lecture notebook to accompany principles of life...life concepts sadava sinauer associates morales...
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Sinauer Associates, Inc. W. H. Freeman and Company
Copyright © 2012 Sinauer Associates, Inc. Cover photograph © Fred Bavendam/Minden Pictures.
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© 2012 Sinauer Associates, Inc.
Cell Membranes and Signaling 5
2
POL HillisSinauer AssociatesMorales Studio Figure 05.01 Date 06-28-10
Carbohydrates are attached to the outer surface of proteins(forming glycoproteins) or lipids (forming glycolipids).
In animal cells, some membrane proteins associate with filamentsin the extracellular matrix.
Peripheral membraneproteins do not penetratethe bilayer at all.
Some membrane proteins interact with the interior cytoskeleton.
Cholesterol molecules interspersed among phospholipid tails in thebilayer influence the fluidity offatty acids in the membrane.
Some integral proteins cross the entire phospholipidbilayer; others penetrate onlypartially into the bilayer.
Phospholipid
Extracellularmatrix
Outside of cell
Inside of cell
Cytoskeleton
FIGURE 5.1 Membrane Molecular Structure (Page 63)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 3
POL HillisSinauer AssociatesMorales Studio Figure INTXT05.02 Date 06-15-10
Hydrophilic R groups (sidechains) in exposed partsof the protein interact withaqueous environments.
Hydrophobic R groups interact with the hydrophobiccore of the membrane awayfrom water.
Hydrophobicinteriorof bilayer
Outside of cell(aqueous)
Inside of cell(aqueous)
IN-TEXT-ART (Page 65)
POL HillisSinauer AssociatesMorales Studio Figure INTXT05.03 Date 06-15-10
Exposed regions of membraneglycoproteinsbind to each other, causing cells to adhere.
Cells
IN-TEXT-ART (Page 66)
POL HillisSinauer AssociatesMorales Studio Figure INTXT05.01 Date 06-15-10
“Head”
“Tails”
IN-TEXT-ART (Page 64)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 4
POL HillisSinauer AssociatesMorales Studio Figure 05.02 Date 06-15-10
The cells are fused together to create a heterokaryon.
The mouse cell has a membraneprotein that can belabeled with a green dye.
The human cell has a membraneprotein that can be labeled with a red dye.
Initially, the mouse and human membrane proteins are on different sides of the heterokaryon.
After 40 minutes, the mouse and human membrane proteins are intermixed.
Go to yourBioPortal.com for original citations, discussions,and relevant links for all INVESTIGATION figures.
METHOD
Membrane proteins can diffuse rapidly in the plane of the membrane.
Proteins embedded in a membrane can diffuse freely within the membrane.
METHOD
FIGURE 5.2 Rapid Diffusion of Membrane Proteins A human cell can be fused to a mouse cell in the laboratory, forming a single large cell (heterokaryon). This phenomenon was used to test whether membrane proteins can diffuse independently in the plane of the plasma membrane.
HYPOTHESIS
CONCLUSION
1
Mouse cell Human cell
Membraneproteins
RESULTS
3
2
ANALYZE THE DATAThe experiment was repeated at various temperatures
with the following results:
Plot these data on a graph of Percentage Mixed vs. Temperature. Explain these data, relating the results to the concepts of diffusion and membrane fluidity.
Temperature (°C)
0152026
Cells with mixed proteins (%)
084277
INVESTIGATION
Heterokaryon
(Page 66)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 5
LIFE Concepts Sadava Sinauer AssociatesMorales Studio Figure 05.00 in text art #4 Date 12-27-09
IN-TEXT-ART (Page 67)
LIFE Concepts Sadava Sinauer AssociatesMorales Studio Figure 05.03 Date 12-27-09
Cells lose waterand shrivel.
from the cell wall(wilting).
Cells take up water, swell, and burst.
Cell stiffens but generallyand pulls away retains its shapebecause cellwall is present.
Cell body shrinks
Animal cell(red blood cells)
Plant cell(leaf epithelialcells)
H2O
H2O
H2O
H2O
H2O
(C) Hypotonic on the outside (dilute solutes outside)
(B) Isotonic (equivalent solute concentration)
(A) Hypertonic on the outside (concentrated solutes outside)
Inside of cell
Outsideof cell
H2O
FIGURE 5.3 Osmosis Can Modify the Shapes of Cells (Page 68)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 6
LIFE Concepts Sadava Sinauer AssociatesMorales Studio Figure 05.04 Date 01-20-10
A polar substance is more concentrated on the outside than the inside of the cell.
Binding of a stimulus molecule causes the pore to open…
3 …and the polar substance can diffuse across the membrane.
