Division Essay

Cell Communication/Death/Division Essay Cell Communication/Death/Division Essay CELL COMMUNICATION - animal cells = gap junctions to send signals (must be in direct contact) - plant cells = plasmodesmata - local signaling - signaling over a short distance - cell to cell recognition - local regulators - long-distance signaling - nervous/endocrine system in animals - plants use hormones, transported through vascular system - three stages of cell signaling - signaling molecule binds to the receptor protein - signal is converted into a form that can produce a cellular response - the transduced signal triggers a cellular response - G-protein receptors make up 60% of our cells - quorum sensing - capacity of bacteria to exhibited coordinated behavior in response to a particular population density CELL DEATH - apoptosis - controlled cell suicide - components are chopped up and packaged into vesicles = digested by scavenger cells - "blebbing" vs. apoptosis - triggered by death-signaling, DNA damage, protein misfolding - caspases - main proteases that carry out apoptosis - proteases - protein - digesting enzyme - necrosis - death by cell injury - cell bursts, â€Å"stuff† flies out - enzymes are unleashed into the ECF - results in inflammation, redness, pain, etc. - DNA is organized in chromosomes. -DNA is wrapped around histone proteins = chromatin (long thin fiber) -condenses further during mitosis = chromatin = chromosomes - mitotic chromosome = 2 sister chromatids -chromatids narrow at the centromere (not necessarily in the center) -homologous = same information - mitosis - divides the cell’s DNA between 2 daughter nuclei -4 phases = prophase, metaphase, anaphase, telophase - semi-conservative replication - conserve half of original piece = build two new ones - original piece is called the template strand INTERPHASE - G1 - 1st Gap - cell growth - S - DNA synthesis - chromosomes are copied -each daughter cell gets identical copy -error rate is about 1/100 million bases - G2 - 2nd Gap - further cell growth. organelles, proteins, membranes are created. Nucleus is well-defined, and DNA is loosely packed in long chromatin fibers (aka squiggly in the middle). PROPHASE - chromatin condenses = visible chromosomes - centrioles move to opposite poles of cell - spindle fibers go across cell to form mitotic spindle - microtubules - nucleolus disappears/nuclear envelopes burst TRANSITION TO METAPHASE/PROMETAPHASE - spindle fibers attach to centromeres - thus creating kinetochores - microtubules attach at kinetochores - connects centromeres to centrioles - chromosome begins to move METAPHASE - chromosomes align along the middle of the cell (metaphase plate) - spindle fibers coordinate movement - ensures that the chromosomes separate properly (1 copy per new nucleus) ANAPHASE - sister chromatids are separated at the kinetochores - move to opposite poles (pulled by centromeres) - microtubules lengthen as poles move further apart TELOPHASE - chromosomes arrive at opposite poles - nuclei form and chromosomes disperse - cytokinesis begins CYTOKINESIS - animal cells - constriction of actin microfilaments around equator of cell = cleavage furrow - splits cell in two - plant cells - cell plate forms - vesicles fuse = forms 2 cell membranes - new cell wall laid between membranes - new cell wall fuses with existing cell wall EVOLUTION OF MITOSIS - mitosis in eukaryotes likely evolved from binary fission in bacteria characteristics of binary fission: - single circular chromosome - no membrane bound organelles - no mitotic spindle REGULATION OF CELL DIVISION - multicellular organisms - must coordinate cell division across tissues/organs -timing,