PHYL 2041 Study Guide - Fall 2018, Comprehensive Midterm Notes - Sodium Channel, Protein, Potassium Channel
12 Oct 2018
School
Department
Course
Professor
PHYL 2041
MIDTERM EXAM
STUDY GUIDE
Fall 2018
Physiology 2041
Lecture 1/Sept. 4, 2018
[Membrane Transport]
Biological membranes = lipids that comes in different forms and shapes. (cholesterol,
phospholipids, glycolipids); lipids have a hydrophobic tail and a hydrophilic head.
- Membranes also contain proteins in them (peripheral, integral)
- Membranes are very fluid structures with their proteins moving.
Plasma membranes = membrane that separates the intracellular contents from the
extracellular environment.
- They are crucial in tissue organization
- They allow the cell to achieve a certain structure and to communicate/connect with
other cells. cell communication occurs via neurotransmitter receptors and hormone
receptors.
- They also maintain cellular homeostasis and acts as a barrier to the movement of
molecules and selectively transports other molecules. Hormones are in different
concentrations inside/outside the cell. Thus, the membrane is responsible for making
sure that they are in the correct concentrations.
• Membrane bound organelles:
1) Smooth ER: lipid synthesis site; acts as calcium storage, which is also important in
muscle cells and neurons.
2) Rough ER: translation of mRNA into membrane associated proteins or for secretion
out of the cell.
3) Golgi: protein + lipid sorting and modification.
4) Mitochondria: ATP synthesis and calcium storage.
5) Endosomes/Lysosomes: sorting (E) and degradation (L)
6) Nucleus: genome of the cell; DNA/RNA synthesis.
Some substances make it across membranes through diffusion (gases); many are also lipophilic
that are readily permeable and can diffuse through membranes.
Most substances cannot readily pass through biological membranes – need to be transported.
A lot of transport that occurs in cells has some travelling from one organelle to another.
(exocytosis) likewise, endocytosis also occurs.
Membrane transport proteins allows select substances to get across biological membranes.
find more resources at oneclass.com
find more resources at oneclass.com
[Forces driving Membrane Transport]
1) Uncharged molecules – facilitated diffusion:
o Depend on the relative concentrations of a solute in/out of the cell; if there is a
large difference, then the net transport will be higher than what it would be if
there is a small difference, and thus be faster. [CONCENTRATION: high → low]
o FD is driven by the thermal motion of molecules that are catalyzed by solute
carriers (glucose), and thus the speed of diffusion is affected by it.
o FICK’S FIRST LAW OF DIFFUSION – equation quantifies the rate at which a
molecule diffuses from A to B; equilibrium is reached when the intracellular
concentration of the solute is equal to the extracellular concentration of the
solute.
2) Water – osmosis
o Osmosis helps move water across cell membranes.
Water will be transported across the semi-permeable membrane entirely
dependent on the force with which the water travels across it.
o The osmotic pressure of a solution depends on the number of molecules in the
solution.
o If you were to put neurons (from dissection) in water instead of an isotonic
solution, the neurons will burst. You always have to make sure that the solution
is isotonic.
3) Ions – a bit complicated
- Concentration/Electrical gradient:
o There are channels inside the membrane that may only facilitate the movement
of potassium or sodium (very specific)
o The diffusion of ions is driven by the concentration gradient as well as the
electrical gradient. there is no net movement of ions if the concentration
gradient and the electrical gradient (aka. Electrochemical gradient) add up to
zero.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Biological membranes = lipids that comes in different forms and shapes. (cholesterol, phospholipids, glycolipids); lipids have a hydrophobic tail and a hydrophilic head. Membranes also contain proteins in them (peripheral, integral) Membranes are very fluid structures with their proteins moving. Plasma membranes = membrane that separates the intracellular contents from the extracellular environment. They allow the cell to achieve a certain structure and to communicate/connect with other cells. Cell communication occurs via neurotransmitter receptors and hormone receptors. They also maintain cellular homeostasis and acts as a barrier to the movement of molecules and selectively transports other molecules. Hormones are in different concentrations inside/outside the cell. Some substances make it across membranes through diffusion (gases); many are also lipophilic that are readily permeable and can diffuse through membranes. Most substances cannot readily pass through biological membranes need to be transported. A lot of transport that occurs in cells has some travelling from one organelle to another. (exocytosis) likewise, endocytosis also occurs.
