Hormones structure and function

Question 1

What are most hormones soluble in?

Answer 1

Water - therefore do not cross cell membranes, they interact with cells via receptors

Question 2

What hormones CAN cross the cell membrane?

Answer 2

Lipid soluble hormones, e.g. testosterone

Question 3

What are hormones?

Answer 3

Signalling molecules - messengers. They are secreted from a gland-like cell and circulate in the blood and have impacts upon target cells

Question 4

What are target cells?

Answer 4

Cells that respond to a hormone (highly selective). They only respond to those hormones for which they have the cognate receptors

Question 5

What are the 3 types of responses to hormones?

Answer 5

1) Endocrine
2) Paracrine
3) Autocrine

Question 6

What is an endocrine response?

Answer 6

Delivered when target cell is some distance away from secretary cell

Question 7

What is a paracrine response?

Answer 7

Where the target cell is closer to the secretary cell - sometimes right next to it (in the pancreas)

Question 8

What is an autocrine response?

Answer 8

Where a hormone is released from secretary cell and loops back to have an effect on ITSELF (e.g. beta cell secretes insulin and has a negative feedback cell)

Question 9

What has an effect on hormone response?

Answer 9

Distance travelled by the hormone

Question 10

What are small chemical hormones?

Answer 10

Modified amino acids e.g. adrenaline, dopamine

Question 11

What are peptide hormones?

Answer 11

Sequences of amino acids, generally in the range 3-20 e.g. endorphin (any more than 20 AAs and it becomes a protein hormone)

Question 12

What are protein hormones?

Answer 12

Proteins may be larger single polypeptide chains e.g. growth hormone has 191 AAs and is a large protein)

Question 13

What sort of hormone is insulin?

Answer 13

Protein hormone with 2 different subunits (A and B chains of insulin)

Question 14

What are complex chemical hormones?

Answer 14

e.g. lipid-derived steroids, testosterone, cortisol etc

Question 15

What may molecules with similar shapes do?

Answer 15

Bind to similar receptors and this may lead to side effects or cross reactivity

Question 16

What are Oxytocin and Antidiuretic Hormone (ADH) produced by?

Answer 16

The posterior pituitary gland.
They’re very similar structures - only differ by 2 amino acids
They are PEPTIDE HORMONES

Question 17

What effects can Oxytocin have?

Answer 17

Can have a slight anti-diuretic (as well as primary endocrine function) function and will bind to receptors

Question 18

What effects can ADH have?

Answer 18

Can cause uterine contractions because it binds to oxytocin receptor

Question 19

What are Growth Hormone and prolactin and what are they produced by?

Answer 19

PROTEIN HORMONES produced by the anterior pituitary.

Question 20

What does Growth Hormone do?

Answer 20

Stimulates growth, cell division and regeneration. It is a mitogen (stimulates mitosis) specific only to specific to certain kinds of cells

Question 21

What does prolactin do?

Answer 21

Protein closely related to GH and Placental Lactogen (PL) with properties and functions resembling both a hormone and a cytokine (stimulating growth)

Question 22

What are FSH and TSH produced by?

Answer 22

Protein hormones produced in the anterior pituitary.

They have hetero-dimeric structures, both parts bind to receptor (e.g. insulin)

Question 23

What does TSH stand for and what does it bind to?

Answer 23

Thyroid Stimulating Hormone, binds to TSH receptor in thyroid cells)

Question 24

What does FSH stand for and what does it bind to?

Answer 24

Follicle Stimulating Hormone, binds to FSH receptor in ovarian cells

Question 25

What is insulin?

Answer 25

Hetero-dimer produced by the pancreas hetero-dimer. It’s composed of 2 amino acid chains with disulphide bridges (these form specific 3D structures so that the structure can lock on to cognate receptors) holding them together (monomeric structure)

Question 26

What can insulin form?

Answer 26

Can form dimers, trimers and crystalline structures (if stored in secretary granules) – breaks down as they are secreted with high concentration of hormone

Question 27

Why can’t the oral route be used for delivering peptide and protein pharmaceuticals?

Answer 27

Because proteins get digested and broken down in the stomach

Question 28

What are 3 options for peptide and protein drug delivery?

Answer 28

1. Injection IV or SC
2. Aerosols for inhalation
3. Depot formulations, modified release systems (e.g. microspheres) etc used for delivery of growth hormone
    To reduce need for multiple injections – better compliance etc

Question 29

What does Tyrosine give rise to?

Answer 29

Adrenaline, noradrenaline and dopamine

Question 30

What is PNMT?

Answer 30

Expression of this enzyme is induced by cortisol (STRESS) and associated with the production of adrenaline

Question 31

Why is more adrenaline produced compared to noradrenaline?

Answer 31

4 times as many adrenaline producing cells in the medulla, therefore more adrenaline is produced compared to noradrenaline

Question 32

What hormone is derived from tryptophan?

Answer 32

Melatonin

Question 33

What are lipid-derived hormones?

Answer 33

Steroid hormones: progesterone, testosterone, cortisol, oestradiol

Question 34

What is steroidogenesis?

Answer 34

A synthetic process that begins with cholesterol as a substrate and, through a series of enzymatic reactions, produces a wide array of bioactive interrelated signaling molecules