Biology (topic 6) Homeostasis (without nephron) (2)

What is glycogenesis?

Conversion of glucose to glycogen

What does insulin binding to receptors result in?

Chemical signal which causes vesical with channel proteins for glucose to fuse with membrane of target cell

What do increased channel proteins in muscle and liver cells do?

Make membrane more permeable to glucose as a result of transport proteins fusing

What happens after a decrease in blood glucose levels are detected by the pancreas ?

a cells in pancreas secrete glucagon

Glucagon causes an increase in blood glucose by :

Activates enzymes that

They convert amino acids to glucose (Gluconeogenesis)

And that convert glycogen to glucose (glycogenolysis)

What is gluconeogenesis?

The synthesis of glucose from non carboyhdrate molecules e.g amino acids

What is glycogenolysis ?

Breaking down glycogen to produce glucose

What activates the enzymes involved in gluconeogenesis and glycogenolysis?

Glucagon

What is the second messenger model?

When a hormone (First messenger)

triggers the production of a second messenger which is the enzymes involved in glycogenolysis and gluconeogenesis

Describe the steps in the second messenger model.

Glucagon binds to receptors on target cell

Activates G protein

G protein activates adenylate cyclase

Adenylate cyclase catalyzes conversion of ATP to cAMP (second messenger)

cAMP activates enzyme protein kinase A

Which initiates a cascade of reactions resulting in activation of enzymes that do Glycogenolysis

What do G proteins activate in the second messenger model ?

Adenylate cyclase

What does Adenylate cyclase do in the second messenger model?

Catlyises the conversion of ATP to cAMP

What does cAMP activate in the second messenger model?

Enzyme protein kinase A

What does protein kynesis A do in the second messenger model ?

Initiates a cascade (chain) of reactions that results in the activation of enzymes

The enzymes break down glycogen to glucose (glycogenolysis)

what hormones are involved in the second messenger model?

Glucagon and Adrenalin

What’s the difference between the second messenger model where glucagon or adrenalin is the first messenger?

Same mechanism

Glucagon:

Is released when blood glucose is low

Is released to restore levels

Adrenalin:

Is released during fight or flight

Is released for rapid energy

Less gluconeogenesis than glucagon

What is diabetes?

When homeostatic control of glucose has failed or deteriorated

What is type one diabetes?

Pancreas fails to produce or does not produce enough insulin

Caused by autoimmune attack on B cells

Occurs during childhood

What is the treatment for type one diabetes?

Insulin injection that are calculated on the basis of insulin intake and exercise

What is type 2 diabetes?

Insulin receptors are no longer responsive to insulin

Occurs in adults

Risk factors : obesity , high carbohydrate diet, age, family history

What is treatment for type two diabetes?

Low carbohydrate diet

Exercise

Medication

How can the rise in type 2 diabetes be combated?

Promotion of eating well

Reduced intake of processed food

Approaching food industrys to reformulate products reducing sugar and fat contents

What is a calibration curve?

Graph used to identify concentrations of unknown solutions

What is colorimetry?

When colorimeter is used to determine concentration of substances

Light passes through a sample , the transmission or absorbance of light is measured

Describe the practical: colourimetry usage to determine concentration of glucose

Add quantitative benedicts reagent to glucose solution

The solution starts blue , a loss of blue colour indicates a high concentration of glucose

(Dark blue = low glucose)

(colourless = high glucose)

Dark blue colour allows less transmission of light

Colorimeter is set to red

Make a calibration curve with a dilution serious of none glucose concentrations

Plot the glucose concentration

Find the percentage of light transmission that matches the sample

What colour is the light in the colorimetry practical determining the concentration of glucose and why?

Red

Because it is complementary to blue so the blue solution will be absorbed by red light

(blue light would be reflected)

What is added to glucose in the colorimetry practical to determine concentration of glucose?

Quantitative benedicts reagent