2
1
Stimulusmolecule(ligand)
Hydrophobicinterior of bilayer
Binding site
Channelprotein
Outside of cell
Inside of cell
Hydrophilic pore
Closed channel
FIGURE 5.4 A Ligand-Gated Channel Protein Opens in Response to a Stimulus (Page 69)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 7
POL HillisSinauer AssociatesMorales Studio Figure 05.02 Date 06-15-10
This oocyte does not have aquaporins in the cell membrane.
This oocyte has aquaporins inserted experimentally into the cell membrane.
AquaporinmRNA
Aquaporin channel
Water does not diffuse into the cell, so it does not swell.
Water diffuses into the cell through the aquaporin channels, and it swells.
3.5 minutes inhypotonic solution
Proteinsynthesis
Go to yourBioPortal.com for original citations, discussions,and relevant links for all INVESTIGATION figures.
Aquaporin increases the rate of water diffusion across the cell membrane.
Aquaporin increases membrane permeability to water.
METHOD
FIGURE 5.5 Aquaporins Increase Membrane Permeability to Water A protein was isolated from the membranes of cells in which water diffuses rapidly across the membranes. When the protein was inserted into oocytes, which do not normally have it, the water permeability of the oocytes was greatly increased.
HYPOTHESIS
CONCLUSION
RESULTS
ANALYZE THE DATA
INVESTIGATION
Oocytes were injected with aquaporin mRNA (red circles) or a solution without mRNA (blue circles). Water permeability was tested by incubat-
ing the oocytes in hypotonic solution and measuring cell volume. After time X in the upper curve, intact oocytes were not visible:
A. Why did the cells increase in volume?B. What happened at time X?C. Calculate the relative rates (volume increase per minute) of swelling in the control and experimental curves. What does this show about the effectiveness of mRNA injection?
Rel
ativ
e vo
lum
e
1 2 3 4 5
X
Time (min)
1.1
1.0
1.2
1.3
1.4 With mRNA
Without mRNA
For more, go to Working with Data 5.1 at yourBioPortal.com.
(Page 70)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 8
LIFE Concepts Sadava Sinauer AssociatesMorales Studio Figure 05.06 Date 06-28-10
…releasing the glucose.
The carrier protein returnsto its original shape, readyto bind another glucose.
3 …which then changes the protein’s shape…
Glucose binds to the protein…
The carrier protein has a glucose binding site.
4
21
5
All carriers are occupied.
Some carriers are occupied.
Outside of cell
Inside of cell
Low glucose concentration
High glucose concentration
Glucose concentrationoutside the cell
Glucose carrier protein
Glucose
Rat
e of
diff
usio
nin
to th
e ce
ll
(A)
(B)
FIGURE 5.6 A Carrier Protein Facilitates Diffusion (Page 71)
TABLE 5.1 Membrane Transport Mechanisms FACILITATED DIFFUSION (CHANNEL OR CARRIER SIMPLE DIFFUSION PROTEIN) ACTIVE TRANSPORT
Cellular energy No No Yes required?
Driving force Concentration Concentration ATP hydrolysis (against gradient gradient concentration gradient)
Membrane protein No Yes Yes required?
Specificity No Yes Yes
(Page 71)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 9
LIFE Concepts Sadava Sinauer AssociatesMorales Studio Figure 05.07 Date 01-20-10
Hydrolysis of ATP phosphorylates thepump protein and changes its shape.
3 Na+ and 1 ATP bind to the protein “pump.”
3 The shape changereleases Na+ outsidethe cell and enables K+ to bind to the pump.
Release of Pi returns thepump to its original shape,releasing K+ to the cell'sinterior and once againexposing Na+ binding sites.The cycle repeats.
4
2
1
We can’t make these as smooth and oval as previous proteins because we need to attach the molecuels on the edges and we need the room to squeeze them in. I took off a few irrregularities.
Outside of cell
High Na+ concentration,low K+ concentration
Inside of cell
High K+ concentration,low Na+ concentration
ADPNa+
Na+
K+K+
K+
Na+–K+ pump
Pi
PiPi
Pi
ATP
FIGURE 5.7 Primary Active Transport: The Sodium–Potassium Pump (Page 72)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 10
LIFE Concepts Sadava Sinauer AssociatesMorales Studio Figure 05.08 Date 01-20-10
A vesicle fuses with the plasma membrane. The contents of the vesicle are released, and itsmembrane becomes part of the plasma membrane.
The plasma membranesurrounds a part of theexterior environment and buds off as a vesicle.
