Physiology 31 Lecture
Chapter 5 – Membrane Dynamics
I. Overview
A. Membranes in the Body
B. Cell Membranes
C. Body Fluid Compartments
D. Movement Across Cell Membranes
E. Molecular Movement Across the Epithelium
F. Electrical Disequilibrium in the Body
G. Integrated Membrane Processes
II. _________ in the Body may be cell membranes or epithelial tissues
A. ___________ tissues line body cavities and separate compartments.
1. Epithelial tissues compose ________ and mucous membranes
2. ___________ membranes secrete mucus and line hollow tubes, such as the _____,
respiratory, and urogenital tracts.
3. __________ membranes secrete serous fluid, are composed of mesothelium, and line
ventral body cavities. These membranes include the
a. __________ that line the thoracic cavity and cover the lungs
b. _____________ that surrounds the heart
c. _____________ that lines the abdominal cavity and covers the internal organs
B. Cell membranes that enclose cells and their organelles are ___________ permeable,
compartmentalizing the cells
III. Cell Membranes
A. ______________ of the cell membrane include
1. Physical ____________, separating intracellular fluid (ICF) from the extracellular fluid
(ECF)
2. Regulation of ____________ of materials with the environment
3. _________________ between the cell and its environment via receptors
4. Structural ________ – cytoskeletal proteins maintain cell shape and junctions between
adjacent cells and the extracellular matrix (ECM). Cell __________ include
a. __________ junctions – fluid tight seals between cells
b. ___________ junctions, such as desmosomes – spot-rivet like attachments between
cells and the ECM that allow stretching
c. ______ junctions – protein pores between cells that allow ions to move from cell to
cell
B. Cell membranes have been described as a fluid ______ model with
1. A double layer of fluid phospho________ with
2. A mosaic of ___________ embedded in the lipids and
3. ________ attached to the lipids and proteins on the cell surface
C. Two types of _______ compose the cell membrane – phospholipids and cholesterol
1. ________lipids form a bilayer around the cell
a. Phosphate heads are ______ (hydrophilic), thus interact with the intracellular and
extracellular aqueous environments
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b. Lipid tails are _________ (hydrophobic), thus interact with each other in the
membrane interior
c.
______ uncharged molecules (O2, CO2), H2O, and _______ can move directly
through the bilayer.
2. _____________ in the membrane makes it impermeable to water soluble molecules and
keeps the membrane flexible
D. Membrane ___________ may be peripheral or integral
1. _________ proteins are attached to the inner and outer surfaces of the cell membrane,
and include ______ and structural proteins
2. ____________ proteins extend into, and often through, the membrane. These proteins
include
a. ____________ proteins, which have 3 roles
1) Maintain the cell’s ________
2) Create cell __________ that hold cells together
3) Attach cells to the _______
b. __________ - catalysts that bind specific substrates in the ICF or ECF and speed up
chemical reactions
c. ____________ are two types:
1) Those that bind a specific substance (________), such as a hormone or
neurotransmitter, and trigger cellular activities
2) ___________ Markers - major histocompatibility complex (MHC)
_______proteins (and glycolipids) that allow cells to recognize what is “self” and
“nonself.”
