Hormones

Question 1

What is the overall function of hormones?

Answer 1

To bring about changes in the activity of the target cell or organ

Question 2

What are endocrine hormones produced by?

Answer 2

A cell or group of cells

Question 3

Name 5 properties of endocrine hormones

Answer 3

1. Secreted form cells into the blood
2. Travel through the blood to distant organs
3. Are able to exert effects at very low concentrations
4. Act by binding onto specific receptors
5. Have their action terminated by negative feedback

Question 4

What are the 3 classes of endocrine hormones

Answer 4

Peptide - composed of chins of amino acids
Steroid - derived from cholesterol
Amine of which there are 2 types catecholamines and thyroid hormones - derived from tryptophan or tyrosine

Question 5

Where are peptide hormones initially produced and in what form?

Answer 5

In the ribosome as a preprohormone

Question 6

Where are preprohormones cleaved?

Answer 6

Cleaved in the rough endoplasmic reticulum into the prohormone

Question 7

What is the fate of the pro hormone?

Answer 7

It is packaged into vesicles in the golgi apparatus and when triggered is degraded by proteolytic enzymes into the active hormone which enters the ECF and then the blood

Question 8

What else is produced when the pro hormone is cleaved?

Answer 8

Inactive peptide fragment which can have an active function for example in insulin cleavage C-peptide is produced and can be measured in diabetes

Question 9

Why would we measure C-peptide instead of insulin directly in diabetes?

Answer 9

It will give a value of how much insulin is being produced by the patient themselves rather than the combined value with the injected insulin.

Question 10

Are peptide hormones water soluble?

Answer 10

Yes, they are hydrophilic

Question 11

Can they passively diffuse across the cell membrane?

Answer 11

No, because they are lipophobic they must bind to a surface receptor

Question 12

Name two mechanisms by which peptide hormones can bing abut the phosphorylation of proteins within the cell.

Answer 12

Either via a G-protein coupled receptor e.g. cAMPor by activating tyrosine kinase

Question 13

Do peptide hormones have a short or long half-life and why?

Answer 13

Short because they are water soluble so they dissolve easily in the plasma

Question 14

When are peptide hormones synthesised?

Answer 14

They are made in advance and stored in secretory vesicles

Question 15

Give 2 examples of peptide hormones

Answer 15

Insulin and parathyroid hormone

Question 16

What are steroid hormones and where are they derived from?

Answer 16

They are lipid hormones derived form cholesterol

Question 17

Where are they synthesised?

Answer 17

In the adrenal cortex, gonads and placenta

Question 18

When are they synthesised and why?

Answer 18

Directly as needed because they are highly lipophilic so cannot be maintained within lipid membranes, they immediately diffuse into the blood

Question 19

How are they transported through the blood?

Answer 19

Bound to carrier proteins, which increases their half-life significantly by protecting them form degradation

Question 20

where are they produced?

Answer 20

Smooth endoplasmic reticulum

Question 21

Where are steroid receptors located?

Answer 21

On the inside of the cell and are either cytoplasmic or nuclear receptors

Question 22

How do steroid bring about a response?

Answer 22

Activation or depression of gene function by altering transcription of protein

Question 23

Are steroids fast in bringing about their response?

Answer 23

No, they take a long time but persist over a long time for example growth

Question 24

Where are amine hormones derived from?

Answer 24

The amino acid tyrosine with the exception of melatonin which is produced by tryptophan

Question 25

What are the two types of amino hormone?

Answer 25

Catecholamines and thyroid hormones

Question 26

Which class of hormone do catecholamines characteristically mimic?

Answer 26

Peptide hormones

Question 27

Give an example of catecholamines

Answer 27

Epinephrine and noradrenaline

Question 28

Which class do the thyroid hormones mimic?

Answer 28

Steroid hormones

Question 29

Give an example of thyroid hormones

Answer 29

Thyroxine

Question 30

Can steroid and thyroid hormones freely cross into the target cell when bound to a carrier protein?

Answer 30

No, only free hormone can cross into the cell, this is important as it maintains the equilibrium

Question 31

How are the concentrations of hormones controlled?

Answer 31

By negative feedback pathways

Question 32

Can hormones have permissive effects?

Answer 32

Yes, for example the combination of epinephrine and thyroid hormone will vastly increase the the amount of lipolysis

Question 33

What are the three major groups of neurohormones?

Answer 33

Catecholamines which are made by modified neurones in the adrenal medulla
Hypothalamic Neurohormones secreted from the posterior pituitary
hypothalamic neurohormones that control release of hormones form the anterior pituitary