(A) Endocytosis
(B) Exocytosis
Plasma membraneOutside of cell
Inside of cell Endocytotic vesicle
Secretory vesicle
FIGURE 5.8 Endocytosis and Exocytosis (Page 73)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 11
LIFE Concepts Sadava Sinauer AssociatesMorales Studio Figure 05.09 Date 06-28-10
The protein clathrin coats the cytoplasmic side of the plasma membrane at a coated pit.
The endocytosed contents are surrounded by a clathrin-coated vesicle.
Coatedvesicle
Coatedvesicle
Coatedpit
Cytoplasm
Outsideof cell
Outsideof cell
Specificsubstancebinding toreceptorproteins
Clathrinmolecules
Clathrinmolecules
Specificsubstancebinding toreceptorproteins
Cytoplasm
Coated pit
FIGURE 5.9 Receptor-Mediated Endocytosis (Page 74)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 12
LIFE Concepts Sadava Sinauer AssociatesMorales Studio Figure 05.10 Date 12-27-09
Circulating signalssuch as hormones are transported by the circulatory system and bind to receptors on distant cells.
Autocrine signals bind to receptors on the same cell that secretes them.
Cells without receptors for a particular signal do not respond to that signal.
Paracrine signals bind toreceptors on nearby cells.
Circulatory vessel(e.g., a blood vessel)
Target cell
Target cell
Target cell
ReceptorSecreting cell
FIGURE 5.10 Chemical Signaling Concepts (Page 75)
POL HillisSinauer AssociatesMorales Studio Figure 05.11 Date 06-15-10
A signal moelculearrives at the target cell.
1
A signal molecule binds to a receptor protein in the cell surface or inside the cytoplasm.
2
Signal binding changes the three-dimensional shape of the receptor and exposes its active site.
3
The activated receptor activates asignal transduction pathway tobring about cellular changes.
4
Signal molecule
Receptor
Inactivesignal transductionmolecule
Activatedsignal transductionmolecule
Short-termresponses:enzyme activation,cell movement
Long-termresponses:altered DNAtranscription
FIGURE 5.11 Signal Transduction Concepts (Page 76)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 13
LIFE Concepts Sadava Sinauer AssociatesMorales Studio Figure 05.12 Date 12-27-09
Growth factor (ligand) fits noncovalently into receptor.
Two receptor subunits are transmembrane proteins.Outside of cell
Ligand
Inside of cell
Cell membrane
FIGURE 5.12 A Signal Binds to Its Receptor (Page 76)
POL HillisSinauer AssociatesMorales Studio Figure INTXT05.05 Date 06-15-10
Signal molecule
Receptor
R + L RL
IN-TEXT-ART (Page 76)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 14
LIFE Concepts Sadava Sinauer AssociatesMorales Studio Figure 05.14 Date 12-27-09
Hormone binding to the receptoractivates the G protein. GTP replaces GDP.
2The G protein and effectorprotein are inactive until thesignal arrives.
1
The GTP on the G protein is hydrolyzed to GDP but remains boundto the G protein.
4
Part of the activated G protein activates an effector protein that converts thousands of reactants to products, thus amplifying the action of a single signal molecule.
3
Outside of cell
Inside of cell
Signal (hormone)
G protein-linkedreceptor Inactive
G proteinInactive effectorprotein Reactant Product
Amplification
ActivatedG protein
Activatedeffector protein
GDP GTP GDP
FIGURE 5.14 A G Protein–Linked Receptor (Page 78)
POL HillisSinauer AssociatesMorales Studio Figure 05.13 Date 06-15-10
A conformational change in the receptor transmits the signal tothe cytoplasm.
2
The receptorbinds thesignal.
1
…which phos-phorylates targets, triggering a cas-cade of chemical responses insidethe cell.
3
4
The signal activates the receptor’s protein kinase domain in the cytoplasm…
Cellular responses
Target
Outside of cell
Inside of cell
Receptor
Proteinkinasedomain(inactive)
Signal(insulin)
P
Phosphategroups
PPPP
ATPADP
FIGURE 5.13 A Protein Kinase Receptor (Page 77)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 15
POL HillisSinauer AssociatesMorales Studio Figure 5.15 Date 06-24-10
2
Cytoplasm containsinactiveglycogen phosphorylase
Membranes containepinephrine receptors
Liver
3 The membranes are removed by centrifugation, leaving only the solution in which they were incubated.
4 Drops of membrane-freesolution areadded to thecytoplasm.
The hormone epinephrine is added to the membranes and allowed to incubate along with the substrate for synthesis of a second messenger.
Liver tissue is homogenizedand separated into plasma membrane and cytoplasm fractions.
