1. Membrane Structure and Function
Chapter 7
Membrane Structure and Function

2. Phospholipid bilayer Hydrophobic regions of protein Hydrophilic
Fig What component of the cell membrane deals with the fluid part of the model? The mosaic part?
Phospholipid
bilayer
Figure 7.3 The fluid mosaic model for membranes
Hydrophobic regions
of protein
Hydrophilic
regions of protein

3. Unsaturated hydrocarbon tails with kinks Saturated hydro- carbon tails
Fig. 7-5b How else can animal cells adjust the fluidity of the cell membrane?
Fluid
Viscous
Unsaturated hydrocarbon
tails with kinks
Saturated hydro-
carbon tails
Figure 7.5b The fluidity of membranes
(b) Membrane fluidity

4. Membrane proteins Mixed proteins after 1 hour Mouse cell Human cell
Fig If, after many hours, the protein distribution still looked like that in the third image above, would you be able to conclude that proteins don’t move within the membrane? What other explanation could there be?
RESULTS
Membrane proteins
Mixed proteins
after 1 hour
Mouse cell
Figure 7.6 Do membrane proteins move?
Human cell
Hybrid cell

5. EXTRACELLULAR N-terminus SIDE C-terminus CYTOPLASMIC SIDE  Helix
Fig Why is this called a transmembrane protein?
EXTRACELLULAR
SIDE
N-terminus
Figure 7.8 The structure of a transmembrane protein
C-terminus
CYTOPLASMIC
SIDE
 Helix

6. (b) Enzymatic activity (c) Signal transduction
Fig Some transmembrane proteins can bind to a particular ECM molecule and, when bound, transmit a signal into the cell. Use the proteins shown here to explain how this might occur.
Signaling molecule
Enzymes
Receptor
ATP
Signal transduction
(a) Transport
(b) Enzymatic activity
(c) Signal transduction
Figure 7.9 Some functions of membrane proteins
Glyco-
protein
(d) Cell-cell recognition
(e) Intercellular joining
(f) Attachment to
the cytoskeleton
and extracellular
matrix (ECM)

7. ER Transmembrane glycoproteins Secretory protein Glycolipid Golgi
Fig Number the order of the protein pathway. ER
Transmembrane
glycoproteins
Secretory
protein
Glycolipid
Golgi
apparatus
Vesicle
Figure 7.10 Synthesis of membrane components and their orientation on the resulting membrane
Plasma membrane:
Cytoplasmic face
Extracellular face
Transmembrane
glycoprotein
Secreted
protein
Membrane glycolipid

8. Animation: Membrane Selectivity
Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment
Animation: Membrane Selectivity
Animation: Diffusion
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

9. Membrane (cross section)
Fig. 7-11a Is the movement of the dye random? Explain your answer.
Molecules of dye
Membrane (cross section)
WATER
Figure 7.11a The diffusion of solutes across a membrane
Net diffusion
Net diffusion
Equilibrium
(a) Diffusion of one solute

10. (b) Diffusion of two solutes
Fig. 7-11b True or False. Once a dye molecule moves to one side, it is impossible for it to move back to the original side it was on.
Net diffusion
Net diffusion
Equilibrium
Figure 7.11b The diffusion of solutes across a membrane
Net diffusion
Net diffusion
Equilibrium
(b) Diffusion of two solutes

11. Higher concentration Lower Same concentration concentration of sugar
Fig If an orange dye capable of passing through the membrane was added to the left side of the tube above, how would it be distributed at the end of the process? Would the solution levels in the tube on the right be affected?
Lower
concentration
of solute (sugar)
Higher concentration
of sugar
Same concentration
of sugar
H2O
Selectively
permeable
membrane
Figure 7.12 Osmosis
Osmosis

12. cell cell _________ solution _______ solution _________ solution H2O
Fig Fill in the missing information.
_________ solution
_______ solution
_________ solution
H2O
H2O
H2O
H2O
(a)_______
cell
________________
Normal
___________________
H2O
H2O
H2O
H2O
Figure 7.13 The water balance of living cells
(b) Plant
cell
_____________
___________
_____________

13. (a) A contractile vacuole fills with fluid that enters from
Fig How does the paramecium counteract osmosis?
50 µm
Filling vacuole
(a) A contractile vacuole fills with fluid that enters from
a system of canals radiating throughout the cytoplasm.
Contracting vacuole
Figure 7.14 The contractile vacuole of Paramecium: an evolutionary adaptation for osmoregulation
(b) When full, the vacuole and canals contract, expelling
fluid from the cell.

