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Chapter 5

Chapter 5 notes


Department
Biological Sciences
Course Code
BIOD27H3
Professor
A.Elia
Chapter
5

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Chapter 5- Membrane Dynamics
Cont’d from page 165-177
Resting Membrane Potential
-body’s solutes such as lactate and pyruvate are also ions, therefore they carry a net
electric charge
-sodium dominates the ECF, on the anion side chloride ions mostly remain with Na in the
ECF
-potassium is major cation within the cells
-phosphate ions negatively charged proteins are major anions of the ICF
-intracellular have more anions therefore net negative charge, extracellular have more
cations therefore net positive charge. This is why intracellular and extracellular are not in
electrical equilibrium but electrical disequilibrium
-Electrical Review
oAtoms neutral; positively charged protons, negatively charged electrons, and
uncharged neutrons
oRemoval or addition of electrons is what creates charged particles we know as
ions
oFor every positive ion there is a matching negative ion somewhere in the body
(ex. NaCl)
oRules to follow for electricity in physiological systems:
1. The law of conservation of electrical charge
Net amount of electrical charge produced in any process is zero.
This means that for every positive charge on an ion, there is an
electron on another ion. Overall human body is electrically neutral
2. opposite charges attract, but two charges of the same type repel each
other. Protons and electrons in ions exhibit this attraction
3. separating positive charges from negative charges requires energy. Ex.
Separating protons from electrons
4. separated positive and negative charges move freely toward each other,
this material is called a conductor (ex. Water). If the separated charges are
unable to move through material that separates them the material is an
insulator. ( ex phospholipid bilayer)
-The Cell membrane enables separation of electrical charge in the body
oSeparation of electrical charge takes place across membrane
oIn a molecule where it is electrically and chemically at equilibrium, when it is
placed in aqueous solution the phospholipid bilayer of the cell, is not permeable to
ions. Active transport carrier protein is inserted into membrane. This carrier uses
energy to move positive ions out of cell against concentration gradient. Negative
ions attempt to follow positive ions because of attraction. Since membrane is
impermeable to negative ion, they remain trapped inside.
oElectrical gradient; difference in net charge between to regions. (inside of cell
negative compared to outside)
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