Proteins

Question 1

what does the synthesis of a polypeptide hormone generally begin with?

Answer 1

The synthesis of a polypeptide hormone generally begins with the formation of an initial larger protein called a preprohormone.

Question 2

Where does the preprohormone enter?

Answer 2

enters the lumen of the rough endoplasmic reticulum where it will be cleaved into the prohormone precursor.

Question 3

Where are proteins and polypeptides generally stored?

Answer 3

Proteins and polypeptides are generally stored in intracellular vesicles.

Question 4

protein hormones can be subgrouped into:

Answer 4

The protein hormones can be subgrouped into gonadotrophic glycoproteins, somatomammotrophic polypeptides, cytokines and small peptides.

Question 5

1) Gonadotrophic glycoproteins

Answer 5

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Question 6

how many gonadotrophins there are? Why are they called that?

Answer 6

There are three gonadotrophins: follicle stimulating hormone (FSH), luteinizing hormone (LH) and chorionic gonadotrophin (CG), so called because they stimulate the gonads.

Question 7

to what they are closely related?

Answer 7

They are closely related to a fourth hormone called thyroid stimulating hormone (TSH).

Question 8

Where are FSH, LH and TSH produced and where is CG produced?

Answer 8

FSH, LH and TSH are produced in the anterior pituitary gland and CG is produced in the placenta.

Question 9

What are these hormones considered as?

Answer 9

These hormones are heterodimeric globular protein consisting of two glycosylated polypeptides (α and β chains).

Question 10

how is the stimulation bten3amal/when does it occur?

Answer 10

The release of LH and FSH from the gonadotrophs following appropriate stimulation is by exocytosis, which occurs when vesicle proteins fuse with proteins in the cell membrane.

Question 11

what happens to the gonadotrophins when they are in the general circulation?

Answer 11

Once in the general circulation, the gonadotrophins are transported in the plasma, with little or no binding to plasma proteins, to their target cells in the gonads.

Question 12

What are both LH and FSH involved in?

Answer 12

LH and FSH are both involved in the regulation of steroid and gamete production in the testes and ovaries.

Question 13

2) Somatomammotrophic polypeptides

Answer 13

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Question 14

What are the members of this family known for?

Answer 14

The members of this family are known for their effects on mammary glands and the growth of tissues.

Question 15

What do they consist mainly of?

Answer 15

They consist mainly of three members: prolactin (PRL), placental lactogen (PL) and growth hormone (GH; also called Somatotrophin).

Question 16

what do each consist of?

Answer 16

Each consists of a single polypeptide chain.

Question 17

What do PRL and PL do/ what does GH do?

Answer 17

PRL and PL are particularly concerned with lactation while GH plays a role in puberty.

Question 18

3) Cytokines

Answer 18

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Question 19

What are cytokines and what do they have?

Answer 19

Cytokines are also polypeptides, having one or two chains.

Question 20

In what ways do they tend to act mainly in ?

Answer 20

They tend to act mainly in an autocrine, paracrine and less often in an endocrine way.

Question 21

what are examples of cytokines?

Answer 21

Inhibins and activins are examples of cytokines.

Question 22

4) Small peptides

Answer 22

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Question 23

how many small peptides are there that have important roles in reproduction?

Answer 23

There are three small peptides that have important roles in reproduction.

Question 24

each of them is made in the form of what?

Answer 24

Each of them is made in the form of a larger polypeptide precursor, the active hormones being cleaved out just before they are secreted.

Question 25

what are GnRH/how are they derived?

Answer 25

Gonadotrophin-releasing hormone (GnRH) is a decapeptide derived by cleavage from a larger precursor called prepro-GnRH.

Question 26

What are oxytocin and vasopressin and how are they mainly produced?

Answer 26

Oxytocin and vasopressin are nanopeptides, which are mainly produced by neurons in the hypothalamus.

Question 27

why is oxytocin released into the blood?

Answer 27

Oxytocin is released into the blood to act on the uterus and the mammary glands, specifically during pregnancy and lactation.