Download Checklist unit 7: membrane structure and function

BIOLOGY SEMESTER ONE
UNIT 7
CHECKLIST UNIT 7: MEMBRANE STRUCTURE AND FUNCTION
In this module you will investigate cellular membrane structure and function. Cellular
membranes are made of a fluid phospholipid bilayer embedded with proteins. The proteins
function in transport, enzymatic activity, signal transduction, cell-cell recognition, and
intercellular joining. The phospholipid bilayer functions to separate the interior of the cell from
the extracellular matrix in which it resides.
This separation of the interior of the cell from its environment allows for controlled exchange of
substances between the cell and its surroundings. The cell membrane is selectively permeable,
allowing certain substances easy access in and out while limiting others.
Passive transport of materials across the membrane does not have an associated energy cost.
Such transport includes diffusion (referred to as osmosis when water is the substance moving
across the membrane) and facilitated diffusion (when transport is aided by proteins). Active
transport occurs when the cell uses energy to transport materials across its membrane.
Transport is active when ATP fuels the movement of substances against their electrical or
concentration gradients. Ion pumps and co-transport are two mechanism of active transport.
Materials may also be moved across the cell membrane by means of exocytosis and
endocytosis. These are usually used for bulk transfer (when there is more than one molecule to
be move at a time). During exocytosis, vesicles bring materials to the cell, fuse with the cell
membrane and release their contents into it. During endocytosis, molecules enter the cell as
the membrane pinches inward, creating a vesicle to the inside containing the desired
molecules. The three types of endocytosis are phagocytosis, pinocytosis, and receptor
mediated endocytosis.
LEARNING OBJECTIVES
At the end of this module you should be able to:
1. Explain how the fluid mosaic model of membrane structure explains experimental
findings:
a. Actual membranes adhere more strongly to water than do artificial membranes
composed only of phospholipids.
b. Membranes with different functions may differ in type and number of
membrane proteins.
c. Membrane proteins are not very water-soluble.
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BIOLOGY SEMESTER ONE
UNIT 7
d. EMs of freeze-fracture membrane preparations show protein particles
interspersed in a smooth matrix.
2. Explain how membrane fluidity is influenced by temperature and membrane
composition, and explain how cholesterol resists changes in membrane fluidity as
temperatures change.
3. Understand the various functions of membrane proteins.
4. Explain the role of membrane carbohydrates in cell-cell recognition.
5. Define diffusion and understand why it is a passive and spontaneous process; compare
with osmosis, facilitated diffusion, and active transport.
6. Explain why a concentration gradient of a substance across a membrane represents
potential energy.
7. Describe how living cells with and without cell walls regulate water balance.
8. Describe the two forces that combine to produce an electrochemical gradient.
9. Explain how an electrogenic pump creates voltage across a membrane.
10. Describe the process of cotransport.
11. Explain how large molecules are transported across a cell membrane.
12. Distinguish between exocytosis and receptor-mediated endocytosis.
CHECK LIST
 Read Chapter 7: Membrane Structure and Function of Campbell and Reece’s Biology, 8th
Ed.
 As you are reading, address each of the learning objectives listed above.
 It is recommended that you make flash cards for the terminology list provided. This will
be beneficial for studying for the midterm and final exams later in the semester.
 Review the Power point Lecture “Bio 103 Lecture 3b: Membrane Structure and
Function. “
 Review the BioFlix Video “Membrane Transport” from the Mastering Biology Website
and complete the study Sheet associated with the vido.
 For extra practice try the Self Quiz or Practice Test on the Mastering Biology Website.
To log onto the website, use the access code provided in your textbook. You will also
find other resources, such as downloadable MP3 tutorials for each chapter, a glossary,
and an electronic copy of your text- you can catch up on your reading anywhere!
KEY TERMS
active transport
adenosine triphosphate
(ATP)
amphipathic
aquaporin
carbohydrate
concentration gradient
diffusion
electrochemical gradient
electrogenic pump
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endocytosis
exocytosis
facilitated diffusion
flaccid
gated channel
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BIOLOGY SEMESTER ONE
UNIT 7
glycogen
glycolipid
glycoprotein
hypertonic
hypotonic
integral protein
ion channel
isotonic
ligand
low-density lipoprotein
(LDL)
membrane potential
model
myosin
osmoregulation
osmosis
passive transport
peripheral protein
phagocytosis
pinocytosis
plasma membrane
plasmolysis
proton pump
receptor-mediated
endocytosis
selective permeability
sodium-potassium pump
tonicity
transport protein
turgid
ROOT WORDS TO KNOW
amphi- = dual (amphipathic molecule: a molecule that has both a hydrophobic and a
hydrophilic region)
aqua- = water; -pori = a small opening (aquaporin: a transport protein in the plasma membrane
of a plant or animal cell that specifically facilitates the diffusion of water across the membrane)
co- = together; trans- = across (cotransport: the coupling of the "downhill" diffusion of one
substance to the "uphill" transport of another against its own concentration gradient)
electro- = electricity; -genic = producing (electrogenic pump: an ion transport protein
generating voltage across a membrane)
endo- = inner; cyto- = cell (endocytosis: the movement of materials into a cell; cell eating)
exo- = outer (exocytosis: the movement of materials out of a cell)
hyper- = exceeding; -tonus = tension (hypertonic: a solution with a higher concentration of
solutes) hypo- = lower (hypotonic: a solution with a lower concentration of solutes)
iso- = same (isotonic: solutions with equal concentrations of solutes)
phago- = eat (phagocytosis: cell eating)
pino- = drink (pinocytosis: cell drinking)
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BIOLOGY SEMESTER ONE
UNIT 7
plasm- = molded; -lyso = loosen (plasmolysis: a phenomenon in walled cells in which the
cytoplasm shrivels and the plasma membrane pulls away from the cell wall when the cell loses
water to a hypertonic environment)
SOURCES
Campbell, N. A. (2008). Biology, Eighth Edition. San Francisco: Pearson, Benjamin Cummings.
Krogh, D. (2000). Biology, A Guide to the Natural World. Upper Saddle River: Prentice Hall.
Pearson Education. (2010). Retrieved 2010, from Mastering Biology : http://session.masteringbiology.com
NANSLO Biology Core Units and Laboratory Experiments
by the North American Network of Science Labs Online,
a collaboration between WICHE, CCCS, and BCcampus
is licensed under a Creative Commons Attribution 3.0 Unported License;
based on a work at rwsl.nic.bc.ca.
Funded by a grant from EDUCAUSE through the Next Generation Learning Challenges.
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