Unit 10: Cell communication (growth, repair, reproduction)

• signal transduction pathway: process by which a signal or chemical is transmitted through a cell and causes a change in its activity.
• Quorum sensing: A process by which bacteria communicate with each other to coordinate their behavior
• signaling molecule: a molecule that is released from one cell and binds to a receptor on another cell
• paracrine signaling: allows cells to communicate with each other by releasing signaling molecules that bind to and activate surrounding cells.
• synaptic signaling: the process of transmitting signals and neurotransmitters from one neuron to another
• endocrine signaling: hormones are released into the bloodstream and travel to target cells
• growth factors: aka local regulators stimulate nearby target cells to grow and divide
• relay molecules: the molecules that causes a change in signal transduction pathway
• ligand: a molecule that specifically binds to another molecule
• G Protein-Coupled Receptors: a type of receptor that activates G protein when GTP is attached. Activated G protein attaches to the enzyme which activates cellular response.
• growth factor: signaling molecule that stimulates cellular response
• dimerization: 2 monomers form a dimer
• tyrosine kinase: two protein receptors that become activated and form a dimer when a ligand binds (in a process called dimerization) which adds a phosphate from an ATP molecule to each tyrosine where relay proteins can bind to each phosphorylated tyrosine, triggering a transduction pathway.
• ligan-gated ion channel: membrane receptor that acts as a gate. Signaling molecule binds to receptor, allowing ions to flow through.
• transcription factors: controls which genes are turned on/off and which are transcribed into mRNA.
• intracellular receptors: hydrophobic molecules (aldosterone) pass through plasma membrane and activates receptor to enter the nucleus to bind to specific genes, turning them on or off to translate mRNA into a protein.
• protein kinase: an enzyme that transfers phosphate groups from ATP to a protein
• phosphorylation cascade: cellular pathway containing different protein kinases that transmit the signal down the chain.
• what is the cause of the change in shape of protein kinases?

  the shape changes because of the newly added phosphate groups which also alters the function of the protein
• does the g protein also act as an enzyme?

  yes, g protein is also GTPase
• cyclic AMP: a second messenger that is produced by the breakdown of ATP and is responsible for the intracellular signal transduction by activating to protein kinase A
• adenylyl cyclase: an enzyme that converts ATP to cAMP in response to an extracellular signal
• relay proteins: transport proteins that carry the signal from the receptor to the effector
• Second messengers are small molecules and ions that relay signals received by cell-surface receptors to effector proteins. (ex: cAMP, IP3, calcium)
• what are the two other second messengers involved in the release of calcium?

  Inositol trisphosphate (IP3) and diacylglycerol (DAG).
• what signaling molecule is used for intracellular pathways?

  steroid hormones, hydrophobic molecules pass easily through the membrane to bind to a receptor.
• what is the general process of a nuclear signaling pathway?

  initial signaling molecule, a growth factor, triggers phosphorylation cascade, where the last kinase in the sequence enters the nucleus and activates a gene-regulation protein (transcription factor), stimulating transcription of a specific gene.
• what is the general pathway response for a steroid hormone?

  steroid hormones pass through plasma membrane to bind to a receptor in the cytoplasm or on the nucleus, activating it. the hormone receptor complex enters nucleus and binds to specific genes to act as a transcription factor, stimulating transcription of the gene into mRNA into a protein.
• what is the general pathway of a phosphorylation cascade?

  each protein adding a phosphate group to the next one in line. phosphorylation activates each protein and dephosphorylation returns it to its inactive form, resulting in a change of shape.
• what is protein kinase?

  An enzyme that transfers a phosphoryl group from ATP to the side chain of a serine, threonine, or tyrosine residue in a protein
• what is a cross talk pathway?

  A cross talk pathway refers to the communication and interaction between different signaling pathways in a biological system.
• apoptosis: cellular death where agents package DNA and other fragments to be digested by scavenger cells
• proteases: enzymes that break down proteins into amino acids
• nucleases: enzymes that break down DNA and RNA into smaller fragments
• what are the main enzymes used for apoptosis?

  proteases (caspases) and nucleases
• what is the general signaling pathway in G protein receptors?

  the first messenger activates a G protein coupled receptor, which activates a specific G protein. G protein activates adenylyl cyclase, which catalyzes the conversion of ATP to cAMP. cAMP acts as a second messenger and activates another protein, usually protein kinase A, leading to cellular response.
• what are the types of cell-surface transmembrane receptors?

  G protein-coupled receptors (GPCRs), receptor tyrosine kinases (RTKs), ion channel receptors
• what is the role of ced-9 in apoptosis?

  ced-9 acts as a brake in the absence of a death signaling molecule (inhibited). however, when it receives a death signal it triggers a cascade of events leading to cell death.
• chromatin: entire complex of DNA and proteins that builds the chromosome
• Chromosome condensation is the dramatic reorganisation of the long thin chromatin strands into compact short chromosomes that occurs in mitosis and meiosis.