Hormones Flashcards
Define “hormone”
Chemical messengers released directly into blood
Where are hormones released from?
Endocine glands
Where are hormones carried?
In the blood stream
Why aren’t hormones released via ducts?
So cells in glands are not themselves affected by products
How are hormones produced? 4
- Either in inactive form
- Or packaged within secretory vesicles by Golgi Apparatus
- Fuse with cell surface membrane
- Contents released by exocytosis
Why is every hormone specific?
Each hormone only affects specific target cells to modify cell activity
What are the 2 types of hormone?
- Steroid
- Peptide
How do steroid hormones work in cells?
- Pass through cell membrane
- Binds directly to repressor molecule in cytoplasm
- Hormone receptor complex activated
- Acts as transcription factor
What is the structure of a steroid hormone? 2
- Formed from lipids
- Complex ring structures
What is the structure of a peptide hormone?
- Protein chains made from 10-300 amino acids
Why can’t peptide hormones pass through the cell membrane? 2
- Charged
- Not lipid soluble
How do peptide hormones work in cells? 5
- Bind to complementary receptor molecules in cell membrane
- Activates second messenger molecules in cell cytoplasm
- Activate enzymes called protein kinases
- These trigger a cascade [chain of reactions] in the cell
- Transcription factors are activated
How do transcription factors work?
- Transcription factors bind to region of DNA adjacent to DNA to be transcribed : promoter region
- Form a transcription intitation complex with RNA polymerase
- Allows transcription of gene
What two types of molecules can hormones be in relation to transcription factors?
- Repressors
- Activators
How do repressor molecules affect transcription?
- Bind to transcription factors
- Prevents them from attaching to promotor region
- Can’t form transcription initiation complex
- Transcription factor absent
- Gene cannot be transcribed
