Resp & Cell Comm Review

Resp & Cell Comm Review

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


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


• What’s different in the electron sharing of the reactants vs. the products?

• Where does this energy come from?

• Which atoms got oxidized/reduced?


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.


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


Fig. 9.8

BIG PICTURE


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.



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

http://www.youtube.com/watch?v=xbJ0nbzt5Kw

http://www.youtube.com/watch?v=FFBr3ANCkb4


Fig. 9.16

Big Picture

• alcohol fermentation:

• performed by yeast; used in brewing and winemaking.


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.


Fig. 9.17b


Fig. 9.18

• Some organisms (facultative anaerobes), including

yeast and many bacteria, can survive using either

fermentation or respiration.

• human muscle cells too.


Fig. 9.19

• 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


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


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


• 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


• 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


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


• 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

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter7/animations.html


• 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


• 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


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


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.


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


• 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


• 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


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

Documents

Resp & Cell Comm Review