Hormonal Action

Question 1

signal transduction

Answer 1

a hormonal signal transformed into intracellular events that affect cellular function

Question 2

signal transduction pathway

Answer 2

sequence of events from the time that the hormone binds to the receptor to the final response in target cell

Question 3

Domains of membrane bound receptors

Answer 3

1. ligand binding/extracellular domain: forms the HR complex
   a. ligand= substance that binds to the receptor
2. transmembrane domain
3. cytoplasmic domain

Question 4

2 classes of membrane bound receptors

Answer 4

1. intrinsic enzymatic activity
   a. phosphorylation
2. require intracellular secondary messengers to exert effects
   a. role of G proteins, enzyme amplification, and protein phosphorylation

Question 5

Enzymes with intrinsic enzymatic activity

Answer 5

• part of the cytoplasmic domain that PHOSPHORYLATE (add phosphate to) and thus activate intracellular proteins
  ex: tyrosine kinase domain becomes activated when the hormone binds at the ligand binding site

after binding, TK changes shape to allow for interaction with protein kinase

phosphorylation–> ATP–> ADP (phosphate goes to PK–> activation of PK)–> alteration in cellular function

Question 6

receptors that require a second messenger

Answer 6

• coupled to G-proteins: become activated when ligand binds to the receptor
• hormone binding to g-coupled receptor–> activation of adenylate cyclase–> formation of cAMP–> activation of PK–> enzyme phosphorylation–> products of phosphorylated proteins

-ORRR… G-proteins open up ion channels–> influx of calcium–> cAMP production–> kinase activation

Question 7

protein phosphorylation

Answer 7

• addition of a phosphate to a protein
• protein–> phosphorylated protein via protein kinase and ATP–> ADP
• phosphorylation of protein associated with synthesis of new proteins, signal transduction, cell differentiation, cell proliferation, etc.

Question 8

intracellular receptor hormonal action

Answer 8

• steroid receptors (can also be membrane-receptors)
• steroid-receptor complex binds to DNA to either activate/inhibit DNA transcription (this HR complex is a transcription factor, as it can stimulate/inhibit transcription)