • OR some use insulin pump to deliver insulin continuously


Why does insulin levels have to be carefully controlled?

∵ too much insulin = very low blood glucose levels = hypoglycaemia


What can people with type 1 diabetes also do as well insulin therapy?

Eat regularly and control simple carbohydrate intake 


Name 4 risk factors for type 2 diabetes 

  • Obesity 
  • Lack of exercise 
  • Age
  • Poor diet


When does type 2 diabetes occur?

When β cells don't produce enough insulin or when body's cells don't respond to insulin


Why does body's cells not respond to insulin in type 2 diabetes & what does this mean?

  • ∵ receptors on membranes don't work properly
    • tertiary structure has changed
  • ∴ cells don't take up enough glucose
    • Means blood glucose conc. is higher than normal

Decks in A-level Biology Oxford AQA Class (41):