What are Hormones? Some Important points in Cell Signaling

Free Online Lectures of Biochemistry for Medical, Dental and Allied Health Sciences by Biochemistry Club

Cell Signaling

How extracellular signals (like hormones) can trigger a cellular response?


Try to fill in the blanks yourself
_________ cellular messenger.
Released from a ________     _____ .
Transported in _________ from an endocrine cell to a ________ cell (somewhere else) with a receptor.
Where is that receptor?
To answer that we have to determine the Class of hormones.

Where is that receptor?
It depends on the ________ of hormones.
There are ____ classes of hormones.

  1. Steroid hormones – Estrogen, testosterone.
  2. Peptide/polypeptide hormones – Insulin, glucagon.
  3. Amino acid derivatives – Epinephrine.

Answers for fill in the blanks:

Inter; ductless; gland; blood; target; class; 3.

Hormones may be Polar or Non Polar.


They are water soluble and cannot diffuse through the plasma membrane and receptors are outside the membrane.


They are lipid soluble and insoluble in water and can diffuse through the membrane, receptors are inside the cell.

Hormone binding

What happens when a hormone binds to a receptor?
____________    __________ occurs.
A series of steps is caused by this hormone binding event:

  • alter _________ activity.
  • alter ______        __________ .

Answers for fill in the blanks: 

signaling; cascade; enzyme; gene; transcription.

Signal Transduction

The process by which an extracellular signal is converted (and amplified) into a cellular response
Often involves ___________ .
1st messenger – the ___________ (or another extracellular signal that initially arrives at the target cell (receptor).
2nd messenger – a molecule made _________ the cell in response to the _______________ event (1st messenger).
Impacts activity of the cell.
Usually created in ____________ amount.
_________ signal.

Answers for fill in the blanks:

2nd messenger; hormone; inside; hormone binding; high/large; amplify.

All these lectures are organized and listed in detail in their proper sections. To view these lessons please visit the Hormones & Signal Transduction Section. This can be approached by directly clicking the Biochemistry II button or it can also be approached from the drop down menu in Biochemistry II tab. Once you reach the section click the curriculum tab to view the full list in the section.
Any further questions or inquiries are welcome.
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