Anu Singh-Cundy • Michael L. Cain
Discover Biology
FIFTH EDITION
CHAPTER 7
Cell Membranes, Transport, and
Communica5on
© 2012 W. W. Norton & Company, Inc.
The Plasma Membrane is
Gate and Gatekeeper
• Transport proteins
• only certain substances enter or leave the cell
• LOTS of energy needed to maintain the
chemical balance between the interior and
exterior of the cell
Diffusion cuts down on how much energy would be needed
Diffusion
Passive Movement down a Concentra5on
Gradient
• Diffusion passive transport of a substance from a
region of higher concentra5on to a region of
lower concentra5on un5l it has reached
equilibrium
• Small substances diffuse faster than larger
substances
• Heat increases the rate of diffusion
• The greater the difference in concentra5on of
two substances, the greater the rate of diffusion
Osmosis
• SPECIAL kind of diffusion
• S5ll passive diffusion
• moves water
(ONLY WATER)
Osmosis
• hypotonic soluAon
• hypertonic soluAon
• isotonic soluAon
Facilitated Membrane Transport
• passive transmembrane movement of a
substance with assistance of transport
proteins:
– Channel proteins
– Carrier proteins
BUT Some Carrier proteins NEED
ENERGY
– Ac5ve carrier proteins
• Immune cells use phagocytosis to ingest large
par5cles such as a bacteria or viruses
http://www.youtube.com/watch?v
=JnlULOjUhSQ
Cellular Connec5ons
• Vertebrate animals have three types of cell
junc5ons:
– Anchoring junc5ons
– Tight junc5ons
– Gap junc5ons
Cell Signaling
• based on signaling molecules
• A target cell receives a signal through
receptor proteins located on the plasma
membrane
• Signaling molecules at the cell surface relay
signals through the cytoplasm through a series
of events known as signal transducAon
pathways
Concept Quiz
The main difference between active and
passive transport is
A.
Passive transport goes up a concentration
gradient.
B.
Active transport goes down a concentration
gradient.
C.
Active transport requires energy.
D.
Passive transport requires energy.
Concept Quiz
A.
B.
C.
D.
______ are connections between
animal cells that allow
communication.
Plasmodesmata
Gap junctions
Anchoring junctions
Tight junctions
Concept Quiz
__________ involves the ingestion of
specific molecules by the membrane
A. Endocytosis
B. Pinocytosis
C. Exocytosis
D. Receptor‑mediated endocytosis