Chapter 11: Cell Communication

Cell to cell recognition: Yeast cells: secrete chemical signals which bind to specific receptors Start to grow towards each other Forms new cell that contains all genes from both cells

Signal Transduction Pathways: process by which a signal on a cell’s surface is converted into a specific cellular response in a series of steps

Phosphorylation Cascade Protein kinase is activated by a relay molecule Transfer of phosphate group from an active protein kinase to an inactive protein kinase Ultimately brings about a cellular response Protein phosphatase- enzyme Dephosphorylates protein kinases

Secondary Messengers Carry signal to cells interior Small, non protein, water soluble Diffuse through out the cell Examples:cAMPCa++

Signal Molecules: CellBacteriaProteins

Local and Long-Distance Signaling: cells communicate via chemical messengers

Local Signaling: paracrine signaling Involves secreting cell and target cell Example: growth factors synaptic signaling Involves neurons as the secreting cell Neurotransmitters Target cell- could be another nerve cell, muscle cell etc…

Long distance signaling: Hormones Released by endocrine system Pancreas releases insulin Travels to different parts of the body via the circulatory system Another example in plants: Ethylene: gas secreted by fruits speeds up ripening process in other fruits Auxins

Three stages of cell signaling: 1. reception- detection of the signal molecule by the target cell Signal Molecules (ligand) Surface Receptors G- Protein Linked Receptors Tyrosine- Kinase Receptors Ion Channel Receptors Intracellular Receptors

Three stages of cell signaling: 2. transduciton- signal converted to a specific cellular response Involves conformational change of proteins Can be single step but usually involves multiple steps

Three stages of cell signaling: 3. response: a multitude of cellular activity including: enzyme catalysis, rearrangement of the cytoplasm, activation of specific genes

Three stages of cell signaling: This three step process ensures the right cells and cell processes are activated at the right time

The Role of membrane carbohydrates in Cell- Cell recognition Glycolipids : short carbohydrate chain covalently bound to proteins Amphipathic Receptor site Glycoproteins: short carbohydrate chain covalently bound to lipids Cell to cell contact and communication