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BIOL 155 Chapter Notes -Membrane Transport Protein, Facilitated Diffusion, Membrane Transport

Course Code
BIOL 155
Lawrence Harris

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Biology 153/155
Based on lecture and text material, you should be able to do the following:
define selective permeability and indicate its importance in biological membranes
list the major constituents of cell membranes and indicate the general membrane
function of each
discuss the hydrophilic and hydrophobic nature of membrane phospholipids and discuss
why this is important in forming a lipid bilayer
distinguish between intrinsic and extrinsic membrane proteins and state the reason why
they exist in these different locations
discuss the concept of membrane fluidity
illustrate how some proteins move freely within the membrane while others are anchored
in stationary positions within the membrane
define diffusion (without having to use the phrase "all other things being equal") and list
the physical factors that determine the rate of diffusion
describe which types of molecules can diffuse through cell membranes and the routes
through which they diffuse
describe the different types of membrane transport proteins and how it is believed they
assist the movement of molecules across the membrane
describe how these proteins can be so specific with regards to which molecules they will
describe the process of active transport by membrane transport proteins
illustrate the manner in which facilitated diffusion differs from active transport
define osmosis (in terms of water molecules, not solute particles) and describe the
physical factors which determine the direction and rate of osmosis
compare the structure and function of tight junctions, desmosomes, and gap junctions
list the primary functions served by membranes in cells
define organelle
describe the structure, composition and function of the cell nucleus
describe the structure and function of ribosomes
describe the structure and function of mitochondria
define the endomembrane system
distinguish between the structure and function of smooth and rough endoplasmic
describe the structure and function of the Golgi apparatus and lysosome
define endocytosis and exocytosis, and distinguish between pinocytosis and phagocytosis
describe how new cell membranes are formed
describe the concept of membrane flow and use it to show how new cell membrane is
transported from its site of synthesis to the plasma membrane.
define cytoskeleton and provide examples of cytoskeletal components
define glycocalyx and discuss its function
Cell Growth and Reproduction

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list the phases of the cell cycle and describe the events of each phase
describe DNA replication
define gene and explain the function of genes
define transcription
distinguish between mRNA, tRNA, and rRNA
define translation
describe the process of protein synthesis
Cell Living structural and functional unit of all organisms
Genetic Code Information encoded in nucleotide base sequences.
Nucleus (nucle = pit, kernel) The control center of a cell; contains genetic
material in the form of diffuse chromatin threads or condensed
Cytoplasm (cyto = cell; plasm = shaped or molded) The cellular material surrounding
the nucleus and enclosed by the plasma membrane.
Organelle (elle = little) Small cellular structure (ribosome, mitochondrion, etc.) that performs
specific function(s) for the cell as a whole. With the exception of ribosomes all
organelles are membrane bound.
Hydrophilic and (hydro = water; phil = love; phob = fear, dislike) Terms that refer to
Hydrophobic molecules or portions of molecules that interact with water and
charged particles (hydrophilic) or only interact with non-polar molecules
Passive Transport Membrane transport processes that do not require cellular energy; e.g.
diffusion, osmosis, facilitated diffusion.
Tonicity (ton = strength) A measure of the ability of a solution to cause a change in cell
shape or tone by promoting the osmotic flow of water.
Active Transport Membrane transport processes for which ATP is required.
Mitosis Process during which the chromosomes are redistributed to two daughter nuclei;
nuclear division. Typically followed by a cytoplasmic division (cytokinesis).

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The cell theory assumes the following:
1) The cell is the basic unit of life
2) The activity of an organism is dependent on the individual and collective activities of its
3) The biochemical activities of cells are determined by subcellular structures
4) All cells arise from pre-existing cells
Most cells are small, depend on external energy sources, selectively regulate exchange of material
with their environments and use information in their DNA to regulate their chemistry.
Each cell contains the genetic information necessary to produce an entire organism. Thus:
There are many examples where an entire plant can be produced from only a small part of
a plant
Organelles can be sustained in culture but none can reproduce an entire cell, not even the
There is tremendous diversity in diameter, length and shape of different cells.
A. STRUCTURE (pp 68-70)
The Fluid Mosaic Model
Biological membranes have two components:
1. Phospholipid bilayer and
2. Proteins
Phospholipid bilayer:
. Polar phosphate heads and non-polar lipid tails orient initially through hydrophilic and
hydrophobic interactions.
. Weak bonds between the non-polar lipid tails stabilize the membrane - this produces a highly
organized and oriented structure dictated by polarity.
. Cholesterol has a polar and a short non-polar region. It binds with the phospholipid head and
stabilizes the outer portion of the membrane.
Proteins are incorporated into the membrane in the following ways:
. Extrinsic or peripheral proteins are attached to either the external or internal surface of the
. Intrinsic or integral proteins project through both surfaces (span the bilayer).
All these proteins act as one or more of the following:
transport proteins
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