REPRODUCTIVE HORMONES

• The reproductive system starts to become functional when males and females are in the puberty stage
• At the age of 12 to 15 years old, the hypothalamus in the brain becomes active in producing Gonadotropin-releasing Hormone (GnRH)
• Gonadotropin-releasing Hormone (GnRH) release


  1. GnRH is released

  2. GnRH acts on the anterior pituitary gland
• Anterior pituitary gland


  Produces two hormones that target both the cells of the testes and ovaries
• Hormones produced by anterior pituitary gland

  • Follicle-stimulating hormone (FSH)
  • Luteinizing hormone (LH)
• Effects of FSH


  1. FSH is carried by the blood to the gonads

  2. In both males and females, FSH triggers the meiotic division of sperm cells in the testes and egg cells in the ovary, giving rise to haploid sex cells
• Effects of LH


  1. LH release from the anterior pituitary gland targets the gonads

  2. LH's effect on the testes and ovaries is to produce sex hormones
• Testis


  • Contains long coiled seminiferous tubules with three important types of cells: Sertoli cells, Leydig cells, and primary spermatocytes
• Spermatogenesis


  1. Primary spermatocytes divide meiotically and produce the secondary haploid spermatocytes

  2. These develop into sperm cells
• Sertoli cells


  • Nourish the developing and dividing primary spermatocytes
  • Regulate the production of FSH in the pituitary gland by producing Activin and Inhibin proteins
• Leydig cells


  • Produce the hormone testosterone
  • Testosterone is needed for spermatogenesis
• Testosterone from Leydig cells


  Attaches to the Androgen-binding protein produced by the Sertoli cells, thus increasing the concentration of testosterone in the seminiferous tubules which are needed to continue the production of sperm cells
• Ovarian follicle development


  1. FSH from anterior pituitary reaches ovaries

  2. Follicle cells that enclose egg cell start to grow and mature

  3. Secondary oocyte inside follicle undergoes growth and maturation

  4. Follicle cells produce and secrete estrogen and inhibin
• Estrogen


  Main sex hormone in females, causes feminine physical changes and maintains uterine lining
• Inhibin


  Signals anterior pituitary and hypothalamus to stop producing and releasing FSH
• Ovulation


  1. LH from anterior pituitary stimulates follicle cells to grow and mature

  2. Follicle breaks open, releasing mature egg cell
• Corpus luteum


  Gland formed from ruptured follicle, produces and secretes progesterone
• Progesterone


  Prepares female's body for possible pregnancy, causes further thickening of uterine endometrium, signals posterior pituitary to secrete hormones for milk production and childbirth
• Nucleic acids


  Polymers composed of monomeric units called nucleotides
• Functions of nucleic acids

  • Holds the genetic information
  • Serves as the template for the synthesis of proteins
• Types of nucleic acids

  • Deoxyribonucleic acid (DNA)
  • Ribonucleic acid (RNA)
• Nucleotides


  Composed of the phosphate group, sugar, and nitrogenous base
• Sugar in nucleotides


  Ribose is the pentose in RNA, deoxyribose is the pentose in DNA
• Difference between ribose and deoxyribose

  In ribose, oxygen is attached to carbon 2, while in deoxyribose there is no atom attached to carbon 2
• Phosphate group


  Consists of a phosphorus atom at the center and four oxygen atoms, also present in Adenosine triphosphate (ATP)
• Nitrogen bases


  • Purines (adenine, guanine)
  • Pyrimidines (thymine, cytosine, uracil)
• Difference between purines and pyrimidines

  Purines are double-ring structures, pyrimidines are single-ring structures, purines are bigger than pyrimidines
• Thymine and uracil


  Thymine is only found in DNA, uracil is only found in RNA
• Structure of nucleotides


  1. Pentose and nitrogen bases are held by the glycosidic covalent bond

  2. Phosphate group is attached to pentose by an ester covalent bond
• Formation of polynucleotide


  Nucleotides bind together to form a long polynucleotide with a sugar-phosphate backbone
• Location of DNA


  • Nucleus of the cell, mitochondria, and the chloroplast of a plant cell
• Structure of DNA


  Double helix structure, like a twisted ladder, with phosphate and ribose sugar forming the sides, and complementary bases forming the rungs
• Complementary base pairing in DNA

  Adenine pairs with Thymine, Cytosine pairs with Guanine
• Role of DNA


  Contains all the genetic information about the organisms, dictates the appearance and provides the information for making proteins
• Role of RNA


  Carries the genetic information from the DNA in the nucleus to the cytoplasm of the cell, involved in the synthesis of the protein needed by the body
• Types of RNA


  • Messenger RNA (mRNA)
  • Ribosome RNA (rRNA)
  • Transfer RNA (tRNA)
• Functions of RNA types

  • mRNA directs protein synthesis, originated from the nucleus of the cell
  • rRNA is the site of protein synthesis
  • tRNA serves as the adapter molecules during protein synthesis