3.4.7 Hormones and the Control of Blood Glucose Concentration Flashcards
What organ monitors blood glucose concentration?
Pancreas
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
- 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
- Increases permeability of muscle-cell membranes to glucose
- 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
- 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
- Glucagon binds to specific receptors on cell membranes of liver cells
- Glucagon actives enzymes in liver cells that break down glycogen into glucose (glycogenolysis)
- Glucagon activates enzymes that form glucose from glycerol and amino acids
- Known as gluconeogenesis
- 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
- Adrenaline binds to receptors in cell membrane of liver cells
- Activates glycogenolysis
- Inhibits glycogenesis
- 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
- Adrenaline and glucagon bind to receptors and activate enzyme = adenylate cyclase (aka adenylyl cyclase)
- Adenylate cyclase converts ATP into cAMP (second messenger)
- cAMP activates protein kinase A (enzyme)
- 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?
Hyperglycaemia
What is it called when blood glucose is very low?
Hypoglycaemia
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
How can type 2 diabetes be treated?
- By eating a healthy, balanced diet, losing weight and regular exercise
- Glucose-lowering medication
- Insulin injections
Explain why this symptom of diabetes occurs: increased hunger and thirst
- Glucose from blood can’t enter cells ∴ body can’t convert food you eat into energy
- Lack of energy = increase in hunger
- Thirsty ∵ urinate a lot
Explain why this symptom of diabetes occurs: need to urinate excessively
When there’s excess glucose present in blood → kidneys react by flushing it out of blood and into urine
Explain why this symptom of diabetes occurs: tiredness
- Due to high blood glucose levels
- Causes slower circulation
- Due to low blood glucose levels
Explain why this symptom of diabetes occurs: weight loss
- Glucose from blood can’t get into body’s cells to use as energy
- ∴ body starts burning fat and muscle for energy = reduction in overall body weight
Explain why this symptom of diabetes occurs: blurred vision
High blood glucose levels = lens of eye to swell
Explain why this symptom of diabetes occurs: genital itching, recurring thrush infection
High conc. of glucose → provides conditions for yeast infections
State what you could use to determine the concentration of glucose in a urine sample
Colorimetry
Explain why many people who suffer from Type 2 diabetes often have high blood pressure (3)
- High glucose in blood
- Lowers water potential of blood
- Diffusion/osmosis of water from cells into the blood
- Increases blood volume
