LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick Cell Communication & Apoptosis Chapter 11

Cancer & Cell Cycle Control Checkpoints: Molecular “Stop” or “Go” signals At G 1, G 2 (Interphase) –And M phases of –The cell either “Stops” and goes into G 0 or “Goes” and continues on the cell cycle. –Molecules that do this signaling include protein kinases (cyclin-dependent kinases)

Images to consider: Cell signaling Apoptosis

How do chemical control systems work? CdK control is similar to other control systems in the cell. How do cells communicate? How do messages reach cells?

Overview: Cellular Messaging Cell-to-cell communication in multicellular and unicellular organisms Universal mechanisms of cellular regulation (evolutionary connectiveness) Chemical signals are the most frequent type Ex) the fight-or-flight response is triggered by a signaling molecule called epinephrine © 2011 Pearson Education, Inc.

Figure 11.1

Epinephrine: Fight or flight Epinephrine (hormone, a.k.a. adrenaline) binds to a receptor in liver cells A signal transduction pathway occurs The response is the breakdown of glycogen in the liver cells into glucose The released energy makes fight or flight possible.

11.1: Local (close) Signaling Chemical messengers Cell junctions directly connect the cytoplasm of adjacent cells –Gap junctions in animals –Plasmodesmata in plants Direct contact or cell to cell recognition Local regulators, messenger molecules that travel only short distances © 2011 Pearson Education, Inc.

Figure 11.4 Plasma membranes Gap junctions between animal cells Plasmodesmata between plant cells (a) Cell junctions (b) Cell-cell recognition

Figure 11.5a Local signaling Target cell Secreting cell Secretory vesicle Local regulator diffuses through extracellular fluid. (a) Paracrine signaling (b) Synaptic signaling Electrical signal along nerve cell triggers release of neurotransmitter. Neurotransmitter diffuses across synapse. Target cell is stimulated.

Plants and animals use chemicals called hormones A cell’s response is determined by whether or not it has a receptor specific to that signal © 2011 Pearson Education, Inc. Long distance signaling

Figure 11.5b Long-distance signaling Endocrine cell Blood vessel Hormone travels in bloodstream. Target cell specifically binds hormone. (c) Endocrine (hormonal) signaling

11.1 The Three Stages of Cell Signaling: A Preview Cells receiving signals go through three processes –Reception –Transduction –Response © 2011 Pearson Education, Inc. Animation: Overview of Cell Signaling

Figure Plasma membrane EXTRACELLULAR FLUID CYTOPLASM ReceptionTransduction Response Receptor Signaling molecule Activation of cellular response Relay molecules in a signal transduction pathway Stages of Cell Signaling: Signal-transduction pathway: The multiple steps that convert a signal into a cellular response

Concept 11.2: Reception Target cell receives the message via a receptor protein (usually found in the plasma membrane,) making a ligand. Ligand: the combination of the signal molecule + the receptor protein. © 2011 Pearson Education, Inc.

Figure 11.7d Signaling molecule (ligand) Gate closed Ions Ligand-gated ion channel receptor Plasma membrane Gate open Cellular response Gate closed

Transduction Signal transduction pathway=multiple steps to relay the signal as (mostly through proteins-protein kinases, can be cAMP or Ca 2+ ions) Analogy: falling dominoes: –the receptor activates another protein, which activates another, and so on, until the protein producing the response is activated © 2011 Pearson Education, Inc.

Figure G protein First messenger (signaling molecule such as epinephrine) G protein-coupled receptor Adenylyl cyclase Second messenger Cellular responses Protein kinase A GTP ATP cAMP

Response Varied, examples include: Turn on or off genes (triggering protein synthesis) Open or close ion channels Cell division © 2011 Pearson Education, Inc.

Figure Growth factor Receptor Reception Transduction CYTOPLASM Response Inactive transcription factor Active transcription factor DNA NUCLEUS mRNA Gene Phosphorylation cascade P

Figure Reception Transduction Response Binding of epinephrine to G protein-coupled receptor (1 molecule) Inactive G protein Active G protein (10 2 molecules) Inactive adenylyl cyclase Active adenylyl cyclase (10 2 ) ATP Cyclic AMP (10 4 ) Inactive protein kinase A Active protein kinase A (10 4 ) Inactive phosphorylase kinase Active phosphorylase kinase (10 5 ) Inactive glycogen phosphorylase Active glycogen phosphorylase (10 6 ) Glycogen Glucose 1-phosphate (10 8 molecules)

Figure Signaling molecule Receptor Relay molecules Response 1 Cell A. Pathway leads to a single response. Response 2Response 3 Response 4 Response 5 Activation or inhibition 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.

Concept 11.5: Apoptosis Apoptosis=programmed or controlled cell suicide Cell parts chopped up/ packaged into vesicles & digested by scavenger cells Apoptosis prevents enzymes from leaking out of a dying cell and damaging neighboring cells © 2011 Pearson Education, Inc.

Figure  m Apoptosis of a human white blood cell.

Triggers & Method Triggered by –An extracellular death-signaling ligand –DNA damage in the nucleus –Protein misfolding in the endoplasmic reticulum Caspases=enzymes that cut up proteins (they carry out apoptosis.) © 2011 Pearson Education, Inc.

Evolved early in animal evolution –essential for the development and maintenance of all animals (ex. making fingers) Diseases (Possible links) –Parkinson’s and Alzheimer’s –Lack of apoptosis may contribute to some cancers © 2011 Pearson Education, Inc. Evolution & Importance of Apoptosis

Figure Interdigital tissue Cells undergoing apoptosis Space between digits 1 mm