Flashcards in Reproductive Molecules Deck (45):
Name the 3 most important groups of molecules for human development
Glycoproteins, steroids and prostaglandins
Describe the structure of steroids
Lipids, 27C compound skeleton with four fused rings (different functional groups attached). Cholesterol is the core molecule.
Give examples of steroids
Oestradiol, oestrone, oestriol, progesterone and testosterone
What causes differences between steroid compounds?
Different functional groups
Describe the structure of the oestrogens
18 carbon steroids
Describe the structure of the progestagens
21 carbon steroids
Describe the structure of the androgens
19 carbon steroids
Explain the differences between oestradiol, oestrone and oestriol
Oestrone has 1 -OH group, oestradiol has 2 and oestriol has 3.
Generally, what does steroid synthesis involve cellularly?
Oxidative enzymes in the mitochondria and ER
What is the first step in steroid synthesis?
Conversion of cholesterol to pregnelolone
Describe steroid synthesis in males
GnRH released from hypothalamus --> anterior pituitary releases FSH and LH --> LH stimulates Leydig cells to produce testosterone --> testosterone and FSH act on Sertoli cells --> in Sertoli testerone converted to DHT by 5a reductase --> Sertoli cells then secrete ABP --> ABP binds testosterone and carries to seminiferous tubes --> spermatogenesis
Describe steroid synthesis in females
GnRH released from hypothalamus --> anterior pituitary releases FSH and LH --> LH stimulates testosterone production by theca cells in ovarian follicle --> testosterone enters granulosa cells (around oocyte) and is converted to oestrogen (17B-oestradiol) by aromatase --> oestradiol stimulates LH receptors on granulosa cells --> enables response to LH surge --> ovulation
What group of molecules are androgens, oestrogens and progestogens?
Describe the role of androgens
Maintain male somatic tissue diffentiation, secondary male traits, support spermatogenesis, influence sexual and aggressive behaviour (both genders), promote protein anabolism, somatic growth and ossification, regulate anterior pituitary release, induce body hair (females) - pubic and underarm.
Describe the role of oestrogens
Growth of mammary gland and endometrium, female secondary traits, prepare uterus for sperm movement, increase vascular permeability, regulate gonadotrophin secretion
Describe the role of progestagens
Luteal form prepares endometrium for implantation (secretory phase of menstrual cycle), placental form maintains endometrium in pregnancy after ~10-12 weeks
Name 4 common androgens, and list them in terms of their potency
DHT, testosterone, androstenedione, DHEA
Name 3 common oestrogens, and list them in terms of their potency
17b oestradiol, oestriol, oestrone
How do steroids act on cells?
Small and lipophilic so can pass through by simple diffusion to bind to nuclear or cytoplasmic receptor
Describe the structure of glycoproteins
Oligosaccharide chain attached to protein side chains
Describe the synthesis of glycoproteins
Oligosaccharide chain is added in post-translational modification known as glycosylation
What group of molecules do gonadotrophins belong to?
Glycoproteins; they are hormones
Name 6 gonadotrophins
FSH, LH, hCG, inhibin, activing, relaxin
Where are what produces LH and FSH?
Anterior pituitary gland, by gonadotrophs
Where are what produces hCG?
Placenta - by syncytiotrophoblasts
Outline the role of FSH
Stimulates growth of immature follicles (female)
Enhances ABP production from Sertoli cells in men to help in spermatogenesis
Outline the role of LH
Surge triggers ovulation, and converts residual follicle --> corpus luteum (produces progesterone in fertilisation). LH needed to retain luteal function, and it supports thecal cells (these supply precursors for oestradiol production) and LH acts on Leydig cells to produce testosterone.
Outline the role of hCG
Maintains corpus luteum in pregnancy
Outline the role of inhibin
Males: produced by Sertoli cells to inhibit FSH and GnRH release when sperm count is high
Females: produced by Granulosa cells to give negative control of FSH production during menstrual cycle
Outline the role of activin
Part of transforming growth factor B family; increases FSH release and enhances response to LH in men and women
Outline the role of relaxin
Females: produced in menstrual cycle for follicle development and oocyte maturation, and in pregnancy for ligament relaxation and labour.
Men: in seminal fluid to enhance sperm motility
How do glycoproteins act on a cell?
Bind to a G-protein coupled receptor with large extracellular domains which bind to the hormone
Describe the structure of prostaglandins
Lipid compound (derived from FAs) with 20C (including 5C ring)
Where are prostaglandins present?
In almost all tissues and organs including the uterus and seminal fluid
What are the effects of prostaglandins?
muscle contraction, vasodilation, inflammation, hormone regulation, cell growth control and temperature regulation
Which prostaglandin is involved in labour?
PGF2a; activates contractions of myometrium and causes cervical ripening
Which prostaglandins are present in seminal fluid?
PGE1, PGE2, PGF1a, PGF2a
How do prostaglandins act on a cell?
Attach to a G-protein couple cell surface receptor
Where is growth hormone releasing hormone (GHRH) released?
Where is oxytocin released?
Where is prolactin released?
How many subunits are there in a glycoprotein?
2; alpha and beta
In what glycoproteins is the alpha subunit identical?
FSH, LH, hCG and TSH (92 amino acids)
What is the significance of the beta subunit in glycoproteins?
Confers specific biological action