2
1
The activity of previously inactive liver glycogen phosphorylasewas measured with and without epinephrine incubation,with these results:
A. What do these data show?
B. Propose an experiment to show that the factor that activates the enzyme is stable on heating and give predicted data.
C. Propose an experiment to show that cAMP can replace the particulate fraction and hormone treatment and give predicted data.
Condition
HomogenateHomogenate + epinephrineCytoplasm fractionCytoplasm + epinephrineCytoplasm + membranesCytoplasm + membranes + epinephrine
Enzyme activity (units)
0.42.50.20.40.42.0
For more, go to Working with Data 5.2 at yourBioPortal.com.
INVESTIGATION
A second messenger mediates between receptor activation at the plasma membrane and enzyme activation in the cytoplasm.
A soluble second messenger, produced by hormone-activated membranes, is present in the solution and activates enzymes in the cytoplasm.
Go to yourBioPortal.com for original citations, discussions, and relevant links for all INVESTIGATION figures.
HYPOTHESIS
FIGURE 5.15 The Discovery of a Second Messenger Glyco-gen phosphorylase is activated in liver cells after epinephrine binds to a membrane receptor. Sutherland and his colleagues observed that this activation could occur in vivo only if fragments
of the plasma membrane were present. They designed experi-ments to show that a second messenger caused the activation of glycogen phosphorylase.
METHOD
CONCLUSION
ANALYZE THE DATA
Active glycogen phosphorylase is present in the cytoplasm.RESULTS
(Page 79)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 16
LIFE Concepts Sadava Sinauer AssociatesMorales Studio Figure 05.15 Date 12-27-09
CH2O–O P
O
O–PP O
O
O–O
O
O–H H
OH OH
NH2
N
N
N
N
C
CH
O CH2
H H
O OH
NH2
N
N
N
N
C
CH
O
HC
C
C
C
C
CH
HC
O
O
–O
P
HC
CHHC
ATP cAMP PPi+
ATP
Phosphate groups
Cyclic AMP (cAMP)
Adenylylcyclase
Adenine
FIGURE 5.16 The Formation of Cyclic AMP (Page 79)
LIFE The Science of Biology 9E Sadava Sinauer AssociatesMorales Studio Figure 07.20 Date 04-20-09
Phosphorylation activates glycogen phosphorylase, releasing stored glucose molecules from glycogen.
Release of glucose by carrier transport fuels “fight-or-flight” response.
Phosphorylation, inducedby epinephrine binding,inactivates glycogensynthase, preventing glucose from being stored as glycogen.
1
The protein kinase cascade amplifies the signal. Here, for every molecule of epinephrine bound, 20 molecules of cAMP are made, each of which activates a molecule of protein kinase A.
2
3
4
Epinephrine
cAMP
Active phosphorylase kinase
Glucose 1-phosphate
Inactive protein kinase A
Inactive phosphorylase kinase
Inactive glycogen phosphorylase
Glycogen
Glucose
Blood glucose
Epinephrinereceptor
Inside of cell
Plasmamembrane
Outside of cell
Outside of cell
10,000
10,000
1,000
100
20
20
1
ATP
ActivatedG proteinsubunit
Activatedadenylylcyclase
Active protein kinase A
Active glycogen phosphorylase
Active glycogensynthase
Inactive glycogensynthase
GTP
FIGURE 5.17 A Cascade of Reactions Leads to Altered Enzyme Activity (Page 80)
© 2012 Sinauer Associates, Inc.
Chapter 5 | Cell Membranes and Signaling 17
LIFE Concepts Sadava Sinauer AssociatesMorales Studio Figure 05.17 Date 12-27-09
Inactiveenzyme
InactiveG protein
ActiveG protein
Adenylylcyclase
(A)
(B)
(C)
Activeenzyme
GDP
ATP
ATP
GTP
P
Protein kinase
Proteinphosphatase
Receptor binding
GTPase
cAMPPhosphodiesterase
AMP
Pi
FIGURE 5.18 Signal Transduction Regulatory Mechanisms (Page 81)
LIFE The Science of Biology 9E Sadava Sinauer AssociatesMorales Studio Figure 07.04 Date 05-18-09
N
N
N
N
NH2
H HHH
N
N
N
O
O
N
H3C
CH3
CH3
OH
OH
OH
ON
AdenosineCaffeine
Outsideof cell
Plasmamembrane
Insideof cell
The similar structures of caffeine and adenosine allow them both to bind to the receptor, but only adenosine triggers signal transduction.
The adenosine receptoroccurs in the brain cells.
(B)(A)
Adenosine and caffeine both fit the receptor.
FIGURE 5.19 Caffeine and the Cell Membrane (Page 82)