1. Cell-Cell Communication Signals sent to other cells Three levels  Direct contact  Local Paracrine Synaptic  Long distance Endocrine

2. Fig. 11-4 Plasma membranes Gap junctions between animal cells (a) Cell junctions Plasmodesmata between plant cells (b) Cell-cell recognition

3. Fig. 11-5 Local signaling Target cell Secreting cell Secretory vesicle Local regulator diffuses through extracellular fluid (a) Paracrine signaling(b) Synaptic signaling Target cell is stimulated Neurotransmitter diffuses across synapse Electrical signal along nerve cell triggers release of neurotransmitter Long-distance signaling Endocrine cell Blood vessel Hormone travels in bloodstream to target cells Target cell (c) Hormonal signaling

4. The Three Stages of Cell Signaling: A Preview Earl W. Sutherland discovered how the hormone epinephrine acts on cells Sutherland suggested that cells receiving signals went through three processes:  Reception  Transduction  Response Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

5. Concept 11.2: Reception: A signal molecule binds to a receptor protein, causing it to change shape The binding between a signal molecule (ligand) and receptor is highly specific A shape change in a receptor is often the initial transduction of the signal Most signal receptors are plasma membrane proteins Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

6. Concept 11.3: Transduction: Cascades of molecular interactions relay signals from receptors to target molecules in the cell Signal transduction usually involves multiple steps Multistep pathways can amplify a signal: A few molecules can produce a large cellular response Multistep pathways provide more opportunities for coordination and regulation of the cellular response Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

7. Nuclear and Cytoplasmic Responses Ultimately, a signal transduction pathway leads to regulation of one or more cellular activities The response may occur in the cytoplasm or may involve action in the nucleus Many signaling pathways regulate the synthesis of enzymes or other proteins, usually by turning genes on or off in the nucleus The final activated molecule may function as a transcription factor Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

8. Fig. 11-7b G protein-coupled receptor Plasma membrane Enzyme G protein (inactive) GDP CYTOPLASM Activated enzyme GTP Cellular response GDP P i Activated receptor GDP GTP Signaling molecule Inactive enzyme 1 2 3 4

9. Fig. 11-8-5 Hormone (testosterone) EXTRACELLULAR FLUID Receptor protein Plasma membrane Hormone- receptor complex DNA mRNA NUCLEUS New protein CYTOPLASM

10. Biological Energetics How cells obtain and energy needed for survival Two types of organisms  Autotrophs  Heterotrophs Net loss of energy as it is transferred through organisms

11. Autotrophs Are able to synthesize macromolecules by using small molecules from environment  Do not consume other organisms to obtain molecules Vast majority are photosynthetic  Use energy from sunlight to power anabolic reactions All biological energy originates with autotrophs  Life is solar powered

12. Heterotrophs Consume other organisms and utilize energy obtained from catabolic degradation of macromolecules  Rely on the presence of autotrophs as original energy source  Loss of energy in transfer means that the balance between heterotrophs and autotrophs is crucial Can consume autotrophs or other heterotrophs Saprophytes-consume dead organisms “decomposers”  Bacteria, fungi, scavengers

13. Photosynthesis and respiration Photosynthesis is the use of solar energy to power anabolic reactions-autotrophs Respiration is the process in which macromolecules are degraded to obtain cellular power-heterotrophs They are complementary processes  One relies on the products of the other and they are linked biologically

14. Photosynthesis Takes place in the chloroplasts of plants and in the cytoplasm of photosynthetic bacteria Requires CO 2 and a source of Hydrogen  Usually water but can be H 2 S  Ultimately results in Glucose and Oxygen production (water also)  CO 2 +6H 2 O +Light energy--->C 6 H 12 O 6 + 6O 2 Oxygen production by plants is essential for other life to exist

15. Photosynthesis 2 Actually two stages in Photosynthesis  Light cycle-Sunlight is used to synthesize ATP and other energy storing molecules Made up of Photosystems I and II  Calvin Cycle or Dark Cycle-Energy from ATP and other molecules is used to synthesize sugars

16. Chloroplasts Light reactions happen in Thylakoids of Granum Calvin cycle happens in Stroma  Chlorphyll is the molecule that catches solar energy in chloroplasts  Other chromoplasts exist that contain different molecules for catching solar energy

17. Why are chlorplasts green? Absorbs Red and Blue light Green light is transmitted or reflected making plants appear green