resp & cell comm review - isd 622 & cell comm review. two main catabolic processes:...
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Two main catabolic processes:
• fermentation: partial degradation of sugars in the
absence of oxygen.
• cellular respiration: uses oxygen to complete the
breakdown of many organic molecules.
• more efficient and widespread
• Most steps occur in mitochondria.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Photosynthetic organisms store energy in organic molecules.
• These are available to…
• themselves, and …
• others that eat them.
Introduction
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 9.1
• ATP (adenosine triphosphate):
• chemical equivalent of a loaded spring.
• trio of PO4- groups are unstable, high-energy.
• ATP ADP + PO4 powers most cellular work
• ATP must be constantly recycled from ADP and PO4
2. Cells recycle the ATP they use for work
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• What’s different in the electron sharing of the reactants vs. the products?
• Where does this energy come from?
• Which atoms got oxidized/reduced?
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 9.3
low energy e- positions
high energy e- positions
glycolysis, the Krebs cycle, the electron
transport chain, and chemiosmosis via
ATP synthase & H+ gradient.
• substrate-level phosphorylation generates the few
ATP’s produced in glycolysis and the Krebs cycle.
• How is this different
from oxidative
phosphorylation?
• no e- transport
chain.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 9.7
• energy investment phase: 2 ATP create reactants with
high free energy by phosphorylating glucose.
• energy payoff phase:
• 4 ATP via substrate-
level phosphorylation
• NAD+ is reduced
to NADH.
• Net Production?
• 2 ATP + 2 NADH
• 2 pyruvate
• NOT used?
• O2
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 9.8
BIG PICTURE
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Fig. 9.10
• More than ¾ of the original energy in one glucose is
still present in two molecules of pyruvate.
• For each
Acetyl CoA
that goes in...
• Lots of high energy
electron carriers are
produced…
• Net of 2 NADH
• 1 FADH2
• Also produced?
• one ATP
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 9.12
Know
THIS
one!
• electron transport
chain:
• Thousands of copies in
the cristae of each
mitochondrion.
• Most parts are proteins
that accept electrons, then
pass them along.
• Electrons drop in free
energy as they pass down
the chain.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 9.15
+ 2 H+
Note the location!
Note what is being pumped!
• ATP synthase in the cristae
makes ATP from ADP & Pi.
• osmos – “to push”
• chemiosmosis*: using a
chemical’s “push”
• Push of H+ gradient powers
ATP synthase
• http://www.youtube.com/watch?v=xbJ0nbzt5Kw
• start at 40 seconds, watch next 3:10
• http://www.youtube.com/watch?v=FFBr3ANCkb4
• 5 min of Ninja Respiration fun!
* vs. substrate level
phosphorylationCopyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 9.14
• alcohol fermentation:
• performed by yeast; used in brewing and winemaking.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 9.17a
• lactic acid fermentation:
• Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt.
• Muscle cells switch from aerobic respiration to lactic acid fermentation to generate ATP if O2 is scarce.
• lactate is convertedback to pyruvate in the liver.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 9.17b
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 9.18
• Some organisms (facultative anaerobes), including
yeast and many bacteria, can survive using either
fermentation or respiration.
• human muscle cells too.
• ex: phosphofructokinase
catalizes 3rd glycolysis step
• high ATP levels enzyme
inhibition
• high ADP/AMP levels enzyme
activation.
• inhibition by citrate slows
glycolysis until Krebs cycle “catches
up”.
Fig. 9.20
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 11
Cell Communication
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Evolution of Cell Signaling
• Yeast cells
– Identify their
mates by cell
signaling
factorReceptor
Exchange of
mating factors.
Each cell type
secretes a
mating factor
that binds to
receptors on
the other cell
type.
1
Mating. Binding
of the factors to
receptors
induces changes
in the cells that
lead to their
fusion.
New a/ cell.
The nucleus of
the fused cell
includes all the
genes from the
a and a cells.
2
3
factorYeast cell,
mating type a
Yeast cell,
mating type
a/
a
a
Figure 11.2
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 11.3 (b) Cell-cell recognition. Two cells in an animal may communicate by interaction between molecules protruding from their surfaces.
• In local signaling, animal cells
– May communicate via direct contact
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In other cases, animal cells
– Communicate using local regulators
(a) Paracrine signaling. (b) Synaptic signaling
Local regulator
diffuses through
extracellular fluid
Target cell
Secretory
vesicle
Electrical signal
along nerve cell
triggers release of
neurotransmitter
Neurotransmitter
diffuses across
synapse
Target cell
is stimulated
Local signaling
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In long-distance signaling
– Both plants and animals
use hormones
– Why do only certain
cells respond? Hormone travels
in bloodstream
to target cells
(c) Hormonal signaling. Specialized
endocrine cells secrete hormones
into body fluids, often the blood.
Hormones may reach virtually all
body cells.