d. __________ (“gates”) - water-filled pores that open and close to allow specific
substances, such as water or ions (e. g.: K+, Cl-, Na+), to cross. Channels include
those that are
1) ___________ gated – triggered to open or close by chemical ligands that bind to
them
2) __________ gated – triggered by voltage changes
3) _____________ gated – triggered by a physical change (e.g.: temperature or
pressure)
e. _____________ - bind specific substrates (small organic molecules and ions) and
move them across the membrane via shape changes in the protein
E. Membrane _______________ attach to lipids and proteins
1. Glyco_________ are membrane proteins with ________ polymers attached to their
surface
2. Glyco________ are lipids with sugars attached to their surface
3. Collectively, these sugar groups on the extracellular membrane surface are called the
___________, which functions in immune response
IV. Body Fluid Compartments
A. Cell __________ divide the inside of the body into compartments
1. Intracellular fluid (____) is found within cells
2. Extracellular fluid(____) surrounds cells, and is subdivided into
a. ______________ fluid that bathes the cells and
b. __________, the fluid portion of blood
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B. Many _________ can cross capillary walls from plasma to interstitial fluid but
exchange between the intracellular and extracellular fluids is more ____________ by
cell membranes
V. Movement Across Cell Membranes
A. ___________ – movement of particles through a membrane due to ___________
pressure, the force exerted on a membrane by water (e.g., blood pressure forces solutes
from capillaries to tissues)
B. __________ Motion – the random motion of microscopic particles in a solid, liquid or
gas, caused by ____________ with surrounding molecules – is the basis for molecular
movement
C. Two properties of a molecule influence its movement across a cell membrane – _______
and __________
1. ________ molecules, such as O2, CO2, H2O, and nonpolar lipids can ________ freely
through most phospholipid bilayers
2. _________ molecules and ions must be ____________ across via membrane proteins
D. Substances _______ across cell membranes by either passive or active transport
1. ___________ transport is down a substance’s concentration gradient (from ______ to
_____ concentration), thus doesn’t require ATP energy
2. ______ transport is against a substance’s concentration gradient (from ____ to _____
concentration), which requires ____ energy
E. ____________ transport includes simple diffusion, osmosis, and facilitated diffusion
1. Simple ____________ - movement of particles down their concentration gradient from
_______ to _______ concentration until ___________ is established. (No ATP
required) Diffusion ______ is influenced by
a. Temperature – higher temp. = ________ diffusion
b. Molecular Wt. – ______ particles diffuse faster than _______ ones
c. ________________ gradient – greater concentration difference = faster diffusion
d. ____________ – diffusion is rapid over short distances, but slow over long distances
e. Membrane __________ area – larger surface = faster diffusion
f. Membrane ___________ – thicker membranes = slower diffusion
2. ___________ - diffusion of H2O molecules across a membrane, influenced by the
________ (ability of a solution to affect the fluid volume & pressure in a cell) of the
solutions on both sides of the membrane
a. ____tonic solution has a _____ concentration of nonpenetrating _______ (thus, less
water) than another solution. Water diffuses through the membrane _________ the
hypertonic solution
b. ____tonic solution has a solute concentration ______ to another solution. No __
diffusion of water occurs across the membrane. (____% NaCl normal saline solution
is isotonic to human cells)
c. ____tonic solution has a _____ concentration of nonpenetrating ______ (thus, more
water) than another solution. Water diffuses through the membrane ____________
the hypotonic solution
d. ___________ is measured in terms of osmolarity or osmolality
1) _________ is the number of solute osmoles per liter of water (1 osmole = 1 mole
of dissolved particles; e.g.: about ____ mOsM NaCl is isotonic to human cells)
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2) ___________ is the concentration of milliosmoles per ___ water (mOsm/kg); often
used when estimating a person’s body water content
2. _______________ Diffusion (mediated transport) - diffusion of molecules (e.g.: glucose,
amino acids) and ions (e.g.: Na+, Cl-, K+, Ca2+) down their conc. gradient across a
membrane via specific protein __________ and _________ proteins. No ATP required.
F. __________-mediated transport exhibits specificity, competition, and saturation
1. ___________ – carriers, such as GLUT transporters, generally move only ____ type of
molecule, or related molecules
2. Competition – related molecules _________ for binding sites on their transport
proteins. Competitive ___________ can block molecular transport
3. ____________ occurs when a group of transporters are all working at their maximum
rates (transport maximum)
G. _______ Transport - carrier proteins in plasma membrane “pump” molecules or ions into
or out of the cell ________ their concentration gradient (from _____ to _____ concentration).
