Date post: | 20-Jan-2016 |
Category: |
Documents |
Upload: | emil-moody |
View: | 220 times |
Download: | 0 times |
Review
• Amphipathic molecules:– Hydrophobic region and hydrophilic region• Example: Phospholipids and Membrane Proteins
• Molecules that can pass directly through membrane
• Hydrophobic molecules (non-polar): Dissolve in the bilayer• Glucose can transport easily (small molecule)
Cell Membrane Voltage
• All cells have voltage• Cytoplasm of cell is
more negative than the outside of the cell– Unequal distribution of
anions and cations
Membrane potential
• Cellular voltage = Membrane potential– Ranges from -50 mv to -200 mv
• Remember opposites attract!– Cations want to move into the cell since it is more
negative
Electrochemical gradient
• 2 forces drive the diffusion of ions across the membrane!!– The concentration gradient (chemical gradient)– Electric force
Creates an ELECTROCHEMICAL gradient
Sodium Potassium Pump
• Remember the inside of the cell is more negative– If left to nature cations would move into the cell,
messing up this membrane potential– Sodium potassium pump maintains membrane
potential using an ATPase
Steps1. 3 sodium ions from inside the cell bind to the
pump2. ATP is used to change the shape of the
protein3. Sodium is released inside the cell4. 2 potassium ions bond to the pump (changed
shape form) and the pump goes back to original shape
5. 2 potassium ions are released inside the cell
Local regulation• Cells in the vicinity undergo local regulation• Paracrine signaling: – Growth factors stimulate nearby cells to grow and
multiply– Many cells receive and respond to growth factors
at the same time
Local regulation
• Synaptic signaling– Electric signal triggers secretion of a
neurotransmitter (chemical signal) which diffuses across the synapse
– Neurotransmitter stimulates target cell
Long distance signaling
• Hormonal signaling– Specialized endocrine cells secrete hormones,
which travel through blood stream (or other fluids)
Signal Transduction Pathway
• 3 steps– Reception: signal molecule meets receptor
molecule– Transduction: converts signal so that a response
can take place– Response: a cellular response takes place