14. Video: Plasmolysis Video: Turgid Elodea Animation: Osmosis
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

15. Channel protein Solute (a) A channel protein Solute Carrier protein
Fig Which protein deals with changing shape?
EXTRACELLULAR FLUID
Channel protein
Solute
CYTOPLASM
(a) A channel protein
Figure 7.15 Two types of transport proteins that carry out facilitated diffusion
Solute
Carrier protein
(b) A carrier protein

16. The Need for Energy in Active Transport
Animation: Active Transport
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17. 1 2 3 6 5 4 EXTRACELLULAR FLUID [Na+] high Na+ [K+] low Na+ Na+ Na+
Fig Summarize each of the 6 steps.
EXTRACELLULAR
FLUID
[Na+] high
Na+
[K+] low
Na+
Na+
Na+
Na+
Na+
Na+
Na+
[Na+] low
ATP P
Na+ P
CYTOPLASM
[K+] high
ADP 1 2 3 K+
Figure 7.16, 1–6 The sodium-potassium pump: a specific case of active transport K+ K+ K+ K+ P K+ P 6 5 4

18. Facilitated diffusion
Fig How is passive transport similar to active transport? How are they different?
Active transport
Passive transport
ATP
Diffusion
Facilitated diffusion
Figure 7.17 Review: passive and active transport

19. – + H+ ATP H+ – + H+ H+ – + H+ H+ – + H+ H+ – + – + Diffusion of H+
Fig How does the cell produce and then maintain the proton gradient? – + H+
ATP H+ – +
Proton pump H+ H+ – + H+ H+ – + H+
Diffusion
of H+
Sucrose-H+
cotransporter
Figure 7.19 Cotransport: active transport driven by a concentration gradient H+ –
Sucrose + – +
Sucrose

20. Animation: Exocytosis
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21. Animation: Exocytosis and Endocytosis Introduction
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

22. Animation: Phagocytosis
For the Cell Biology Video Phagocytosis in Action, go to Animation and Video Files.
Animation: Phagocytosis
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

23. PHAGOCYTOSIS CYTOPLASM 1 µm EXTRACELLULAR FLUID Pseudopodium
Fig. 7-20a How is the extracellular particle digested once inside the cell?
PHAGOCYTOSIS
EXTRACELLULAR
FLUID
CYTOPLASM
1 µm
Pseudopodium
Pseudopodium
of amoeba
“Food” or
other particle
Bacterium
Food
vacuole
Figure 7.20 Endocytosis in animal cells—phagocytosis
Food vacuole
An amoeba engulfing a bacterium
via phagocytosis (TEM)

24. Animation: Pinocytosis
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

25. PINOCYTOSIS Plasma membrane Vesicle 0.5 µm
Fig. 7-20b How is pinocytosis different from phagocytosis?
PINOCYTOSIS
0.5 µm
Plasma
membrane
Pinocytosis vesicles
forming (arrows) in
a cell lining a small
blood vessel (TEM)
Vesicle
Figure 7.20 Endocytosis in animal cells—pinocytosis

26. Animation: Receptor-Mediated Endocytosis
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

27. Coat protein Receptor Coated vesicle Coated pit Ligand A coated pit
Fig. 7-20c How is receptor mediated endocytosis different from pinocytosis?
RECEPTOR-MEDIATED ENDOCYTOSIS
Coat protein
Receptor
Coated
vesicle
Coated
pit
Ligand
A coated pit
and a coated
vesicle formed
during
receptor-
mediated
endocytosis
(TEMs)
Coat
protein
Figure 7.20 Endocytosis in animal cells—receptor-mediated endocytosis
Plasma
membrane
0.25 µm