BioChem - Amino Acids 2

1st step of Urea Biosynthesis

Collection of NH2 groups into a single molecule of glutamate (Transamination).

2nd step of Urea Biosynthesis

Oxidative deamination

3rd step of Urea Biosynthesis

Transport of ammonia to liver

4th step of Urea Biosynthesis

Urea cycle in liver converts ammonia to urea.

Function of Urea Biosynthesis

To detoxify ammonia and dispose of nitrogen from amino acid breakdown

Enzymes at the start of Urea Biosynthesis

Alanine transaminase (ALT) &

Glutamate transaminase

Compostion of Urea

Ammonia, Carbon Dioxide & Aspartate.

Constituting 80-90% of the nitrogen excreted.

Anterior pituitary gland

The release of hormones from the anterior pituitary gland is controlled by hypothalmic hormones.

Hypothalamic hormones

Corticoliberin (CRH)

Thyroliberin (TRH)

Gonadoliberin (GnRH)

Somatoliberin (GHRH/GRH)

Somatostatin (GHRIH/SRIH)

Prolaktostatin, Dopamine and GAP

Corticoliberin (CRH)

Pituitary hormone: ACTH

Target gland hormone: Hydrocortisone

Thyroliberin (TRH)

Pituitary hormone: TSH

Target gland hormone: T3 & T4

Gonadoliberin (GnRH)

Pitiutary hormone: LH & FSH

Target gland hormone: Androgenes, Estrogenes, Progestins

Somatoliberin (GHRH)

Pituitary hormone: GH

Target gland hormone: IGF-I

Somatostatin (GHRIH/SRIH)

Pitiutary hormone: GH

Target gland hormone: IGF-I

Prolaktostatin, dopamine and GAP

Pituitary hormone: PRL

Target gland hormone: Neurohormones

What are the three groups of anterior pituitary hormones?

Protein hormones (e.g Prolactin)

Glycoprotein hormones (e.g TSH)

Proopiomelanocortin-derived hormones (POMC)

(e.g MSH)

Protein hormones (Made of large polypeptides)

Growth hormone: 191 amino acids.

Most primarily known to be connected to both dwarfism and gigantism as per the name. Secreted in a pulsatile manner. Affects growth of long bones, protein synthesis

Prolactin: 198 amino acids

Initiates and mantains milk secretion (lactation). Excess prolactin (hyperprolactinaemia) can be responsible for infertility.

Glycoproteins (Proteins with sugar chains attached)

Thyroid Stimulating hormone: Responsible for stimulation of the thyroid gland to produce T3 & T4

Human chorionic gonadotropin: Causes corpus luteum of pregnancy to grow and secrete progesterone. Highest secretion at 10 weeks of pregnancy. Reduced secretion with the disappearance of corpus luteum.

POMC-derived hormones (Comes from a large protein called Proopiomelanocortin)

Melanocyte-stimulating hormone: Linked with hyperpigmentation. Stimulate skin cells to create the brown pigment, melanin, by melanogenesis