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Question 1

How does a radioimmuno essay work?

Answer 1

1. A dish that contains antibodies designed for the specific hormone that we need to measure is mixed with radio labelled hormone until equilibrium is reached
2. A known amount of unlablled radioactive hormone is added to the dish to introduce competion
3. Further unlabelled hormone is added
4. A standard curve is established from the information collected above (used as a baseline)
5. A sample from the pateint that contains an unknown amount of unlablled hormone is added to dish 1 (eqiulibrium dish)
6. If a great amount of radiolabelled hormone is displaced (compared to the baseline) then there is a lot of hormone in the sample

If a small amount of radiolablled hormone is displaced (compared to the baseline) then there is a small amount of hormones

Question 2

How do elisa tests work?

Answer 2

1. Add Ab1 (capture antibody) to the 96-well plate
2. A sample with an unknown amount of hormone is then added to the plate, if the hormone is present, it binds to Ab1
3. Ab2 is then added to the plate and it binds to the hormone that is bound to Ab1
4. Ab3 is added to the plate, it contains a flouroscent enzyme. It then binds directly to Ab2
5. If an appropriate susbtrate is added, the reaction between it and the enzyme will cause a color change
6. The more the amount of hormone present, the greater the color change.

Question 3

What is special about the scatchard plot for insulin?

Answer 3

It has a curved line because of the presence of two receptors with different affinities which one plotted individually yield two different slopes, and when combined they yield a curved line.

The R1 receptors have a higher affinity (K1) but are lower in number.

The R2 receptors have a lower affinity (K2) but are higher in number.

Another explanation is that occupied receptors influence the affinity of adjacent, unoccupied receptors by negative cooperativity. In other words when one hormone molecule binds to its receptor, it causes a decrease in the affinity of nearby unoccupied receptors.

Question 4

Why does the bound/free ratio decrease even though the bound molecules are increasing?

Answer 4

Bc of the fact that the are many free receptors at the start which makes molecule binding very easy, so the bound molecules are more than the free ones.

But as more free molecules are added, and more receptors are filled up, it becomes harder for the molecules to bind, so the bound molecules increase at a slower rate than the free molecules that are being added.

This causes the bound/free ratio to decrease,

Question 5

What is the difference in the way that hydrophobic and hydrophilic hormones bind to receptors?

Answer 5

Hydrophilic hormones: Bind to receptors on the plasma membrane since they cannot cross the plasma membrane freely

Hydrophobic hormones: Bind to the receptors either in the cytosol or on the nucleas since they can freely cross the plasma membrane

Question 6

How are the numbers of receptors downregulated and upregulated?

Answer 6

Down regulation: Chronic exposure to the hormone decreases the amount of receptors which causes a decrease in response. It can also cause the receptors to get desentsized without decreasing their number leading to the same decreased respone.

Up regulation: Certain conditions might lead to an increase in receptor number which will lead to an increased response

Question 7

What are the three types of second messengers and give an example for each one?

Answer 7

1. Hydrophilic: water soluble molecules such as: cAMP, cGMP, Ca+2
2. Hydrophobic: Lipid soluble such as: DAG and PIP3
3. Gases: such as: NO, CO, ROS