Requires ___ energy.
1. _________ Active Transport involves ATPases, such as the ___/___ pump, which
pumps Na+ out of cell, K+ into cell
a. Carrier binds intracellular ____
b. Carrier is phosphorylated by ____  ADP + Pi
c. Carrier changes conformation (______)
d. Carrier releases ___ to outside of membrane, then binds extracellular ___
e. ___ dissociates from carrier, and carrier releases ___ inside cell
f. Carrier returns to original __________
2. _________ Active Transport uses the energy provided by primary active transport to
move substances across a membrane. Two types
a. ___________ – movement of one substance moving against its gradient by traveling in
the _______ direction as a substance diffusing with its gradient (e.g., glucose with
Na+)
b. ___________ – movement of one substance moving against its gradient by traveling in
the __________ direction as a substance diffusing with its gradient (e.g., Na+ and H+)
H. ___________ (Bulk) transport - used to move ______ substances (e. g., proteins,
polysaccharides) into and out of cell (Requires ____)
1. _______cytosis - extracellular substances surrounded by a cell membrane and
brought into cell in ___________. Includes
a. _______cytosis in which solid particles are ingested and
b. _______cytosis in which liquids are ingested.
c. _________-mediated endocytosis – ligands (e.g., LDL) bind to membrane
receptors found in clathrin-coated pits
2. _____cytosis - membrane-enclosed secretory __________ fuse with the plasma
membrane, which opens to release their contents outside the cell.
VI. Molecular Movement Across the ____________
A. Recall that epithelial membranes line body cavities and the ______ within them
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B. Molecules moving from one compartment of the body to another (e.g.: through the
epithelium of the GI tract) must cross _____ cell membranes, the
1. ________ membrane on the luminal side of the tube, and the
2. _____________ membrane on the side of the extracellular fluid
C. ______epithelial transport (the movement across epithelial cells) requires both
________ and ________ transport; thus the apical and basolateral membranes have
different membrane _________
1. ___/___ ATPases are usually found in the basolateral membrane
2. Na+/________ symporters are usually found in the apical membrane
3. This “polarized” distribution of transporters allows __________ movement of some
molecules across the epithelium
4. Transport of materials from the lumen to the ECF is called ____________
5. Movement of materials from the ECF to the lumen is called ____________
6. Molecules too large to cross the membrane via transport proteins are generally
transported in ________ (i.e., endo- and exocytosis)
VII. Electrical Disequilibrium in the Body
A. The body is in a state of electrical _________________ because
1. Diffusion and active transport of ions across cell membranes creates a difference in
charge called an electrical gradient (or __________)
2. The inside of the cell is usually more ________ than the outside
3. Movement of an ion across the cell membrane is influenced by the _____________
gradient for that ion.
B. An unstimulated cell’s electrical gradient is referred to as its _________ membrane
_________
1. In most cells, ___ is the main ion that determines the resting membrane potential (more
K+ _______ the cell than outside)
2. Changes in membrane ____________ to ions, such as K+, Na+, Ca2+ and Cl-, will alter
membrane potential and create electrical ___________, which occur in nerve and
muscle tissues
VIII. Integrated Membrane Processes
A. _____ cells of the pancreas secrete ________ in response to rising blood _________
levels after a meal, but how?
1. When blood glucose levels are ___, K+ ATPase channels in beta cell membranes are
_____, allowing K+ to leak out, establishing a resting membrane potential
2. As blood glucose levels ________, glucose enters into ______ cells via glucose
transporters, increasing ____ production via cellular respiration
3. ATP binds to K+ ____ase and _______ the channel, which changes the membrane
potential (_____________)
4. Membrane depolarization opens voltage-gated ____ channels that allow Ca2+ to enter
the cell
5. Ca2+ triggers exocytosis of ________ from vesicles in the beta cells
B. ____________ other than membrane potential are also used for communication and
coordination in the body