Long-distance signaling
Blood
vessel
Target
cell
Endocrine cell
Figure 11.4 C
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
EXTRACELLULAR
FLUID
Receptor
Signal
molecule
Relay molecules in a signal transduction pathway
Plasma membrane
CYTOPLASM
Activation
of cellular
response
Figure 11.5
• Overview of cell signaling
Reception1 Transduction2 Response3
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• G-protein-linked receptors
G-protein-linked
ReceptorPlasma Membrane
EnzymeG-protein
(inactive)CYTOPLASM
Cellular response
Activated
enzyme
Activated
ReceptorSignal molecule
Inactive
enzyme
Segment that
interacts with
G proteins
GDP
GDP
GTP
GTP
P i
Signal-binding site
Figure 11.7
GDP
Some good animations
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Receptor tyrosine kinases – what’s happening?
Signal
molecule
Signal-binding sitea
CYTOPLASM
Tyrosines
Signal
moleculeHelix in the
Membrane
Tyr
Tyr
Tyr
Tyr
Tyr
TyrTyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Dimer
Receptor tyrosine
kinase proteins
(inactive monomers)
P
P
P
P
P
PTyr
Tyr
Tyr
Tyr
Tyr
TyrP
P
P
P
P
PCellular
response 1
Inactive
relay proteins
Activated
relay proteins
Cellular
response 2
Activated tyrosine-
kinase regions
(unphosphorylated
dimer)
Fully activated receptor
tyrosine-kinase
(phosphorylated
dimer)
6 ATP 6 ADP
Figure 11.7
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Ion channel receptors
– critical in nerve cells
Cellular
response
Gate open
Gate close
Ligand-gated
ion channel receptor
Plasma
Membrane
Signal
molecule
(ligand)
Figure 11.7
Gate closed Ions
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Signal molecule
Active
protein
kinase
1
Active
protein
kinase
2
Active
protein
kinase
3
Inactive
protein kinase
1
Inactive
protein kinase
2
Inactive
protein kinase
3
Inactive
protein
Active
proteinCellular
response
Receptor
P
P
P
ATP
ADP
ADP
ADP
ATP
ATP
PP
PP
PP
Activated relay
molecule
iP
P
i
i
P
• A phosphorylation cascade
Figure 11.8
A relay molecule
activates protein kinase 1.1
2 Active protein kinase 1
transfers a phosphate from ATP
to an inactive molecule of
protein kinase 2, thus activating
this second kinase.
Active protein kinase 2
then catalyzes the phos-
phorylation (and activation) of
protein kinase 3.
3
Finally, active protein
kinase 3 phosphorylates a
protein (pink) that brings
about the cell’s response to
the signal.
4
Enzymes called protein
phosphatases (PP)
catalyze the removal of
the phosphate groups
from the proteins,
making them inactive
and available for reuse.
5
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 11.12
321
IP3 quickly diffuses through
the cytosol and binds to an IP3–
gated calcium channel in the ER
membrane, causing it to open.
4 The calcium ions
activate the next
protein in one or more
signaling pathways.
6Calcium ions flow out of
the ER (down their con-
centration gradient), raising
the Ca2+ level in the cytosol.
5
DAG functions as
a second messenger
in other pathways.
Phospholipase C cleaves a
plasma membrane phospholipid
called PIP2 into DAG and IP3.
A signal molecule binds
to a receptor, leading to
activation of phospholipase C.
EXTRA-
CELLULAR
FLUID
Signal molecule
(first messenger)
G protein
G-protein-linked
receptor
Various
proteins
activated
Endoplasmic
reticulum (ER)
Phospholipase CPIP2
IP3
(second messenger)
DAG
Cellular
response
GTP
Ca2+
(second
messenger)
Ca2+
IP3-gated
calcium channel
• “2nd Messenger”
is a general term,
it may actually be
applied to a 3rd
or 4th messenger.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Glucose-1-phosphate
(108 molecules)
Glycogen
Active glycogen phosphorylase (106)
Inactive glycogen phosphorylase
Active phosphorylase kinase (105)
Inactive phosphorylase kinase
Inactive protein kinase A
Active protein kinase A (104)
ATP
Cyclic AMP (104)
Active adenylyl cyclase
(102)
Inactive adenylyl cyclase
Inactive G protein
Active G protein (102 molecules)
Binding of epinephrine to G-protein-linked receptor (1 molecule)
Transduction
Response
Reception
• Amplification of a
transduced signal:
Figure 11.13
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Many pathways
regulate genes
by activating
transcription
factors that turn
genes on or off
Reception
Transduction
Response
mRNANUCLEUS
Gene
P
Active
transcription
factor
Inactive
transcription
factor
DNA
Phosphorylation
cascade
CYTOPLASM
Receptor
Growth factor
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Branching and
“cross-talk”
further help the
cell coordinate
incoming signalsResponse 1
Response 4 Response 5
Response
2
Response
3
Signal
moleculeCell A. Pathway leads
to a single response
Cell B. Pathway branches,
leading to two responses
Cell C. Cross-talk occurs
between two pathways
Cell D. Different receptor
leads to a different response
Activation
or inhibition
Receptor
Relay
molecules
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Signaling Efficiency: Scaffolding Proteins and Signaling Complexes
• Scaffolding proteins
– Can increase the signal transduction efficiency
Signal
molecule
Receptor
Scaffolding
protein
Three
different
protein
kinases
Plasma
membrane
Figure 11.16
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