hormones

• hormones are chemicals released by the endocrine gland cells. they travel through blood. hormones bind to receptors either on the target cell membrane or within the target cell. they are also made from amino acids or cholesterol
• 1. hormones travel through the blood towards the target organs. 


  lipid soluble hormones require carrier proteins to travel in the blood, e.g: thyroid hormones released from thyroid gland. water-soluble hormones do not require carrier proteins, e.g adrenaline released from adrenal gland.
• 2. hormones bind to target cell receptors


  lipid-soluble hormones easily diffuse across the plasma membranes (phospholipid bilayers) to bind to the intracellular receptors inside a target cell's cytosol or nucleus.

  water-soluble hormones cannot cross cell membranes so they bind to receptors of the membrane of a target cell.
• each hormone binds only binds to a receptor designs specifically to receive it
• 3. hormones stimulate target cells to produce a response. 


  when lipid-soluble hormones bind to intracellular receptors, they stimulate creation of new proteins - often enzymes - to produce a response, e.g increased metabolic rate.

  when water-soluble hormones bind to membrane receptors, they activate a 2nd messenger system to produce a response, e.g increased heart rate.
• effects of a hormone stop when it unbinds from the receptor, such as it gets broken down, and/or recycled or excreted in sweat, urine or feces.
• 6 characteristic differences between water and lipid soluble hormones

  A) amines

  B) steroids

  C) pre-made and stored

  D) carrier protein

  E) intracellular receptors

  F) amines

  G) peptides and proteins

  H) pre-made

  I) stored

  J) needed

  K) unbound

  L) plasma membrane receptors

  
• label differences

  A) intracellular receptors

  B) carrier protein

  C) nuclear receptor

  D) cytoplasmic

  E) nucleus

  F) gene transcription

  G) proteins

  H) plasma membrane receptors

  I) activates 2nd messengers

  J) amplified response

  K) big response

  
• lipid-soluble (active mechanism) hormone diffuses across the plasma membrane and binds to receptor in cytosol or in nucleus. this causes a gene activation transcription and mRNA production and translation for protein synthesis. the protein creates a cellular response. this is a slow hormone response because protein synthesis takes time.
• water-soluble (active mechanism) hormone binds to a membrane receptor on a target cell activating the attached G-protein. G-protein activates or inhibits 2nd messengers which affect actions of other proteins. since 2nd messengers are pre-made, this is a fast response